The Absorption Process

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Absorption is the process by which the provisions of digestion are transported into the body’s internal environment, enabling the nutrients to reach the body’s cells. Most absorption takes place in the small intestine, which is composed of three segments: the duodenum, the jejunum, and the ileum. Together, the small intestine accounts for almost ten feet of coiled tube that lies in a human’s lower abdomen.
The lining of the small intestine has hundreds of folds which are covered with villi. Villi are finger-like projections made up of hundreds of cells that increase the small intestines surface area available for absorption of food. Each villus is enveloped with microscopic hairs called microvilli. “Microvilli on the cells of villi provide the absorptive surfaces that allow the nutrients to pass through the body.” (Whitney & Rolfes, 2002, p.75) Between the folds of the villi lie glands called crypts. Crypts secrete intestinal juices into the small intestine which help break down the chyme (a semiliquid mass that food develops into as it is being ground in the stomach) not only physically, but chemically. Nutrients from the chyme are caught among the microvilli which in turn draws the nutrients into the cells of the villi. “The cells of the villi are among the most amazing in the body, for they recognize and select the nutrients the body needs and regulate their absorption.” (Whitney & Rolfes, 2002, p.74) Once a nutrient particle has passed the villi cells, it goes into the body’s vascular system or the lymphatic system. The human body’s vascular system is a closed blood circulatory configuration that efficiently carries nutrients (as well as other things such as hormones, metabolites, and gases) to and from distant actively metabolizing tissues. The blood vascular system consists of arteries, capillaries, and veins. In addition to the blood vascular system, the human body contains a network of thin wal...