MUCOUS MEMBRANE and MUCUS. The mucous membrane is continuous with the skin at all the orifices of the body, and lines the passages by which the internal organs eonininni cate with the outer world. For convc•nceme of description it may be divided into three great tracts—the alimentary mucous membrane, the respiratory mucous membrane. and the genito urinary mucous membrane.
The sliced matte aiacons membrane commences at the lips, and not only forms the inner lining of the intestinal rdual f11)111 the 11111111h to bill gird's; prolongations which after lining the ducts of the various glands (the salivary gloffils. the liver, and the whose products are discharged into this canal. penet To I e innermost recesses of these glands, and constitute• their true seereting ele ment. Besides larger offsets. we lind in the stomach and small intestine an infinite series of minute tubular rirohnigations, the anatomical and function of which are deseribed in article 1)1CFSTION, URlANS OF, The r•rspirrrlorlr unn•uax begins at the nostrils• and under Ilie of Sehnriderian or rituitury membraoc (see NOSE) lines the nasal cavities, from whence it sends on either side an upward prolongation through the lach rymal duct to form the ronjunetira of the eye; backward, through the posterior nares (the coin munication between the nose and the throat), it sends a prolongation through the Eustachian tube to the middle ear (the cavity of the tym panum), and is continuous with the pharyngeal mucous membrane (which is a portion of the alimentary it then, instead of passing down the (esophagus, enters and forms a lining to the larynx, trachea, and bronchial tubes to their terminations. From the continuity of these
two tracts some writers describe them as a single one• under the name of the gastro-pulmonary tract.
The yenito-urinary twat's mciabranr nem•es at the genitourinary orifiees, lines tile excretory passages front the generative and uri nary organs. and is the essential constituent of the glands of both. In the female it becomes continuous with the serous membranee of the ab domen at the timbrbe of the Fallopian tubes. Sec