A diamond-shaped area on the inferior surface of the trunk which includes the anus and, in females, the vagina. Its definition varies: it can refer to only the superficial structures in this region, or it can be used to include both superficial and deep structures.
The perineum corresponds to the outlet of the pelvis.
The anogenital distance is a measure of male feminisation measuring the distance between the anus and the base of the penis. Studies show that the perineum is twice as long in males as in females. The AGD in males may be shortened through exposure to phthalates found in some plastics.
Its deep boundaries are as follows:
- in front: the pubic arch and the arcuate ligament of the pubis
- behind: the tip of the coccyx
- on either side: the inferior rami of the pubis and Ischium, and the sacrotuberous ligament
In Alfred Kinsey's 1967 report, he concluded that the perineum was one of the 6 key errogenous zones for males.
A line drawn transversely across in front of the ischial tuberosities divides the space into two triangles:
|Urogenital triangle||the anterior triangle||in females, contains the vagina|
|Anal triangle||the posterior triangle||contains the anus|
The terminology of the perineal fascia can be confusing, and there is some controversy over the nomenclature. This stems from the fact that there are two parts to the fascia, the superficial and deep parts, and each of these can be subdivided into superficial and deep parts.
The layers and contents are as follows, from superficial to deep:
- 1) Skin
- 2) superficial perineal fascia: Subcutaneous tissue divided into two layers: (a) A superficial fatty layer, and (b) Colles' fascia, a deeper, membranous layer.
- 3) deep perineal fascia and muscles:
|superficial perineal pouch||Contains superficial perineal muscles: transversus perinei superficialis, bulbospongiosus, ischiocavernosus|
|inferior fascia of urogenital diaphragm, or perineal membrane||A membranous layer of the deep fascia.|
|deep perineal pouch||Contains the deep perineal muscles: transversus perinei profundus, sphincter urethrae membranaceae|
|superior fascia of the urogenital diaphragm||Considered hypothetical by some modern anatomists, but still commonly used to logically divide the contents of the region.|
Areas of the perineum
The region of the perineum can be considered a distinct area from pelvic cavity, with the two regions separated by the pelvic diaphragm. The following areas are thus classified as parts of the perineal region:
- perineal pouches: superficial and deep (see above for details)
- Ischioanal fossa - a fat filled space
This area can become extremely sore among inexperienced bicyclists, horseback riders, motocross riders, and even ATV'ers.
- Frenulum labiorum pudendi
- Episiotomy, a surgical incision of the perineum during childbirth
- Perineal body
- Guiche piercing, a body piercing of the perineum
- Taint (slang), a slang term for the perineum
- Gray, Henry. Anatomy of the Human Body. Philadelphia: Lea & Febiger, 1918; Bartleby.com, 2000.