FRANCIS LEROY, BIOCOSMOS / SCIENCE PHOTO LIBRARY FRANCIS LEROY, BIOCOSMOS / SCIENCE PHOTO LIBRARY
Small intestine. Artwork of a section through the duodenum, part of the small intestine. The small intestine is where digestion begins and nutrients are absorbed into the blood. The lumen (white, centre) is lined with villi, the folds in the intestinal surface that greatly increase the surface area for absorption. The smooth muscle layer beneath the villi (orange) is used to mix the food as it passes through the lumen. Surrounding this is circular (white lines) and longitudinal (white dots) muscle tissue, the peristaltic action of which pushes food along the intestine.
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