The Human Body
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179 free The Human Body trivia questions with answers — science & nature quiz, new questions added Oct 2026.
70 free the human body trivia questions with answers. You live in it every day, but how well do you actually know your own body? From the bones in your skeleton to the trillions of cells working around the clock, the human body is the most complex machine on Earth, and it is full of facts that sound made up. This quiz has 179 questions and most of them are pitched so a curious 8- to 12-year-old can play: which organ is the biggest, what blood does, how many teeth an adult has, why you get goosebumps. Mixed in are harder anatomy and physiology questions for older students and adults, so a family or a classroom can play the same set and everyone gets a few right. Every answer has been checked against a reference source, shown under each question once you answer, which makes it safe for a science lesson, a homeschool unit on the body or a family quiz night.
30 of 179 questions with answers and explanations. Play the quiz
Q 01How many bones are in the adult human body?
206
206, far fewer than a newborn has, because many of a baby's bones fuse together as the body grows.
Q 02What is the largest organ in the human body?
Skin
Skin keeps water in and germs out, which is why burns over a large area bring dangerous fluid loss and infection.
Q 03Which type of blood cell is responsible for fighting infections?
White blood cells
White blood cells; the pus in an infected wound is largely made of ones that died fighting the infection.
Q 04What is the hardest substance in the human body?
Tooth enamel
Tooth enamel, which can't regrow once damaged, because the cells that made it die off around the time the tooth erupts.
Q 05Which chamber of the heart pumps blood to the entire body?
Left ventricle
The left ventricle, whose walls are much thicker than the right ventricle's because it pushes blood round the whole body, not just the lungs.
Q 06An extra chromosome 21 causes which condition?
Down syndrome
Down syndrome; its risk climbs with the mother's age, yet most babies with it are born to younger mothers.
Q 07What is the smallest bone in the human body?
Stapes
The stapes, named for its stirrup shape, is the last link in the chain of tiny bones that carries sound into the inner ear.
Q 08Which organ is primarily responsible for filtering blood and producing urine?
Kidneys
The kidneys, which filter well over a hundred litres of fluid a day but turn only a litre or two of it into urine.
Q 09Which small brain region controls body temperature, hunger, thirst and circadian rhythms?
Hypothalamus
The hypothalamus, the body's thermostat; a fever is it turning the set point up in response to an infection.
Q 10What pigment gives human blood its red color?
Hemoglobin
Hemoglobin, an iron-containing protein; when iron runs short the body can't make enough of it, and people turn noticeably pale.
Q 11What is the longest bone in the human body?
Femur
The femur (thighbone) is the longest, heaviest, and strongest bone in the human body, making up about a quarter of a person's total height.
Q 12Approximately how many taste buds does the average human tongue have?
About 2,000 to 8,000
About 2,000 to 8,000, and the taste cells inside them are replaced every week or two.
Q 13What is the primary job of platelets?
Stop bleeding
Platelets stop bleeding by clumping into a plug; aspirin disables them for their whole 8 to 9 day life, which is why it raises bleeding risk.
Q 21What is the name of the thin membrane that covers the outside of bones?
Periosteum
The periosteum is a dense layer of connective tissue that covers the outer surface of most bones. It contains nerves and blood vessels that nourish the bone.
Q 22Which hormone lowers blood sugar levels?
Insulin
Insulin; a 13-year-old Toronto boy dying of diabetes became the first person ever treated with an injection of it.
Q 23Approximately how many neurons are in the human brain?
86 billion
About 86 billion, joined by a roughly equal number of non-neuronal cells.
What type of joint is the knee?
Q 14Which vitamin does the body make for itself when sunlight falls on the body's outer surface?
D
Vitamin D; with enough summer sunshine most people can make all they need, so unlike other vitamins it is only conditionally essential in the diet.
Q 15How many liters of blood does an average adult human body contain?
About 5 liters
The average adult body contains about 5 liters (roughly 1.3 gallons) of blood, which makes up about 7% of total body weight.
Q 16What is the tough fibrous protein that forms hair and nails?
Keratin
Keratin, the same protein that builds feathers, claws, hooves and even rhinoceros horn.
Q 17Which part of the digestive system absorbs most of the nutrients from food?
Small intestine
The small intestine, called small for its narrow width even though it is the longest part of the gut.
Q 18What is the medical term for a resting heart rate below 60 beats per minute?
Bradycardia
Bradycardia, which is common in trained athletes, whose efficient hearts can pump enough blood with fewer beats.
Q 19Which organ produces bile?
Liver
The liver, which can regrow after much of it is removed, so a living donor can give more than half of theirs to a patient.
Q 20Stepping into bright sunlight makes up to a third of people do what?
Sneeze
Sneeze: the photic sneeze reflex, nicknamed ACHOO syndrome, affects roughly 18 to 35% of people and runs in families.
Hinge joint
The knee is classified as a modified hinge joint (ginglymus). While it primarily allows flexion and extension, it also permits slight rotation when the knee is bent.
Q 25What is the medical term for swelling caused by fluid trapped in the body's tissues?
Edema
Edema; pressing a swollen spot can leave a dent that lingers after you let go, a sign doctors call pitting edema.
Q 26Which tiny hair-like structures sweep mucus up and out of the airways?
Cilia
Cilia, about 200 on each airway cell; cigarette smoke can shorten them, leaving coughing as the backup way to clear mucus.
Q 27What is the name of the structure that connects muscle to bone?
Tendon
A tendon; tennis elbow is overuse damage to the one that anchors a forearm muscle at the outer elbow.
Q 28In adults, where are the body's new oxygen-carrying blood cells made?
Bone marrow
Bone marrow, mostly in the pelvis, sternum, skull and vertebrae.
Q 29Into which part of the body do the tear ducts drain excess tears?
Nose
The nose: the ducts empty into the nasal cavity, which is why crying or watery allergy eyes make your nose run.
Q 30What is the colored part of the eye called?
Iris
The iris, whose muscles resize the pupil; its fine patterns differ even between a person's own two eyes, so scanners can identify people by it.