THE PELVIS 357 



along the outer surface of the anal canal to blend with its 

 muscular coat between the internal and external sphincters 



(P- 369)- 



A collection of muscular fibres extending antero-posteriorly 



between the pelvic surface of the urogenital diaphragm and 

 the upper end of the anal canal is termed the Recto-urethralis 

 muscle (p. 369). 



In the female the anterior borders of the two leva tores ani 

 pass one on each side of the vagina and act as a sphincter 

 muscle. 



The principal action of the levator ani is to assist defgecation 

 by drawing the anal canal upwards over the fsecal mass, thus 

 assisting in its expulsion. 



Its nerve-supply is derived from the perineal division of the 

 internal pudendal (S. 2, 3, 4) and directly from S. 3 and 4. 



The Coccygeus is a small muscle which overlaps the posterior 

 border of the levator ani. It extends from the ischial spine to 

 the sides of the sacrum and coccyx, and helps to complete the 

 pelvic floor. 



The Visceral Pelvic Fascia forms the upper layer of the 

 pelvic diaphragm and covers the pelvic surfaces of the levatores 

 ani and the coccygei. Opposite the pubic symphysis, where 

 the two levatores leave a gap, the fascia forms a continuous 

 sheet from side to side. It is very weak in the middle line, but 

 is specially thickened at each side, where it extends backwards 

 to the prostate and the bladder, forming the true pub o-pro static 

 ligaments (anterior pedicles of the bladder). Elsewhere, its 

 circumferential attachment corresponds to the linear origin 

 of the muscles of the pelvic diaphragm. 



When it is traced inwards from the sides, it is found to be 

 in contact with the various pelvic viscera, which it provides 

 with fibrous coverings. On account of this relationship the 

 visceral pelvic fascia is described as consisting of rectal, recto- 

 vesical, and vesical portions. 



Anteriorly the visceral pelvic lascia is specially thickened to 

 form a strong fibrous sheath for the prostate gland. 



The Pelvic Peritoneum is separated from the pelvic dia- 

 phragm by the pelvic viscera and blood-vessels. It covers the 

 front and sides of the upper two-thirds of the rectum (p. 368) 

 and is then reflected forwards on to the upper part of the 

 posterior surface of the urinary bladder, forming the floor of 

 the recto-vesical fossa. It covers the superior surface of the 



