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130 free The Human Body trivia questions with answers — science & nature quiz, new questions added Aug 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 130 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 130 questions with answers and explanations. Play the quiz
Q 01How many bones are in the adult human body?
206
Babies start with dozens more, and many of those fuse together during growth.
Q 02What is the largest organ in the human body?
Skin
It makes up roughly 16% of body mass; among internal organs the title goes to the one that makes bile.
Q 03Which type of blood cell is responsible for fighting infections?
White blood cells
White blood cells (leukocytes) are the body's primary defense against infections and disease. They identify and destroy pathogens.
Q 04What is the hardest substance in the human body?
Tooth enamel
It is about 96% mineral, yet unlike bone it cannot repair itself once damaged.
Q 05Which chamber of the heart pumps blood to the entire body?
Left ventricle
Its walls are much thicker than the right ventricle's because it has to push blood around the whole body rather than just to the lungs.
Q 06How many chromosomes do humans typically have?
46
They come in 23 pairs, one of each pair inherited from each parent.
Q 07What is the smallest bone in the human body?
Stapes
The stapes (stirrup bone) in the middle ear is the smallest bone in the human body, measuring just 2-3 millimeters long.
Q 08Which organ is primarily responsible for filtering blood and producing urine?
Kidneys
They filter the entire blood volume dozens of times a day, reabsorbing almost all of the filtrate and leaving only a litre or two of urine.
Q 09Which small brain region controls body temperature, hunger, thirst and circadian rhythms?
Hypothalamus
It also links the nervous system to the endocrine system by directing the 'master gland' hanging just beneath it.
Q 10What pigment gives human blood its red color?
Hemoglobin
This iron-containing protein binds oxygen; when iron runs short the cells turn pale, the hallmark of iron-deficiency anaemia.
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
They are replaced roughly every 10 to 14 days, though the turnover slows with age.
Q 13What is the primary job of platelets?
Stop bleeding
They gather at a break in a vessel wall and plug it, then trigger the clotting cascade that lays down fibrin to seal it.
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 is responsible for regulating blood sugar levels?
Insulin
Insulin's opposite is glucagon, which raises blood sugar; both come from the islets of Langerhans in the pancreas.
Q 23Approximately how many neurons are in the human brain?
86 billion
There are roughly as many non-neuronal cells again, and each neuron can form thousands of connections.
Q 14Which vitamin does the body make for itself when sunlight falls on the body's outer surface?
D
Ultraviolet B rays convert a form of cholesterol in the outer layers into the vitamin, which is why 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, nails and the outer layer of skin?
Keratin
The same protein family builds feathers, horns, claws and hooves in other vertebrates.
Q 17Which part of the digestive system, about six metres long, absorbs roughly 90% of the nutrients from food?
Small intestine
The small intestine's villi and microvilli give it a surface area of tens of square metres; the large intestine mainly reclaims water.
Q 18What is the average resting heart rate for a healthy adult?
60-100 beats per minute
Ultra-trained endurance athletes can sit as low as 37–38 beats per minute at rest.
Q 19Which organ, the largest solid organ inside the body, is also the one that produces bile?
Liver
It weighs about 1.5 kilograms and handles hundreds of jobs, from detoxification to storing glycogen.
Q 20How many pairs of ribs does a typical human have?
12
Vesalius counting 24 in 1543 caused a stir, since tradition held that men had one fewer than women.
Q 24What type of joint is the knee?
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 percentage of the human body is water?
About 60%
The adult human body is approximately 60% water by weight. The brain and heart are about 73% water, while the lungs are about 83% water.
Q 26At about one millimetre long, which muscle of the middle ear is the smallest skeletal muscle in the body?
Stapedius
It steadies the stirrup bone and dampens loud sounds before they reach the inner ear.
Q 27What is the name of the structure that connects muscle to bone?
Tendon
Tendons are tough bands of fibrous connective tissue that connect muscles to bones. Ligaments, in contrast, connect bone to bone.
Q 28Where in the body are new oxygen-carrying cells of the circulation made?
Bone marrow
In adults it happens mainly in flat bones such as the pelvis, sternum and skull, at a rate of about 2 million cells per second.
Q 29In a living adult, the part of the gut where most nutrients are absorbed is typically how long?
About 3 to 5 metres
Measurements at autopsy run longer, around 6.5 metres, because the muscle relaxes after death; the organ is called "small" for its diameter, not its length.
Q 30What is the colored part of the eye called?
Iris
It also acts as an adjustable aperture, changing the size of the pupil to control how much light gets in.