ISCHIOANAL FOSSA

ischioanal fossa
wedge shaped space on each side of anal canal below pelvic diaphragm
boundaries
- base
  - formed by skin of perineum
- apex
  - formed by line wheere two fascia meet
    - obturator fascia
    - inferior fascia of pelvic diaphragm
  - the line corresponds to origin of levator ani from pelvic wall
- anteriorly
  - limited by posterior border of perineal membrane
- posteriorly fossa reaches
  - lower border of gluteus maximus
  - sacrotuberous ligament
- lateral wall
  - is vertical
    - formed by
      - obturator internus
      - medial surface of ischial tuberosity
- medial wall
  - slopes downwards
    - formed by
      - levator ani with anal fascia in upper part
      - external anal spinchter
recess
- anterior recess
  - extends forwards above perineal membrane
  - reaches almost upto posterior surface of body of pubis
- posterior recess
  - smaller than anterior
  - extends deep to sacrotuberous ligament
- horseshoe recess
  - connects 2 ischioanal fossa behind anal canal
spaces and canals of fossa
- perianal space
  - perianal fascia
    - separates a shallow subcutaneous
      - perianal space
      - from deep ischioanal space
    - fat arranged in loculi tightly
      - so infections are painful
- ischioanal space
  - large and deep
  - fat arranged in loculi loosely
    - by incomplete septa
    - less painful infection due to less tension of swelling
  - lunate fascia arches over
    - ischioanal fat
    - divides in to
      - suprategmental space above fascia
      - tegmental space below fascia
- pudendal canal
  - fascial canal in lateral waal of ischioanal fossa
  - encloses
    - pudendal nerve
    - internal pudendal vessels
  - fascia is fused with lower part of obturator fascia laterally
  - above
    - fused with lunate fascia
  - medially
    - perianal fascia
  - below
    - falciform process of sacrotuberous ligament
contents of ischioanal fossa
- ischioanal pad of fat
- inferior rectal nerve and vessels
- pudendal canal with its contents
- posterior scrotal or posterior labial nerve and vessels
- perineal branch of fourth sacral nerve
- perforating cutaneous branches of nerves S2,S3