The Body by Bryson
Ref: Bill Bryson (2019). The Body: A Guide for Occupants. Swan Publishing.
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Summary
The Human Body and its various systems work together in almost perfect harmony carrying out conscious and subconscious processes continually for decade upon decade. Bryson explains how each individual bodily system works on multiple levels; how we see, how we think, how we hear, how we digest, how we reproduce, and more.
59 elements are needed to construct a human being. Six of these- C, O, H, N, Ca, P- account for 99.1% of what makes us (RSC Calculations).
It takes 7 billion billion billion (7 octillion) atoms to make you.
We have as many as 33 systems within us that let us know where we are and how we are doing.
Not once in the three billion years since life began has your personal line of descent been broken.
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Misc Quotes
“Up until 1865 medicine was almost completely ineffectual where it wasn’t positively harmful.”-David Wootton, Bad Medicine.
“When the great anatomist Andreas Vesalius, as a young man, wanted human remains to study, he stole the body of an executed murderer off a gibbet outside his hometown of Leuven in Belgian Flanders.”
“As James Le Fanu has put it, “While we have the overwhelming impression that the greenness of the trees and the blueness of the sky are streaming through our eyes as through an open window, yet the particles of light impacting on the retina are colourless, just as the waves of sound impacting on the eardrum are silent and scent molecules have no smell. They are all invisible, weightless, subatomic particles of matter travelling through space.” All the richness of life is created inside your head. What you see is not what is but what your brain tells you it is, and that’s not the same thing at all.”
“In Henry VIII’s reign, puberty started at 16 or 17. Now it is more commonly eleven. That’s almost certainly because of improved nutrition.”
“Body size has a great deal to do with how we are affected by gravity. It will not have escaped your notice that a small bug that falls off a tabletop will land unharmed and continue on its way unperturbed. That is because its small size (strictly, its surface area-to-volume ratio) means that it is scarcely affected by gravity. What is less well known is that the same thing applies, albeit on a different scale, to small humans. A child half your height who falls and strikes her head will experience only one thirty-second the force of impact that a grown person would feel, which is part of the reason that children so often seem to be mercifully indestructible.”
“Not less than two hours a day should be devoted to exercise and the weather should be little regarded. If the body be feeble, the mind will not be strong.”-Thomas Jefferson.
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Genetics & the Genome
DNA
DNA exists solely to create more DNA. It is simply an instruction manual for making you. A length of DNA is divided into segments called chromosomes and shorter individual units called genes. The sum of all your genes is the genome.
DNA is extremely stable and can last for tens of thousands of years.
DNA passes on information with extraordinary fidelity. It makes only about one error per every billion letters copied. Still, because your cells divide so much, that is about three errors, or mutations, per cell division. Most of those mutations the body can ignore, but just occasionally they have lasting significance. That is evolution.
Genes: provide instructions for building proteins. Most of the useful things in the body are proteins.
Protein: a larger chain of amino acids; ~a million different proteins have been identified so far, and nobody knows how many more are to be found. They are all made from just twenty amino acids, even though hundreds of amino acids exist in nature that could do the job just as well.
Peptide: A small but unspecified number of amino acids strung together.
Polypeptide: Ten or twelve Amino Acids strung together. Anything larger can be deemed a Protein.
Enzymes: Proteins that speed up chemical changes.
Hormones: Proteins that convey chemical messages.
Hormones are the bicycle couriers of the body, delivering chemical messages all around the teeming metropolis that is you. They are defined as any substance that is produced in one part of the body and causes an action somewhere else.
Antibodies: Proteins that attack pathogens.
Titin: Our largest protein which helps control muscle elasticity.
Only 2% of the human genome codes for proteins, which is to say only 2% does anything demonstrably and unequivocally practical.
You have within you about a hundred personal mutations—stretches of genetic instructions that don’t quite match any of the genes given to you by either of your parents but are yours alone.
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Human Evolution
Phenotypic Plasticity: Environmental adaptation to altered circumstances.
To keep from overheating when we exert ourselves, we became relatively hairless and developed abundant sweat glands.
We evolved a very different head from other primates. Our faces are flat and conspicuously snoutless. We have a high forehead to accommodate our more impressive brain. Cooking has left us with smaller teeth and a more delicate jaw. Inside, we have a short oral cavity and thus a shorter, more rounded tongue, and a larynx that sits lower in the throat. The changes to our upper anatomy left us by happy accident with vocal tracts uniquely able to make articulate speech.
Nuchal Ligament: Holds the head steady when running.
First, we became walkers and climbers, but not runners. Then, gradually, we became walkers and runners, but no longer climbers.
Above all, the adoption of a narrower pelvis to accommodate our new gait brought a huge amount of pain and danger to women in childbirth. Until recent times, no other animal on Earth was more likely to die in childbirth than a human, and perhaps none even now suffers as much.
To power our forward motion, we have a distinctively gigantic muscle in our buttocks, the gluteus maximus, and an Achilles tendon, something no ape has.
The chin is unique to humans, and no one knows why we have one.
The loss of most of our body hair and the gain of the ability to dissipate excess body heat through eccrine sweating helped to make possible the dramatic enlargement of our most temperature-sensitive organ, the brain.
Out of some 250 species of primates, we are the only ones that have elected to get up and move around exclusively on two legs.
Because our ancient ancestors had to survive lean times as well as good, they evolved a tendency to store fat as a fuel reserve—a survival reflex that is now, all too often, killing us. The upshot is that millions of us spend our lives struggling to maintain a balance between paleolithically designed bodies and modern gustatory excess.
Cooking confers all kinds of benefits. It kills toxins, improves taste, makes tough substances chewable, greatly broadens the range of what we can eat, and above all vastly boosts the amount of calories humans can derive from what they eat. It is widely believed now that cooked food gave us the energy to grow big brains and the leisure to put them to use.
We have just three kinds of color receptors compared with four for birds, fish, and reptiles.
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ATP & Energy
Adenosine Triphosphate (ATP): The stuff responsible for the energy in our cells. Every molecule of ATP is like a tiny battery in that it stores up energy and then releases it to power all the activities required by your cells—and indeed by all cells, in plants as well as animals.
A typical mammal uses ~30x as much energy in a day as a typical reptile, which means that we must eat every day what a crocodile needs in a month.
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Central Nervous System (Brain)
Function: Controls most functions of the body and mind.
Major Parts:
Central Nervous System (CNS): The brain and spinal cord.
Peripheral Nervous System (PNS): The nerves radiating out from the central hub of the CNS, that reach out to the other parts of your body.
Somatic Nervous System: Controls voluntary actions (like scratching your head).
Autonomic nervous system: Controls all automatic processes like breathe, pump blood, and digest food.
Sympathetic Nervous System: The part that responds when the body needs sudden actions—what is generally referred to as the fight-or-flight response.
Parasympathetic Nervous System: Sometimes referred to as the “rest and digest” or “feed and breed” system and looks after a miscellany of other, generally less urgent matters like digestion and waste disposal, the production of saliva and tears, and sexual arousal.
Cerebrum: fills most of the cranial vault and is the part that we normally think of when we think of “the brain.” The cerebrum (from the Latin word for “brain”) is the seat of all our higher functions. It is divided into two hemispheres, each of which is principally concerned with one side of the body, but for reasons unknown the wiring is crossed, so that the right side of the cerebrum controls the left side of the body and vice versa. The two hemispheres are connected by a band of fibers called the corpus callosum (meaning “tough material” or literally “calloused body” in Latin). The brain is wrinkled by deep fissures known as sulci and ridges called gyri, which give it more surface area.
Each hemisphere of the cerebrum is further divided into four lobes, each broadly specializing in certain functions:
Frontal: The seat of the higher functions of the brain—reasoning, forethought, problem solving, emotional control and so on. It is the part responsible for personality, for who we are.
Parietal: Manages sensory inputs like touch and temperature
Occipital: Processes visual information.
Temporal: Processes auditory information and encodes memory.
Cerebral Cortex: The brains gray matter. All higher processes—thinking, seeing, hearing, and so on—happen right at the surface, in the four-millimeter-thick sheath of the cerebral cortex.
Cerebellum (latin for “little brain”): Beneath the cerebrum, at the very back of the head, the cerebellum occupies just 10% of the cranial cavity, it has more than half the brain’s neurons. It has a lot of neurons not because it does a great deal of thinking but because it controls balance and complex movements, and that requires an abundance of wiring.
Brain Stem: At the base of the brain, descending from it rather like an elevator shaft connecting the brain to the spine and the body beyond, is the oldest part of the brain, the brain stem. It is the home of our more basic operations: sleeping, breathing, keeping the heart going.
Limbic System: Scattered through the brain rather like nuts in a fruitcake are many smaller structures—hypothalamus, amygdala, hippocampus, telencephalon, septum pellucidum, habenular commissure, entorhinal cortex, and a dozen or so others—which are collectively known as the limbic system (from the Latin limbus, meaning “peripheral”). The structures of the limbic system have a fundamental role in our happiness by controlling and regulating basic processes like memory, appetite, emotions, drowsiness and alertness, and the processing of sensory information.
Basal ganglia: Plays an important part in movement, language, and thought (it is only when they degenerate and lead to Parkinson’s disease that they normally attract attention to themselves).
Hypothalamus: though only about the size of a peanut and weighing barely a tenth of an ounce, it controls much of the most important chemistry of the body. It regulates sexual function, controls hunger and thirst, monitors blood sugar and salts, decides when you need to sleep. It may even play a part in how slowly or rapidly we age.
Hippocampus: central to the laying down of memories. (The name comes from the Greek for “sea horse” because of its supposed resemblance to that creature.)
Amygdala: (Greek for “almond”) specializes in handling intense and stressful emotions—fear, anger, anxiety, phobias of all types. People whose amygdalae are destroyed are left literally fearless, and often cannot even recognize fear in others. The amygdala grows particularly lively when we are asleep, and thus may account for why our dreams are so often disturbing. Your nightmares may simply be the amygdalae unburdening themselves.
Hypothalamus: The control center of the brain; tells the body to cool itself by sweating or to warm itself by shivering and diverting blood flow away from the skin and into the more vulnerable organs.
White Matter: Beneath the gray matter is a much greater volume of white matter, which is so called because the neurons are sheathed in a pale fatty insulator called myelin, which greatly accelerates the speed at which signals are transmitted. Both white matter and gray matter are misleadingly named. Gray matter isn’t terribly gray in life, but has a pinkish blush. It only becomes conspicuously gray in the absence of blood flow and with the addition of preservatives. White matter is also a posthumous attribute because the pickling process turns the myelin coatings on its nerve fibers a luminous white.
Neurons: long and stringy, the better to pass on electrical signals from one to another. The main strand of a neuron is called an axon. At its terminal end, it splits into branch-like extensions called dendrites, as many as 400,000 of them. The tiny space between nerve cell endings is called a synapse. Each neuron connects with thousands of other neurons, giving trillions and trillions of connections—as many connections “in a single cubic centimeter of brain tissue as there are stars in the Milky Way,”
Glia: (the word means “glue” or “putty”) the cells that support neurons in the brain and central nervous system. For a long time, they were assumed to be not too important—their role was thought to be principally to provide a kind of physical support, or extracellular matrix as anatomists put it, for neurons—but now it is known that they engage in a lot of important chemistry, from producing myelin to clearing away wastes.
Cerebrospinal Fluid: Located in the meninges, the brain’s outer membrane, provides a bit of cushioning, but only a bit.
Memory
Memory storage is idiosyncratic and strangely disjointed. The mind breaks each memory into its component parts—names, faces, locations, contexts, how a thing feels to the touch, even whether it is living or dead—and sends the parts to different places, then calls them back and reassembles them when the whole is needed again. A single fleeting thought or recollection can fire up a million or more neurons scattered across the brain. Moreover, these fragments of memory move around over time, migrating from one part of the cortex to another, for reasons entirely unknown. It’s no wonder we get details muddled.
Memories come in two principal varieties: declarative and procedural.
Declarative memory: Memories you can put into words—the names of state capitals, your date of birth, how to spell “ophthalmologist,” and everything else you know as fact.
Procedural memory: Describes the things you know and understand but couldn’t so easily put into words—how to swim, drive a car, peel an orange, identify colors.
Interesting Facts:
To your brain, the world is just a stream of electrical pulses.
Your brain is capable of storing some two hundred exabytes of information, roughly equal to the entire digital content of today’s world (Nature Neuroscience).
The average brain is 75 to 80% water, with the rest split mostly between fat and protein.
Your brain requires only about 400 cal of energy a day—about the same as you get in a blueberry muffin. Try running your laptop for twenty-four hours on a muffin and see how far you get.
Nothing about your brain is distinctively human. We use exactly the same components—neurons, axons, ganglia, and so on—as a dog or hamster.
