486 



THE MUSCULAE SYSTEM. 

 THE MUSCLES OF THE PERINEUM. 



The perineal muscles are naturally separated into a superficial and a deep set 

 by the fascia inferior of the urogenital diaphragm. Superficial to it are the 

 sphincter ani externus, transversus perinei superficialis, bulbocavernosus, and 

 ischiocavernosus ; deep to it are the sphincter muscle of the membranous urethra 

 and the transversus perinei profundus. 



M. Sphincter Ani Externus. This muscle is fusiform in outline, flattened, 

 and obliquely placed around the anus and anal canal. It can be separated into 

 three layers, subcutaneous, superficial, and deep. (1) The most superficial lamina 



Posterior scrotal ( 

 nerves \ 



Perineal branch of 



posterior cutaneous 



nerve of tliigh 



Superficial branch of 



perineal nerve 



Deep branch of 



perineal nerve 



Nervus perinei 



Inferior hsemorrhoidal 

 branches 



Dorsal nerve of penis 



- (displaced) 



- Nerve to corpus 

 cavernosum penis 



__ Nerve to corpus 

 cavernosum urethra 



Perineal nerve 

 Pudeiidal nerve 



Inferior hpemorrhoida 

 branches 



Pudendal nerve 





FIG. 431. THE MUSCLES AND NERVES OF THE MALE PERINEUM. 



consists of subcutaneous fibres decussating posterior and anterior to the anus, 

 without bony attachments. (2) The sphincter ani superficialis constitutes the 

 portion of the muscle. It is attached posteriorly to the coccyx, and, anterioi 

 the anus, it reaches the central point of the perineum. (3) The deep fibres of 

 muscle form, for the most part, a complete sphincter for the anal canal. They 

 continuous with the fibres of the leva tor ani ; they encircle the anal canal, i 

 blend anteriorly with the central point of the perineum and the transvei 

 perinei superficialis muscle. 



M. Corrugator Cutis Ani. The corrugator cutis ani consists of bundles 

 unstriped muscular fibres which radiate from the margin of the anal openii 

 superficial to the external sphincter. 



