100 Fun Facts About Skeleton

How many bones does a typical adult human skeleton have?

206. That is only the textbook count: an extra rib or tiny extra bones along the skull's seams mean some adults have a few more.

What happens to most of the 'extra' bones a baby is born with as the child grows up?

Fuse together. A newborn has dozens more separate bones than an adult, and joining them takes years: the five vertebrae of the sacrum do not fuse into one bone until adulthood.

Which division of the skeleton holds the limbs and their girdles?

Appendicular skeleton. The name comes from the Latin for 'to hang upon': the arms and legs hang from the central column of skull, spine and ribs.

Rickets, which softens children's bones, usually comes from a lack of which vitamin?

Vitamin D. The gut cannot absorb calcium without it, and because skin makes the vitamin in sunlight, children who get too little sun are among those most at risk.

Which bone is the largest and thickest in the human body?

Femur. The thigh bone makes up about a quarter of a person's height, so forensic scientists can estimate how tall someone stood from this single bone.

Which bone is the second largest in the human body?

Tibia. The shinbone carries the body's weight between knee and ankle, while the slender fibula beside it bears almost none and serves mainly as an anchor for muscles.

The smallest and lightest bone in the human body is found where?

In the middle ear. The stapes, shaped like a stirrup, is the last of three tiny bones that relay sound vibrations from the eardrum to the fluid of the inner ear.

Which horseshoe-shaped bone in the neck is the only one in the body not connected to any other bone?

Hyoid. It hangs from muscles and ligaments at the root of the tongue, giving the tongue and the swallowing muscles a movable anchor.

What is the everyday name for the skull's zygomatic bone?

Cheekbone. Its name comes from the Greek for 'yoke', because it links the bones of the face to the side of the skull in an arch you can feel in front of each ear.

What are the 'soft spots' on a newborn's skull called?

Fontanelles. They let the skull plates shift and overlap during birth, then give the fast-growing brain room to expand before they close over.

Which opening in the base of the skull does the spinal cord pass through?

Foramen magnum. In humans it sits well forward under the skull, balancing the head on an upright spine, so its position helps anthropologists tell whether a fossil species walked on two legs.

Which bone is the only movable one in the human skull, hinged just in front of each ear?

Mandible. Its two joints glide as well as hinge, which is what lets the lower jaw grind food from side to side.

Which region of the spine, between the ribs and the hips, forms the lower back?

Lumbar. Vertebrae get bigger down the spine because each must carry more of the body's weight, so these five are the largest of all the movable ones.

A giraffe's neck contains how many vertebrae, the same number as a human's?

Seven. Almost every mammal shares that count, sloths and manatees being the rare exceptions, so a giraffe gets its height by stretching each neck bone, not by adding more.

The topmost vertebra, on which the skull rests, is named after which figure from Greek mythology?

Atlas. Just as the Titan held up the heavens, this ring-shaped vertebra holds up the head, cradling the base of the skull in two curved hollows.

Most ribs join which flat bone at the front of the chest?

Sternum. It is the bone rescuers push on during CPR: hands stacked in the centre of the chest, pressing hard and fast to keep blood flowing.

The lowest two pairs of human ribs are known as what?

Floating. Fixed only to the spine, these short ribs reach only partway round the back, where they partly shield the tops of the kidneys.

The tailbone at the base of the spine takes its name from the Greek word for which bird?

Seen from the side, the last few bones of the coccyx were thought to resemble a cuckoo's beak. It is made of three to five small vertebrae and is the remnant of a vestigial tail.

What are the eight small bones of the wrist called?

Carpals. The boat-shaped scaphoid is the one most often broken, usually when someone throws out a hand to stop a fall.

Which digit of the hand has only two phalanx bones instead of three?

Thumb. It makes up for the missing bone with a saddle-shaped joint at its base, which lets it swing across the palm to meet the other fingers.

A 'march fracture' is a stress fracture of which body part?

Foot. One of the long bones behind the toes cracks under repeated minor pounding, as happens to army recruits on long marches; joggers get it too.

What is the anatomical name for the heel bone, the largest bone in the foot?

Calcaneus. The Achilles tendon, the thickest in the body, anchors to the back of it, so the calf muscles can lever the heel off the ground with every step.

The kneecap is the largest example of which type of bone, one that forms inside a tendon?

