Human Body Quiz
Bones, blood, organs and the brain: 15 anatomy questions to test yourself.
What is the largest organ in the human body?
Got a hunch? Pick the answer that feels right.
Skin
Skin is the largest organ, covering around 2 square meters in an adult and making up roughly 15 percent of body weight.
Skin has three main layers, the epidermis, dermis and hypodermis, and its outer layer fully renews itself about every four weeks.
How many chambers does the human heart have?
Got a hunch? Pick the answer that feels right.
4
The heart has two atria on top and two ventricles below; the right side pumps blood to the lungs and the left side pumps it to the rest of the body.
The left ventricle has the thickest wall of the four chambers because it must push blood all the way around the body.
What is the smallest bone in the human body?
Got a hunch? Pick the answer that feels right.
Stapes
The stapes, or stirrup, sits in the middle ear and measures about 3 millimeters, passing sound vibrations on to the inner ear.
The three ear bones, the malleus, incus and stapes, are the only bones that are already full size at birth.
Which blood type is known as the universal donor?
Got a hunch? Pick the answer that feels right.
O negative
O negative blood has no A, B or Rh antigens on its cells, so it can be given to almost anyone in an emergency without triggering a reaction.
AB positive is the universal recipient, and only about 7 percent of people have O negative blood.
What part of the brain is responsible for balance and coordination?
Got a hunch? Pick the answer that feels right.
Cerebellum
The cerebellum, at the back of the brain beneath the cerebrum, fine-tunes movement, posture and balance using input from the inner ear and muscles.
Although it is only about 10 percent of the brain's volume, the cerebellum contains more than half of its neurons.
How many bones are in an adult human body?
Got a hunch? Pick the answer that feels right.
206
Adults have 206 bones. A newborn has closer to 270, but many, including those of the skull and spine, fuse together during childhood.
The hyoid bone in the neck is the only bone in the body that does not connect to any other bone.
Which organ produces insulin?
Got a hunch? Pick the answer that feels right.
Pancreas
Insulin is made by beta cells in the islets of Langerhans, clusters of cells scattered through the pancreas, and it lets glucose enter the body's cells.
The pancreas also makes digestive enzymes, so it works as part of both the endocrine and digestive systems.
What is the longest bone in the human body?
Got a hunch? Pick the answer that feels right.
Femur
The femur, or thigh bone, is about a quarter of a person's height and is also the strongest bone, able to support around 30 times body weight.
The tibia, or shin bone, is the second longest bone in the body.
Approximately how many liters of blood does the average adult body contain?
Got a hunch? Pick the answer that feels right.
5 liters
An average adult has about 5 liters of blood, roughly 7 to 8 percent of body weight, though the figure varies with size and sex.
A standard blood donation takes around 470 milliliters, and the body replaces the lost plasma within a day or two.
What type of cell carries oxygen throughout the body?
Got a hunch? Pick the answer that feels right.
Red blood cells
Red blood cells carry oxygen bound to hemoglobin, the iron-rich protein that gives blood its red color, and deliver it to every tissue.
Each red blood cell lives about 120 days, and the body makes around 2 million new ones every second.
What is the name of the pigment that gives skin and hair their color?
Got a hunch? Pick the answer that feels right.
Melanin
Melanin is a pigment made by cells called melanocytes; more melanin means darker skin, hair and eyes, and it helps shield DNA from UV light.
Red hair comes from a variant form called pheomelanin, linked to changes in the MC1R gene.
Which part of the eye controls the amount of light entering it?
Got a hunch? Pick the answer that feels right.
Iris
The iris is the colored ring of muscle around the pupil; it contracts in bright light and widens in the dark to control how much light reaches the retina.
Everyone's iris pattern is unique, which is why iris scans are used for identification.
What is the body's largest internal organ?
Got a hunch? Pick the answer that feels right.
Liver
The liver weighs around 1.5 kilograms and performs more than 500 functions, from filtering toxins to making bile and storing energy.
The liver can regenerate, growing back to full size even after up to two thirds of it has been removed.
How many pairs of chromosomes do humans have?
Got a hunch? Pick the answer that feels right.
23
Human cells carry 23 pairs, 46 chromosomes in total, with one of each pair inherited from each parent.
Chimpanzees have 24 pairs; two ancestral ape chromosomes fused to form human chromosome 2.
What gas do humans exhale that plants use for photosynthesis?
Got a hunch? Pick the answer that feels right.
Carbon dioxide
Cells produce carbon dioxide as a waste product of turning food into energy, and the lungs expel it with every breath out.
Exhaled air still contains about 16 percent oxygen, which is why rescue breathing can keep someone alive.
Your results
More to explore
All Science quizzes →About the Human Body Quiz
Your body is doing remarkable things while you read this. Your heart beats around 100,000 times a day, your blood makes a full circuit of the body in about a minute, and your skin replaces its outer layer roughly every month. Anatomy is full of numbers like these, and most people only remember a few of them from school.
