BIOPHOTO ASSOCIATES / SCIENCE PHOTO LIBRARY BIOPHOTO ASSOCIATES / SCIENCE PHOTO LIBRARY
Capillaries in intestinal villi. Light micrograph of a transverse section through villi in the small intestine, showing the blood supply. At bottom are the outer muscle layers in the wall of the small intestine. Villi are finger-like projections on the inner wall, which face the lumen (at top). The villi are adapted for the absorption of digested food. The core of each villus contains blood capillaries (dark), which here have been injected to highlight their structure. Epithelial cells on the surface of each villus absorb food, which is then passed into the bloodstream through this capillary system. The 6 metre long human small intestine contains thousands of villi.
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