1309 



vertebrae; the other to the left, opposite the sacrococcygeal articulation. They 

 are, however, of little importance. 



The adult rectum measures about five inches (12.5 cm.) in length, and at its 

 commencement its calibre is similar to that of the sigmoid flexure, but near its 

 termination it is dilated to form the rectal ampulla. The rectum has no saccu- 

 lations comparable to those of the colon, but a sacculated condition, due to the 

 presence in its interior of valves (shortly to be described), is sometimes seen. 



The peritoneum is related to the upper two-thirds of the rectum, covering at 

 first its front and sides, but lower down its front only; from the latter it is reflected 

 on to the seminal vesicles in the male and the posterior vaginal wall in the female. 



The level at which the peritoneum leaves the anterior wall of the rectum to be 

 reflected on to the viscus in front of it is of considerable importance from a surgical 

 point of view, in connection with removal of the lower part of the rectum. It is 

 higher in the male than in the female. In 

 the former the height of the rectovesical 

 pouch is about three inches (7.5 cm.); that is 

 to say, the height to which an ordinary index 

 finger can reach from the anus. In the 

 female the height of the rectovaginal pouch 

 is about two and a quarter inches (5.2 

 cm.) from the anal orifice. The rectum 

 is surrounded by a dense tube of fascia de- 

 rived from the fascia eiidopelvina, but fused 

 behind with the fascia covering the sacrum 

 and coccyx. The fascial tube is loosely 

 attached to the rectal wall by areolar tissue 

 in order to allow the viscus to distend. 



FIG. 1051. Diagram of rectum, showing Hous- 

 ton's valves in the interior. (Cunningham.) 



Relations of the Rectum. The upper part 

 of the rectum is in relation, behind, with the 

 superior hemorrhoidal vessels, the left Pyriformis 

 muscle, and left sacral plexus of nerves, which 



separate it from the anterior surfaces of the sacral vertebrae; in its lower part it lies directly 

 on the sacrum, coccyx, and Levatores ani, a dense fascia alone intervening; in front, it is sep- 

 arated above, in the male, from the posterior surface of the bladder; in the female, from the 

 posterior surface of the uterus and its appendages by some convolutions of the small intestine 

 (Fig. 1050). To the sides below the peritoneal reflections, the rectum is surrounded by cellular 

 tissue in which on each side lie the lateral sacral artery and the bifurcated hypogastric plexus. 



RECTAL VALVFS 



A R 



FIG. 1052. The anal canal and lower part of the rectum in the fetus. A. Aged four to five months. B. Six 

 months. C. Nine months. In each the anal canal is distinctly marked off from the rectum proper; the columns 

 of Morgagni and the rectal valves are distinct. (Cunningham.) 



This portion of the rectum is separated from the sacrum and coccyx by an interval, the retro- 

 rectal space, which is filled with cellular tissue. The lower or prostatic portion in the male is 

 in relation anteriorly with the triangular portion of the base of the bladder, the seminal vesicles, 

 vasa deferentia, and, more anteriorly, with the prostate gland; in the female, with the posterior 

 wall of the vagina. 



