Editing Male Pelvis (section)

== Perineum ==

* The perineum lies between the pubis, thighs, and buttocks and is limited superiorly by the levator ani.
* Viewed from below, the symphysis pubis, ischial tuberosities, and coccyx outline the diamond shape of the perineum; the inferior ischiopubic rami and sacrotuberous ligaments form its bony and ligamentous walls. A line drawn through the ischial tuberosities divides the perineum into an anal and a urogenital triangle.
* '''Perineal membrane''' (previously called the urogenital diaphragm)
** A sheet of fascia that lies between the two sides of the pubic arch.
** '''Divides the urogenital hiatus into:'''
*** '''Superficial perineal space'''
*** '''Deep perineal space'''
* '''Male urogenital triangle'''
** Borders are pubic symphysis, ischial spines laterally, and perineal body and transverse perinei muscles
** The scrotum hangs from the anterior aspect of the urogenital triangle; in the posterior aspect, skin and subcutaneous fat overlie Colles fascia.
** '''The perineal membrane and the posterior and lateral attachments of Colles fascia limit a potential space known as the superficial pouch.'''
** '''In this superficial pouch, the 3 erectile bodies of the penis have their bony and fascial attachments (the root of the penis).'''
*** '''The paired corpora cavernosa attach to the inferior ischiopubic rami and perineal membrane and are surrounded by the ischiocavernosus muscles.'''
*** '''The corpus spongiosum dilates proximally as the bulb of the penis and is fixed to the center of the perineal membrane. It is encompassed by the bulbospongiosus muscles''' that arises from the perineal body and from a central tendinous raphe and pass around the bulb to attach to the perineal membrane and dorsum of the penis. '''Contraction of the ischiocavernosus and bulbospongiosus muscles compresses the erectile bodies and potentiates penile erection.'''
** Blood supply to the anal and urogenital triangles is derived largely from the internal pudendal vessels.
** The internal pudendal veins communicate freely with the dorsal vein complex by piercing the levator ani.
** The pudendal nerve follows the vessels in their course through the perineum. Its first branch, the dorsal nerve of the penis, travels ventral to the main pudendal trunk in Alcock canal.

* '''Perineal lymphatics'''
** '''The penis, scrotum, and perineum drain into the inguinal lymph nodes.'''
*** '''These inguinal lymph nodes may be divided into a superficial and a deep group, which are separated by the deep fascia of the thigh (fascia lata).'''
** '''Scrotal lymphatics DON’T cross median raphe and drain into ipsilateral superficial inguinal nodes only, whereas penile lymphatics can cross over and drain to superficial and deep inguinal nodes'''