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



  • 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.


Home | Project Anatomy | Gross Anatomy | Topic Index | Chapter 35

Chapter 35: The Male Reproductive System and The Perineum