How to use this quiz: choose an answer before opening the explanation. Each answer is supported by two independent sources checked on 2026-08-27.
10 the human body questions
1 · Warm-up
A typical adult has 206 bones. Roughly how many separate bones does a newborn start with?
- About 270
- About 206
- About 150
- About 350
Show the answer, explanation, and sources
Answer: About 270. A newborn has approximately 270 bones, many of which later fuse.
A newborn's skeleton contains many pieces that join during growth. Fusion—especially in the skull, spine, and pelvis—brings the usual adult count down to 206.
Sources: Cleveland Clinic and National Center for Biotechnology Information.
2 · Warm-up
Which lung has fewer lobes, and which organ occupies the adjacent space?
- Right, for the liver
- Left, for the heart
- Left, for the stomach
- Right, for the heart
Show the answer, explanation, and sources
Answer: Left, for the heart. The left lung has fewer lobes because it shares space with the heart.
The right lung has three lobes, but the left has only two and a cardiac notch. That smaller shape leaves space for the heart's leftward position.
Sources: American Lung Association and National Heart, Lung, and Blood Institute.
3 · Core
The cornea must stay transparent, so it has no blood vessels. Where does much of its oxygen come from?
- The colored iris
- The lens behind it
- Air dissolved through the tear film
- The optic nerve
Show the answer, explanation, and sources
Answer: Air dissolved through the tear film. The cornea absorbs much of its oxygen from the air through the tear film.
Blood vessels would block a clear optical path. Instead, oxygen from the atmosphere dissolves in the tear film and diffuses into the cornea while the eye is open.
Sources: Cleveland Clinic and National Center for Biotechnology Information.
4 · Core
A bone smaller than a grain of rice transmits vibrations. Where in the body is it?
- A fingertip
- The bridge of the nose
- The voice box
- The middle ear
Show the answer, explanation, and sources
Answer: The middle ear. The stapes in the middle ear is the body's smallest bone.
The middle ear contains three small ossicles: the malleus, incus, and stapes. The stapes is the smallest and passes vibrations toward the inner ear.
Sources: Cleveland Clinic and National Center for Biotechnology Information.
5 · Core
When goosebumps rise, what is physically pulling each hair follicle upright?
- A tiny muscle attached to the follicle
- A swelling capillary under the skin
- A sweat gland filling with fluid
- A contracting pocket of body fat
Show the answer, explanation, and sources
Answer: A tiny muscle attached to the follicle. Arrector pili muscles contract to produce goosebumps.
Cold or strong emotion triggers arrector pili muscles attached to hair follicles. Their contraction raises the hair and puckers the surrounding skin.
Sources: National Institutes of Health and Cleveland Clinic.
6 · Core
After surgeons remove a large part of a healthy liver, what can the tissue left behind do?
- Turn nearby spleen tissue into liver
- Grow toward the organ's original size
- Split into a second smaller liver
- Stop working until a transplant arrives
Show the answer, explanation, and sources
Answer: Grow toward the organ's original size. The remaining liver tissue can restore much of the organ's mass and function.
Mature liver cells re-enter the cell cycle and multiply after tissue loss. The organ restores its mass and function, though not necessarily its exact original shape.
Sources: National Institutes of Health and Johns Hopkins Medicine.
7 · Core
As old taste receptor cells wear out, what keeps each taste bud working?
- Nearby nerve endings become new taste cells
- Surviving cells repair every worn receptor
- New receptor cells continually replace them
- Each bud switches to backup smell receptors
Show the answer, explanation, and sources
Answer: New receptor cells continually replace them. Taste buds replace many receptor cells approximately every ten days.
Taste buds continuously recruit new receptor cells as older ones die. Lifespans vary by cell type, with approximately ten days as a commonly cited average.
Sources: Cleveland Clinic and University of Texas Medical School at Houston.
8 · Core
How many bones does one typical adult foot contain?
- Eight
- Fourteen
- Twenty
- Twenty-six
Show the answer, explanation, and sources
Answer: Twenty-six. A typical adult foot contains 26 bones.
Each foot has 26 bones arranged into the toes, midfoot, and hindfoot. Together, both feet account for 52 of the adult skeleton's usual 206 bones.
Sources: MedlinePlus and Cleveland Clinic.
9 · Challenge
One nostril often feels clearer, then the other does hours later. What usually drives this nasal cycle?
- Alternating swelling of tissue inside the nose
- Breathing muscles switching sides in the chest
- A mucus valve opening and closing each passage
- Blood flow cooling one nostril at a time
Show the answer, explanation, and sources
Answer: Alternating swelling of tissue inside the nose. Autonomic changes in nasal tissue produce the nasal cycle.
Autonomic nerves cause spongy tissue on one side to swell while the other side opens, then reverse the pattern. The cycle is often more noticeable during congestion.
Sources: Cleveland Clinic and Journal of Clinical Sleep Medicine.
10 · Challenge
At high altitude, which organs sense low oxygen and release erythropoietin to boost red-cell production?
- The spleen
- The kidneys
- The lymph nodes
- The pancreas
Show the answer, explanation, and sources
Answer: The kidneys. The kidneys release erythropoietin when oxygen levels are low.
Kidney cells respond to low oxygen by releasing erythropoietin, or EPO. That hormone tells bone marrow to increase red-cell production.
Sources: MedlinePlus and Frontiers in Physiology.
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