ANATOMY&PHYSIOLOGY FOR NURSES

THE BODY FLUIDS A about  70 per cent of the body is water in which are dissolved salts and other substances. This watery solution or fluid is partly inside the cells and partly outside, Two- thirds of the fluid is inside the cells, intra - cellular fluid, and is rich in protein and certain salts such as potassium. One- third of the fluid is in the spaces between the cells, the intersitial fluid, but about a quarter of it is in the blood vessels as the blood plasma. THE TISSUE CELL The cell is the smallest unit of living matter in the body capable of leading an independent existence. It is composed of a complex material called protoplasm, which contains water, inorganic salts and important organic substances-proteins, fats, carbohydrates and vitamins. Cells select from the interstitial fluid which surrounds them chemical substances such as amino-acids which the cell builds up into the very complicated substances, e.g proteins, which make up protoplasm. Thus a cell is a very active unit in which the nourishing food materials  eaten  by man are absorbed and assimilated. These materials may be used by the cell to synthesize new protoplasm, in which case the cell increase in size, that is, it grows.  The materials may also be used to replace worn- out parts of the cell. These constructive activities, growth and cell repair, are spoken of as the anabolic functions of the cell, or anabolism.                                                                                                            ..........