The Pelvis 



the side of the rectum, and, enclosing it, passes over the front of the 

 pyriformis and sacrum. Thus the pelvis is completely shut off from 

 the ischio-rectal fossae by the fascia passing on to the sides of the 

 rectum and bladder ; this sheet is the recto-vesical fascia. 



At the level of the upper border of the levator ani the pelvic fascia 

 gives off two sheets, one of which is thin (anal fascia) and passes on 

 the under surface of the muscle to the lower end of the rectum, whilst 

 the other descends along the outer wall of the ischio-rectal fossa (obtu- 

 rator fascia] to cover the obturator internus, to be attached to the bony 

 and ligamentous margin of the pelvic outlet, and to join the posterior 

 layer of the triangular ligament. (The wood-cut is from Gray.) 



THE PLANES OF THE PELVIS 



Obstetricians have divided the true pelvis into three planes, and 

 have given each plane three diameters antero-posterior or conjugate, 



transverse, and obliqtie. 



In the superior plane the 

 brim of the true pelvis the 

 conjugate diameter extends 

 between the sacro-vertebral 

 angle and the crest of the 

 pubes ; it, ab, is the shortest 

 diameter, 4 in., the transverse 

 diameter, tr, beingihe greatest, 

 Sin. 



In the middle plane the 

 pelvic cavity the oblique dia- 

 meter, ob, is the longest, 5 in. ; 

 it extends from the middle of 

 the sacro-sciatic foramen to 

 the obturator membrane. The 

 antero-posterior diameter, be- 

 tween the middle of the sacrum 

 and the symphysis, is 4^ in., 

 the distance between the ischial 

 tuberosities being 4-,' in. 



In the inferior plane out- 

 let the diameter between the 



tip of the movable coccyx and the pubic arch, cf, is 5 in. ; and, whilst the 

 diameter extending obliquely from sciatic ligament to ischial ramus 

 measures about 5 in., the interval between the tuberosities is but 4 in. 



ab> superior, and c/ : inferior plane; ed&nA kg, 

 axes of inlet and outlet. 



Superior plane 

 Middle plane 

 Inferior plane 



Transverse 



. 5 in. 



4*,, 



4 



OMique 



4:,' i". 

 5 

 5 



Antero-posterior 



4 in. 



