In human anatomy, the perineum is generally defined as the surface region in both males and females between the pubic symphysis and the coccyx. The perineum is the region of the body inferior to the pelvic diaphragm and between the legs.
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. One research group stated that the AGD in males may be shortened through exposure to phthalates found in some plastics and personal care products, but the science behind this research has been questioned. Measuring the anogenital distance in neonatal humans has been suggested as a noninvasive method to predict neonatal and adult reproductive disorders.
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 erogenous 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.|
- 4) fascia and muscles of pelvic floor (levator ani, coccygeus)
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 at the lateral sides of anal canal. It is bounded laterally by obturator internus muscle, medially by pelvic diaphragm and anal canal. Its base is the skin.
- Anal canal
- Pudendal canal - contains internal pudendal artery and the pudendal nerve.
- Gray, Henry. Anatomy of the Human Body. Philadelphia: Lea & Febiger, 1918; Bartleby.com, 2000.
- US FDA/CFSAN - Cosmetics - Phthalates and Cosmetic Products
- Validity of anogenital distance as a marker of in utero phthalate exposure. PMID 16393642
- Michelle Welsh, et al.: Identification in rats of a programming window for reproductive tract masculinization, disruption of which leads to hypospadias and cryptorchidism. J. Clin. Invest., 13 March 2008.
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