THE MALE PELVIS 



1383 



cord, penis and urethra, prostate, bladder, ischio-rectal fossa, rectum and anal 

 canal. 



Bony boundaries. — These are the same in either sex. Above and in front is 

 the symphysis pubis, rounded off by the subpubic ligament; diverging downward 

 and laterally from this point on either side are the rami of the pubes and ischia, 

 ending at the tuberosities of the latter. In the middle line behind is the apex of 

 the coccyx, and reaching from this to the tuberosities are the sacro-tuberous (great 

 sacro-sciatic) Hgaments, to be felt by deep pressure, with the lower border of the 

 gluteus maximus overlapping them. 



The depth of the perineum varies greatly— from 5 to 7.5 cm. (2 to 3 in.) in the posterior 

 and lateral part to 2.5 cm. (1 in.) or less in front. In the middle line, extending longitudinally 

 through the perineum, is the raphe, the guide to the urethra, and "the line of safety' (on account 

 of the small size of the vessels here) for operations on it. 



Fig. 111.3. — The M.\le Perineum. (Modified from Hirschfeld and Leveille.) 



Bulbo-cavernosus 



Superficial layer of uro-genital trigone 

 Ischio-cavernosus 



Post. fern, cutaneous nerve 



Perineal nerve 

 Inferior hsemorrhoidal nerve 

 Cutaneous branch of fourth sacral 



Gluteus maximus 

 Tuberosity of ischium 

 Sacro-tuberous ligament 

 Superficial transversus perinei 

 Levator ani 



Sphincter ani eztemus 



Subdivisions. — An imaginary line drawn transversely across the perineum 

 from one tuber ischii to its fellow divides the lozenge-shaped space into two 

 triangles — (1) An anterior, or uro-genital; and 2) a posterior, or rectal. The 

 pelvic floor includes an upper or pelvic diaphragm (formed by the levator ani and 

 coccygeus on each side) and a lower incomplete uro-genital diaphragm (or trigone). 



The pelvic diaphragm (figs. 1113, 1114, 1115; see also figs. 397, 399, 400) 

 is made up of the levator ani coccygeus muscles. It is somewhat funnel- 

 shaped. When viewed from above or below (fig. 395) , its fibres are seen to form 

 horseshoe-like loops, arising on either side anteriorly, and passing posteriorly 

 backward around the uro-genital apertures to be inserted chieflj" in the mid-line 

 posteriorly. The pelvic diaphragm serves primarily for the support of the 

 abdominal viscera. For a detailed description of these muscles, as well as those 

 of the uro-genital diaphragm, see section on the Muscular System. 



