absorption

Meaning of absorption: Absorption is the movement of digested nutrients, or a medication, from the digestive tract or another site into the bloodstream for use by the body.

Definition of absorption

Absorption is the process by which nutrients, fluids, or a medication move from the digestive tract, or from another site such as the skin or muscle, into the bloodstream so they can circulate to the tissues that use them. In digestion, absorption follows the mechanical and chemical breakdown of food and occurs mainly in the small intestine, where the lining is folded into small projections called villi that greatly increase the surface area available for nutrients to cross into the blood and lymphatic vessels.

Absorption is a distinct step from digestion itself, since food can be broken down into smaller components without those components necessarily being absorbed efficiently, a situation seen in certain intestinal diseases.

The term is also used in pharmacology to describe how a drug moves from its site of administration, such as the gut after an oral dose or the skin under a topical patch, into the bloodstream, a process that determines how much of the drug reaches its intended target and how quickly it takes effect.