Sesamoid. The word means 'like a sesame seed', a nod to how small most of them are; the kneecap lifts its tendon away from the joint, giving the thigh muscle extra leverage.

Which bone is a baby most likely to break during a difficult birth?

Collarbone (clavicle). A newborn's break usually needs no treatment: it knits within weeks, and a small hard lump over the healing bone may be the only sign it ever happened.

Hitting your 'funny bone' actually means striking what?

A nerve. The ulnar nerve runs just under the skin where it rounds the elbow end of the upper arm bone, so a knock there sends a sharp tingle down the forearm into the hand.

Which protein forms the fibrous framework of bone?

Collagen. Its fibres give bone a slight spring, so the mineral crystals packed around them can make it hard without leaving it brittle.

Which cells break down old bone tissue, while osteoblasts build new bone?

Osteoclasts. They dissolve bone with acid and enzymes, which clears old tissue for rebuilding and also releases calcium into the blood when the body runs short.

Which condition, especially common in older women, thins the bones until a minor fall can break them?

Osteoporosis. Bone loss speeds up after the menopause as oestrogen falls, and doctors call the disease 'silent' because there are usually no symptoms until a bone breaks.

What is the main job of red bone marrow?

Making blood cells. A newborn's bones hold nothing but this red marrow, but with age fatty yellow marrow replaces much of it, leaving the red kind mainly in the ribs, spine and hips.

What is the hardest substance in the human body, which is not actually bone?

Tooth enamel is almost pure mineral and is not living tissue, so unlike bone, which constantly rebuilds itself, enamel that wears away never grows back.

Sharks, rays and skates have skeletons made mostly of what?

Cartilage. It rarely fossilises, which is why no complete skeleton of the giant prehistoric shark megalodon has ever been found and its size has been estimated mainly from its teeth.

The bony 'keel' on a bird's breastbone exists to anchor what?

Flight muscles. Ostriches and other flightless ratites have a flat breastbone with no keel at all, while penguins keep theirs because they 'fly' underwater.

What is the main structural material of the exoskeleton of insects, crabs and other arthropods?

Chitin. Because the rigid shell cannot stretch, an insect or crab has to shed it in order to grow, and stays soft and vulnerable until the new one hardens.

Whose hand appeared in Röntgen's first X-ray photograph of a human skeleton in 1895?

His wife's. Anna Bertha Röntgen held her hand still over a photographic plate, and the developed image showed the shadows of its bones and of the ring she was wearing.

The hominin skeleton 'Lucy', found in Ethiopia in 1974, was named after a song by which band?

The Beatles. 'Lucy in the Sky with Diamonds' played over and over on a tape recorder as the team celebrated in camp that night, and the nickname stuck.

Which institution bought 'Sue', the most complete T. rex skeleton, at auction in 1997?

Field Museum, Chicago. It won the bidding at about $8.4 million, then the most ever paid for a fossil at auction, with money from McDonald's, Disney and private donors.

The Sedlec Ossuary, a chapel decorated with the bones of thousands of people, stands in which country?

Czechia. Around 1870 František Rint arranged the bones into decorations that include a noble family's coat of arms and a chandelier said to use every bone in the human body.

Which city moved the bones of millions of its dead into old underground quarries from the 1780s?

Paris. Overflowing cemeteries such as Les Innocents had become a health hazard, so their contents were moved into former stone quarries that then lay just outside the city.

In the Winter Olympic sport of skeleton, how does the athlete ride the sled?

Face down, head first. The sled has no steering gear or brakes, so riders guide it by subtly shifting their weight, with their faces just inches above the ice.

Before 2002, skeleton's only two Olympic appearances were both at which Swiss resort, home of the Cresta Run?

St. Moritz. Skeleton grew out of tobogganing on the resort's Cresta Run, and a sled redesigned for artificial bobsleigh tracks later revived international racing and brought it back to the Games.

The Skeleton Coast, a desert shore often shrouded in ocean fog, lies in which country?

Namibia. A cold current running up the coast chills the sea air into dense fog for much of the year, while the desert behind it gets almost no rain.

The Skeleton Dance (1929), with four skeletons cavorting in a graveyard, was the first entry in which Disney series?

Silly Symphonies. Composer Carl Stalling talked Walt Disney into a series of cartoons built around the music, and it was he who suggested opening with dancing skeletons.