Although most of the growth of the brain occurs in the first two years and is 95% completed by the age of ten, the synapses aren’t fully wired until a young person is in his or her mid- to late twenties. That means that the teenage years effectively extend well into adulthood.
Phrenology: the practice of correlating bumps on a skull with mental powers and attributes of character, and it was always a marginal pursuit. Davis’s fundamental ambition was to prove that dark-skinned people were created separately from light-skinned people. He was convinced that a person’s intellect and moral compass were indelibly written in the curves and apertures of the skull and that these were exclusively products of race and class. People with “cephalic peculiarities” should be treated “not as criminals but as dangerous idiots.”
Craniometry: focused on more precise and comprehensive measurements of volume, shape, and structure of the head and brain but in pursuit, it must be said, of equally preposterous conclusions.
Pain: The experience of pain begins just beneath the skin in specialized nerve endings known as nociceptors. (“Noci-” is from a Latin word meaning “hurt.”) Nociceptors respond to three kinds of painful stimuli: thermal, chemical, and mechanical, or at least so it is universally assumed.
Nerve signals are not particularly swift. Light travels at 300 million m/s, while nerve signals move at a decidedly more stately 120 m/s.
The central nervous system can intercept a signal and act on it before passing it on to the brain. That’s why if you touch something very undesirable, your hand recoils before your brain knows what’s going on.
Brain Disorders
Anton-Babinski syndrome: A condition in which people are blind but refuse to believe it.
Riddoch syndrome: Inability to see objects unless they are in motion.
Capgras syndrome: A condition in which sufferers become convinced that those close to them are impostors.
Klüver-Bucy syndrome: Sufferers develop an urge to eat and fornicate indiscriminately (to the understandable dismay of loved ones).
Cotard delusion: Sufferers believe they are dead and cannot be convinced otherwise.
Epilepsy: isn’t really a single disease but a collection of symptoms that can range from a brief lapse of awareness to prolonged convulsions, all caused by misfiring neurons in the brain. Epilepsy can be brought on by illness or head trauma, but very often there is no clear precipitating event, just a sudden, frightening seizure from out of the blue.
Coma: Eyes closed and wholly unaware.
Vegetative state: Eyes open but unaware.
Minimally conscious: Occasionally lucid but mostly confused or unaware.
Locked-in syndrome: Fully alert but paralyzed and often able to communicate only with eye blinks.
Stroke: When a blood vessel that carries Oxygen and Nutrients to the Brain is either blocked by a clot or bursts; the second most common cause of death globally, according to the WHO.
Alzheimer’s: an accumulation of a protein fragment called beta-amyloid in the sufferer’s brain. Nobody is quite sure what amyloids do for us when they are working properly, but it is thought they may have a role in forming memories. In any case, they are normally cleared away after they have been used and are no longer needed. In Alzheimer’s victims, however, they aren’t flushed away but accumulate in clusters known as plaques and stop the brain from functioning as it should. Later in the disease, victims also accumulate tangled fibrils of tau proteins, which are invariably referred to as tau tangles. How tau proteins relate to amyloids and how both relate to Alzheimer’s are also uncertain, but the bottom line is that sufferers experience steady, irreversible memory loss. In its normal progression, Alzheimer’s first demolishes short-term memories, then moves on to all or most memories, leading to confusion, shortness of temper, loss of inhibition, and eventually loss of all bodily functions, including how to breathe and swallow; the third most common cause of Death.
Dementias: A general term for loss of memory, language, problem solving, and other critical thinking abilities. All types are considerably rarer in people who eat a healthy diet, exercise at least moderately, maintain a sound weight, and don’t smoke at all or drink to excess.
Migraine: (the word is a corruption of the French demi-craine, meaning “half the head”) affects 15% of people but is 3x more common in women than in men. Migraines are almost wholly a mystery.
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Circulatory System (Heart, Lungs, Veins, Arteries)
Function
The journey of blood around your body takes about fifty seconds to complete. Curiously, the blood passing through the chambers of the heart does nothing for the heart itself. The oxygen that nourishes it arrives via the coronary arteries, in exactly the way oxygen reaches other organs. The two phases of a heartbeat are known as the systole (when the heart contracts and pushes blood out into the body) and diastole (when it relaxes and refills). The difference between these two is your blood pressure. The two numbers in a blood pressure reading—let’s say 120/80 are the highest and lowest pressures your blood vessels experience with each heartbeat. The first, higher number is the systolic pressure; the second, the diastolic.
Major Parts
The Heart: Weighs less than a pound and is divided into four simple chambers: two atria and two ventricles. Blood enters through the atria (Latin for “entry rooms”) and exits via the ventricles (Latin for “chambers”). The heart is not really one pump but two: one that sends blood to the lungs and one that sends it around the body. The output of the two must be in balance, every single time, for it all to work correctly. Of all the blood pumped out of your heart, the brain takes 15%, but actually the greatest amount, 20%, goes to the kidneys.
Despite the vast differences in heart rates, nearly all animals have about 800 million heartbeats in them if they live an average life.
Blood:
Spin a test tube of blood in a centrifuge and it will separate into four layers: red cells, white cells, platelets, and plasma. Plasma is the most abundant, constituting a little over half of blood’s volume. It is more than 90% water with some salts, fats, and other chemicals suspended in it. That isn’t to say plasma is unimportant, however. It is anything but. Antibodies, clotting factors, and other constituent parts can be separated out and used in concentrated form to treat autoimmune diseases or hemophilia.
Red Blood Cells (RBCs): (formally called erythrocytes) comprise ~44% of the total volume of the blood and are exquisitely designed to do one job: deliver O2. They are very small but superabundant. A teaspoon of human blood contains about twenty-five billion red blood cells, and each one of those twenty-five billion contains 250,000 molecules of hemoglobin, the protein to which O2 willingly clings. RBCs are biconcave in shape—that is, disk shaped but pinched in the middle on both sides—which gives them the largest possible surface area. To make themselves maximally efficient, they have jettisoned virtually all the components of a conventional cell—DNA, RNA, mitochondria, Golgi apparatus, enzymes of every description. A full red blood cell is almost entirely hemoglobin.
A notable paradox of red blood cells is that although they carry O2 to all the other cells of the body, they don’t use oxygen themselves. They use glucose for their own energy needs.
Hemoglobin has one strange and dangerous quirk: it vastly prefers CO to O2. If CO is present, hemoglobin will pack it in.
Each red corpuscle survives for about four months and travel through the body ~150,000x before they are collected by scavenger cells and disposed of in the spleen. You discard about a hundred billion red blood cells every day. They are a big component of what makes your stools brown.
RBCs use NO as their signaling molecule, in large part determine where to dispatch blood as the body’s requirements change from moment to moment.
Platelets (aka thrombocytes): < 1% of blood’s volume. As soon as a bleed starts, millions of platelets begin to cluster around the wound and are joined by similarly vast numbers of proteins, which deposit a material called fibrin. This agglomerates with the platelets to make a plug.
All blood cells are the same inside, but the outsides are covered with different kinds of antigens—that is, proteins that project outward from the cell surface—and that is what accounts for blood types.
Circulatory System Disorders
Bradycardia: Slow Heart Rhythm.
Tachycardia: Fast Heart Rhythm.
Heart attack: Often sudden, occur when oxygenated blood can’t get to heart muscle because of a blockage in a coronary artery. When heart muscle downstream of a blockage is deprived of O2, it begins to die, usually within about 60 minutes.
Cardiac Arrest: the heart stops pumping altogether, usually because of a failure in electrical signaling. When the heart stops pumping, the brain is deprived of oxygen and unconsciousness swiftly follows, with death not far behind unless treatment is quickly applied. A heart attack will often lead to cardiac arrest, but you can suffer cardiac arrest without having a heart attack.
Hypertrophic cardiomyopathy: A condition that makes athletes die suddenly on playing fields. It arises from an unnatural (and nearly always undiagnosed) thickening of one of the ventricles.
Interesting Facts
With an angioplasty, a balloon is inflated inside a constricted coronary blood vessel to widen it, and a stent, or piece of tubular scaffolding, is left behind to keep the vessel permanently open.
Traditionally, it was standard practice for doctors to top up any blood that was lost in trauma: If you’d lost three pints of blood, they would put three pints back in. But then AIDS and hepatitis C came along and donated blood was sometimes contaminated, so they began to use transfused blood more sparingly, and to their astonishment they found that patients often had better outcomes from not receiving transfusions. In an experiment at Stanford Hospital in California, clinicians were encouraged to reduce orders for RBC transfusions except when absolutely required. In five years, transfusions at the hospital fell by a quarter. The result was not only a $1.6 million saving in costs but fewer deaths, quicker average discharges, and a reduction in posttreatment complications.
Legally, in the USA, blood can be kept for transfusion for 42 days. The 42 day rule, which comes from the US FDA, is based on how long a typical red cell remains in circulation.
Even the best-made artificial bloods occasionally drop an O molecule, and in so doing release iron into the bloodstream. Iron is a toxin. Because of the extreme busyness of the circulatory system, even an infinitesimal accident rate will quickly mount up to toxic levels, so the delivery system has to be pretty much perfect. In nature, it is.
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Musculo-Skeletal System
Function: Bones provide support, they protect our interiors, manufacture blood cells, store chemicals, transmit sound (in the middle ear), and even possibly bolster our memory and buoy our spirits thanks to the recently discovered hormone osteocalcin.
Major Parts
Bone: Bone is stronger than reinforced concrete yet light enough to allow us to sprint. All your bones together will weigh no more than about twenty pounds, yet most can withstand up to a ton of compression.
~70% of a bone is inorganic material (primarily Ca and P Salts) and 30% organic.
Collagen: The most fundamental element of bone is collagen. It is the most abundant protein in the body—40% of all your proteins are collagens. Collagen makes the white of the eye but also the transparent cornea. In muscle it forms fibers that behave just like rope in that they are strong when stretched but collapse when pushed together.
Collagen often twins with a mineral called hydroxyapatite, which is strong when compressed and thus allows the body to create good solid structures like bones and teeth.
Tendons: Essentially extensions of muscles that connect muscles to bone; stretchy.
Ligaments: connect bone to bone and are connective tissues.
Bursas: Small sacs that help cushion joints (responsible for bursitis when they break).
Disorders
Herniated (Slipped) Disk: Becoming upright put extra pressure on the cartilage disks that support and cushion the spine, in consequence of which they sometimes become displaced or herniated in what is popularly known as a slipped disk. The best thing you can do to maintain it is to move around a lot, to keep the cartilage bathed in its own synovial fluid.
Hips wear out because they have to do two incompatible things: they must provide mobility for the lower limbs, and they must support the weight of the body. This exerts a lot of frictional pressure on the cartilage on both the head of the femur and the hip socket into which it fits. So instead of swiveling smoothly, the two can start to grind painfully, like a pestle in a mortar.
Our bones lose mass at a rate of about 1% a year from late middle age onward.
Interesting Facts
Retaining muscle mass uses up to 40% of your energy allowance when you are at rest, and much more when you are active.
Studies by NASA have shown that astronauts even on short missions—from five to eleven days—lose up to 20% of muscle mass. (They lose bone density, too.)
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Respiratory System
Function: Network of Organs and tissues that help you breathe by absorbing O2 from the air and delivering it to the cells of the body.
Respiration: the pushing of air past the vocal ligaments; phonation: the process of turning that air into sound; articulation: the refinement of sound into speech.
Major Parts
Lungs: Move O2 into the body and expel CO2 from the body.
Diaphragm: A mammalian invention; pulls down on the lungs from below and helps them to work more powerfully.
Disorders
Asthma (from the Greek “to gasp”)
Hiccup: a sudden spasmodic contraction of the diaphragm, which essentially startles the larynx into closing abruptly, making the famous hic sound.
Nosedrip: In the case of your nose, warm air from your lungs meets cold air coming into the nostrils and condenses, resulting in a drip.
Interesting Facts
Pathogens provoke a vehement response; they will in all likelihood be trapped in the mucus that lines your nasal passages or caught by the bronchi, or tubules, in your lungs. These tiny airways are lined with millions and millions of hairlike cilia that act like paddles (but beating furiously at 16x a second), and they swat the invaders back into the throat, where they are diverted to the stomach and dissolved by hydrochloric acid. If any invaders manage to get past these waving hordes, they will encounter little devouring machines called alveolar macrophages, which gobble them up.
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Digestive System
Function: Convert (via digestion) foods to energy and nutrients to be used by the body.
Roughly speaking, your food spends ~4-6 hours in the stomach, a further 6-8 hours in the small intestine, where all that is nutritious (or fattening) is stripped away and dispatched to the rest of the body to be used or, alas, stored, and up to three days in the colon (large intestine), which is essentially a large fermentation tank where billions and billions of bacteria pick over whatever the rest of the intestines couldn’t manage—fiber mostly.
