This marvelous brain is nonreplaceable, but it appears that you can lose one of its two lobes and still survive and more or less thrive because the two halves, which look alike, really do different jobs. The left half governs your ability to perform intellectual tasks such as math and language. The right half rules your creative and intuitive functions. In addition, the right side of the brain controls muscles on the left side of the body and vice versa. If you injure one side of your brain, the motor deficits will show up on the other, and some function may be restored with new neural connections, but the original dexterity or strength rarely returns in full.2
As proof, think hemispherectomy, the rare surgery that removes one half of the brain in an attempt to ameliorate a seizure disorder or to excise a brain tumor. The procedure is almost always done on children with epilepsy because the young brain is more “plastic” than an adult’s, meaning that it is more capable of establishing the new connections among neurons required to take over tasks once performed by those in the now-missing hemisphere. After this surgery, patients live to tell the tale, but depending on which lobe they’ve lost, like stroke victims they may experience problems ranging from speech impairment to the loss of peripheral vision and reduced sensation or movement on the opposite side of the body.
There is, of course, an exception that proves the rule: “A man in France continues to puzzle scientists nearly a decade after he was found to be living with just 10 percent of a typical human brain. His case was originally published in The Lancet journal in 2007 but was presented [in June 2016 at the 20th annual meeting of the] Association for the Scientific Study of Consciousness conference in Buenos Aires. At the time of the original study, the patient was a 44-year-old man who had been experiencing weakness in his left leg. After examining him, doctors found that about 90 percent of his neurons had eroded, with fluid filling the bulk of his skull…. They believe the condition likely occurred as a result of a related brain disorder called hydrocephalus, which he had as an infant. Despite the reduced brain matter, the man lived a relatively normal life; he was a married civil servant with two kids. He also scored an IQ of 75, which is considered low but not disabled. At the recent conference, cognitive psychologist Axel Cleeremans argued that the rare case shows just how adaptable the brain can be even with an injury. CBC notes Cleeremans sees this case as “a medical miracle—but also a major challenge to theories about consciousness.” Cleeremans claims that “…the brain is continually and unconsciously learning to re-describe its own activity to itself, and these descriptions form the basis of conscious experience.”3
As long as you have it, your brain asks little of you except to use it. The phrase “use it or lose it” sometimes sounds comical, but in relation to your gray matter, it could not be more serious. Everyone knows that growing older may bring some reduction in cognitive functions, the most comforting explanation being that you know so much it takes time to sort through the memory cabinet. But multiple studies show that one way to protect an aging brain is to use it. Neurologists note that the difference between normal aging problems and serious dementia is “where are my keys?” vs. “what are those keys for?” Doing math problems or crossword puzzles won’t ward off the second, but it may, just may, help with the first.
But lose both hemispheres, and you’re done. There is, as yet, no such thing as a brain transplant. As for the rest of your skin and bones and organs and tissues, the future may hold miracles, but right now not even the most advanced prosthetic provides a perfect substitute for any one half of your several pairs of parts. An artificial eye looks good, but it can’t see. An artificial leg may keep you in the race, but it can’t feel the ground. And losing your dominant hand would be a problem because “handedness” begins in the brain, not in the fingers.
REPLACEABLE/REMEDIABLE
Aristotle was an empirical researcher; he took nothing on faith. One excellent example from Generation of Animals (De Generatione Animalium), written sometime in the last half of the fourth century BCE, is his description of breaking open a fertilized chicken to observe and record the development of the animal’s organ. He decided that the most important was the heart, which he described as a hot, dry three-chambered organ, home to intelligence, motion, and sensation. He thought of other vital organs such as the brain and lungs as existing only to cool the heart so it might function. Two hundred years later, Galen agreed: “The heart,” he wrote in On the Usefulness of the Parts of the body (De Usu Partium), “is, as it were, the hearthstone and source of the innate heat by which the animal is governed.”4
More accurately, the heart is the body’s engine, beating more than 100,000 times every day of your life to pump oxygenated blood through miles of blood vessels to distribute nutrients and haul away waste materials. Vital as it is, unlike the brain, the heart may be replaced by transplant. Every year around the world, surgeons perform approximately 3,500 such surgeries, about 2,000 of them in the United States, often after an excruciatingly long waiting period.
