Origin of Nutrients in Extracellular Fluid (ECF)
Extracellular fluid (ECF) usually denotes all body fluid outside the cells.
It provides oxygen to the body and removes carbon dioxide. When each time the blood passes through the body, it also ﬂows through the lungs. The blood picks up oxygen in the alveoli, thus acquiring the oxygen needed by the cells.
It digests food and absorbs different nutrients including CHO, fatty acids, and amino adds, into the ECF. A large portion of the blood pumped by the heart also passes through the walls of the gastrointestinal tract
The liver changes the chemical composition of many of the absorbed substances to more usable forms, and other tissues of the body (e.g. fat cells, kidney, and endocrine glands) help to modify the absorbed substances or store them until they are needed. The liver changes the chemical compositions of many of these substances to more functional forms, and other tissues of the body—fat cells, kidneys etc to help adapt the absorbed substances or store them until they are needed.
This system helps the body to move to the appropriate place to obtain the food required for nutrition. It also provides motility for defense against unfavorable surroundings, without which the whole body, along with its homeostasis mechanisms, could be damaged immediately.