Major Parts:
Stomach: Breaks down food via relatively strong acids.
Nearly everyone equates the location of the stomach with the belly, but in fact it is much higher up and markedly off center to the left. It is about ten inches long and shaped like a boxing glove. The wrist end, where the food enters, is called the pylorus, and the fist part is the fundus.
Epithelium: A single layer of protective cells that line the alimentary canal and protect the body from the acidic digestive juices of the stomach.
Small Intestine is divided into three sections and empties into the large intestine at the ileocecal sphincter.
Duodenum: meaning “twelve,” because that is how many finger widths of space it was deemed to take up in the average man in ancient Rome.
Jejunum: meaning “without food” because the jejunum was often found to be empty in corpses
Ileum: meaning “groin” on account of its proximity to same.
Ileocecal Sphincter: Connector from Small Intestine to Large Intestine.
Large Intestine (aka Bowel or Colon): Essentially a six-foot-long fermentation tank, home of feces, flatus, and all our microbial flora. It reabsorbs large volumes of water, which it returns to the body. It also provides a warm home for vast colonies of microbes that chew away at whatever the smaller intestine hasn’t taken already, in the process capturing lots of useful vitamins like B1, B2, B6, B12, and K, which are also returned to the body. What’s left is dispatched for evacuation as feces.
Stool: Consist largely of dead bacteria, undigested fiber, sloughed-off intestinal cells, and the residues of dead red blood cells.
Peristalsis: Process by which muscle contraction passes food along to the gut; food moves at the rate of about 1”/min.
Epiglottis: opens when we breathe and closes when we swallow, sending food in one direction and air in another.
Saliva: Almost entirely water, ~0.5% of it is anything else, but that tiny portion is full of useful enzymes—proteins that speed up chemical reactions. Among these are amylase and ptyalin, which begin to break down sugars in carbohydrates while they are still in our mouths. Chew a starchy food like bread or potato for a bit longer than normal and you will soon notice a sweetness. Unfortunately for us, bacteria in our mouths like that sweetness, too; they devour the liberated sugars and excrete acids, which drill through our teeth and give us cavities. Saliva also contains a powerful painkiller called opiorphin. It is six times more potent than morphine, though we have it only in very small doses.
Tongue: coated with taste buds which are clumps of taste receptor cells found in the bumps on your tongue, which are formally called papillae. They come in three different shapes: circumvallate (or rounded), fungiform (mushroom shaped), and foliate (leaf shaped). They are among the most regenerative of all cells in the body and are replaced every ten days.
When you eat, the tongue darts about like a nervous host at a cocktail party, checking the taste and shape of every morsel in preparation for dispatching it onward to the gullet.
Our tongue can only identify the familiar basics of sweet, salty, sour, bitter, and umami (a Japanese word meaning “savory” or “meaty”).
Energy & Nutrients
Vitamins: organic chemicals like plants and animals; the term describes 13 chemical oddments that we need to function smoothly but are unable to manufacture for ourselves.
Minerals: inorganic chemicals, originating from soil or water.
Carbohydrates: compounds of C, H, and O, which are bound together to form a variety of sugars—glucose, galactose, fructose, maltose, sucrose, deoxyribose (the stuff found in DNA), &c. Some of these are chemically complex and known as polysaccharides, some are simple and known as monosaccharides, and some are in between and known as disaccharides. Virtually all carbohydrates in the diet come from plants, with one conspicuous exception: lactose, from milk.
Fats: Comprised of C, H, and O, but in different proportions with the effect of making fat easier to store
Lipoproteins: Breakdown of fats in the body with cholesterol and proteins which travel through the bloodstream. Come in two principal types:
High Density Lipoproteins (HDL):
Low Density Lipoproteins (LDL): Referred to as “Bad Cholesterol” because they tend to form plaque deposits on the walls of blood vessels.
Cholesterol: Most is locked up in the cells doing useful work whereas a small part, ~7% floats around in the bloodstream. Of that 7%, 1/3 is good cholesterol while 2/3 is bad.
A good deal of fat is sent off to tens of billions of tiny storage terminals called adipocytes, which exist all over the body.
Saturated Fat: Sounds greasy and unhealthy, but in fact it is a technical description of carbon-hydrogen bond. As a rule, animal fats tend to be saturated and vegetable fats to be unsaturated.
Trans Fats (aka Hydrogenated Oil): An artificial form of fat made from vegetable oils; they are much worse for your heart than any other kind of fat. They raise levels of bad cholesterol, lower levels of good cholesterol, and damage the liver.
Carbohydrates and fats are the principal fuel reserves of the body, but they are stored and used in different ways. When the body needs fuel, it tends to burn up the available carbohydrates and store any spare fat.
Fiber (aka Roughage): the material in fruits, vegetables, and other plant foods that the body cannot fully break down. It contains no calories and no vitamins, but it helps to lower cholesterol and slows the rate at which sugar gets into the bloodstream and is then turned into fat by the liver, among many other benefits.
Interesting Facts
You can’t digest food while you are exercising because the body shunts blood away from the digestive system in order to meet the increased demand to supply oxygen to the muscles.
Scoville Hotness: A bell pepper: 50-100 Scovilles, Jalapeños: 2,500 to 5,000 Scovilles.
Synthetic umami aka monosodium glutamate, or MSG.
Calorie (actually a kilocalorie): the amount of energy required to heat one kg of water by one degree centigrade.
A single standard-sized can of soda pop contains about 50% more sugar than the daily recommended maximum for an adult.
Heinz ketchup is almost one-quarter sugar. It has more sugar per unit of volume than Coca-Cola.
A sixteen-ounce bottle of Pepsi has about thirteen teaspoons of added sugar and no nutritive value at all. Three apples would give you just as much sugar but compensate by also giving you vitamins, minerals, and fiber, not to mention a greater feeling of satiation.
A striking marker of just how confused nutrition advice can be was a finding by an advisory committee for the American Heart Association that 37% of American nutritionists rate coconut oil—which is essentially nothing but saturated fat in liquid form—as a “healthy food.” Coconut oil may be tasty, but it is no better for you than a big scoop of deep-fried butter.
Because our bodies cannot produce salt, we must consume it in our diets. The problem is in determining how much is the right amount. Take too little and you grow lethargic and weak, and eventually you die. Take too much and your blood pressure soars and you run the risk of heart failure and stroke.
Modern fruits are almost 50% poorer in Fe than they were in the early 1950s, and about 12% down in calcium and 15% in vitamin A. Modern agricultural practices, it turns out, focus on high yields and rapid growth at the expense of quality.
Flatus consists primarily of CO2 (up to 50%), H (up to 40%), and N (up to 20%). About a third of people produce CH4, a notorious GHG, while two-thirds produce none at all.
The smell of a fart is composed largely of H2S, even though H2S accounts for only about one to three parts per million of what is expelled. H2S in concentrated form—as in sewage gas—can be highly lethal, but why we are so sensitive to it in trace exposures is a question science has yet to answer.
All the gases of flatus can make a pretty explosive combination, as was tragically demonstrated in Nancy, France, in 1978 when surgeons stuck an electrically heated wire up the rectum of a sixty-nine-year-old man to cauterize a polyp and caused an explosion that literally tore the patient apart. According to the journal Gastroenterology, this was just one of “many recorded examples of explosion of colonic gas during anal surgery.”
Heimlich seriously undermined his reputation by championing a treatment called malaria therapy, in which people were purposely infected with low doses of malaria in the belief that it would cure them of cancer, Lyme disease, and AIDS, among much else. His claims for the treatment were not supported by any actual science. Partly because he had become an embarrassment, in 2006 the American Red Cross stopped using the term “Heimlich maneuver” and started calling it “abdominal thrusts.”
Responsibility for food safety is split among a raft of federal agencies in America in a way that rather defies logic. The Food and Drug Administration is responsible for the skin of sausages, but the Food Safety and Inspection Service is responsible for what goes inside them. Cheese pizzas are looked after by one agency, but meat pizzas by another. And so it goes through a whole range of foodstuffs. Altogether fifteen agencies have a regulatory role in some aspect or other of American food safety. No one agency has overall control.
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Urinary (Renal) System
Function: Eliminate wastes from the body, regulate blood volume and blood pressure, control levels of electrolytes and metabolites, and regulate blood pH.
Major Parts
Kidneys: Filter blood and help the body eliminate waste products and liquids.
Ureters: Narrow tubes that that carry urine from the kidneys to the bladder.
Bladder: The urinary bladder is rather like a balloon in that it is designed to swell as we fill it. (In an average-sized man it holds about a British pint, or about six-tenths of a quart; in a woman, rather less.
Urethra: Transport urine from the bladder.
Urine flow: Kidneys- Ureters- Bladder- Urethra.
Urinary Disorders:
Stones: One unfortunate feature the bladder has in common with both the gallbladder and the kidneys is a tendency to form stones—hardened balls of Ca and salts.
Interesting Facts
Historic Kidney Stone Surgery: While four men held Pepys down, the surgeon, Thomas Hollyer, inserted an instrument called an itinerarium up his penis and into the bladder to fix the stone in place. Then he took a scalpel and quickly and deftly—but excruciatingly—cut a three-inch-long incision through the perineum (the area between the scrotum and the anus). Peeling back the opening, he gently cut into the exposed and quivering bladder, thrust a pair of duck-billed forceps through the opening, captured the stone, and extracted it.
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Endocrine System
Function: Regulation of body processes through hormone production.
Major Parts
Liver: Weighs ~3.3 lbs when fully grown (roughly the same as the brain) and fills much of the central abdomen just below the diaphragm. Among its many jobs, it manufactures hormones, proteins, and the digestive juice known as bile. It filters toxins, disposes of obsolescent red blood cells, stores and absorbs vitamins, converts fats and proteins to carbohydrates, and manages glucose (specifically the liver converts glucose into glycogen—a more compact chemical). Perhaps the most wondrous feature of the liver is its capacity to regenerate. You can remove two-thirds of a liver and it will grow back to its original size in just a few weeks.
Spleen: roughly the size of your fist, weighs half a pound, and sits fairly high up on the left side of your chest. It does important work monitoring the condition of circulating blood cells and dispatching white blood cells to fight infections. It also acts as a reservoir for blood so that more can be supplied to muscles when suddenly needed, and it aids the immune system.
Gallbladder: stores bile from the liver and passes it on to the intestines. (“Gall” is an old word for “bile.”)
Gland: Any organ in the body that secretes chemicals.
Endocrine Gland: secretes products directly into the bloodstream.
Adrenal: Located on the top of each kidney, produce sex and cortisol hormones.
Hypothalamus: Located in the brain; the link between the endocrine and nervous systems. Produces and releases inhibiting hormones, which start and stop the production of hormones throughout the body.
Ovaries (in women): In women, testosterone is produced about half and half between the ovaries and the adrenal glands, but in much smaller amounts, and boosts libido, but mercifully leaves their common sense undisturbed.
Pancreas: A gland that is essential to life. The pancreas is a jellylike organ, about 6” long, shaped roughly like a banana (and about the same size), tucked behind the stomach in the upper abdomen. As well as insulin, it produces the hormone glucagon, which is also involved in regulating blood sugar, and the digestive enzymes trypsin, lipase, and amylase, which help digest cholesterol and fats. Altogether every day it produces over a quart of pancreatic juice, a pretty prodigious amount for an organ of its size.
Parathyroid: Controls the Ca levels in the blood stream.
Pineal: Located in the center of the brain and receives information about the state of the light-dark cycles to produce melatonin.
Pituitary: often called the master gland because it controls so much. It produces (or regulates the production of) growth hormone, cortisol, estrogen and testosterone, oxytocin, adrenaline, and much else. When you exercise vigorously, the pituitary squirts endorphins into your bloodstream. Endorphins are the same chemicals released when you eat or have sex. They are closely related to opiates.
Kidney: invariably called the workhorses of the body. Each day they process about 190 quarts of water—that is the amount a bath holds up to the overflow level—and 3.3 lbs of salt. They are startlingly small for the amount of work they do, weighing just 5 oz each. They are not in the small of the back, as everyone thinks, but higher up, about at the bottom of the rib cage. The right kidney is always lower because it is pressed down upon by the asymmetrical liver.
Filtering wastes is their principal function, but they also regulate blood chemistry, help maintain blood pressure, metabolize vitamin D, and maintain the vital balance between salt and water levels within the body. Eat too much salt and your kidneys filter out the excess from your blood and send it to the bladder so that you can pee it all away. Eat too little and the kidneys take it back from the urine before it leaves your body. The problem is that if you ask the kidneys to do too much filtering over too long a period, they get tired and stop functioning terribly well. As the kidneys become less efficient, the Na levels in your blood creep up, pushing your blood pressure dangerously high.