If your entire stomach is removed, perhaps to eliminate a cancer, your surgeon may connect your small intestine directly to your esophagus, and once recovered, you will be able to eat small meals. After surgery to remove a cancerous or damaged colon, he or she can link what remains to an opening in the skin where you attach a bag to capture stool, or the surgeon may create a pouch in the small intestine that allows you to eliminate naturally through the rectum. In 2006, biologists from Wake Forest University School of Medicine and Boston Children’s Hospital reported the experimental transplantation of bioengineered urinary bladders grown from the patients’ own cells.5 In 2014, after several unsuccessful attempts elsewhere, Swedish surgeons performed nine uterine transplants enabling the recipients to become pregnant.6 As for your glands, some single, some multilobed, if you lose one or it turns sluggish, it may be possible to make up the difference with hormone therapies such as insulin injections for a dawdling pancreas or thyroid hormones for a lethargic thyroid gland.
TRANSPLANTATION WAITING LIST, UNITED STATES, 12:14 PM, APRIL 26, 2016
All* 120,991
Kidney 100, 106
Pancreas 1,005
Kidney/pancreas 1,911
Liver 14,711
Intestine 266
Heart 4,130
Lung 1,455
Heart/Lung 44
* The number for “All candidates” is less than the sum of all those who are waiting because some patients need more than one organ.
[Source: HHS Organ Procurement & Transplantation Network, https://optn.transplant.hrsa.gov/data/]
(ALMOST) RELIABLY REDUNDANT
Some pairs of body parts do work even if one goes missing, although not as well as two together.
If you lose one eye, you can still see, but you will lose peripheral vision on the side where the eye is missing, and your depth perception, a product of binocular vision, will be impaired.
You can hear with one ear, but not in stereo, so it may take a minute for you to decide if the footsteps you hear coming toward you from behind are coming from the left or the right.
You can filter waste from your body with only one kidney, but you will be at higher risk for high blood pressure, and if you were previously a boxer, wrestler, football player, MMA star, or cage fighter, you will certainly want to reconsider your athletic choices so as to protect your remaining kidney.
You can breathe with only one lung. Pope Francis does just fine with less than two whole ones, having lost a large part of one lung due to an infection as a teenager. But you will likely have less endurance than you would with two.
You can live without one or two fingers and toes, one hand, one foot, one arm, or one leg. Actually, so long as your heart beats and your brain functions, you can soldier on fully conscious even without all twenty digits, both hands and feet and arms and legs, but that is not a condition to be desired.
On the other hand, here’s the unalloyed good news: You can enjoy an entirely successful reproductive and sex li
fe with just one ovary or testicle.
USEFUL BUT DISPENSABLE
Some organs and parts have valid jobs to perform, but if you lose them, you probably won’t miss them because other parts may step in to take up the slack.
The gallbladder. Bile is a greenish-yellowish-brownish fluid made in the liver and stored in the gallbladder. When you eat, the gallbladder releases some of the stored bile, which then flows through the common bile duct to the small intestine, where it is used to help digest fats. Unfortunately, the gallbladder sometimes mashes bile pigments, cholesterol, and calcium together into hard crystalline “stones” that can painfully block the duct and may lead to an infection. Cholecystectomy (from the Greek words chol meaning bile, kystis meaning bladder, and -ektomia meaning cut out) surgically removes the gallbladder and eliminates the stones but does not interfere with the benefits of bile, which will now go directly from the liver to the intestine so efficiently that you will probably never notice the difference.
