140 HUMAN EMBRYOLOGY AND MORPHOLOGY. 



They can only be artificially separated from each other. It is 

 more accurate and easier to describe fasciae, then, not as separate 

 structures, but as adjuncts of the structures which they surround 

 or ensheath. 



The Pelvic Fascia, which strengthens the pelvic floor, is com- 

 posed of the sheaths of four muscles : 



(1) The Levator Ani; 



(2) The Obturator Internus ; 



(3) The Pyriformis ; 



(4) The Constrictor Urethrae and deep Transversus Perinei. 

 The fibrous capsules of the following viscera also form part 



of it: 



(1) Prostate and Vesiculae Seminales in the male ; 



(2) Vagina and Uterus in the Female ; 



(3) The Bladder ; 



(4) The Eectum. Under the title of pelvic fascia these eight 

 elements are combined. 



I. The Obturator Fascia is the sheath on the inner or pelvic 

 aspect of the obturator interims ; the sheath on the outer side of 

 the muscle is formed by the periosteum and obturator membrane. 

 The obturator fascia is attached at the circumference of the 

 muscle. There it becomes continuous with the periosteum of the 

 os innominatum. The part above the white line (supra-linear) is 

 intra-pelvic ; the part below (infra-linear) is perineal and situated 

 on the outer wall of the ischio-rectal fossa. 



II. The Recto-vesical and Anal Fasciae. — The levatores ani form 

 a muscular floor for the pelvis, stretching from the white line of 

 one side to the white line of the other. The sheath on their under 

 surface — on the inner wall of the ischio-rectal fossa — forms the 

 anal fascia. On the upper surface, their sheath forms the greater 

 part of the recto-vesical fascia. The pelvic viscera rest on the 

 upper surface of the levatores ani and the capsules of the viscera 

 are continuous with the sheath on the upper surface of the 

 muscles. The combined visceral capsules and upper sheath of 

 the levatores ani form the recto-vesical fascia. 



III. The Triangular Ligament is the sheath of the constrictor 

 urethrae muscle (Fig. 112). The inferior transverse fibres of the 

 constrictor form really a separate muscle — the deep transverse 

 perineal. The apex of the prostate rests on the muscle, its 



