| Structure/Space | Description/Boundaries | Significance |
|---|---|---|
| anal triangle | posterior subdivision of the diamond-shaped perineum; its boundaries are: anteriorly - posterior margin of the perineal membrane (corresponds to an imaginary line connecting the ischial tuberosities); posterolaterally - sacrotuberous ligament | anal triangle is the location of the terminal end of the gastrointestinal tract (anus) |
| ischioanal fossa | a fat-filled space located lateral to the anal canal and inferior to the pelvic diaphragm; its boundaries are: superomedially - pelvic diaphragm (anterior recess extends superior to the urogenital diaphragm); medially - external anal sphincter muscle and anal canal; laterally - obturator internus fascia and ischial tuberosity; posterolaterally - sacrotuberous ligament and gluteus maximus m.; (posterior recess extends superior to the gluteus maximus m.) | the fat and loose connective tissue in the ischioanal fossa compresses to allow passage of feces; also known as: ischiorectal fossa |
| natal cleft | midline cleft between the buttocks | natal cleft lies between the gluteus maximus muscles |
| perineum | a diamond-shaped space forming the outlet of the pelvis; its boundaries are: anterolaterally - inferior pubic ramus, ischial ramus and ischial tuberosity; posterolaterally - sacrotuberous ligament | perineum is subdivided into the anal triangle and urogenital triangle by an imaginary line connecting the ischial tuberosities |
| urogenital triangle | anterior subdivision of the diamond-shaped perineum; its boundaries are: anterolaterally - inferior pubic ramus, ischial ramus; posteriorly - posterior margin of perineal membrane (corresponds to an imaginary line connecting the ischial tuberosities) | urogenital triangle is the location of the terminal portion of the urinary tract and genital tract |