In Saint-Saëns's Danse macabre (1874), which instrument imitates the sound of rattling bones?

Xylophone. Saint-Saëns later poked fun at his own hit, quoting the tune on the same instrument for the 'Fossils' in The Carnival of the Animals.

The skull-faced villain Skeletor schemes from Snake Mountain against which hero?

He-Man. Later versions of the story made the feud a family one: Skeletor was once Keldor, half-brother of the hero's father, King Randor.

Skeleton hero Jack Skellington of The Nightmare Before Christmas holds which title in Halloween Town?

The Pumpkin King. Weary of staging the same Halloween every year, he tries to take over Christmas instead; Danny Elfman sang the role while Chris Sarandon spoke it.

Which artist painted Posada's skeleton La Calavera Catrina full-length in a 1940s mural?

Diego Rivera. He set her arm in arm with José Guadalupe Posada, the printmaker who first drew her, and painted himself as a boy holding her other hand.

The TV drama Bones was inspired by the life and novels of which real forensic anthropologist?

Kathy Reichs. The heroine is named after Temperance Brennan, the forensic anthropologist of her novels, and she worked on the series as a producer to keep its science on track.

A 'skeleton key' gets its name because what has been done to it?

Filed down to its essential parts. With most of the bit cut away, only a bare frame is left, and it slips past the wards inside old locks so that one key opens many doors.

In Shakespeare's Hamlet, whose skull does the prince hold and address in the graveyard scene?

Yorick. The gravedigger says the skull belonged to the king's jester, and Hamlet, who rode on his back as a boy, begins his lament with 'Alas, poor Yorick'.

Which part of the skeleton shows the greatest difference between human males and females?

The pelvis. A woman's is broader, with a wider opening adapted for childbirth, which makes it the most useful bone for telling the sex of an unidentified skeleton.

The pop of a cracked knuckle comes from gas bubbles in which lubricating liquid inside the joint?

Synovial fluid holds dissolved nitrogen, which comes out of solution when a joint is pulled apart. The gas needs about 20 minutes to dissolve again, so the same knuckle cannot be cracked twice in a row.

Astronauts lose over one percent of their bone mass for every month spent in orbit because of what?

Microgravity takes the body's weight off the skeleton, and bone that has nothing to carry wastes away. Even on Mars, where gravity is about a third of Earth's, bones would be expected to thin.

Which English king's skeleton was dug up beneath a Leicester car park in 2012, five centuries after his death?

Richard III was the last English king killed in battle, at Bosworth in 1485. DNA from descendants of his sister Anne helped to confirm the bones, which were reburied in Leicester Cathedral in 2015.

Which animal can never crawl out of its shell, because the shell is built from its own ribs and backbone?

Turtle shells are living skeleton, not a house: the domed carapace is the animal's own ribs and spine joined to plates of bone in the skin.

Which structures, shed and regrown every year, are made of the fastest-growing bone in any mammal?

Antlers are bare, dead bone once their 'velvet' skin is lost, while a horn keeps a bony core under a sheath of keratin. Reindeer are the only deer whose females grow them too.

Which metal, the most abundant in the human body, keeps roughly 99 percent of its supply in the skeleton?

Calcium is released from bone into the bloodstream under tight control, so the skeleton doubles as the body's mineral bank as well as its frame.

Which flat, roughly triangular bone on the back of the rib cage is commonly called the shoulder blade?

Scapula bone is usually so thin in places in humans that it is semitransparent. Three groups of muscles anchor to it, including the rotator cuff.

Which tough band of fibrous tissue ties one bone to another across a joint, as the ACL does in the knee?

A ligament joins bone to bone, while a tendon joins muscle to bone and fascia links muscle to muscle. Stretching or tearing one is what doctors mean by a sprain.

The yellow marrow that fills most of an adult's bones gets its colour because it is packed with what?

Fat cells crowd yellow marrow, the dominant kind in adult bones. A newborn's bones hold only the red kind, which is steadily converted as the child grows older.

Which joint condition, nicknamed 'the disease of kings', is caused by uric acid crystals, often in the big toe?

Gout earned its royal nickname from its link to a rich diet. In about half of cases the joint that flares is the one at the base of the big toe.

Which bone at the front of the knee takes its name from a Latin word for a shallow dish?

