GENERAL HISTOLOGY: STRUCTURE OF ORGANS 35 



c) The circular muscle layer consists of smooth muscle cells running parallel 

 to the plane of section. The boundaries of the individual muscle cells are not 

 clear, but the whole layer appears to be made up of parallel fibrillar stria tions. 

 The conspicuous nuclei are long and spindle-shaped. 



d) The longitudinal muscle layer contains a considerable quantity of white 

 fibrous connective tissue which stains blue, in which are imbedded smooth 

 muscle cells running at right angles to the plane of section, and thus appearing 

 as circles. Understand why the nuclei may or may not appear in the circular 

 cross-section. Numerous blood vessels are present in this layer. 



e) The serous coat is a very thin membrane looking like a line closely applied 

 to the outer surface of the preceding coat. At intervals its flattened nuclei are 

 seen. As already explained the serous coat is the visceral peritoneum. 



Draw a small portion of the intestinal wall showing the appearance and cell 

 structure of the fiber layers accurately and in detail. The drawing should be 

 four or five inches in width. 



C. STRUCTURE OF THE STOMACH 



Examine slide "Frog stomach" (see Holmes, p. 140). Observe that the 

 general appearance and arrangement of layers of the stomach wall are the same 

 as in the case of the small intestine, except that the coats are thicker, especially 

 the mucous and muscular coats. The particular point of interest about the 

 stomach wall is the formation of glands in the mucosa. 



i. The gastric glands. -The mucosa of the stomach is thrown up into regu- 

 lar folds or rugae, which appear as conical elevations in section. The lining 

 epithelium does not form an even layer over these folds but is itself folded in and 

 out in such a way as to produce a large number of long tubular glands set closely 

 together with their long axes parallel. It may be noted in passing that all 

 glands are produced by such infoldings of epithelia. Narrow strands of the 

 tunica propria separate the glands from each other. Find a place on the slide 

 where the glands are cut parallel to their long axes and examine one of the gastric 

 glands in detail with the high power. (Their appearance is somewhat different 

 in different regions of the stomach. Consult Holmes, p. 140.) The parts of 

 a gastric gland are mouth, neck, and body or fundus. The mouth is the longest 

 part and contains a narrow canal leading from the interior of the gland into the 

 cavity of the stomach. The cells near the beginning of the mouth are very elon- 

 gated, with clear free ends, probably containing mucus, and slender-tailed nuclei. 

 Farther down the mouth, the cells and nuclei become more rounded. The region 

 where the mouth ceases is the neck and consists of a few cells which contain 

 large clear spaces. The gland may branch in the neck region so that two or 

 more bodies are attached to one mouth. Below the neck the body or fundus is 

 composed of polygonal granular cells, whose function is to secrete the gastric juice. 



Draw a gastric gland in detail. 



