FASCIA OF THE PELVIS. 409 
of urine or semen. In the female it acts as a feeble sphincter of the vagina. The ischio- 
cavernosus and bulbo-cavernosus help in erection of the penis or clitoris. The compressor 
urethre constricts the membranous urethra, and in the female helps to flatten and fix the wall of 
the vagina. It also assists in causing erection of the penis or clitoris by compression of the veins 
in relation to it. 
FASCIA OF THE PELVIS. 
The bony pelvic basin, placed obliquely, deeper and more hollowed behind than 
in front, is to a large extent completed by ligaments (sacro-sciatic ligaments, 
obturator membrane and triangular ligament). It is almost entirely clothed 
internally by muscles: by the pyriformis on each side behind, the obturator internus 
at the side, and the compressor urethre in contact with the triangular ligament 
Corpus spongiosum penis 
| Corpus cavernosum 
Pubo-prostatic ligaments oa : : 
I ; | Superficial fascia of perineum 
Capsule of prostate gland \ ; | COMPRESSOR URETHRA: MUSCLE 
ros c 2 ese ~ Triangular ligament 
Prostate gland Ge LL g g 
Posterior layer of triangular ligament 
7 — Pubie arch 
=e _-— Obturator membrane 
ae OBTURATOR INTERNUS 
Parietal (obturator) layer of 
pelvic fascia 
XS EX = Ischio-rectal fossa 
SOs) ae 
WSs aa Anal fascia 
SS OBTURATOR EXTERNUS 
LEVATOR ANI 
Visceral layer of pelvic fascia 
axa 
az 
mae 
~ Innominate bone (ischium) 
Recto-vesical layer of pelvic 
fascia (enclosing vasa deferentia 
and vesicule seminales) 
Rectal layer of pelvic fascia 
Rectum 
PyYRIFORMIS 
~ Sacrum 
Fic. 303.—DISSECTION OF THE PELVIC FASCIA FROM ABOVE (diagrammatic). 
in front. Indeed, the bones of the pelvis only appear in the cavity in two places ; 
the spine of the ischium projects into the cavity laterally, and the pubis appears 
in its anterior wall. 
The pelvic fascia forms a cylindrical membrane lining the wall of the pelvis, as 
an aponeurosis for its muscles. It is attached above and below to the inlet and 
outlet of the pelvis; above to the promontory of the sacrum, ilio-pectineal line, and 
back of the pubis; below to the coccyx, great sacro-sciatic ligament, tuber ischii, 
and the base of the triangular ligament. This cylindrical membrane is the 
parietal pelvic fascia ; it forms the pyriformis fascia behind, the obturator fascia 
at the side of the pelvis, and the so-called posterior layer of the triangular ligament 
in front. As this fascia traverses the pelvic wall it obtains attachments to the 
back of the pubis anteriorly, and to the spine of the ischium on each side. It is 
deficient in relation to the obturator groove, through which the obturator artery 
and nerve pass to reach the thigh. 
Between the back of the pubis and the spine of the ischium the white line 
extends, a thickened band of the fascia, which roughly indicates the line of 
separation of the pelvic cavity from the ischio-rectal fossa. The white line serves 
two purposes: it gives origin to fibres of the levator ani muscle, and from it a 
secondary sheet of fascia, known as the visceral pelvic fascia, arches downwards and 
inwards across the floor of the pelvis to be connected with the pelvic viscera. This 
membrane is thin and, unimportant behind, as it passes forwards from the lower 
sacral vertebre to the rectum. It is thicker at the sides and front of the pelvis, 
oe 