Patella tissue is still soft at birth: a baby's kneecap only begins turning to bone at about age three, and the job is not finished until around puberty.

Which single long bone forms the upper arm, running all the way from the shoulder to the elbow?

Humerus bones tend to break at a narrow point just below the head, a spot named the surgical neck because it keeps surgeons so busy.

Which bone forms the bony point of the elbow and runs down the little-finger side of the arm?

Ulna bones end in the olecranon, a hook-like tip that slots into a hollow in the upper-arm bone each time the elbow straightens.

Which slender bone on the outer side of the lower leg carries almost none of the body's weight?

Fibula is Latin for a clasp or brooch: beside the shinbone it looks like the pin of a safety pin. For its length it is the most slender of all the long bones.

Which triangular bone at the base of the spine sits wedged between the two hip bones?

Sacrum is short for the Latin os sacrum, 'sacred bone', a translation of the Greek name used by Galen. English speakers once simply called it the holy bone.

Which part of each hip bone takes the body's weight when sitting, earning the nickname 'sit bone'?

Ischium bones end in a thick, rough knob that can be felt simply by sitting on the fingers. The gap between a cyclist's two knobs is one factor in choosing a bicycle saddle.

Which bone of the skull forms the forehead and the roofs of both eye sockets?

Frontal bone holds a pair of air-filled sinuses behind the brow that are absent or barely begun at birth and do not reach full size until after puberty.

Which paired bone forms the upper jaw and the front of the hard palate?

Each maxilla holds the upper teeth and is hollowed out by a sinus, an air space that does not reach full size until the adult teeth have come through.

Which name is shared by the cluster of bones that forms the ankle and heel, including the talus?

Tarsals sit in two groups, a rear pair and a front five. The talus on top is the one that meets the two bones of the lower leg to make the ankle joint.

Which tip of the breastbone, named from the Greek for 'sword', can snap during CPR chest compressions?

Xiphoid process tissue stays soft for decades and typically turns to bone only around the age of 40, when some people notice the hard lump for the first time and take it for a growth.

Under Wolff's law, a tennis player's racquet arm grows stronger bones than the other arm because bone adapts to what?

Mechanical load is the signal: Julius Wolff, a 19th-century German surgeon, argued that healthy bone reshapes itself to suit the forces placed on it. Weightlifters gain bone density the same way.

Which lifelong process removes old bone and lays down new, replacing about a tenth of the adult skeleton each year?

Remodeling runs fastest in babies: during the first year of life almost 100 percent of the skeleton is replaced.

Which long-lived cells, the most common in mature bone, sit walled into tiny pits called lacunae?

Osteocytes are simply bone-building cells that became trapped in the matrix they secreted. They never divide, yet their average half-life is 25 years.

Which thin membrane covers the outer surface of every bone except where a joint surface lies?

Periosteum is more than wrapping: after a fracture, reserve cells stored in it turn into the builders that drive the healing.

What is the anatomical name for the central shaft of a long bone such as the thighbone?

Diaphysis means the main midsection of a long bone: a tube of dense cortical bone whose hollow centre usually holds marrow.

Which zone of cartilage near each end of a child's long bones is replaced by a thin line in adulthood?

Growth plate tissue exists only in children and adolescents. Rising oestrogen at puberty, in boys as well as girls, runs down its stock of dividing cells until lengthening stops.

Cancellous tissue, found inside the ends of a thighbone, goes by which everyday name?

Spongy bone makes up only about 20 percent of total bone mass, yet it has nearly ten times the surface area of the dense kind that surrounds it.

Which cylindrical unit of compact bone, also called a Haversian system, has rings of tissue around a central canal?

Osteon cylinders are only about a third of a millimetre across, and the canal running down the centre of each one carries the bone's blood supply.

Which crystalline mineral makes up as much as 70 percent of the weight of human bone?

Hydroxyapatite crystals are laid into a matrix of protein fibres to make bone, and a close relative of the same mineral builds the dentin of teeth.

Which type of joint, where one bone rotates around a peg on another, lets the head turn from side to side?

Pivot joints permit rotation and nothing else. The one at the top of the neck supplies 40 to 70 percent of the head's turning, and others let the forearm twist.

What name is given to the immovable fibrous joints that lock the bones of the skull together?

Sutures start out wide in an unborn baby, which lets the plates of the skull shift slightly during birth.

