ANATOMY&PHYSIOLOGY FOR NURSES

MEMBRANES.  Layers of specialized cells which line the cavities of the body are described as membrane.  The three principal membranes are; Mucous membrane Synovial membrane Serous membrane All these membranes secrete a fluid to lubricate or moisten the cavity they line. Mucous Membranes is found lining the alimentary tract, the respiratory tract, and parts of the genito-urinary tract. It varies in character in the different areas. In the digestive tract it consists of columnar epithelial cells closely packed together. Some of them  become distended with mucous secretion and are then called goblet cells. The cell becomes more and more distended and finally ruptures and discharges its secretion on to the surface. Mucus is  the secretion of the membrane and consists of water,salts, and a protein, mucin, which gives the sticky or viscid character to the secretion. Synovial Membrane lines the cavities of joints. It consists of fine connective tissue, with a layer of squamous endothelial cells on the surface. The secretion of synovial membrane is thick and glairy in character. Serous Membranes are found in the chest and abdomen, covering the organs contained therein and lining these cavities. The pleura covers the lungs and lines the thorax The pericardium covers the heart as a double layer. The peritoneum covers the abdominal organs and lines the abdomen. ( These membranes are described in the chapters dealing with these various organs.)        The characteristics which are common to all three serous membranes are, that each consists of a double layer of membrane having an intervening potential cavity which receives the fluid secreted by the membrane. This serous fluid is very similar to blood serum or lymph.  It acts as a lubricant, and in addition it contains protective substances, and removes harmful products, passing these on to the lymphatic system to be dealt with.