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Health

1,016 cards. Each one is a 40-second story with a five-minute read behind it. Page 7 of 17.

361. Why Addison's disease can tan skin that never sees the sunIn Addison's disease the adrenal glands stop making enough cortisol, and the pituitary responds by shouting louder, pumping out a hormone that shares its parent molecule with a sk…
362. Sleeping sickness works by hijacking the brain's internal clockA tsetse fly bite can deliver a single-celled parasite that eventually slips past the blood-brain barrier. Once inside, it scrambles the genes that keep the body's daily rhythm, f…
363. Agoraphobia is not simply a fear of open spacesThe name means fear of the marketplace, but agoraphobia centres on feeling trapped somewhere escape or help seems out of reach: a bus, a queue, a crowded mall. Many sufferers firs…
364. Akathisia is a restlessness so intense its name means 'cannot sit'Some medicines, above all older antipsychotics, can leave people with an unbearable inner urge to move: pacing, rocking, shifting from foot to foot, then needing to sit, then need…
365. Some people feel emotions but cannot find words for themAlexithymia, sometimes called emotional blindness, is not an absence of feeling. People with it may know they feel bad, yet struggle to tell sadness from anger, or an emotion from…
366. An abscess is the body walling off an infection, and the wall backfiresWhen bacteria invade tissue, the body floods the spot with white blood cells and then seals the resulting pus inside a capsule of healthy cells. That barrier protects neighbouring…
367. The Abyssinian cat's name points to Ethiopia, but its genes point elsewhereThe first Abyssinians shown in England arrived from Abyssinia, today's Ethiopia, and the breed kept the name. Yet genetic studies trace its ancestry to Southeast Asia and Europe. …
368. Acromegaly is gigantism that arrives after the body has stopped growingFlood a child's body with growth hormone and the result is extreme height. Do it after the growth plates have closed and bones can no longer lengthen, so hands, feet, jaw and brow…
369. 2C-B, Shulgin's 1974 invention, is now tested head-to-head against MDMA and psilocybinThe chemist Alexander Shulgin created 2C-B in 1974 and ranked it among his favourite compounds. A decade later it was sold as a substitute for ecstasy, and by the mid-1990s the Un…
370. Fox cancelled 9-1-1, and on ABC it grew into a network's top dramaAfter six seasons, Fox dropped its first-responder drama 9-1-1 in May 2023. ABC picked it up the same day. A year later the seventh-season finale drew about 9.6 million viewers ac…
371. The first 9/11 demolition claim appeared online within six hoursLess than six hours after the attacks of September 11, a chatroom post suggested the towers had been brought down by controlled demolition. That idea became the best known of many…
372. Aachen's hot springs drew Celts, Romans and finally CharlemagneWarm mineral springs explain almost everything about Aachen. People settled beside them some 5,000 years ago, Celts worshipped a healing god there, Romans built bathhouses, and Ch…
373. Everest's 1996 storm had been forecast before the summit push beganOn 10 and 11 May 1996, eight climbers died descending Everest in a blizzard. Years later one mountaineer reported that forecasts of a major storm, building after 8 May and peaking…
374. Swyer syndrome: XY chromosomes, a female body and a uterusPeople with Swyer syndrome carry a 46,XY karyotype yet develop a typically female body, complete with a uterus. Their gonads never become working testes or ovaries, so puberty usu…
375. Trees lift water a hundred metres using pipes made of dead cellsThe plumbing that carries water up a tree is built from cells that have already died. Xylem conduits are empty tubes, and the pull comes from leaves: as water evaporates, tiny cur…
376. Yellowjacket larvae pay their babysitters in sugarAdult yellowjackets live mostly on sugar, yet they spend summer hunting insects to chew up for their grubs. In return the larvae ooze a sweet liquid the workers drink. When prey r…
377. A ten-metre tyrannosaur relative wore feathers twenty centimetres longYutyrannus, a cousin of Tyrannosaurus from early Cretaceous China, is the largest dinosaur known with direct fossil evidence of feathers. Its adult was perhaps 10 metres long and …
378. A twining vine's spin has nothing to do with the sun or the hemisphereSome climbing plants always twist clockwise and others always anticlockwise, whichever hemisphere they grow in. Runner beans and bindweed turn one way, honeysuckle and black bryon…
379. Some visual illusions fool our judgement but apparently not our grasping handsShow people the Ebbinghaus illusion and their perceptual judgements go wrong, yet some studies find that when they reach out and grasp, no error appears. That split fuels a theory…
380. Only certain bacteria and archaea can make vitamin B12, the most complex vitaminVitamin B12 is the most chemically intricate of all vitamins, built around a cobalt atom, and no plant or animal can manufacture it: only certain bacteria and archaea do. Animals …
