Which part of the body takes most of its oxygen directly from the surrounding air instead of from the blood?
- The eardrum
- The retina
- The cornea
- The taste buds on the tongue
Why C? And why not the others?
Correct answer: C. The cornea
The cornea, the eye's clear front window, has no blood vessels at all, because vessels would scatter light and blur your vision. Instead, when your eyes are open, oxygen from the atmosphere dissolves into the tear film and diffuses straight into the corneal tissue; when your eyelids close, nearby conjunctival vessels take over the supply. The eardrum is a tempting pick since it also sits exposed to air, but it carries its own blood supply. The retina is the opposite of the right idea, being one of the most blood-hungry, oxygen-demanding tissues in the body, and taste buds are bathed in saliva yet fully fed by blood vessels beneath them.
Source: NIH StatPearls: Biochemistry, Tear Film