The process by which fluids or other substances are taken up by body tissues. The term is commonly applied to the uptake of the nutrients from food into blood and lymph from the digestive tract. The major site of absorption is the small intestine, which is lined with microscopic finger-like projections called villi (see villus). The villi greatly increase the surface area of the intestine, thereby increasing the rate of absorption.
Uptake by the body tissues of ?uids or other substances. For example, food is absorbed from the digestive tract into the blood and lymph systems. Food is absorbed mainly in the small INTESTINE (jejunum and ileum), which is lined by multiple villi that increase its surface area. (See also DIGESTION; ASSIMILATION.)
n. (in physiology) the uptake of fluids or other substances by the tissues of the body. Digested food is absorbed into the blood and lymph from the alimentary canal. Most absorption of food occurs in the small intestine – in the jejunum and ileum – although alcohol is readily absorbed from the stomach. The small intestine is lined with minute finger-like processes (see villus), which greatly increase its surface area and therefore the speed at which absorption can take place. See also assimilation; digestion.
Drugs are usually administered distant to their site of action in the body; they must then pass across cell membranes to reach their site of action. For example, drugs given by mouth must pass across the gut membrane to enter the bloodstream and then pass through the endothelium of vessel walls to reach the site of action in the tissues. This process is called absorption and may depend on lipid di?usion, aqueous di?usion, active transport, or pinocytosis – a process in which a cell takes in small droplets of ?uid by cytoplasmic engulfment.... drug absorption
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