380 



DISSECTION OF THE PELVIS. 



and over 

 pyriformis. 



Pelvic fascia 

 divided into 

 three parts, 

 viz. : 



Obturator 

 fascia : 



attach- 

 ments ; 



relations. 



Fascia of 

 pyriformis. 



Recto- 

 vesical 

 fascia later. 



upper end of the thyroid foramen, where it bounds the aperture 

 through which the vessels and nerve issue. A portion of the bone 

 is then to be cut out behind the foramen, and extending into the 

 small sciatic notch, as in the figure ; and the obturator internus 

 muscle is to be carefully separated from the fascia and taken away. 



Lastly, by turning back the pyriformis muscle and the great 

 sciatic nerve, a thin piece of the fascia covering those structures will 

 be exposed in the great sacro- sciatic foramen (fpy}. 



The PELVIC FASCIA is a thin membrane which covers the deep 

 surface of the muscles bounding the cavity, and may be described 

 in three parts. Two of these are parietal and line the wall of the 

 pelvis, one covering the obturator internus muscle is named the 

 obturator fascia, and the other extending over the pyriformis muscle 

 is the fascia of the pyriformis. The third portion of the fascia is 

 reflected inwards from the wall of the pelvis on the upper surface 

 of the levator ani and enters into the formation of the floor of the 

 pelvis, and supports the rectum and bladder, whence it is known 

 as the recto-vesical fascia. 



The obturator fascia (fig. 142) invests closely the pelvic portion 

 of the obturator internus muscle, arid is fixed to the bone around 

 the attachment of the fleshy fibres. Thus, it is attached above to 

 the ilio-pectineal line of the hip-bone between the sacro-iliac articu- 

 lation and the upper end of the obturator foramen ; at the latter spot 

 it joins the obturator membrane over the edge of the muscle, so as 

 to form the floor of the canal transmitting the obturator vessels and 

 nerve ; and in front it is fixed to the body of the pubis, following 

 the border of the muscle. Below, it is inserted into the inner side 

 of the inferior ramus of the pubis. and the ramus and tuberosity of 

 the ischium in conjunction with the falciform process of the great 

 sacro-sciatic ligament. Behind, it is fixed to the hip-bone along 

 the anterior margin of the great sciatic notch ; and between 

 the ischial spine and the tuberosity, it is united with the great 

 sacro-sciatic ligament, where the obturator internus issues from the 

 pelvis. 



From the inner surface of this membrane the recto-vesical fascia 

 is given off, along a curved line extending from the ischial spine to 

 the upper and inner part of the obturator foramen (fig. 142, * *). 

 Above this line the obturator fascia bounds the cavity of the pelvis 

 at the side, and is in contact with the peritoneum ; while below, it 

 looks into the ischio-rectal fossa, except over a small space in 

 front, w r here it is closely united with the pubic origin of the levator 

 ani (I a). 



The fascia of the pyriformis (fpy) is very thin, and is continued 

 backwards from the hinder part of the obturator fascia to the sacrum, 

 passing over the front of the sacral plexus and the pyriformis 

 muscle, but beneath the internal iliac vessels, by whose gluteal, 

 sciatic and pudic branches it is perforated. 



The recto-vesical fascia may now be seen in part by looking into 

 the pelvis ; and the student may notice a whitish line extending 

 from the low r er part of the pubis, close to the symphysis, to the 



