134 THE MUCOUS MEMBRANE. 



THE MUCOUS MEMBRANE. 



This constitutes the second division of the Cutaneous Sys- 

 tem. It lines the whole interior of the surface of the body, 

 having communication with the exterior world. It is 

 consequently coextensive with the digestive, pulmonary, 

 urinary, and genital organs. It is continuous, as before 

 stated, with the skin. Its color varies from a pale rose to 

 a beautiful red. Its density also varies, being thinner in the 

 urethra and genital organs than in the intestines. Its 

 tenacity is so slight, it tears easily in the attempt to raise it. 



Like the skin, it has two surfaces, the one free, the other 

 adherent. The free surface presents valvulee, folds and 

 wrinkles, cavities or depressions, and papillary and villous 

 projections. The adhering surface is covered by a fibro 

 cellular tissue, which gives the mucous membrane its 

 solidity. It has two principal divisions. 



1st. The gastro-pulmonary. 



2d. The genito urinary. 



The first division lines the mouth, where it is continuous 

 with the skin of the lips, and successively the pharynx, 

 oesophagus, stomach, and intestines, to the anus, where it 

 again runs into the skin. In this route it sends off numer- 

 ous prolongations to all the excretory ducts of the glands, 

 communicating with the alimentary canal, as the salivary 

 glands, tonsils, liver and pancreas. It extends to the nose 

 under the name of pituitary membrane, lining it and the 

 different sinuses. Through the nasal and lachrymal duct it 

 reaches the eye, covering the interior of the eyelids, and the 

 globe of the eye. From the back part of the mouth we follow 

 it in one direction through the Eustachian tube, into the 

 cavity of the tympanum, and the mastoid cells, by another 

 route we trace it into the larynx trachea, bronchi, and all 

 .their ramifications in the lungs. 



The 2d division or genito urinary, beginning at the glans 

 penis, is found lining the urethra, bladder, ureters, infundi- 

 bulum, and even calyces of kidneys, while in the female it 

 also covers the labia, clitoris, and vagina. 



