418 



DISSECTION OF THE PELVIS. 



Mucous 



thfckand 

 vascular; 



folds in it. 



" Rectal 



bands are shorter than the other strata of the wall, and thus give 

 and circular rise to the sacculations. The circular fibres describe arches around 

 the intestine, and become thicker and stronger towards the anus, 

 where they are collected along the anal canal into the band of the 

 internal sphincter muscle (p. 240). 



The mucous coat is more moveable than in the colon, and resembles 

 * n tn * s res P ect tne lining f tne oesophagus ; it is also thicker and 

 more vascular than in the rest of the large intestine. 



When the bowel is contracted the mucous lining is thrown into 

 numerous accidental folds, for the most part transverse or oblique ; 

 but in the anal canal they are longitudinal, enclosing submucous 

 Permanent muscular fibres, and form the columns of Morgagni. There are also 

 permanent transverse folds of the intestinal wall (Rectal valves) 

 corresponding to the depressions between the sacculi externally. The 

 largest and most regular of these are in the lower portion of the gut, 

 one being on the right side and front about three inches from the 

 anus, and corresponding approximately to the spot where the recto- 

 vesical pouch of peritoneum ends, another on the left side about 

 one inch higher, and a third, which is less constant, on the left side 

 posteriorly, below the first. These folds will be seen by laying 

 open the gut along the front, provided it is tolerably fresh. 



The mucous membrane has the same general structure as in the 

 colon, but towards the anus the secretory apparatus disappears. 



Slood-vessels. The arteries are supplied from three different 

 sources, viz., superior haemorrhoidal of the inferior mesenteric, 

 middle haemorrhoidal of the internal iliac, and inferior htemorrhoidal 

 of the internal pudic. All three sets anastomose on the lower end 

 of the gut; but only the upper haemorrhoidal, which is the largest, 

 arrangement requires notice here. The final branches of this artery, about six in 

 hLmor- ri r number, pierce the muscular layer three inches from the anus, and 

 rhoidai. descend between the mucous and muscular coats as far as the 

 internal sphincter, where they unite in loops just within the anus. 



The veins have no valves, and communicate freely in a large 

 plexus (hoernorrhoidal) between the muscular and mucous coats, 

 round the lower end of the gut. Above they join the inferior 

 mesenteric vein, and through it reach the vena portaa ; and below 

 they pour some blood into the internal iliac vein by the middle and 

 inferior hsemorrhoidal branches. 



Nerves and lymphatics. The nerves of the intestine are obtained 

 from the sympathetic ; but those of the external sphincter come 

 Lymphatics, from the spinal nerves. The lymphatics terminate in the chain of 

 glands on the sacrum. 



structure of 



Arteries 



Veins are 

 vaives Ut 



Nerves. 



SECTION III. 



ANATOMY OF THE FEMALE PELVIC VISCERA. 



To remove Dissection. In the case of the female pelvis, the bladder, urethra, 

 era ' the genital organs and the rectum are to be removed together for 



