50 Fun Facts About Musculoskeletal System

Which bone, the longest in the human body, makes up roughly a quarter of a person's height?

The femur averages about 26.7% of a person's height in both men and women. That steady ratio lets anthropologists estimate how tall someone stood from a single thigh bone.

Which stirrup-shaped bone of the middle ear is the smallest and lightest in the human body?

The stapes takes its name from the Medieval Latin word for a stirrup. Classical Latin had no such word, because stirrups did not exist in the ancient world.

Which muscle is the largest in the human body and keeps the trunk upright when standing?

The gluteus maximus is far bulkier in humans than in other primates, whose flatter hips cannot hold them standing erect. Its most powerful action is hauling the body upright after stooping.

Which stiffening of the muscles sets in after death because cells run out of the energy molecule ATP?

Rigor mortis happens because muscle fibres need ATP to let go, not to grip. Once the supply runs out the filaments stay locked together, and the stiffness peaks about 13 hours after death.

Which Greek hero gives his name to the thickest tendon in the human body, at the back of the ankle?

Achilles was held by the heel when his mother Thetis dipped him in the River Styx, which left that one spot unprotected. The oldest known record of the tendon's name is in a 1693 anatomy text.

Which German physicist discovered X-rays and soon photographed the bones of his wife's hand with them?

Wilhelm Röntgen took the picture of Anna Bertha's hand about six weeks after his discovery. In 1901 the rays earned him the very first Nobel Prize in Physics.

Which horseshoe-shaped bone in the neck is the only one in the body not joined to another bone?

The hyoid is anchored by muscles and helps the tongue move and the throat swallow. In an adult murder case, finding it fractured strongly suggests strangulation.

Which nerve at the elbow causes the electric tingle known as hitting the funny bone when it is struck?

The ulnar nerve is the largest in the human body left unprotected by muscle or bone, which is why a knock at the elbow jolts it so easily.

A baby is born with around 270 bones, but how many does a typical adult human skeleton have?

206 is the usual adult total because many of a newborn's separate bones fuse together during growth. The figure leaves out the small extra bones that some people have.

Which Italian scientist found that a dead frog's leg muscles twitched when struck by an electric spark?

Luigi Galvani put the twitch down to an electric fluid stored in animal tissue. His rival Volta coined the word galvanism for him, and the verb galvanize still carries his name.

Which bone at the front of the knee is the largest sesamoid bone in the human body?

The patella is still soft cartilage when a baby is born and only starts turning to bone at about age three. Like every sesamoid bone, it sits embedded inside a tendon.

Which bone, better known as the collarbone, is the only long bone in the body that lies horizontally?

The clavicle is the first bone to start hardening in the embryo, at five to six weeks, yet one of the last to finish, at about 21 to 25 years. It is also the most commonly broken bone.

Which bone, the largest and strongest of the face, is the only one in the skull that can move?

The mandible is the lower jawbone and holds the bottom row of teeth. Strong as it is, it tends to change shape in old age.

Which thigh muscle, the longest in the human body, is named after the Latin word for a tailor?

The sartorius runs obliquely across the front of the thigh. Its name most likely refers to the cross-legged position in which tailors once sat to work.

Which chewing muscle is often claimed to be the strongest in the human body for its bite force?

The masseter owes its edge to working against a much shorter lever arm than other muscles. Guinness once recorded a bite of 4,337 newtons held for two seconds.

Which dome-shaped muscle beneath the lungs is the main muscle of breathing, drawing air in as it contracts?

The diaphragm moves downward as it contracts, enlarging the chest cavity so that the drop in pressure pulls air into the lungs. It also walls off the heart and lungs from the abdomen.

Which type of muscle is striped like skeletal muscle yet contracts without conscious control?

Cardiac muscle is found only in the wall of the heart. Its cells are packed with mitochondria, which makes them highly resistant to fatigue.

Which bands of fibrous tissue connect one bone to another and are more elastic in double-jointed people?

Ligaments tie bone to bone, whereas tendons tie muscle to bone. A dislocated joint is set quickly because overstretched ones leave it weak and prone to slipping out again.

Which mineral, about 99% of which sits in the skeleton, must also be present for any muscle to contract?

Calcium was shown to drive muscle contraction as early as 1882. It works by binding to proteins such as troponin, which then allow the fibres to pull.

Which nutrient, made in sunlit skin, prevents the childhood bone-softening disease rickets?

Vitamin D was discovered in 1922 during the hunt for what children with rickets were missing. A century earlier, it had been observed in Germany that young children fed cod liver oil did not develop the disease.

Which bone-thinning condition becomes far more common in women after menopause as oestrogen levels fall?

Osteoporosis takes its name from the Greek for porous bones. It typically causes no symptoms at all until a bone breaks, most often in the wrist, spine, shoulder or hip.

Which condition, usually arising between ages ten and twenty, curves the spine sideways into an S or C?

Scoliosis comes from an Ancient Greek word meaning a bending. The usual teenage form has no clear cause, and minor curves are simply watched rather than treated.

Which painful condition, once nicknamed the disease of kings, most often strikes the joint at the base of the big toe?

Gout flares when needle-shaped crystals of uric acid settle in a joint. It earned its royal nickname through its link to rich food and obesity.

Which soft tissue in the core of large bones produces about 500 billion new blood cells every day?

Red marrow is the only kind a newborn baby's bones contain. With age, much of it is gradually converted into the fatty yellow kind.

Which type of joint, of which the knee is the body's largest example, permits motion in only one plane?

Hinge joints swing one way, as a door does. The knee and ankle are less typical examples, because they allow a slight rotation or side-to-side movement in some positions.