What the kidneys don’t return to the body via the bloodstream, they pass on to the second and more familiar of our bladders, the urinary one, for disposal. Each kidney is connected to the bladder by a tube called a ureter.
Testes (in men): In males, testosterone is produced mostly by the testes, with a little from the adrenal glands, and does three things: it makes a man fertile, it endows him with virile attributes like a deep voice and the need to shave, and it profoundly influences his behavior, giving him not only his sex drive but also a taste for risk and aggression.
Thymus: Located in the chest between the lungs, it makes White Blood Cells (WBCs).
Thyroid: A small butterfly shaped gland in the neck just in front of the trachea; produces hormones that help regulate the bodies metabolism.
Exocrine Glands: secretes products onto a surface (like sweat glands onto skin or salivary glands into the mouth).
Hormones: the bicycle couriers of the body, delivering chemical messages all around the teeming metropolis that is you. They are defined as any substance that is produced in one part of the body and causes an action somewhere else.
Cortisol: a stress hormone that regulates blood pressure.
Ghrelin: (the first three letters stand for “growth-hormone related”), is produced mostly in the stomach but also in several other organs. When we get hungry, our ghrelin levels rise, but it isn’t clear whether ghrelin causes hunger or merely accompanies it.
Glucagon: Regulates blood sugar.
Insulin: a small protein that is vital in maintaining a very delicate balance of blood sugar in the body. Too much or too little produces terrible consequences. We go through a lot of insulin. Each molecule only lasts from 5-15 minutes, so the demand for replenishment is relentless. Insulin, a hormone, cannot be given orally, because it is broken down in the gut before it can be absorbed and put to use, so it must be injected, which is both a tedious process and a crude one.
Leptin: aids in regulating appetite.
Melatonin: Regulates sleep and wake cycles.
Triiodothyronine: Produced in the thyroid and regulate the body’s metabolism.
Thyroxine: Produced in the thyroid and regulate the body’s metabolism.
Disorders
Type 1 diabetes: the body stops producing insulin. Tends to be inherited. Type 1 diabetes is associated with a fault in a person’s HLA (human leukocyte antigen) genes, only some people with the fault get diabetes.
Type 2 diabetes: insulin is less effective, usually because of a combination of decreased production and because the cells on which it acts don’t respond as they normally would. This is referred to as insulin resistance. Type 2 is usually a consequence of lifestyle. But it’s not quite as simple as that. Although type 2 is unequivocally associated with unhealthy living, it also tends to run in families, suggesting a genetic component.
Interesting Facts
Brown-Séquard ground up the testes of domesticated animals (dogs and pigs are most often cited, but no two sources seem to quite agree on which animals he favored), injected the extract into himself, and reported feeling as frisky as a forty-year-old. In fact, any improvement he sensed was entirely psychological. Mammalian testes contain almost no testosterone because it is sent out into the body as quickly as it is made, and in any case we manufacture very little of it.
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Cutaneous System (Skin & Sweating)
Function: provides warmth, cushioning, and camouflage, shields the body from ultraviolet light, and allows members of a group to signal to each other that they are angry or aroused.
Major Parts & Functions
Epidermis: Outer Layer of the Skin
Stratum Corneum: Outermost surface of the epidermis and comprised entirely of dead cells.
Squamae ("scales"): Skin Flakes
Dermis: Inner Layer of the Skin where all the skin's active systems are found- blood and lymph vessels, nerve fibers, the roots of hair follicles, the glandular reservoirs of sweat and sebum. Beneath that, and not technically part of the skin, is a subcutaneous layer where fat is stored. Though it may not be part of the cutaneous system, it’s an important part of your body because it stores energy, provides insulation, and attaches the skin to the body beneath.
Hair Follicles: they sprout hairs and secrete sebum (from sebaceous glands), which mixes with sweat to form an oily layer on the surface. This helps to keep skin supple and to make it inhospitable for many foreign organisms.
Sweating: We seep watery fluids onto nearly bare skin, which cools the body as it evaporates, turning us into a kind of living air conditioner.
Sweating is activated by the release of adrenaline; why when you are stressed, you break into a sweat.
Sweat on its own is actually odorless. It needs bacteria to create a smell. The two chemicals that account for the odor—isovaleric acid and methanediol—are also produced by bacterial actions on some cheeses, which is why feet and cheese can often smell so very alike.
Sweat glands come in two varieties:
Eccrine: Eccrine glands are numerous and produce the watery sweat that dampens your shirt on a sweltering day.
Apocrine: Apocrine glands are confined mostly to the groin and armpits (technically the axilla) and produce a thicker, stickier sweat. It is eccrine sweat in your feet—or more correctly the chemical breakdown by bacteria of the sweat in your feet—that accounts for their lush odor.
Unlike the rest of the body, the palms don’t sweat in response to physical exertion or heat, but only from stress. Emotional sweating is what is measured in lie detector tests.
We perspire to keep cool, but quadrupedal mammals lose heat by respiration—by panting. If they can’t stop to collect themselves, they overheat and become helpless.
Cutaneous System Interesting Facts
Your skin microbes are exceedingly personal. The microbes that live on you depend to a surprising degree on what soaps or laundry detergents you use, whether you favor cotton clothing or wool, whether you shower before work or after.
We do not have any receptors for wetness. We have only thermal sensors to guide us, which is why when you sit down on a wet spot, you can’t generally tell whether it really is wet or just cold.
If a breeze plays lightly on your cheek, it is your Meissner’s corpuscles that let you know. When you put your hand on a hot plate, your Ruffini corpuscles cry out. Merkel cells respond to constant pressure, Pacinian corpuscles to vibration.
Skin gets its color from a variety of pigments, of which the most important by far is a molecule formally called eumelanin but known universally as melanin. It is one of the oldest molecules in biology and is found throughout the living world. It doesn’t just color skin. It gives birds the color of their feathers, fish the texture and luminescence of their scales, squid the purply blackness of their ink. It is even involved in making fruits go brown. In us, it also colors our hair. Its production slows dramatically as we age, which is why older people’s hair tends to turn gray.
In regions like northern Europe and Canada, it isn’t possible in the winter months to extract enough vitamin D from weakened sunlight to maintain health no matter how pale one’s skin, so vitamin D must be consumed as food, and hardly anyone gets enough—and not surprisingly. To meet dietary requirements from food alone, you would have to eat fifteen eggs or six pounds of swiss cheese every day, or, more plausibly if not more palatably, swallow half a tablespoon of cod liver oil.
Pruritus: Itching
Blackhead: Occurs when the pores become blocked with little plugs of dead skin and dried sebum. If the follicle additionally becomes infected and inflamed, the result is the adolescent dread known as a pimple.
Erythema (aka Sun Burn): The red of sunburn is because the tiny blood vessels in the affected areas become engorged with blood, making the skin hot to the touch.
Horripilation: In all mammals, when they are cold, the muscles around their hair follicles contract causing the tell-tale “Goose Bumps.”
Fingerprints: The plow lines that make up our fingerprints are papillary ridges. They are assumed to aid in gripping, in the way tire treads improve traction on roads, but no one has ever actually proved that. Others have suggested that the whorls of fingerprints drain water better, make the skin of the fingers more stretchy and supple, or improve sensitivity, but again no one really knows what they are there for.
Dermatoglyphics: The study of fingerprints.
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Integumentary System (Hair)
Function: Hair is unique to mammals, providing warmth, cushioning, and camouflage, shields the body from UV light, and allows members of a group to signal to each other that they are angry or aroused.
Hair Types
Glabrous: hairless skin.
Conspicuous (or Terminal Hair): Hair on your head and body.
Vellus Hair: Downy hair you find on a child’s cheek.
Interesting Facts:
We are actually as hairy as our cousins the apes. It’s just that our hair is much wispier and fainter.
Altogether we are estimated to have five million hairs.
The only known cure for baldness is castration.
A hormone called dihydrotestosterone tends to go slightly haywire as we age, directing hair follicles on the head to shut down and more reserved ones in the nostrils and ears to spring to dismaying life.
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Optical System (Eyes & Vision)
Function: The eyes send a hundred billion signals to the brain every second. When you “see” something, only about 10% of the information comes from the optic nerve. Other parts of your brain have to deconstruct the signals—recognize faces, interpret movements, identify danger. In other words, the biggest part of seeing isn’t receiving visual images; it’s making sense of them.
Major Parts
Rods & Cones: Found at the rear of the eye and detect light; the blood vessels that keep them oxygenated are in front of them.
Rods: Help us see in dim conditions but provide no color.
Cones: work when the light is bright and divide the world up into three colors: blue, green, and red.
Lens & Cornea: Found in the front part of the eye; captures passing images and projects them onto the back wall of the eye.
Retina: Found at the back of the eye, where photoreceptors convert light images into electrical signals that are passed on to the brain via the optic nerve.
Cornea: Dome-shaped goggle not only protects the eye from worldly assaults but actually does two-thirds of the eyeball’s focusing. The lens, which gets all the credit in the popular mind, does only about a third of the focusing. It has five layers, laminated into a space just slightly over a half a mm thick; Epithelium, Bowman’s membrane, Stroma, Descemet’s membrane, Endothelium.
Fovea: the part of the eye that has the most photoreceptors—that really does the seeing (from a Latin word for “shallow pit”; the fovea inhabits a slight depression).
Tears: Lubricate the eyes; tears not only keep our eyelids gliding smoothly but also even out tiny imperfections on the eyeball surface, making focused vision possible. They also contain antimicrobial chemicals, which successfully keep most pathogens at bay. Tears come in three varieties:
Basal Tears: Functional ones that provide lubrication.
Reflex Tears: Tears that emerge when the eye is irritated by smoke or sliced onions or similar.
Emotional Tears: Self- evident. We are the only creatures that cry from feeling, as far as we can tell. Why we do so is another of life’s many mysteries. We get no physiological benefit from erupting in tears.
Iris: What gives the eye its color. It is composed of a pair of muscles that adjust the opening of the pupil, rather like the aperture on a camera, to let in or keep out light as needed. Superficially, the iris looks like a neat ring, encircling the pupil, but closer inspection shows that it is in fact “a riot of spots, wedges, and spokes,” in the words of Daniel McNeill, and these patterns are unique to each of us, which is why iris recognition devices are now increasingly used to identify us at security checkpoints.
Sclera (Greek for “hard”): the white of the eye. Our sclera’s are unique among primates. They allow us to monitor the gazes of others with considerable precision, as well as to communicate silently.
Optical Disorders
Color Blind: People who lack one of the three types of cones, so they don’t see all the colors, just some of them.
Achromatopes: People who have no cones at all, and are genuinely color-blind.
Floaters (aka Muscae Volitantes or “hovering flies”): clumps of microscopic fibers in the jellylike vitreous humor of your eye, which cast a shadow on the retina. Floaters are a common occurrence as you get older, and are generally harmless, though they can indicate a retinal tear.
Interesting Facts
For each visual input, it takes a tiny but perceptible amount of time—about two hundred milliseconds, one-fifth of a second—for the information to travel along the optic nerves and into the brain to be processed and interpreted. To help us deal better with this fractional lag, the brain does a truly extraordinary thing: it continuously forecasts what the world will be like a fifth of a second from now, and that is what it gives us as the present. That means that we never see the world as it is at this very instant, but rather as it will be a fraction of a moment in the future. We spend our whole lives, in other words, living in a world that doesn’t quite exist yet.
Look at your thumbnail at arm’s length; that’s about the area you have in full focus at any given instant. But because your eye is constantly darting—taking four snapshots every second—you have the impression of seeing a much broader area. The movements of the eye are called saccades (from a French word meaning “to pull violently”), and you have about a quarter of a million of them every day without ever being aware of it. (Nor do we notice it in others.)
All the nerve fibers leave the eye via a single channel at the back, resulting in a blind spot about fifteen degrees off center in our field of vision. The optic nerve is fairly hefty—it is about the thickness of a pencil—which is quite a lot of visual space to lose. You can experience this blind spot by means of a simple trick. First, close your left eye and stare straight ahead with the other. Now hold up one finger from your right hand as far from your face as you can. Slowly move the finger through your field of vision while steadfastly staring straight ahead. At some point, rather miraculously, the finger will disappear. Congratulations. You have found your blind spot.
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Olfactory System (Smell)
Function: When we sniff or inhale, odor molecules in the air drift into our nasal passages and come into contact with the olfactory epithelium- a patch of nerve cells containing some 350 to 400 types of odor receptors. If the right kind of molecule activates the right kind of receptor, it sends a signal to the brain, which interprets it as a smell.