The spleen. Practically all vertebrates, including fish, have a spleen.7 Yours is approximately four inches long, a brownish organ sitting next to your stomach in the upper part of your abdomen. The spleen is not a gland, but it does function as part of your lymphatic system, metabolizing the hemoglobin and recycling the iron from old red blood cells, discarding the useless old cells, and acting as a storage vat for an extra supply of blood that comes in handy should you experience a hemorrhagic emergency. The spleen also fights infection with white blood cells (lymphocytes and macrophages) that protect and heal by surrounding and destroying dead tissue, bacteria, and other foreign matter. But if you develop an illness such as severe lupus or sickle cell anemia that makes your spleen shrivel up like a prune, or if your spleen is irreparably damaged in an accident or on the playing field, it can be safely removed, leaving you alive and healthy although at higher risk of infection. Certainly, you will want to keep your immunizations up to date, and your doctor may advise your taking antibiotics before surgery or after an injury. Of course, like other body parts, the spleen is not without its odd attributes. For example, suppose you are in that automobile accident or hit really hard in the midsection, damaging your spleen so badly that splenectomy is the only option. Now suppose that a small piece of your spleen breaks off and remains in your body. Chances are that it—the piece of spleen, not the body—will grow larger and begin to churn out blood cells. Even more interesting, anywhere from one-in-ten to about three-in-ten of us have a second “accessory” spleen, smaller than the primary organ but capable, again, of filtering and discarding red blood cells while providing the anti-infection white ones.8, 9
The fifth toe. You can also do without your fifth toe, the one that went “wee wee wee all the way home,” but it will take a bit of getting used to. This digit is valuable for apes that use the fingers and toes on both hands and feet to hold onto branches while swinging through the trees. We don’t swing through trees, but we do stand on feet stabilized by five long metatarsal bones, one reaching back from each toe to the center of the foot. Removing the fifth toe itself would not be a disaster so long as your surgeon cuts carefully to avoid removing its connecting metatarsal, which could affect your balance.
The highly adaptable human male breast. “It is well known that in the males of all mammals, including man, rudimentary mammae exist. These in several instances have become well developed, and have yielded a copious supply of milk. Their essential identity in the two sexes is likewise shewn by their occasional sympathetic enlargement in both during an attack of the measles,” Darwin wrote in The Descent of Man.10 Nonetheless, in ordinary life, he considered the male breast and its nipple a total waste of tissue. He was, and still is, not alone in this, but he was wrong and so are his fellow believers. With few exceptions such as horses, monotremes (egg-laying mammals such as the platypus), brown rats (Rattus norvegicus), the common house mouse, and some other rodents, all male mammals have breasts and nipples, holdovers from that moment in the womb when we were not yet obviously male or female.11 And, surprisingly, sometimes these tissues are functional. Only the Indonesian male fruit bat lactates spontaneously, but, believe it or not, under the right conditions, the human male breast can be coaxed to perform. The trick lies in the hormones, specifically prolactin, a.k.a. luteotropic hormone or luteotropin, a protein that plays a role in triggering the production of breast milk. Prolactin is produced and secreted by the pituitary, a pea-size, two-lobe gland located in a hollow behind your nose at the base of the brain. The pituitary has two lobes, once again, like the brain, a pairing of different-but-equally-important parts. The back lobe makes ADH, the antidiuretic hormone that regulates fluid balance; the front lobe churns out growth hormones, the thyroid stimulating hormone TSH, the adrenal stimulating adrenocorticotrophic hormone ACTH, and prolactin. Jack Newman, the pediatrician who in 1984 created the first Canadian hospital-based breastfeeding clinic at Toronto’s Hospital for Sick Children,12 explains that taking some medicines such as the antipsychotic Thorazine© may cause the pituitary to secrete higher levels of prolactin. Other drugs linked to higher prolactin levels include but are not limited to the heart medicine digoxin, tricyclic antidepressants such as amitryptiline (Elavil©), the antiischizophrenic drug risperidone (RisperDAL©), various opioids such as morphine, some amphetamines, the antireflux medicine cimetidine (Tagamet©), and some drugs used to treat high blood pressure (reserpine, verapamil, methyldopa [Aldomet©]). A pituitary tumor that raises the body’s prolactin level just might trigger male lactation. Sometimes even a drastic physical change can do the same, one example being starvation, which affects the liver’s ability to absorb excess hormones. When normal food intake resumes, the body’s glands go back to work sooner than the liver and prolactin levels may rise, causing spontaneous male lactation, a phenomenon observed in survivors of concentration camps after World War II.13