381. Latin medical language once called the vulva the parts to be ashamed ofWestern medicine long labelled the female external genitals pudenda membra, Latin for parts to be ashamed of, while some ancient religions revered the vulva and major Hindu tradit…
382. Web colours rest on 24 bits, enough for 16,777,216 distinct shadesEvery hex colour code on the web packs three bytes, one each for red, green and blue, with intensities running from 0 to 255. That adds up to 24 bits and 16,777,216 possible colou…
383. White matter keeps maturing until middle age, long after grey matter peaksWhite matter was long dismissed as passive packing, yet its fatty, insulated fibres shape learning by relaying and coordinating signals between brain regions. One small study meas…
384. In most cases of transverse myelitis, the cause of the spinal inflammation is never foundTransverse myelitis is a rare inflammation that spreads across the full cross-section of the spinal cord, disrupting movement, sensation and bladder control below the damaged leve…
385. Two sphincters, one voluntary and one not, guard the exit from the bladderThe human urethra, the tube carrying urine out of the bladder, averages about 4 cm in women but 18 to 20 cm in men, because in males it runs the length of the penis. One study of …
386. Urinary tract infections were described on an Egyptian papyrus around 1550 BCRoughly 400 million urinary tract infections occur every year, and they are the most common bacterial infection in women; half of all women get at least one in their lifetime. The…
387. Humans usually have 33 vertebrae, yet about 10 percent of people break the patternA typical human spine stacks 33 vertebrae: seven in the neck, twelve in the chest, five in the lower back, five fused into the sacrum and four forming the tailbone. Totals can ran…
388. Your shinbone is named after a Roman fluteThe tibia takes its name from the flute of the same name. It is the second-largest bone in the body after the femur and carries almost all the weight passing from knee to ankle, w…
389. Lime trees have nothing to do with limes, but everything to do with carvingThe lime trees lining English avenues are no relation to the citrus fruit. Their soft, nearly grainless wood filled German altarpieces and puppet workshops, their inner bark cloth…
390. The big toe, not the thumb, is the most human digitThumbs get the credit for making us human, yet every primate has one, and ours is still partly primitive. The most evolved digit on the human body is the big toe. Its anatomy also…
391. You have more tonsils than you think, arranged in a defensive ringMost people picture two lumps at the back of the throat, but humans are born with four kinds of tonsil forming a ring around the entrance to the airway and gut. Their pitted surfa…
392. Linnaeus ranked living things long before anyone knew they had evolvedKingdom, class, order, genus, species: the ladder Carl Linnaeus popularised was a quick identification guide, built on how organisms looked, with no idea of common descent behind …
393. Every sense except smell passes through the thalamus on its way upDeep in the brain sit two egg-shaped lumps of grey matter, each about four centimetres long. Sight, hearing, touch and taste all route through them before reaching the cortex; onl…
394. A British diver smelled the missing Thai football team before he saw themIn 2018 twelve boys and their coach spent more than a week trapped on a rock shelf deep inside a flooded Thai cave. Two British divers finally reached them after running out of gu…
395. Milling grain strips out vitamin B1, so 59 countries put it backThiamine, vitamin B1, is a bitter, oddly smelly white powder that your cells cannot run without: it helps turn sugar into usable energy and helps nerves build myelin. Refining gra…
396. Pandas, koalas and some dinosaurs found their own ways to grip like thumbsThe human thumb gets its name from an ancient root meaning swelling, since it is the stoutest digit. What makes it special is a mobile base that lets its pad meet each fingertip s…
397. The thymus trains your immune cells, then quietly turns to fatBehind the breastbone sits an organ that is biggest in childhood and fades after puberty. The thymus is a boot camp for T cells: most recruits are culled, either for failing to re…
398. Your fight-or-flight system switches on moments before you even wake upThe sympathetic nervous system is famous for panic: racing heart, wide pupils, goosebumps. But it never fully rests. It quietly tunes blood sugar, body temperature and blood flow …
399. The synapse was named decades before anyone could actually see oneCharles Sherrington coined the word synapse in 1897 for a gap between nerve cells that no microscope of the day could show. Only in the 1950s did electron microscopes reveal the c…
400. The fluid in your joints thickens on impact, then thins again instantlySynovial fluid looks like raw egg white, and its name probably means exactly that. It is also a clever material: when a joint takes a sudden jolt, the fluid stiffens to cushion it…