Interesting Facts
Our sense of smell is the only one of the five basic senses not mediated by the hypothalamus. When we smell something, the information, for reasons unknown, goes straight to the olfactory cortex, which is nestled close to the hippocampus, where memories are shaped.
One of the early symptoms of Alzheimer’s is smell loss.
Disorders
Anosmia: Total smell loss, Hyposomia: Partial smell loss. Somewhere between 2-5% of people in the world suffer from one or the other, which is a very high proportion.
Cacosmia: where everything smells like feces.
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Auditory System (Ears & Hearing)
Major Parts
Ear (pinna from the Laton for “fin” or “feather”): the floppy shell on the side of our heads.
Ear Canal: Channel sound from the ear into the eardrum.
Tympanic Membrane (aka Eardrum): boundary between the outer ear and the middle ear. The tiny quivering’s of the eardrum are passed to the three smallest bones in the body, collectively known as ossicles.
Ossicles: the three bones of the middle ear; the malleus, incus, and stapes (hammer, anvil, and stirrup). The ossicles exist to amplify sounds and pass them on to the inner ear via the cochlea.
A pressure wave that moves the eardrum by less than the width of an atom will activate the ossicles and reach the brain as sound.
Cochlea (means snail): a snail shaped structure filled with 2700 delicate hairlike filaments called stereocilia which wave like ocean grasses as sound waves pass across them.
Flow of Sound: Sound- Ear- Ear Canal- Tympanic Membrane- Ossicles- Cochlea: the brain then puts all the signals together and works out what is has just heard.
Interesting Facts
We have a sense of balance, of acceleration and deceleration, of where we are in space (what is known as proprioception), of time passing, of appetite.
Acoustic Reflex: a muscle which jerks the stapes away from the cochlea, essentially breaking the sound circuit, whenever a very intense sound is perceived.
Eustachian tube: forms a kind of escape tunnel for air between the middle ear and the nasal cavity. Everyone knows that uncomfortable feeling you get in your ears when you change heights rapidly, as when coming in to land in an airplane. It is known as the Valsalva effect, and it arises because the air pressure inside your head fails to keep up with the changing air pressure outside it.
Disorders
The stereocilia tend to wear out as we age, and they do not regenerate. Once you disable a stereocilium, it remains lost to you forever. There isn’t any particular reason for this. Stereocilia grow back perfectly well in birds. They just don’t do it in us.
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Vestibular System (Balance)
Function:
The ear is responsible for keeping you balanced.
Major Parts:
Otolith Organs and Semicircular Ducts which act like the gyroscope in a plane. Inside the vestibular channels is a gel that acts a little like the bubbles in a carpenter’s level, in that the gel’s movements from side to side or up and down tell the brain in which direction we are traveling.
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Reproductive System (Sex & Birth)
Function: Sex may dilute our personal contribution to posterity, but it is great for the species. By mixing and matching genes, we get variety and that gives us safety and resilience. It makes it harder for diseases to sweep through whole populations. It also means that we can evolve. We can hold on to beneficial genes and discard ones that impede our collective happiness. Cloning gives you the same thing over and over. Sex gives you Einstein and Rembrandt—and a lot of dorks, too, of course.
Major Parts:
Vulva: vaginal opening, labia, clitoris.
Fetal Development:
3 weeks: Embryo (Greek and latin for “swollen”) has a beating heart.
8 weeks: Now called a fetus (latin for “fruitful”).
15 weeks: Eyes develop.
40 weeks: Birth (after 41 cycles of cell division).
Interesting Facts:
Sperm (Greek for “to sow”): first recorded in English in The Canterbury Tales.
One of the most extraordinary features of early life is that nursing mothers produce over two hundred kinds of complex sugars—the formal name is oligosaccharides—in their milk that their babies cannot digest because humans lack the necessary enzymes. The oligosaccharides are produced purely for the benefit of the baby’s gut microbes—as bribes, in effect. As well as nurturing symbiotic bacteria, breast milk is full of antibodies. There is some evidence that a nursing mother absorbs a little of her suckling baby’s saliva through her breast ducts and that this is analyzed by her immune system, which adjusts the amount and types of antibodies she supplies to the baby, according to its needs. Isn’t life marvelous? Although formulas have greatly improved over the years, no formula can fully replicate the immunological benefits of mother’s milk.
The average quantity of semen released at orgasm is 3 to 3.5 mL (about a teaspoonful), with an average spurt distance of 7-8”.
G spot: named for Ernst Gräfenberg, a German gynecologist and scientist who fled Nazi Germany for America and there developed the intrauterine contraceptive device (IUD), which was originally called the Gräfenberg ring.
A twenty-week-old fetus will weigh no more than 3-4 oz but will already have 6 million eggs inside her. That number falls to 1 million by the time of birth and continues to fall, though at a slower rate, through life. As she enters her childbearing years, a woman will have about 180,000 eggs primed and ready to go. Why she loses so many eggs along the way and yet enters her childbearing years with vastly more than she will ever need are two of life’s many imponderables.
The age of first menstruation for women has fallen from fifteen in the late nineteenth century to just twelve and a half today, at least in the West. Since 1980, the age of puberty has fallen in America by eighteen months. About 15% of girls now begin puberty by age seven.
Childbirth: The causes in America include higher rates of maternal obesity, greater use of fertility treatments (which produce more failed outcomes), and increased incidence of the rather mysterious disease known as preeclampsia.
Preeclampsia (formerly Toxemia): a condition in pregnancy that leads to high blood pressure in the mother, which can be a danger to both her and her baby.
Cephalopelvic disproportion: When a baby’s head is too big for smooth passage through the birth canal.
Puerperal fever: Into the 1930s, it was responsible for 4 out of every 10 maternal hospital deaths in Europe and America. As late as 1932, one mother in every 238 died in (or from) childbirth.
If ever there was an event that challenges the concept of intelligent design, it is the act of childbirth. We have made surprisingly little progress in making the process more bearable. As the journal Nature noted in 2016, “Women in labour have pretty much the same pain-relief options as their great grandmothers—namely gas and air, an injection of pethidine (an opioid) or an epidural anesthetic.” According to several studies, women are not terribly good at remembering the severity of the pain of childbirth; almost certainly this is a kind of mental defense mechanism to prepare them for further births.
Babies born by Cesarean section are robbed of an initial microbial wash (through the vagina). The consequences for the baby can be profound. Various studies have found that people born by C-section have substantially increased risks for type 1 diabetes, asthma, celiac disease, and even obesity and an eightfold greater risk of developing allergies. Cesarean babies eventually acquire the same mix of microbes as those born vaginally—by a year their microbiota are usually indistinguishable—but there is something about those initial exposures that makes a long-term difference.
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Immune System
Function: all parts of the immune system contribute to a single task, to identify anything that is in the body that shouldn’t be there and, if necessary, kill it.
Earwax, skin, and tears. Any invader that gets past these outer defenses—and comparatively few do—will quickly run into swarms of “proper” immune cells, which come pouring out of lymph nodes, bone marrow, the spleen, the thymus, and other corners of the body.
Major Parts
White Blood Cells (leucosytes)
Lymphocytes:
B-Cells: The B in B cells comes, a little oddly, from “bursa of Fabricius,” an appendix-like organ in birds where B cells were first seen. Humans and other mammals don’t have a bursa of Fabricius. Our B cells are made, coincidentally, in the bone marrow.
Antibodies: Proteins produced by B-Cells to attack invading organisms.
T-Cells: T cells are more faithful to their source. Though created in the bone marrow, they emerge from the thymus, a small organ in the chest just above the heart and between the lungs. T cells are a kind of elite corps in the immune system, and the dead cells found in the thymus were lymphocytes that had failed to pass muster because they were either not very good at identifying and attacking foreign invaders or because they were too eager to attack the body’s own healthy cells.
Helper T- cell: Helper T cells help other immune cells act, including helping B cells produce antibodies.
Memory T-cells: remember the details of earlier invaders and are therefore able to coordinate a swift response if the same pathogen shows up again—what is known as adaptive immunity. Memory T-cells are extraordinarily vigilant. I don’t get mumps, because somewhere inside me are memory T-cells that have been protecting me from a second attack for more than sixty years. When they identify an invader, they instruct B cells to produce proteins known as antibodies, and these attack the invading organisms
Killer T-Cell: Killer T cells kill cells that have been invaded by pathogens
NK Cells: Kill abberant cells, such as virally infected cells.
Messenger Cells
Cytokines: A loose category of small proteins important in cell signaling including stimulation of the immune system to fight off a foreign pathogen or attack tumors.
Chemokines: Specific cytokines that function by attracting cells to the site of an infection.
Histamine: A signaling molecule, sending messages between cells helping your body to get rid of something that’s bothering you such as an allergen, which signals your body to sneeze, cough, tear up, or itch.
Phagocytes: WBC’s that protect the body by ingesting harmful foreign particles, bacteria, and dead or dying cells.
Macrophages: specialized cells involved in the detection, phagocytosis (engulfment), and destruction of bacteria and other harmful organisms. They also present antigens to T-Cells and initate inflammation by releasing cytokines.
Monocytes: Bone marrow derived leukocytes that circulate in the blood and spleen; ability to recognize danger signals via pattern recognition receptors. Present injuries, secrete chemokines, proliferate in response to infection and injury.
Granulocytes: WBCs with small protein containing granules that help the immune system fight off infection, particularly bacterial infections.
Neutrophils: Among the first cells to travel to the site of an infection and attack and ingest antigens, killing them by releasing special enzymes.
Eosinophils: Help fight infection and play a role in the body’s immune response.
Basophils: Aid in Fighting infection and blood clotting.
Interferons: proteins that are made and released in response to antigens.
Prostaglandins: A group of lipids made at the site of tissue damage or infection that control processes such as inflammation, blood flow, formation of blood clots.
Antigens: Bacteria, Viruses, Fungi, Poisons, Parasites, Cancer Cells.
Interesting Facts
Vaccination: inducing the body to produce useful antibodies against a particular scourge without actually making oneself sick.
Inflammation: Blood vessels in the vicinity of an injury dilate, allowing more blood to flow to the site, bringing with it white blood cells to fight off invaders. That causes the site to swell, increasing the pressure on surrounding nerves, resulting in tenderness.
Unlike red blood cells, white blood cells can leave the circulatory system to pass through surrounding tissues, like an army patrol searching through jungle. When they encounter an invader, they fire off attack chemicals called cytokines, which is what makes you feel feverish and ill when your body is battling infection. It’s not the infection that makes you feel dreadful, but your body defending itself. The pus that seeps from a wound is simply dead white cells that have given their lives in defense of you.
Pathogens provoke a vehement response; they will in all likelihood be trapped in the mucus that lines your nasal passages or caught by the bronchi, or tubules, in your lungs. These tiny airways are lined with millions and millions of hairlike cilia that act like paddles (but beating furiously at 16x a second), and they swat the invaders back into the throat, where they are diverted to the stomach and dissolved by hydrochloric acid. If any invaders manage to get past these waving hordes, they will encounter little devouring machines called alveolar macrophages, which gobble them up.
An increase of only a degree or so in body temperature has been shown to slow the replication rate of viruses by a factor of 200.
An allergy is simply an inappropriate response by the body to a normally harmless invader.
American chemist Linus Pauling, who had the distinction of winning not one but two Nobel Prizes (for chemistry in 1954 and for peace in 1962). Pauling believed that massive doses of vitamin C were effective against colds, flu, and even some cancers. He took up to 40,000 mg of vitamin C daily (the recommended daily dose is 60 mg) and maintained that his large intake of vitamin C had kept his prostate cancer at bay for 20 years. He had no evidence for any of his claims, and all have been pretty well discredited by subsequent studies. Thanks to Pauling, to this day many people believe that taking a lot of vitamin C will help to get rid of a cold. It won’t.
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Pathogens
Antigens: Harmful cells that attack the body including Bacteria, Viruses, Fungi, Poisons, Parasites, Cancer Cells. Of the million or so microbes that have been identified, just 1,415 are known to cause disease in humans—very few, all things considered.
An infectious disease is one caused by a microbe; a contagious disease is one transmitted by contact.
Bacteria:
Horizontal Gene Transfers: Bacteria can swap genes among themselves, as if they were Pokémon cards, and they can pick up DNA from dead neighbors which massively accelerates their capacity to adapt to whatever nature and science throw at them. The DNA of bacteria is less scrupulous in its proofreading, too, so they mutate more often, giving them even greater genetic nimbleness.
Quorum: Bacteria only mount an attack when they have assembled sufficient numbers.
Studies on Microbe Transfer:
Passionate kissing alone, according to one study, results in the transfer of up to one billion bacteria from one mouth to another, along with about 0.7 mg of protein, 0.45 mg of salt, 0.7 micrograms of fat, and 0.2 micrograms of “miscellaneous organic compounds” (that is, bits of food).