The foreskin. Finally, the king of all dispensables: The foreskin. Nobody seems to know for sure why male circumcision and the more traumatic female genital mutilation to remove the clitoris achieved ritual status, although one might reasonably speculate that in early patriarchal society one primary goal was to make sex more pleasurable for men and less pleasurable for women. Some speculate that the anesthesia-free surgery might simply have demonstrated one’s ability to withstand pain at the entrance into adulthood. And in some situations, such as battles fought in less than concealing uniforms, male circumcision did offer a quick way to differentiate friend from foe at a glance. Whatever explanation you prefer, the facts remains that the foreskin is definitely not useless. From the moment a baby boy is born, and some say even in the womb, this slip of skin protects the sensitive tip of the penis. Scientists study everything, so you will not be surprised to read that there are data attesting both to the fact that male circumcision reduces sexual pleasure or enhances it, with conflicting arguments to bolster each opinion.14 But equally important and more reliable data proving that removing the foreskin does provide health benefits such as a lower risk of urinary infections that might escalate to kidney damage, a lower risk of sexually transmitted diseases/ STDs such as HIV, and a lower risk of cancer of the penis for him and cervical cancer for her. As a result, while there are foreskin defenders who equate male circumcision with the more traumatic female version, in 2012, the American Academy of Pediatrics (AAP), while not recommending routine circumcision for all newborn boys, says its benefits outweigh the risks.15, 16 No one has ever come up with a similar medical justification for removing the clitoris.
FOUR (REALLY PRETTY MUCH) USELESS HUMAN BODY PARTS
This list may not be as poetic as Dorothy Parker’s, but the cartilage, bone, and soft tissue below could correctly have been included on Darwin’s list of things the human body would never miss if they suddenly, magically disappeared.
The Adam’s apple. Both men and woman have Adam’s apples, the bony cartilage sitting on top of the thyroid gland and wrapped around the larynx. The difference is that a man’s voice box is larger,
and so his Adam’s apple is more prominent. But it is still of no use whatsoever except, as some have noted, to embarrass the body by visibly jumping up and down in response to an emotional trigger such as fear or excitement or joy. And you probably know that the Adam’s apple is called an Adam’s apple because when Eve gave Adam the forbidden fruit and he bit off a chunk, a piece stuck in his throat. So it should be called Eve’s apple, right? But it isn’t.
Extra ribs. The rib cage is a frame that protects your heart, lungs, and kidneys, while serving as a sturdy attachment site for many of the muscles stretching through your upper body and abdomen. How many ribs do you really need to do this? Fewer than you may have. Chimps and gorillas have 13 pairs of ribs. As a rule, humans have 12, and no, men don’t have one less rib than women do. This myth, based on the tale of Adam’s losing a rib to make Eve, was so widely accepted that it came as a shock to many when advances in human dissection showed that both men and woman have the same number of ribs. Of course, there are exceptions to every rule, and although it does not go by gender, some of us do have more than 12 sets. Anywhere from one in 500 to eight in 100 humans have an extra one or two cervical (neck) ribs sitting above what is considered the first rib at the top of the normal human rib cage. This is one case where more is definitely less because the only thing these extra ribs seem to do is press against or compress blood vessels or nerves in the neighborhood, causing shoulder or neck pain or numbness and tingling or even blood clots in the arms and hands and sometimes a reduced ability to move the fingers in order to grasp and hold things such as a pencil.
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