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50 free Hard Human Body trivia questions with answers — science & nature quiz, new questions added Aug 2026.
This hard human body trivia quiz is for people who already know there are 206 bones and want to go deeper: which bone touches no other bone, which muscle is barely a millimetre long, how many nephrons filter each kidney, how many alveoli line the lungs, which cranial nerve wanders down to the gut, and who published the first correct account of the circulation of the blood in 1628. It mixes anatomy, physiology, cell biology and the history of medicine, from Vesalius to the discovery of insulin. Expect numbers, Latin names and the odd trick where the obvious answer is wrong. It is written for medical and nursing students, biology teachers, quiz-league players and anyone who has ever fallen down a Gray's Anatomy rabbit hole. Every answer was checked against Wikipedia and standard references, and each question shows the sentence it rests on. All 50 questions are free with no sign-up. For a gentler round, try our main Human Body trivia page or Human Body Trivia for Seniors.
30 of 50 questions with answers and explanations. Play the quiz
Q 01Roughly how many bones does a newborn baby have before many fuse together?
About 270
Adults end up with around 206, not counting the little accessory bones some people have. Fusion in the skull, spine and pelvis accounts for the drop.
Q 02Which is the only bone in the human body that does not connect to any other bone?
The hyoid
It sits in the neck, held in place by muscles and ligaments, and anchors the tongue. Its fracture is a classic forensic sign of strangulation.
Q 03The kneecap is the largest example of what type of bone?
Sesamoid
Sesamoid bones grow inside tendons. The patella glides over the femur and protects the front of the knee joint.
Q 04Which muscle, just over a millimetre long, is the smallest skeletal muscle in the body?
The stapedius
It steadies the stapes in the middle ear and contracts to dampen loud sounds. Its nerve is a branch of the facial nerve.
Q 05Which muscle, running diagonally across the thigh, is the longest in the human body?
The sartorius
Its old French name was couturier, the tailor, because sitting cross-legged as tailors once did uses every one of its actions.
Q 06Roughly what fraction of a healthy young adult's body weight is skeletal muscle?
About 40 percent
There are more than 600 skeletal muscles. Muscle also has endocrine functions that researchers are still mapping.
Q 07Which spinal nerve is the longest and widest single nerve in the body?
The sciatic
It is the largest branch of the sacral plexus and runs from the back of the pelvis down to the foot.
Q 08Which cranial nerve, numbered X, wanders down from the brainstem to control the heart, lungs and gut?
The vagus
One count found about 105,000 fibres in the right vagus and 87,000 in the left. Its name is Latin for 'wandering'.
Q 09Between which two vertebrae does the adult spinal cord end, tapering into the cauda equina?
The first and second lumbar
It is about 45 cm long in men and 43 cm in women, which is why lumbar punctures are done lower down, below the cord.
Q 10How many vertebrae does the human spinal column normally have, counting the fused sacrum and coccyx?
33
Seven cervical, twelve thoracic, five lumbar, then the fused sacral and coccygeal segments. Giraffes also have seven neck vertebrae.
Q 11Which ribs are the 'floating' ribs, attached to no part of the sternum?
The eleventh and twelfth pairs
Ribs one to seven are 'true' ribs joining the sternum directly; eight to twelve are 'false', and the last two float free at the front.
Q 12Roughly how many nephrons does a healthy adult have in each kidney?
1 to 1.5 million
A mouse kidney manages with about 12,500. One-fifth of the blood entering the kidneys is filtered at the glomerulus.
Q 13Roughly how many alveoli does a typical pair of human lungs contain?
480 million
Together they give a gas-exchange surface of 70 to 80 square metres, and each alveolus is wrapped in capillaries covering about 70 percent of it.
Q 21Andreas Vesalius's landmark 1543 anatomy text is known by what short title?
De Humani Corporis Fabrica
'On the fabric of the human body in seven books' overturned much of Galen. Vesalius taught at Padua and became physician to Emperor Charles V.
Q 22Who illustrated the first edition of Gray's Anatomy in 1858?
Henry Vandyke Carter
Gray was only 31 when it was published and died of smallpox three years later. The book is still in print.
Q 23Insulin was first isolated from dog pancreas in 1921 in whose laboratory at the University of Toronto?
John Macleod
Q 14Why is the left lung smaller than the right?
It shares the chest with the heart
Together the lungs hold about 2,400 kilometres of airways.
Q 15Roughly how many new red blood cells does an adult produce every second?
About 2.4 million
Each one lives 100 to 120 days. Red cells are about 84 percent of all the cells in your body.
Q 16Why do mature human red blood cells have no nucleus?
To leave maximum room for haemoglobin
The nucleus is expelled during development, so a red cell is essentially a flexible sack of haemoglobin with a membrane around it.
Q 17How many oxygen molecules can one haemoglobin molecule carry?
Four
Each of its four subunits binds one oxygen molecule. In tissues it also mops up excess oxygen as an antioxidant.
Q 18Plasma makes up what share of blood by volume?
About 55 percent
Plasma itself is 92 percent water, carrying proteins, glucose, salts and hormones. Blood is classed as a connective tissue.
Q 19Karl Landsteiner's 1901 blood-group labels were A, B and which letter, later changed to O?
C
He was working at the University of Vienna. There are now 48 recognised blood group systems, but ABO and Rh matter most for transfusion.
Q 20Which physician published De Motu Cordis in 1628, first fully describing blood circulation?
William Harvey
Earlier writers such as Servetus and Colombo had described parts of it. He published the book in Frankfurt.
Banting and Best did the bench work; Banting and Macleod shared the 1923 Nobel Prize, and each split his share with a colleague.
Q 24Which cells of the pancreatic islets secrete insulin?
Beta
Their alpha-cell neighbours release glucagon when glucose is low. Only about one percent of the pancreas is endocrine tissue.
Q 25What proportion of the pancreas is exocrine, digestive tissue rather than hormone-producing?
99 percent
The endocrine one percent secretes insulin, glucagon, somatostatin and pancreatic polypeptide.
Q 26Which three hormones does the thyroid gland secrete?
T3, T4 and calcitonin
The most common cause of an underactive thyroid worldwide is iodine deficiency. The gland sits below the Adam's apple.
Q 27The hypothalamus links the nervous system to the endocrine system via which gland?
The pituitary
It releases 'releasing hormones' that tell that gland what to secrete or hold back.
Q 28Which steroids do the adrenal glands produce alongside adrenaline?
Aldosterone and cortisol
They sit on top of the kidneys, hence their other name, suprarenal glands.
Q 29What is the brain's largest white-matter structure, linking the two hemispheres?
The corpus callosum
It is about 10 centimetres long. Cutting it was once a treatment for severe epilepsy, producing the famous split-brain patients.
Q 30What does the word 'cerebellum' mean in Latin?
Little brain
It does not start movements but fine-tunes their coordination, precision and timing.