--6533--

Blood-Free Tissue
The only living tissue in the human body that contains no blood vessels is the transparent cornea of the eye. It's the firm, smooth outer shell that arcs across in front of the iris and pupil.
The cornea contains no blood vessels because it must be perfectly clear. Even one tiny capillary would cast the shadow of hundreds of streaming blood cells into the light coming through the pupil.
Without blood to provide oxygen and nutrients, the cornea must get them from somewhere else. Nutrients come from the tears and from the liquid (aqueous humor) that fills the chamber behind the cornea. Oxygen is no problem, since the cornea is in direct contact with the air.

__________________
-Toast-
"It takes a lot of brains to enjoy satire, humor and wit - but none to be offended by them." -- Johnny Hart ("BC", cartoonist, 2000)
"Analyzing humor is like dissecting a frog: Nobody really enjoys it and the frog generally dies as a result." -- E. B. White