In one study, a volunteer was fitted with a device that leaked a thin fluid at his nostrils at the same rate that a runny nose would. The volunteer then socialized with other volunteers, as if at a cocktail party. Unknown to any of them, the fluid contained a dye visible only under ultraviolet light. When that was switched on after they had been mingling for a while, the participants were astounded to discover that the dye was everywhere—on the hands, head, and upper body of every participant and on glasses, doorknobs, sofa cushions, bowls of nuts, you name it.
In a study called “Bacterial Transfer Associated with Blowing Out Candles on a Birthday Cake,” Dawson’s team found that candle blowing across a cake increased the coverage of bacteria on it by up to 1,400%, which sounds pretty horrifying but is in fact probably not much worse than the kinds of exposures we encounter in normal life anyway.
The largest source of foodborne illness is not meat or eggs or mayonnaise, as commonly supposed, but green leafy vegetables. They account for one in five of all food illnesses.
Transmission: Whether or not a disease becomes epidemic is dependent on four factors: how lethal it is, how good it is at finding new victims, how easy or difficult it is to contain, and how susceptible it is to vaccines.
Asymptomatic carrier: infectious but without symptoms.
Zoonotic: living in proximity to domesticated animals meant that their diseases became our diseases. Leprosy, plague, TB, typhus, diphtheria, measles, influenzas- all vaulted from goats and pigs and cows and the like straight into us. By one estimate, about 60% of all infectious diseases come from animals (are zoonotic).
Major Pathogens:
Diphtheria: Before a vaccine was introduced in the 1920s, diphtheria struck down more than 200,000 people a year in America, killing 15,000 of them. Children were especially susceptible. It usually started with a mild temperature and a sore throat, so at first was easily mistaken for a cold, but it soon became much more serious as dead cells accumulated in the throat, forming a leathery coating (the term “diphtheria” comes from the Greek for “leather”; the disease, incidentally, is correctly pronounced “diff-theria,” not “dip-theria”) that made breathing increasingly difficult, and the disease spread through the body, shutting down organs one by one.
Typhoid and typhus: have similar names and symptoms but are different diseases. Both are bacterial in origin and marked by sharp abdominal pain, listlessness, and a tendency to grow confused. Typhus is caused by a rickettsia bacillus; typhoid is caused by a type of salmonella bacillus and is the more serious of the two. A small proportion of people infected with typhoid, between 2-5%, are infectious but have no symptoms of illness, making them highly effective vectors. The most famous such carrier was a shadowy cook and housekeeper named Mary Mallon who became notorious in the early years of the twentieth century as Typhoid Mary.
Tuberculosis (TB): TB is the deadliest infectious disease on the planet killing ~1.5-2 million annually.
German parasitologist Theodor Bilharz (1825–62), who is often called the father of tropical medicine. His entire career was devoted, at constant risk to himself, to trying to understand and conquer some of the world’s worst infectious diseases. Schistosomiasis—also known as bilharzia is named in his honor.
Influenza: All flus have names like H5N1 or H3N2. That is because every flu virus has two types of proteins on its surface—hemagglutinin and neuraminidase—and these account for the H and N in their names. H5N1 means that the virus combines the fifth known iteration of hemagglutinin with the first known iteration of neuraminidase, and for some reason that is a particularly nasty combination.
H5N1: commonly known as bird flu, kills between 50-90% of victims.
Methicillin-resistant Staphylococcus aureus (MRSA)
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Microbiome
Microbiome: You are home to trillions and trillions of tiny living things, and they do you a surprising amount of good. They provide you with about 10% of your calories by breaking down foods that you couldn’t otherwise make use of, and in the process extract beneficial nutriments like vitamins B2 and B12 and folic acid.
You are likely to have something like 40,000 species of microbes calling you home—900 in your nostrils, 800 more on your inside cheeks, 1,300 on your gums, as many as 36,000 in your GI tract, though such numbers must constantly be adjusted as new discoveries are made.
For years, it was commonly stated that we each contain ten times as many bacterial cells as human ones. It turns out that that confident-sounding figure came from a paper written in 1972 that was little more than a guess. In 2016, researchers from Israel and Canada did a more careful assessment and concluded that each of us contains about thirty trillion human cells and between thirty and fifty trillion bacterial cells (depending on a lot of factors like health and diet), so the numbers are much closer to being equal—though it should also be noted that 85% of our own cells are red blood cells, which aren’t true cells at all, because they don’t have any of the usual machinery of cells (like nuclei and mitochondria), but are really just containers for hemoglobin.
Looked at genetically, you have about twenty thousand genes of your own within you, but perhaps as many as twenty million bacterial genes, so from that perspective you are roughly 99% bacterial and not quite 1% you.
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Antibiotics
In the US, 80% of antibiotics are fed to farm animals, mostly to fatten them. Fruit growers can also use antibiotics to combat bacterial infections in their crops. In consequence, most Americans consume secondhand antibiotics in their food (including even some foods labeled as organic) without knowing it.
Antibiotics are about as nuanced as a hand grenade. They wipe out good microbes as well as bad.
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Sleep
Function
Sleep has been tied to a great many biological processes—consolidating memories, restoring hormonal balance, emptying the brain of accumulated neurotoxins, resetting the immune system.
Falling asleep: First comes the business of relinquishing consciousness, which for most of us takes between five and fifteen minutes to achieve fully. This is followed by a period in which we slumber lightly but restoratively, as in a nap, for about 20 minutes. Sleep is so shallow in these first two stages that you may be asleep but think you are awake. Then comes a deeper sleep, lasting about an hour, from which it is much harder to rouse a sleeper. (Some authorities divide this period into two stages, giving the sleep cycle five distinct periods rather than four.) Finally comes the rapid eye movement (or REM) phase, when we do most of our dreaming. As the night passes, the periods of REM sleep tend to lengthen.
Interesting Facts
Real hibernation involves profound unconsciousness and a dramatic fall in body temperature—often to around zero Celsius. By this definition, bears don’t actually hibernate.
The amount of sleep needed varies markedly among animals. Elephants and horses get by on just two or three hours a night. Why they need so little is unknown.
Extraordinarily, some birds and marine mammals are able to switch off one half of their brain at a time, so that one half remains alert while the other is snoozing.
Newborn babies spend at least 50% of their sleep time (which is most of their time anyway) in the REM phase. For fetuses it may be as much as 80%.
Circadian Cycles
Photosensitive Retinal Ganglion Cells: Receptors that detect daytime and night and pass this information on to two tiny bundles of neurons within the brain, roughly the size of a pinhead, embedded in the hypothalamus and known as suprachiasmatic nuclei. These two bundles (one in each hemisphere) control our circadian rhythms. They are the body’s alarm clocks. They tell us when to rise and shine and when to call it a day.
Pineal: produces the hormone melatonin that helps the brain track day length.
Melatonin levels within us rise as evening falls and peak in the middle of the night, so it would seem logical to associate them with drowsiness, but in fact melatonin production also rises at night in nocturnal animals when they are most active, so it is not promoting sleepiness.
The pressure to sleep grows more intense the longer we stay awake. This is in large part a consequence of an accumulation of chemicals in the brain as the day goes by, in particular one called adenosine, which is a by-product of the output of ATP (or adenosine triphosphate), the little molecule of intense energy that powers our cells. The more adenosine you accumulate, the drowsier you feel. Caffeine slightly counteracts its effects, which is why a cup of coffee perks you up. Normally, the two systems operate in synchronicity, but occasionally they deviate, as when we cross several time zones on a long-distance plane flight and we experience jet lag.
The circadian cycles of teenagers can be up to two hours adrift from those of their elders, turning them into comparative night owls.
Sleep Issue
Narcolepsy: commonly associated with extreme drowsiness at inappropriate times, but many with the condition have as much trouble staying asleep as staying awake. The condition affects four million people around the world. It is caused by a lack of a chemical in the brain called hypocretin, which exists in such tiny amounts that it was only discovered in 1998.
Parasomnias: Common sleep disorders that include sleepwalking, confusional arousal (when the victim appears to be awake but is profoundly muddled), nightmares, and night terrors.
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Oncology
Cancer: Abnormal cell division without limit. Cancer cells grow without direction or influence from outside agents like hormones. They engage in angiogenesis, which is to say they trick the body into giving them a blood supply. They disregard any signals to stop growing. They fail to succumb to apoptosis, or programmed cell death. Because cancer cells are so seemingly normal, the body sometimes fails to detect them and doesn’t invoke an inflammatory response as it would with a foreign agent.
Metastasize: Spread of cancer cells to other parts of the body.
Cancer is the price we pay for evolution. If our cells couldn’t mutate, we would never get cancer, but we also couldn’t evolve.
Carcinomas: Comprise 80% of cancers, arise in epithelial cells, the cells that make up skin and organ lining.
Cancer Treatments: Main types- Surgery, Radiation, Chemotherapy, CAR-T.
Chimeric Antigen Receptor T-Cell Therapy (CAR T-cell therapy): involves genetically altering a cancer sufferer’s T cells, then returning them to the body in a form that allows them to attack and kill cancer cells.
Interesting Facts
50% of men over 60 and 75% over 70 have prostate cancer at death without being aware of it.
Although no one can say to what extent pollutants in air and water contribute to cancers, it has been estimated that it may be as much as 20%.
Viruses and bacteria cause cancers, too. The WHO in 2011 estimated that 6% of cancers in the developed world and 22% in low- and middle-income countries are attributable to viruses alone. Altogether, it has been estimated, pathogens may account for a quarter of all cancers globally.
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Aging & Death
Cause of Aging: Although exact causes are unknown, theories fall into three broad categories:
Genetic mutation theory: your genes malfunction and kill you.
Wear-and-tear theory: the body just wears out.
Waste accumulation theory: your cells clog up with toxic by-products.
Physiology of Aging
The bladder becomes less elastic and cannot hold as much, which is why one of the curses of aging is being forever on the lookout for a restroom.
Skin loses elasticity and becomes drier and more leathery.
Blood vessels break more readily and create bruises.
The immune system fails to detect intruders as reliably as it once did.
The number of pigment cells usually decreases, but those that remain sometimes enlarge, producing age spots, or liver spots, which of course have nothing to do with the liver.
The layer of fat directly associated with skin also thins, making it harder for elderly people to stay warm.
The amount of blood pushed out with each heartbeat falls gradually as we age. If nothing else gets you first, your heart will eventually give out. That is a certainty. And because the amount of blood being moved around by the heart falls, your organs get less blood, too. After the age of 40, the volume of blood going to the kidneys decreases by an average of 1% a year.
Physiology of Death
Death becomes apparent very quickly. Almost at once the blood begins to drain from the capillaries near the surface, leading to the ghostly pallor associated with death.
Tissue deterioration starts almost at once, which is why “harvesting” (surely the ugliest term in medicine) organs for transplant is such an urgent business.
Livor Mortis: Pooling of Blood in the lowest parts of the body, as gravity demands, turning the skin there purple in a process known as livor mortis.
Autolysis: Rupturing of Internal cells with enzymes spilling out and beginning a self-digesting process.
The Liver will continue to break down alcohol after death, even though it has absolutely no need to do so.
Cells die at different rates; Brain cells go quickly, in no more than about three or four minutes, but muscle and skin cells may last for hours—perhaps a whole day.
Rigor Mortis: muscle stiffening that sets in between 30 minutes and 4 hours after death, starting in the facial muscles and moving downward through the body and outward to the extremities, lasts for a day or so.
Issues:
Obesity: The current generation of young people is forecast to be the first in recorded history not to live as long as their parents because of weight-related health issues.
According to one study, being a committed couch potato (defined as someone who sits for six hours or more per day) increases the mortality risk for men by nearly 20% and for women by almost double that.
Interesting Facts:
Across the planet as a whole, life expectancy grew from 48.1 years for men in 1950 (which is as far back as global records reliably go) to 70.5 today; for women the rise was from 52.9 to 75.6 years. In 1950, 216 children in every thousand—nearly a quarter—died before the age of five. Today the figure is just 38.9.
At some point between 1900 and 1912, a random patient with a random disease, consulting a doctor chosen at random, had for the first time in history a better than 50-50 chance of profiting from the encounter.
America spends more on health care than any other nation—two and a half times more per person than the average for all the other developed nations of the world. One-fifth of all the money Americans earn—$10,209 a year for every citizen, $3.2 trillion. In consequence of all these factors, the United States records a really quite spectacular 11 traffic deaths per 100,000 people every year, compared with 3.1 in the United Kingdom, 3.4 in Sweden, and 4.3 in Japan.
About one-fifth of all deaths are sudden, as with a heart attack or car crash, and another fifth come quickly, following a short illness. But the great majority, about 60%, are the result of a protracted decline.
