658 



ORGANS OF DIGESTION. 



The circular fibres are continuous above with the Inferior constrictor: their 

 direction is transverse at the upper and lower parts of the tube, but oblique in 

 the central part. 



The muscular fibres in the upper part of the oesophagus are of a red color, 

 and consist chiefly of the striped variety ; but below, they consist entirely of the 

 involuntary muscular fibre. 



The cellular coat connects loosely the mucous and muscular coats. 



The mucous coat is thick, of a reddish color above, and pale below. It is 

 loosely connected with the muscular coat, and disposed in longitudinal plicos, 

 which disappear on distension of the tube. Its surface is studded with minute 

 papillae, and it is covered throughout with a thick layer of squamous epithelium. 



The cesophageal glands are numerous small compound glands, scattered through- 

 out the tube ; they are lodged in the submucous tissue, and open upon the surface 

 by a long excretory duct. They are most numerous at the lower part of the tube, 

 where they form a ring round the cardiac orifice. 



THE ABDOMEN. 



The Abdomen is the largest cavity of the trunk of the body, and is separated, 

 below, from the pelvic cavity by the brim of the pelvis. It is of an oval form, the 

 extremities of the oval being directed upwards and downwards ; it is wider above 

 than below, and measures more in the vertical than in the transverse diameter. 



Fig. 331. The Regions of the Abdomen and their Contents. 

 (Edge of Costal Cartilages in dotted outline.) 



Boundaries. It is bounded, in front and at the sides, by the lower ribs, the 

 Transversales muscles, and venter ilii ; behind, by the vertebral column, and the 

 Psose and Quadrati lurnborum muscles ; above, by the Diaphragm ; below, by the 