Which shock-absorbing pads between the vertebrae are said to 'slip', though in fact they only bulge?

Discs do not physically slip: one bulges, usually in a single direction. Their gradual shrinking with age is part of the reason people get shorter.

Which pad inside the knee, often torn by a twisting sports injury, takes its name from the Greek for 'crescent'?

Meniscus tears can also come from something as harmless as squatting or walking, and each knee has two of the pads to tear, one on either side.

Which condition curves the spine sideways into an S or C shape, most often appearing between ages ten and twenty?

Scoliosis in its most common form causes little physical impairment beyond back pain, even untreated. Some growing patients wear a fitted brace every day until growth stops.

Which degenerative joint disease is the most common form of arthritis, affecting hundreds of millions of people?

Osteoarthritis affected about 237 million people in 2015, some 3.3 percent of the world's population. It breaks down the smooth lining of a joint and the bone beneath it.

Which genetic disorder, commonly called brittle bone disease, can also turn the whites of the eyes blue?

Osteogenesis imperfecta is a group of genetic disorders rather than a single one, and it can also bring loose joints, hearing loss and short stature.

Which partial fracture, where one side of the bone breaks while the other only bends, occurs mostly in children?

Greenstick fractures are named for the way a young, green branch splinters on one side instead of snapping. They most often strike the long bones of the forearm.

What is the term, also known as luxation, for a joint injury in which the bones are forced apart?

Dislocation is most common at the shoulder. A partial one, in which the bones keep some contact, is called a subluxation.

Which bony bulge at the base of the big toe, known to doctors as hallux valgus, is linked to tight shoes?

Bunion sufferers have a big toe that leans toward its neighbours, pushing the joint at its base outward. High heels and a family history both raise the risk.

What is the scientific study of bones called, a field that helps archaeologists read age and sex from remains?

Osteology specialists also study teeth and animal skeletons; work on the non-human bones from a dig has a name of its own, zooarchaeology.

Which medical specialty for bones and joints has a name coined in 1741 from the Greek for 'straight' and 'child'?

Orthopedics began with children: the French physician Nicolas Andry coined the word for a book on correcting and preventing deformities in the young.

What term describes a skeleton carried inside the body, like a human's, rather than worn outside like a crab's?

Endoskeleton designs allow much larger bodies for the same weight of skeleton, because the soft tissues sit outside the frame instead of being boxed in by it.

Which Gilded Age tycoon paid for casts of the Diplodocus skeleton 'Dippy' to be given to museums around the world?

Andrew Carnegie's gifts made 'Dippy' the most-viewed dinosaur skeleton in the world. The London cast, agreed after King Edward VII admired a sketch of the bones, stood on display from 1905 to 2017.

The spiritual 'Dem Bones', which links up a skeleton bone by bone, retells which Old Testament prophet's vision?

Ezekiel visits a valley of dry bones and prophesies that they will rise again at God's command. The song's melody was written by James Weldon Johnson and his brother.

Which anatomist published De humani corporis fabrica in 1543, with landmark studies of the human skeleton?

Andreas Vesalius gathered the bones he studied from cemeteries. The book's more than 250 woodcuts are now generally credited to the studio of Titian.

Which winged bone at the base of the skull cradles the pituitary gland in a hollow called the sella turcica?

Sphenoid bone helps join the braincase to the face: it meets the ethmoid, the vomer, the palatine and the occipital, among others.

Which bony bump on each side of the ankle is formed by the lower ends of the two leg bones?

Malleolus is Latin for 'small hammer'. The inner bump belongs to the shinbone and the outer one to its slender neighbour, so every ankle has a pair.

To estimate a child's 'bone age', radiologists usually compare standard images with an X-ray of which body part?

Left hand and wrist X-rays are matched against reference images of children of known age; the closest likeness gives the bone age, whatever the birth certificate says.

Which shallow socket on the shoulder blade holds the rounded head of the upper-arm bone?

Glenoid cavity walls are so low that a rim of tough tissue, the labrum, runs around the edge to deepen the socket. The name comes from the Greek for 'socket'.

The 'whalebone' that stiffened old corsets and collars was never bone at all, but which whale product?

Baleen is keratin, the stuff of fingernails and hair, and it hangs in plates inside a whale's mouth to strain food from seawater.