174 ABDOMEN 



M. Transversus Perinei Profundus et M. Sphincter 

 Urethrae Membranaceae (O.T. Compressor Urethras Muscle). 

 The deep transverse muscle of the perineum is a small 

 fan -shaped muscle which lies between the fasciae of 

 the urogenital diaphragm. It has a tendinous origin 

 from the margin of the pubic arch at the junction of the 

 pubic and ischial rami. Expanding as it passes medially, 

 it unites with its fellow of the opposite side in a median 

 raphe, below and behind the membranous par.t of the urethra. 

 Its posterior border lies in the angle between the inferior 

 and superior fasciae of the urogenital diaphragm, and its 

 anterior border is blended with the external layer of the 

 sphincter muscle of the membranous urethra. The sphincter 

 of the membranous urethra consists of internal and external 

 groups of fibres. The internal group is formed of circular 

 fibres which embrace the urethra ; they are continuous above 

 with the muscular fibres of the. prostate and below with the 

 circular muscular fibres around the posterior part of the 

 cavernous portion of the urethra. The external layer consists 

 of transverse fibres which arise, together with the deep trans- 

 verse muscle of the perineum, from the margin of the pubic 

 arch and from the inferior fascia of the urogenital diaphragm. 

 As they approach the median plane some of the fibres pass 

 anterior and some posterior to the membranous part of the 

 urethra, and they blend with the corresponding fibres of the 

 opposite side. Both muscles are supplied by one or two 

 delicate twigs from the perineal division of the pudendal nerve. 



Dissection. Clean the internal pudendal artery, following it 

 forwards, from the point where it enters the postero-lateral angle 

 of the deep pouch (Fig. 83) to its terminal division into the 

 dorsal and profunda arteries of the penis. At the same time 

 clean the dorsal nerve of the penis which lies lateral to the 

 internal pudendal artery. Next secure the branch from the 

 internal pudendal artery to the bulb of the urethra, and follow 

 it medially through the fibres of the deep transverse muscle. 

 As the artery approaches the bulb look for the bulbo-urethral 

 gland, which lies a little posterior and lateral to the urethra, 

 under cover of the posterior fibres of the deep transverse muscle. 

 The staff, introduced at the commencement of the work, is still 

 in the urethra, therefore the position of the membranous part 

 of that canal is easily defined by pressing the tip of the index 

 finger against the staff as it lies in the deep pouch of the uro- 

 genital triangle. 



Art. Pudenda Interna (O.T. Internal Pudic). The in- 

 ternal pudendal artery is a branch of the hypogastric. It 



