- Wedge-shaped space filled with fat lateral to the Anal Canal
- Base: Skin over the anal region of the Perineum
- Medial wall: External Anal Sphincter of Anal Canal and sloping Levator Ani muscles
- Lateral wall: Ischial Tuberosity below with Obturator Internus (covered by its fascia) above
- Apex of wedge = Where the medial and lateral walls meet – where the Levator Ani is attached to its tendinous origin over the Obturator Fascia
- Base of anterior boundary – posterior border of the Perineal Body and muscles of the Urogenital Diaphragm
- Posterior boundary – Sacrotuberous Ligament overlapped by the lower border of Gluteus Maximus
- Fat in lower part of the fossa adjacent to the skin – small lobules
- Fat in upper reaches of the fossa – large lobules
- Each fossa has an anterior recess that passes forwards above the Perineal Membrane
- Potentially as far as the posterior surface of the Body of the Pubis
- Recesses of two sides do not communicate across the midline
- NB: Thus, Ischiorectal Fossa extends anteriorly above the Urogenital Diaphragm
- Because the Ischiorectal Fossa extends forwards below the Levator Ani muscles which are attached to the Body of the Pubic Bone above the level of the Urogenital Diaphragm
- Posteriorly, the two fossae communicate with one another, low down through the fibrofatty tissue of the Retrosphincteric Space within the Anococcygeal Ligament
- Provides a horseshoe-shaped path for infection spread