The average person born before 1945 could expect to enjoy only about 8 years of retirement before being permanently eliminated from the living, but someone born in 1971 can expect more like 20 years of retirement, and someone born in 1998 can, on current trends, expect perhaps 35 years—but all funded in each case by roughly 40 years of labor.
In every period in history, in every society examined, women have always lived several years longer on average than men. And they still do now, even though men and women are subjected to more or less identical health care.
According to the U.S. Institute of Medicine, part of the National Academy of Sciences, about 40% of adult Americans—100 million people—are experiencing chronic pain at any given moment. One-fifth of them will suffer it for more than 20 years. Altogether chronic pain affects more people than cancer, heart disease, and diabetes combined.
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Men and Women
Chromosomes: Females- XX, Males- XY.
For a man, the average journey time from mouth to anus is 55 hours. For a woman, typically, it is more like 72.
Women
Women are anatomically different in one other very significant way: they are the sacred keepers of human mitochondria—the vital little powerhouses of our cells. Sperm pass on none of their mitochondria during conception, so all mitochondrial information is transferred from generation to generation through mothers alone.
Women are twice as likely as men to get multiple sclerosis, 10x more likely to get lupus, 50x more likely to suffer a thyroid condition known as Hashimoto’s thyroiditis. Altogether, 80% of all autoimmune diseases occur in women.
Women (and we are talking here about healthy, fit women) carry about 50% more fat on their frames than fit, healthy men. This not only makes the woman more agreeably soft and shapely to suitors but also gives her reserves of fat she can call upon for milk production during times of hardship. Women’s bones wear out sooner, particularly after menopause, so they suffer more breaks in later life. Women get Alzheimer’s twice as often (partly because they also live longer) and experience higher rates of autoimmune diseases. They metabolize alcohol differently, which means they get intoxicated more easily and succumb to alcohol-related diseases like cirrhosis faster than men do.
Women and men have heart attacks in quite different ways. A woman suffering a heart attack is more likely to experience abdominal pain and nausea than a man, which makes it more probable that it will be misdiagnosed.
Men
Men get Parkinson’s disease more often and commit suicide more, even though they suffer less from clinical depression. They are more vulnerable to infection than females (and not just humans but across nearly all species). That may indicate some hormonal or chromosomal difference that hasn’t yet been determined, or it may simply be that males on the whole lead riskier, more infection-prone lives. Men are also more likely to die from their infections and from physical injury, though again whether that is because we are hormonally compromised or just too proud and foolish to seek medical attention promptly (or both) is an unanswerable question.
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Chronology
1999: EU bans the agricultural use of antibiotics.-The Body by Bryson.
Late 1990s: Pharmaceutical companies began pushing Opioids as a long-term solution to pain. A promotional video made by Purdue Pharma, the maker of the opioid OxyContin, featured a physician who specializes in pain treatment looking straight into the camera and claiming with evident sincerity that opioids were perfectly safe and hardly ever addictive. “We doctors were wrong in thinking that opioids can’t be used long term. They can be and they should be,” he added.-The Body by Bryson.
1999- 2014: by one estimate, a quarter of a million Americans died from opioid overdoses. Opioid abuse remains for the most part a peculiarly American problem. The United States has 4% of the world’s population but consumes 80% of its opioids. About two million Americans are thought to be opioid addicts. Another ten million or so are users. The cost to the economy has been put at over $500 billion a year in lost earnings, medical treatments, and criminal proceedings.-The Body by Bryson.
1995: Discovery of Leptin; the field of endocrinology experienced a seismic moment when Jeffrey Friedman, a geneticist at Rockefeller University in New York, found a hormone that no one thought could possibly exist. He named it leptin (from a Greek word for “thin”). Leptin was produced not in an endocrine gland but in fat cells. Leptin drew massive and immediate interest not just because of the surprise of where it was produced but even more because of what it does: it helps to regulate appetite.-The Body by Bryson.
1990: Two teams in London, at the National Institute for Medical Research and at the Imperial Cancer Research Fund, identified a sex-determining region on the Y chromosome that they dubbed the SRY gene, for “sex-determining region Y.”-The Body by Bryson.
1986: Sweden bans the agricultural use of antibiotics.-The Body by Bryson.
8 May, 1980: The WHO announced that smallpox had been eradicated from Earth.-The Body by Bryson.
1972: Prions were discovered by Dr. Stanley Prusiner of the University of California at San Francisco. While still training as a neurologist, he examined a 60-year-old woman who was suffering from a sudden onset dementia so severe that she couldn’t manage even the simplest and most familiar tasks, like how to put a key in a door. Prusiner became convinced that the cause was a misshapen infectious protein which he called a prion.-The Body by Bryson.
1969: Invention of Cyclosporine; the Sandoz company converted Herr Frey’s little bag of dirt, and a similar sample subsequently found in Wisconsin, into a best-selling medicine called cyclosporine.-The Body by Bryson.
1968: New England Journal of Medicine published a letter—not an article or a study, but simply a letter—from a doctor noting that he sometimes felt vaguely unwell after eating in Chinese restaurants and wondered if it was the MSG added to the food that was responsible. The headline on the letter was “Chinese-Restaurant Syndrome,” and from this small beginning it became fixed in many people’s minds that MSG was a kind of toxin. In fact, it isn’t. It appears naturally in lots of foods, like tomatoes, and has never been found to have deleterious effects on anybody when eaten in normal quantities.-The Body by Bryson.
1968: Development of combined Chemotherapy and Radiation Therapy; Donald Pinkel of St. Jude Children’s Research Hospital in Memphis, Tennessee, was convinced that giving drugs in moderate dosages, which was then the standard practice, allowed some leukemic cells to escape and to bounce back after treatment stopped. That’s why remissions were always temporary. Pinkel blasted the leukemic cells with the full range of available drugs, frequently in combinations, always at the highest possible dosages, accompanied by bouts of radiation, with some successful results.-The Body by Bryson.
1967: At exactly the time that René Favaloro was perfecting bypass surgery in Cleveland, Christiaan Barnard, a surgeon in Cape Town, attracted far more of the world’s attention by transplanting the heart of a young woman fatally injured in a car accident into the chest of a 54 yr old man named Louis Washkansky.-The Body by Bryson.
1964: The U.S. surgeon general announced an unequivocal link between smoking and lung cancer, but the announcement had little effect. The number of cigarettes smoked by the average American over the age of 16 fell slightly from 4,340 a year before the announcement to 4,200 afterward, but then climbed back to about 4,500 and stayed there for years. Remarkably, the American Medical Association took fifteen years to endorse the surgeon general’s finding.-The Body by Bryson.
Jan, 1964: The first heart transplant of any type involving a human occurs when Dr. James D. Hardy in Jackson, Mississippi, transplanted a chimpanzee’s heart into a man named Boyd Rush. The patient died within an hour.-The Body by Bryson.
1961: Leonard Hayflick, then a young researcher at the Wistar Institute in Philadelphia, made a discovery that nearly everyone in his field found impossible to accept. He discovered that cultured human stem cells—that is, cells grown in a lab, as opposed to in a living body—can divide only about 50x before they mysteriously lose their power to go on. Hayflick also found that the cells he cultured could be frozen and kept in storage for any length of time and when thawed would resume their decline from precisely where they had left off. For about a decade, Hayflick’s findings languished. But then a team of researchers at the University of California at San Francisco discovered that stretches of specialized DNA at the end of each chromosome called telomeres fulfill the role of tallying device. With each cell division, telomeres shorten until eventually they reach a predetermined length (which varies markedly from one cell type to another) and the cell dies or becomes inactive. Free radicals are wisps of cellular waste that build up in the body in the process of metabolism. They are a by-product of our breathing oxygen. As one toxicologist has put it, “The biochemical price of breathing is aging.” Antioxidants are molecules that neutralize free radicals, so the thinking is that if you take a lot of them in the form of supplements, you can counter the effects of aging. Unfortunately, there is no scientific evidence to support that.-The Body by Bryson.
1958: Swedish engineer named Rune Elmqvist, working in collaboration with the surgeon Åke Senning of the Karolinska Institute in Stockholm, built a pair of experimental cardiac pacemakers at his kitchen table. The first was inserted into the chest of Arne Larsson, a forty-three-year-old patient (and himself an engineer) who was very near death from a heart arrhythmia as a result of a viral infection. The device failed after just a few hours. The backup was inserted and it lasted for three years, though it kept breaking down and the batteries had to be recharged every few hours. As technology improved, Larsson was routinely fitted with new pacemakers and lived another forty-three years. When he died in 2002 at the age of eighty-six, he was on his twenty-sixth pacemaker and had outlived both his surgeon Senning and his fellow engineer Elmqvist. The first pacemaker was about the size of a pack of cigarettes. Today’s are no bigger than one American quarter and can last up to 10 years.-The Body by Bryson.
1957: It took a surprisingly long time to realize that a lot of the things we eat can make you seriously unhealthy. The person most responsible for our enlightenment was a nutritionist from the University of Minnesota named Ancel Keys. Keys embarked on the study that would permanently seal his fame. The Seven Countries Study compared the dietary habits and health outcomes of 12,000 men in seven nations: Italy, Greece, the Netherlands, Yugoslavia, Finland, Japan, and the United States. Keys found a direct correlation between levels of dietary fat and heart disease—a conclusion that is hardly surprising now but was revolutionary then. In 1957, with his wife, Margaret, Keys produced a popular book called Eat Well and Stay Well, which promoted what we now know as the Mediterranean diet.-The Body by Bryson.
1953: Eugene Aserinsky discovers REM sleep while a grad student at the U. of Chicago; 90 minutes after his subject young Armond had settled down into what was normally a peaceful night’s sleep, Aserinsky was surprised to see the monitor’s unspooling graph paper jerk to life and begin the kinds of jagged tracings associated with an active, wakeful mind.-The Body by Bryson.
1952: The concept of the limbic system is invented by American neuroscientist, Paul D. MacLean; the Limbic system plays a fundamental role in our happiness by controlling and regulating basic processes like memory, appetite, emotions, drowsiness and altertness, and the processing of sensory information.-The Body by Bryson.
Sep, 1952: Lillehei introduced a refinement (to heart surgery) known as controlled cross-circulation in which the patient was hooked up to a temporary donor (usually a close family member) whose blood was circulated through the patient during the period of surgery. The technique worked so well that Lillehei became widely known as the father of open-heart surgery and enjoyed a great deal of acclaim and financial success.-The Body by Bryson.
1950: Evarts Ambrose Graham, a chest surgeon and professor at Washington University in St. Louis. Graham famously (but facetiously) maintained that we might as plausibly blame lung cancer on the development of nylon stockings because they had become popular at the same time as smoking. But when a student of his, the German-born Ernst Wynder, sought permission to conduct a study on smoking and cancer in the late 1940s, Graham gave his consent, mostly in the expectation that it would disprove the theory of a link between smoking and cancer once and for all. In fact, Wynder demonstrated conclusively that there was a link—so much so that Graham was persuaded by the evidence to change his mind. In 1950, the two men published a joint paper in The Journal of the American Medical Association outlining a clear statistical link between smoking and lung cancer. Soon afterward, the British Medical Journal ran a study with more or less identical findings by Richard Doll and A. Bradford Hill of the London School of Hygiene and Tropical Medicine. Although two of the world’s most prestigious medical journals had now demonstrated a clear association between smoking and lung cancer, the findings had almost no effect. People just loved smoking too much to quit. The average American adult was smoking four thousand cigarettes a year. Interestingly, quite a lot of valuable cancer research in the 1950s was done by scientists funded by the cigarette industry who were urgently searching for causes of cancer other than cigarettes.-The Body by Bryson.
1948-1958: Framinghams Cardiovascular Risk study identifies most of the major risks for heart disease; diabetes, smoking, obesity, poor diet, chronic indolence, and so on. In fact, the term “risk factor” is said to have been coined in Framingham.-The Body by Bryson.
1945: A research chemist in California named Denham Harman read an article about aging in his wife’s Ladies’ Home Journal and developed a theory that free radicals and antioxidants are at the heart of human aging.-The Body by Bryson.
24 Mar, 1944: After his plane was shot down, by the time Alkemade managed to haul himself out of his turret and reach for his parachute, he found it was on fire and beyond salvation. He decided to leap from the plane anyway rather than perish horribly in flames, so he hauled open a hatch and tumbled out into the night. He was three miles above the ground and falling at 120 miles per hour. “It was very quiet,” Alkemade recalled years later, “the only sound being the drumming of aircraft engines in the distance, and no sensation of falling at all. I felt suspended in space.” Rather to his surprise, he found himself to be strangely composed and at peace. He was sorry to die, of course, but accepted it philosophically, as something that happened to airmen sometimes. The experience was so surreal and dreamy that Alkemade was never certain afterward whether he lost consciousness, but he was certainly jerked back to reality when he crashed through the branches of some lofty pine trees and landed with a resounding thud in a snowbank, in a sitting position. He had somehow lost both his boots, and had a sore knee and some minor abrasions, but otherwise was quite unharmed.-The Body by Bryson.
