35 : The Male Reproductive System and The Perineum

PERINEUM
Definition and Boundaries	The perineum is the diamond shaped region demarcated by 4 angles • anteriorly – symphysis pubis • posteriorly – tip of the coccyx • laterally – 2 ischial tuberosities The pubic arch and the sacrotuberous ligaments form its sides Note:The sacrotuberous ligament is overlapped by the lower border of the gluteus maximus.



The perineum is divided into 2 triangles by a line joining the 2 ischial tuberosities. These are: • Urogenital triangle – anteriorly • Anorectal triangle – posteriorly


	In the centre of the perineum is a small fibrous mass the perineal body. Attached here is the base of the perineal membrane. 5 muscles insert in this body from 5 directions. These are: • External anal sphincter – posterior • Transverse perinei superficialis- from right and left • Bulbospongiosus – anterior • part of levator ani (from lateral and superior)


Urogenital triangle
Boundaries anteriorly – symphysis pubis posteriorly – line joining the 2 ischial tuberosities and perineal body laterally – pubic arch


Urogenital diaphragm
This is a thin sheet of striated muscle which stretches between the 2 sides of the pubic arch. It occupies the urogenital triangle. Has 3 parts • anterior fibres – run transversely • posterior fibres – are the muscle Transverse perinei profundus • Middle fibres – circular and encircle the urethra and form the sphincter urethrae


The urogenital diaphragm has 2 fascial coverings – superior and inferior urogenital fascia. The inferior urogenital diaphragm fascia is called the Perineal membrane. The narrow space enclosed by fascia of the urogenital diaphragm is the Deep perineal pouch.