These 15 questions cover the skeleton, the circulatory system, the brain, the senses and the cells that keep everything running. It suits students revising biology, anyone in a health-related job, or the plain curious. Each answer comes with an explanation of why it is right and an extra fact worth remembering the next time the topic comes up.
You will find 15 multiple choice questions here, each with four options. Difficulty: Easy. Most people finish in about 6 minutes, and every answer comes with a short explanation and one extra fact worth keeping.
How to play
Read the question and pick one of the four answers. The correct answer is revealed straight away with a short explanation, then press Next question to keep going. At the end you get your score out of 15 and a full review of your round. Play again any time and the questions arrive in a fresh order. There is no timer and no account.
Good to know before you play
How difficult is the human body quiz?
It is mostly school-level biology with a few trickier questions on bones and blood. Most people score 11 or more out of 15.
Is the quiz suitable for students?
Yes. It fits middle school and high school biology, and the explanations reinforce the facts rather than just marking answers right or wrong.
Can I retake the quiz?
Yes. Reload the page and the questions reset, which makes it a handy revision tool before a test.
Answer key: all 15 questions with explanations
- What is the largest organ in the human body?
Skin Skin is the largest organ, covering around 2 square meters in an adult and making up roughly 15 percent of body weight. Skin has three main layers, the epidermis, dermis and hypodermis, and its outer layer fully renews itself about every four weeks. - How many chambers does the human heart have?
4 The heart has two atria on top and two ventricles below; the right side pumps blood to the lungs and the left side pumps it to the rest of the body. The left ventricle has the thickest wall of the four chambers because it must push blood all the way around the body. - What is the smallest bone in the human body?
Stapes The stapes, or stirrup, sits in the middle ear and measures about 3 millimeters, passing sound vibrations on to the inner ear. The three ear bones, the malleus, incus and stapes, are the only bones that are already full size at birth. - Which blood type is known as the universal donor?
O negative O negative blood has no A, B or Rh antigens on its cells, so it can be given to almost anyone in an emergency without triggering a reaction. AB positive is the universal recipient, and only about 7 percent of people have O negative blood. - What part of the brain is responsible for balance and coordination?
Cerebellum The cerebellum, at the back of the brain beneath the cerebrum, fine-tunes movement, posture and balance using input from the inner ear and muscles. Although it is only about 10 percent of the brain's volume, the cerebellum contains more than half of its neurons. - How many bones are in an adult human body?
206 Adults have 206 bones. A newborn has closer to 270, but many, including those of the skull and spine, fuse together during childhood. The hyoid bone in the neck is the only bone in the body that does not connect to any other bone. - Which organ produces insulin?
Pancreas Insulin is made by beta cells in the islets of Langerhans, clusters of cells scattered through the pancreas, and it lets glucose enter the body's cells. The pancreas also makes digestive enzymes, so it works as part of both the endocrine and digestive systems. - What is the longest bone in the human body?
Femur The femur, or thigh bone, is about a quarter of a person's height and is also the strongest bone, able to support around 30 times body weight. The tibia, or shin bone, is the second longest bone in the body. - Approximately how many liters of blood does the average adult body contain?
5 liters An average adult has about 5 liters of blood, roughly 7 to 8 percent of body weight, though the figure varies with size and sex. A standard blood donation takes around 470 milliliters, and the body replaces the lost plasma within a day or two. - What type of cell carries oxygen throughout the body?
Red blood cells Red blood cells carry oxygen bound to hemoglobin, the iron-rich protein that gives blood its red color, and deliver it to every tissue. Each red blood cell lives about 120 days, and the body makes around 2 million new ones every second. - What is the name of the pigment that gives skin and hair their color?
Melanin Melanin is a pigment made by cells called melanocytes; more melanin means darker skin, hair and eyes, and it helps shield DNA from UV light. Red hair comes from a variant form called pheomelanin, linked to changes in the MC1R gene. - Which part of the eye controls the amount of light entering it?
Iris The iris is the colored ring of muscle around the pupil; it contracts in bright light and widens in the dark to control how much light reaches the retina. Everyone's iris pattern is unique, which is why iris scans are used for identification. - What is the body's largest internal organ?
Liver The liver weighs around 1.5 kilograms and performs more than 500 functions, from filtering toxins to making bile and storing energy. The liver can regenerate, growing back to full size even after up to two thirds of it has been removed. - How many pairs of chromosomes do humans have?
23 Human cells carry 23 pairs, 46 chromosomes in total, with one of each pair inherited from each parent. Chimpanzees have 24 pairs; two ancestral ape chromosomes fused to form human chromosome 2. - What gas do humans exhale that plants use for photosynthesis?
Carbon dioxide Cells produce carbon dioxide as a waste product of turning food into energy, and the lungs expel it with every breath out. Exhaled air still contains about 16 percent oxygen, which is why rescue breathing can keep someone alive.
Browse other categories
Every category has its own quizzes, each with instant explanations.