Which shoulder muscle, a common site for injections, is named after the triangular Greek letter it resembles?

The deltoid is shaped like the Greek capital delta. It is the prime mover when the arm is lifted out to the side.

Which group of three muscles at the back of the thigh bends the knee and straightens the hip?

The hamstrings take the first half of their name from an Old English word for the bend of the knee. The string is their cord-like tendons, felt on either side behind the knee.

Which paired muscle of the abdomen, crossed by bands of connective tissue, forms the visible six-pack?

The rectus abdominis is one long, flat muscle on each side of the midline, and its Latin name means straight abdominal. Tendon bands split each into separate bellies, which bulge when tensed.

Which protein, the most abundant in mammals, gives bone and tendons their tensile strength?

Collagen takes its name from the Greek for glue, because boiling animal skin and sinew was the early way of making glue. The oldest glue ever found, over 8,000 years old, is made of it.

Which flat bone, better known as the shoulder blade, has a Latin name that may once have meant a spade or shovel?

The scapula may have been named for its spade-like shape, though the origin is uncertain. Medical terms use the prefix omo- for it instead, taken from the Ancient Greek word for shoulder.

Which necktie-shaped flat bone in the chest do surgeons cut open to reach the heart?

The sternum is split in an operation called a median sternotomy. Because it contains blood-forming tissue, doctors sometimes take biopsy samples from it too.

Which small bone at the base of the spine is the remnant of a vestigial tail in humans?

The coccyx is named after the Greek word for cuckoo, because its last few segments look like the bird's beak when seen from the side.

Which Titan of Greek mythology gives his name to the topmost vertebra, the one that supports the skull?

Atlas bore the weight of the heavens just as the first neck vertebra bears the head. Ancient art shows his globe resting lower down, at the base of the neck.

Which five vertebrae, sitting between the rib cage and the pelvis, are the largest in the spinal column?

Lumbar vertebrae are the biggest because they help support the weight of the body above them. Most people have five, though some have four or six.

Which bones of the fingers and toes share their name with an ancient Greek battle formation?

Phalanges are named for the phalanx, in which soldiers stood side by side in rows like fingers or toes. The body has 56 of them, fourteen on each hand and foot.

Which bone of the shin, the second largest in the human body, shares its name with a kind of flute?

The tibia is the larger, stronger and more frontal of the two bones below the knee. Its slim partner sits behind it and to the outside.

Which soft membranous gaps between a baby's skull bones gradually close over as the bone hardens?

Fontanelles at the back of the head close within the first few months of life. The large one at the front can still be felt until a child is about 18 months old.

Which Brussels-born anatomist showed in a 1543 book that Galen had dissected monkeys rather than humans?

Andreas Vesalius is often called the founder of modern human anatomy. He published the book at 28, and his own dissections proved that the human lower jaw is one bone, not two.

Which egg-white-like liquid inside joints releases the gas bubbles blamed for the sound of cracking knuckles?

Synovial fluid cuts friction between the cartilage surfaces of a joint. Stretching the joint leaves too little of it to fill the space, so dissolved carbon dioxide rushes out as a bubble.

Which crescent-shaped pads of cartilage cushion the knee joint and are often torn in sports injuries?

Menisci take their name from the Greek for crescent. The two in each knee cover about 70% of the joint surface, spreading load and absorbing shock.

Which group of four muscles and their tendons keeps the shoulder stable through its wide range of motion?

The rotator cuff is remembered as the SITS muscles, after the four initials. Tears most often involve the first of them, the supraspinatus, whose tendon runs beneath a bony arch.

Which motor protein forms the thick filaments of muscle, its heads walking along thin filaments of actin?

Myosin pulling on actin is the basis of the sliding filament theory. Two research teams, each including a scientist named Huxley, introduced it independently in 1954.

Which repeating unit between two Z-lines is the smallest functional unit of striated muscle?

Sarcomere comes from the Greek words for flesh and part. Lined up end to end, they give the tissue its alternating dark and light bands under the microscope.

Which large, many-nucleated bone cells dissolve old bone tissue by secreting acid onto it?

Osteoclasts are named from the Ancient Greek for bone and broken. Their acid frees the mineral locked in bone so that it can pass back into nearby blood vessels.

Which neurotransmitter, whose release Botox blocks, do motor nerves use to tell skeletal muscle to contract?

Acetylcholine is released into the gap between a nerve ending and a muscle fibre. Botulinum toxin stops that release, which is why it paralyses the muscles it reaches.

Which oxygen-storing muscle protein gives red meat its colour and is abundant in diving whales and seals?

Myoglobin holds oxygen in reserve for heavy exercise, which suits animals that hold their breath on long dives. It binds oxygen more tightly than the hemoglobin in blood does.

Which cartilage layer near each end of a child's long bones is where the bones grow in length?

The epiphyseal plate, or growth plate, exists only in children and adolescents. Rising oestrogen at puberty in both sexes turns it to bone, and lengthening stops for good.

Which large back muscle, worked by pull-ups and chin-ups, has a Latin name meaning broadest of the back?

Latissimus dorsi muscles have even been used in heart surgery. Surgeons wrapped one around a failing heart and stimulated it electrically to squeeze in time with each beat.

Which German surgeon gives his name to the law that healthy bone adapts to the loads placed upon it?

Julius Wolff published the idea in 1892. Tennis players bear it out, since the bones of the racquet arm grow stronger than the other, while astronauts in microgravity lose bone density.

Which type of muscle contraction, as in holding a plank, builds tension without any change in length?

Isometric joins the Greek words for equal and measuring, because the muscle's length and the joint's angle stay the same. Pushing against an immovable object works the same way.