Surgical Anatomy of the Perineum and Ischio- 



Rectal Region. 



Dissection. The student should select a well-developed muscular subject, free from fat, and 

 the dissection should be commenced early, in order that the parts may be examined in as recent 

 a state as possible. A staff having been introduced into the bladder, and the subject placed in 

 the position shown in Fig. 455, the scrotum should be raised upwards, and retained in that posi- 

 tion, and the rectum moderately distended with tow. 



The space which is now exposed, corresponds to the inferior aperture, or 

 outlet of the pelvis. Its deep boundaries are, in front, the pubic arch -and sub- 

 pubic ligament ; behind, the tip of the coccyx ; and on each side, the ramus of 

 the pubes and ischium, the tuberosity of the ischium, and great sacro-sciatic 

 ligament. The space included by these boundaries is somewhat lozenge-shaped, 

 and is limited on the surface of the body by the scrotum, in front, by the but- 

 tocks behind, and on each side by the inner side of the thighs. It measures, 

 from before backwards, about four inches, and about three in the broadest part 

 of its transverse diameter, between the ischial tuberosities. A line drawn trans- 

 versely between the anterior part of the tuberosity of the ischium, on each side, 

 in front of the anus, subdivides this space into two portions. The anterior 

 portion contains the penis and urethra, and is called the perineum. The poste- 

 rior portion contains the termination of the rectum, and is called the ischio-rectal 

 region. 



ISCHIO-RECTAL EEGION. 



The Ischio-rectal Eegion corresponds to the portion of the outlet of the 

 pelvis situated immediately behind the perineum : it contains the termination 

 of the rectum. A deep fossa, filled with fat, is seen on either side of the intes- 

 tine, between it and the tuberosity of the ischium : this is called the ischio-rectal 

 fossa. 



The ischio-rectal region presents, in the middle line, the aperture of the anus ; 

 around this orifice, the integument is thrown into numerous folds, which are 

 obliterated on distension of the intestine. The integument is of a dark color, 

 continuous with the mucous membrane of the rectum, and provided with nume- 

 rous follicles, which occasionally inflame and suppurate, and may be mistaken 

 for fistulse. The veins around the margin of the anus are occasionally much 

 dilated, forming a number of hard, pendent masses, of a dark bluish color, 

 covered partly by mucous membrane, and partly by the integument. These 

 tumors constitute the disease called external piles. 



Dissection. Make an incision through the integument, along the median line, from the base 

 of the scrotum to the anterior extremity of the anus ; carry it round the margins of this aper- 

 ture to its posterior extremity, and continue it backwards about an inch behind the tip of the 

 coccyx. A transverse incision should now be carried across the base of the scrotum, joining 

 the anterior extremity of the preceding ; a second, carried in the same direction, should be made 

 in front of the anus ; and a third at the posterior extremity of the gut. These incisions should 

 be sufficiently extensive to enable the dissector to raise the integument from the inner side of 

 the thighs. The flaps of skin corresponding to the Ischio-rectal region (Fig. 455, 2), should 

 now be removed. In dissecting the integument from this region, great care is required, other- 

 wise the External Sphincter will be removed, as it is intimately adherent to the skin. 



The superficial fascia is exposed on the removal of the skin : it is very thick, 

 areolar in texture, and contains much fat in its meshes. In it are found rami- 

 fying two or three cutaneous branches of the small sciatic nerve; these turn 



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