401. Your hip and knee joints were invented by fish with jaws 400 million years agoScientists once assumed fluid-filled joints evolved when animals crawled onto land. The evidence now points much further back, to the first jawed vertebrates of the Silurian and D…
402. Reindeer eyes turn from gold to deep blue for the Arctic winterShine a torch at a cat at night and its eyes blaze back, thanks to a mirror behind the retina called the tapetum lucidum. Reindeer take the trick further: each winter theirs shift…
403. Sisal is named after a Mexican port that probably never grew itSisal fibre ties hay bales, stuffs mattresses and covers dartboards, yet the agave it comes from carries the name of a colonial Yucatan shipping port, not its likely birthplace in…
404. One person in 10,000 carries every major organ in mirror imageIn situs inversus the heart sits on the right, the liver on the left and even the lungs swap their lobe counts. Because everything flips together, most people with it feel perfect…
405. SIBO is a common diagnosis that medicine still struggles to defineThe colon teems with microbes, but the small intestine normally hosts far fewer. When too many settle there, the result is called small intestinal bacterial overgrowth. Yet as of …
406. Why people with a narrowed spine often feel better leaning forwardSpinal stenosis squeezes the nerves running through the backbone, and a telltale sign is that symptoms ease when a person bends forward, as over a shopping trolley. Up to 8 percen…
407. The brain's striped striatum lights up for surprise, not just rewardDeep beneath the cortex sits the striatum, named for its stripes of grey and white matter. It helps turn intentions into movement and cues into cravings, and brain scans show it r…
408. The world's tallest tree species also hides a record-sized genomeCoast redwoods have topped 116 metres, taller than any other living tree, and can live around 2,000 years. Hidden inside is another giant: a six-fold set of chromosomes and, per G…
409. Giant sequoias need fire, and a small beetle, to release their seedsA giant sequoia can hold 11,000 cones that stay green and shut for up to 20 years. Most seeds escape only when fire's rising heat dries the cones, or when longhorn beetle larvae b…
410. The phrase 'sex worker' was invented by an activist in 1978Carol Leigh, an activist from inside the industry, coined 'sex worker' in 1978 to describe a job rather than brand a person. The label spread to the World Health Organization and …
411. Male mantises sneak up on females when the wind hides their footstepsFor some male insects and spiders, courtship can end with being eaten. So they have evolved tricks: males of one mantis species approach while gusts mask their noise, Pisaura spid…
412. Doctors dropped 'frigidity' and 'impotence' for more precise, less judgmental termsMedicine once lumped sexual problems under blunt labels: impotence for men, frigidity for women. Modern classification splits them into four families, desire, arousal, orgasm and …
413. Japan's first on-screen film kiss, half hidden by an umbrella, caused a sensationIn 1946 a Japanese film showed a kiss, discreetly half-masked by an umbrella, and the country was electrified. Yet two centuries earlier, woodblock artists had produced erotic pri…
414. The ink that marks voters' fingers comes from alchemists' 'lunar caustic'Silver nitrate stains skin so stubbornly that election officials use it to mark fingers and stop people voting twice. Alchemists called it lunar caustic, because they linked silve…
415. When a clownfish mother dies, her mate turns into the new femaleIn a clownfish anemone the biggest fish is the breeding female and the runner-up is her male partner. If she dies, he often bulks up and becomes female, and the largest of the non…
416. Buffalo Soldiers were the first rangers of Sequoia National ParkBefore the National Park Service existed, the job of guarding Sequoia's giant trees fell to Black cavalry and infantry troops, the Buffalo Soldiers. Their commander, Captain Charl…
417. The rectum is named the straight gut, though in humans it curvesRectum is Latin for straight, a label inherited from the Greek physician Galen. The trouble is that Galen dissected animals, whose rectum really is straight. In people it bends al…
418. Your retina is brain tissue, and it is wired back to frontThe retina grows out of the embryonic brain, making it the one piece of the central nervous system anyone can look at without surgery. It is also built inside out: light must pass…
419. Seven true ribs, five false ones, and two that float freeEvery rib is anchored to the spine, but only the top seven pairs reach the breastbone on their own. Three more borrow cartilage from the rib above, which lets the lower chest swin…
420. Why vitamin B2 turns urine bright yellow, and who actually makes itAnimals cannot make riboflavin; bacteria, fungi and plants do. Our bodies do not store it either, so whatever we absorb beyond need is flushed out by the kidneys, tinting urine a …

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