1943: still a student, Schatz followed a hunch that soil microbes might provide an additional antibiotic to put alongside the new drug penicillin, which, for all its value, didn’t work against bacteria of a type known as Gram-negative. This included the microbe responsible for TB. Schatz patiently tested hundreds of samples and in just under a year came up with streptomycin, the first drug to vanquish Gram-negative bacteria. It was one of the most important microbiological breakthroughs of the twentieth century.-The Body by Bryson.
1943: Development of Chemotherapy; A US Navy Supply ship, the SS John Harvey, carrying mustard gas bombs as part of its cargo, was caught in a German bombing raid on the Italian port of Bari. The Harvey was blown up, releasing a cloud of mustard gas over a wide area, killing an unknown number of people. Realizing that this was an excellent, if accidental, test of the mustard gas’s efficacy as a killing agent, the navy dispatched a chemical expert, Lieutenant Colonel Stewart Francis Alexander, to study the effects of the mustard gas on the ship’s crew and others nearby. Luckily for posterity, Alexander was an astute and diligent investigator, for he noticed something that might have been overlooked: mustard gas dramatically slowed the creation of WBC’s in those exposed to it. From this, it was realized that some derivative of mustard gas might be useful in treating some cancers.-The Body by Bryson.
1937: Development of Radiation Therapy; the mother of John and Ernest Lawrence was diagnosed with Uterine Cancer. As head of the new Radiation Lab at UCLA, Ernest Lawrence had just invented the cyclotron, a particle accelerator that generated massive amounts of radioactivity as a side effect of energizing protons. They had in effect the most powerful X-ray machine in the country at their disposal, capable of generating a million volts of energy. Without any certainty what the consequences would be—no one had ever tried anything remotely like this on humans before—the brothers aimed a deuteron beam directly into their mother’s belly. It was an agonizing experience, so painful and distressing to poor Mrs. Lawrence that she begged her sons to let her die. “At times I felt very cruel in not giving in,” John recorded later. Happily, after a few treatments, Mrs. Lawrence’s cancer went into remission and she lived another 22 years. More important, a new field of cancer treatment had been born.-The Body by Bryson.
1935-1945: Horrifying as the German experiments were, they were outdone, in scale if not cruelty, by the Japanese. Under a doctor named Shiro Ishii, the Japanese built an enormous complex of more than 150 buildings spread over almost 1,500 acres at Harbin in Manchuria with the avowed purpose of determining human physiological limitations through any means necessary. The facility was known as Unit 731.-The Body by Bryson.
Nobody knows how many people died in Unit 731, but one estimate has put the number as high as 250,000.
Most were granted immunity from prosecution in return for sharing what they had learned with their American captors. Shiro Ishii, the physician who had conceived and run Unit 731, was extensively debriefed and then allowed to return to civilian life.
1929: German Doctor Forssmann was a young, newly qualified doctor working in a hospital near Berlin when he became curious to know if it would be possible to gain direct access to the heart by means of a catheter. Without any idea what the consequences would be, he fed a catheter into an artery in his arm and cautiously pushed it up toward his shoulder and on into his chest until it reached his heart, which, he was gratified to discover, didn’t go into arrest when a foreign object invaded it. Then, realizing he needed proof of what he had done, Forssmann walked to the hospital’s radiology department, on another floor of the building, and had himself X-rayed to show the shadowy and startling image of the catheter in situ in his heart. Forssmann’s procedure would eventually revolutionize heart surgery.-The Body by Bryson.
1928: while Alexander Fleming was away on a holiday from his job as a medical researcher at St. Mary’s Hospital in London, some spores of mold from the genus Penicillium drifted into his lab and landed on a petri dish that he had left unattended. Thanks to a sequence of chance events—that Fleming hadn’t cleaned up his petri dishes before departing on holiday, that the weather was unusually cool that summer (and thus good for spores), that Fleming remained away long enough for the slow-growing mold to act—he returned to find that the bacterial growth in the petri dish had been conspicuously inhibited.-The Body by Bryson.
At Oxford, a team of biochemists led by the Australian-born Howard Florey began searching for a more effective alternative and in the process rediscovered Fleming’s penicillin paper. The principal investigator at Oxford was an eccentric German émigré named Ernst Chain, he persevered and found to his astonishment that penicillin not only killed pathogens in mice but had no evident side effects. It appeared to be the perfect drug: one that could devastate its target without wreaking collateral damage. Under Florey’s command, Oxford gave over a significant amount of resources and research space to growing mold and patiently extracting from it tiny amounts of penicillin. By early 1941, they had just enough to trial the drug on a policeman named Albert Alexander, who was a tragically ideal demonstration of how vulnerable humans were to infections before antibiotics. While pruning roses in his garden, Alexander had scratched his face on a thorn. The scratch had grown infected and spread. Alexander had lost an eye and now was delirious and close to death.-The Body by Bryson.
With Britain preoccupied by World War II and the United States not yet in it, the quest to produce bulk penicillin moved to a U.S. government research facility in Peoria, Illinois. Two years after testing had begun, a lab assistant in Peoria named Mary Hunt brought in a cantaloupe from a local grocery store. It had a “pretty golden mold” growing on it, she recalled later. That mold proved to be two hundred times more potent than anything previously tested. Every bit of penicillin made since that day is descended from that single random cantaloupe. Within a year, American pharmaceutical companies were producing 100 billion units of penicillin a month. As early as 1945, in his Nobel acceptance speech, Fleming warned that microbes could easily evolve resistance to antibiotics if they were carelessly used.-The Body by Bryson.
Late, 1920: in one of the happiest but most improbable episodes in the history of scientific progress, a struggling young general practitioner in London, Ontario, read an article about the pancreas in a medical journal and got an idea for how he might effect a cure. His name was Frederick Banting, and he knew so little about diabetes that he misspelled it as “diabetus” in his notes.-The Body by Bryson.
1921: Insulin is discovered by Sir Banting, Charles Best, and JJR Macleod; possibly the first great triumph of medical science. They did almost everything wrong. As one observer put it, their experiments were “wrongly conceived, wrongly conducted, and wrongly interpreted.” Yet within weeks they were producing pure insulin.-The Body by Bryson.
11 Jan, 1922: Insulin is first used in the treatment of diabetes.
1910: Salvarsan is developed by the German immunologist Paul Ehrlich.-The Body by Bryson.
1902: Trans Fats are invented by a German Chemist and marketed as a healthy alternative to butter or animal fat.-The Body by Bryson.
Nov, 1901: at a psychiatric hospital in Frankfurt am Main, Germany, a woman named Auguste Deter presented herself to the pathologist and psychiatrist Alois Alzheimer, complaining of persistent and worsening forgetfulness. She could feel her personality draining away, like sand from an hourglass. “I have lost myself,” she explained sadly. When at last she died in 1906, he had her brain sent to him for autopsy. Alzheimer found that the poor woman’s brain was riddled with clumps of destroyed cells.-The Body by Bryson.
1900: Nearly half of deaths are from infectious diseases compared with just 3% now.-The Body by Bryson.
1900: The term “virus” originates when a Dutch botanist, Martinus Beijerinck, found that the tobacco plants he was studying were susceptible to a mysterious infectious agent even smaller than bacteria. At first he called the mysterious agent contagium vivum fluidum but then changed it to “virus,” from a Latin word for “toxin.”-The Body by Bryson.
1898: Marie and Pierre Curie discover radium in France.-The Body by Bryson.
1896: Wilhelm Röntgen announces his discovery of X-Rays.-The Body by Bryson.
1896: The “Chemical Composition of American Food Materials” is published, working out the calories and nutritional values of many known foods- some 4,000 in all.-The Body by Bryson.
1887: The Calorie is introduced in an article on “Food Energy” by American Chemist Atwater. To Atwater and his contemporaries, all that made one food superior to another was how well it served as fuel. So it was believed that fruits and vegetables provided comparatively little energy and needed to play no part in the average person’s diet. Instead, he suggested that we should eat a lot of meat—two pounds every day. Atwater’s most unsettling discovery—to himself as much as to the world at large—was that alcohol was an especially rich source of calories, and thus an efficient fuel.-The Body by Bryson.
1887: Invention of the Petri Dish & Agar; Koch had a lab assistant named Julius Richard Petri who devised the shallow dish with a protective lid that bears his name. Petri dishes took up very little space, provided a sterile and uniform environment, and effectively eliminated the risk of cross-contamination. But there was still a need for a growing medium. Various gelatins were tried, but all proved unsatisfactory. Then Fanny Hesse, the American-born wife of another junior researcher, suggested that they try agar. Fanny had learned from her grandmother to use agar to make jellies because it didn’t melt in the heat of an American summer.-The Body by Bryson.
1884: German microbiologist Robert Koch reports that cholera is wholly caused by a bacillus (a rod-shaped bacterium).-The Body by Bryson.
1884: Danish bacteriologist, Hans Christian Gram, develops a technique for distinguishing the two major types of bacteria by what color they turned when stained on a microscopic slide. The difference between the two types has to do with the thickness of their cell walls and how easily or not they are penetrated by antibodies.-The Body by Bryson.
1883: The Bertillon system is designed to identify fingerprints, and in its first year of operation, it unmasks 241 fraudsters. Fingerprinting was actually only an incidental part of Bertillon’s system, but when he found a single fingerprint on a window frame at 157 rue du Faubourg Saint-Honoré and used that to identify the murderer as one Henri Léon Scheffer, it caused a sensation.-The Body by Bryson.
1882: Robert Koch discovers Tubercle Bacillus (aka Consumption). Until late in the 19th century, it was believed to be inherited. The medical community realized beyond doubt that it was infectious—a far more unnerving proposition to loved ones and carriers alike.-The Body by Bryson.
1880s: Chromosomes are discovered by German Heinrich Gottfried von Waldeyer-Hartz.-The Body by Bryson.
1872: “The Expression of the Emotions in Man and Animals” by Charles Darwin is published.-The Body by Bryson.
2 Aug, 1869: German surgeon, Gustav Simon, who removed a diseased kidney from a female patient without having any certain idea what would happen and was delighted to discover—as presumably was the patient—that it didn’t kill her. It was the first anyone realized that humans can survive with just one kidney.-The Body by Bryson.
1866: English eminent physician John Langdon Haydon Down first described the condition that we now know as Down’s syndrome in a paper called “Observations on an Ethnic Classification of Idiots,” but he referred to it as “Mongolism” and its victims as “Mongoloid idiots” in the belief that they were suffering an innate regression to an inferior, Asiatic type. Down believed, and no one seems to have doubted him, that idiocy and ethnicity were conjoined qualities. He also listed “Malay” and “Negroid” as regressive types.-The Body by Bryson.
1859: “On the Origin of Species” by Charles Darwin is published.-The Body by Bryson.
1858: Henry Gray publishes “Anatomy: Descriptive and Surgical (Gray’s Anatomy),” the most influential anatomical work of the period.-The Body by Bryson.
1823: Czech Anatomist Jan Purkinje establishes the uniqueness of fingerprints (though in fact the Chinese had made the same discovery more than a thousand years earlier and for centuries Japanese potters had identified their wares by pressing a finger into the clay before baking).-The Body by Bryson.
Dec, 1799: Not long after he had retired as America’s first president, Washington spent a long day on horseback in foul weather inspecting Mount Vernon, his plantation in Virginia. Returning home later than expected, he sat through dinner in damp clothes. That night he developed a sore throat. Soon he had difficulty swallowing, and his breathing became labored. Three physicians were called in. After a hurried consultation, they opened a vein in his arm and drained eighteen ounces of blood, almost enough to fill a British pint glass (or overfill an American one). Washington’s condition only worsened, however, so his throat was blistered with a poultice of cantharides—what is more commonly known as Spanish fly—to draw out bad humors. For good measure, he was given an emetic to induce vomiting. When all of this failed to produce any visible benefit, he was bled three times more. Altogether about 40 percent of his blood was removed over two days. Upon his death, yet another doctor visited and proposed that they revive—indeed, resurrect—the deceased president by rubbing his skin gently to stimulate blood flow and transfusing him with lamb’s blood, to replace the blood he had lost and refresh what remained. His family mercifully decided to leave him to his eternal rest.-The Body by Bryson.
500 Ka: Hominins begin making tipped spears.-The Body by Bryson.
2 Ma: Hominins begin endurance running and, with it, persistence hunting.-The Body by Bryson.
6 Ma: Early hominins begin walking.-The Body by Bryson.