666 



ORGANS OF DIGESTION 



The circular fibres form a -uniform layer over the whole extent of the stomach, 

 beneath the longitudinal fibres. At the pylorus, they are most abundant, and 

 are aggregated into a circular ring, which projects into the cavity, and forms, with 

 the fold of mucous membrane covering its surface, the pyloric valve. 



The oblique fibres are limited chiefly to the cardiac end of the stomach, where 

 they are disposed as a thick uniform layer covering both surfaces, some passing 

 obliquely from left to right, others from right to left, round the cardiac orifice. 



The cellular coat consists of a loose, filamentous, areolar tissue, connecting the 

 mucous and muscular layers. It is sometimes called the submucous coat. It 

 supports the bloodvessels previous to their distribution to the mucous membrane ; 

 hence it is sometimes called the vascular coat. 



The mucous membrane of the stomach is thick ; its surface smooth, soft, and 

 velvety. During infancy, and immediately after death, it is of a pinkish tinge : 

 but in adult life, and in old age, it becomes of a pale straw or ash-gray color. 

 It is thin at the cardiac extremity, but thicker towards the pylorus. During the 

 contracted state of the organ, it is thrown into numerous plaits or rugae, which, for 

 the most part, have a longitudinal direction, and are most marked towards the lesser 

 end of the stomach, and along the greater curvature. These folds are entirely 

 obliterated when the organ becomes distended. 



Structure of the mucous membrane (fig. 335). When examined with a lens, the 

 inner surface of the mucous membrane presents a peculiar honey-comb appearance, 



Fig. 335. Minute Anatomy of Mucous Membrane of Stomach. 



Slbut/is of Tubu.lt ^ .Orlfie* of Tulf 



from being covered with small shallow depressions or alveoli, of a polygonal or 

 hexagonal form, which vary from l-100th to l-350th of an inch in diameter, and 

 are separated by slightly elevated ridges. In the bottom of the alveoli are seen 

 the orifices of minute tubes, the gastric follicles, which are situated perpendicu- 

 larly side by side, in the entire substance of the mucous membrane. They are 

 short, and simply tubular in character towards the cardiac end ; but at the pyloric 

 end, they are longer, more thickly set, convoluted, and terminate in dilated saccular 

 extremities, or subdivide into from two to six tubular branches. The gastric 

 follicles are composed of a homogeneous basement membrane, lined upon its free 

 surface by a layer of cells, which differ in their character in different parts of the 

 stomach. Towards the pylorus, these tubes are lined throughout with columnar 

 epithelium ; they are termed the mucous glands, and are supposed to secrete the 

 gastric mucus. In other parts of the organ, the deep part of each tube is filled 

 with nuclei, and a mass of granules ; above these is a mass of nucleated cells, the 

 upper fourth of the tube being lined by columnar epithelium. These are called 

 I\\Q peptic glands, the supposed agents in the secretion of the gastric juice. 



Simple follicles are found in greater or less number over the entire surface of 

 the mucous membrane ; they are most numerous near the pyloric end of the 

 stomach, and especially distinct in early life. The epithelium lining the mucous 

 membrane of the stomach and its alveoli is of the columnar variety. 



