Perineum

The perineum is a significant anatomical region situated between the anus and the external genital structures. In human beings, this area corresponds to the space between the anus and the scrotum in males, and between the anus and the vulva in females. It forms part of the pelvic outlet and comprises surface features, muscles, fasciae and deeper supportive structures that play essential roles in continence, childbirth and sexual function.

Etymology

The term perineum derives from Late Latin, which in turn originates from the Greek perinaios or perineos, traditionally associated with the male genitals. Earlier linguistic roots include terms referring to the penis and scrotum. Historically, the structure was regarded as a predominantly male anatomical feature due to the prominence of the perineal raphe, a line of fusion extending from the scrotal septum towards the anus. The concept was further supported by observations of virilisation, which produces a greater anogenital distance in males. Over time, folk etymological interpretations broadened the term’s application, so that it is now recognised in both sexes without distinction.

Anatomical Structure

The perineum is commonly described as the external surface region extending from the pubic symphysis anteriorly to the coccyx posteriorly. It lies inferior to the pelvic diaphragm and is bordered laterally by the ischial tuberosities. In overall configuration it forms a diamond-shaped area incorporating the anus and, in females, the vaginal opening.
An anatomical line connecting the two ischial tuberosities divides the perineum into two triangular subdivisions:

• Urogenital triangle (anterior region): includes the penis and scrotum in males, and the vulva in females.
• Anal triangle (posterior region): contains the anal canal and its associated structures.

Formally, the boundaries are defined anteriorly by the pubic arch and the inferior pubic ligament; posteriorly by the coccyx; and laterally by the inferior pubic rami, ischial tuberosities and the sacrotuberous ligaments. The pelvic floor forms the superior limit, while skin and superficial fascia constitute the inferior surface.

The Perineal Body

The perineal body, or central tendon of the perineum, is a pyramidal fibromuscular mass located at the junction of the urogenital and anal triangles. In males, it lies between the bulb of the penis and the anus; in females, it is situated between the vagina and anus, lying slightly anterior to the latter.
This structure is vital for pelvic floor integrity, especially in females. Rupture of the perineal body—commonly occurring during vaginal childbirth—can widen the separation between the anterior fibres of the levator ani muscles, increasing the risk of pelvic floor dysfunctions such as uterine prolapse, rectocele and cystocele. Preventive approaches during childbirth, including perineal massage in late pregnancy, may help reduce the risk of tears.
Multiple muscles converge at and attach to the perineal body, including:

• External anal sphincter
• Bulbospongiosus muscle
• Superficial transverse perineal muscle
• Anterior fibres of the levator ani
• External urethral sphincter (male or female variation)
• Deep transverse perineal muscle

Perineal Fascia

The fasciae of the perineum are complex and subject to differing nomenclature due to their multilayered structure. They are broadly categorised into superficial and deep components, and each of these can be further divided. The superficial layers are closest to the skin, while the deep fasciae envelop muscles and define boundaries of perineal pouches.

Perineal Subdivisions and Related Spaces

The perineum is considered separate from the pelvic cavity, the two regions being divided by the pelvic diaphragm. A notable subset of the perineum is the perianal area, which specifically encompasses the region immediately surrounding the anus.
Important associated anatomical spaces include:

• Perineal pouches (superficial and deep): containing muscles, fasciae and neurovascular structures relevant to urogenital function.
• Ischioanal fossa: a fat-filled recess on either side of the anal canal, bounded laterally by the obturator internus muscle and medially by the pelvic diaphragm and anal canal. It houses the internal pudendal artery and pudendal nerve and communicates anteriorly with the deep perineal pouch.

Clinical Significance

One clinically important measurement associated with this region is the anogenital distance (AGD), defined as the distance from the midpoint of the anus to the underside of the scrotum in males or the posterior commissure of the vulva in females. AGD is naturally greater in males and is approximately twice the length observed in females. In neonates, AGD has been proposed as a non-invasive marker of prenatal androgen exposure and may help predict later reproductive health outcomes.
Vaginal childbirth imposes substantial mechanical stress on the pelvic floor. Approximately 85% of women experience some degree of perineal tearing during delivery, with nearly 70% requiring suturing. Trauma to the region is associated with short-term morbidity, discomfort and long-term pelvic floor weakness, which may become clinically apparent in later life when compensatory mechanisms diminish. Persistent issues can include sexual dysfunction, pelvic organ prolapse and chronic perineal pain.
In certain instances, excessive suturing of the perineum following childbirth—sometimes colloquially termed the husband stitch—has been criticised for potentially causing painful intercourse or altered vaginal tightness.
The perineum is also considered an erogenous zone, with tactile sensitivity contributing to sexual response in both males and females.

Society and Culture

Culturally, several informal terms exist for the perineum, including taint or gooch in American slang and notcha in some Australian contexts.
A contemporary social trend known as perineum sunning involves exposing the perineal region to direct sunlight. Proponents claim unverified benefits such as enhanced energy, improved sleep and increased libido. However, there is no scientific evidence supporting these assertions, and the practice carries significant risks due to the sensitivity of the skin in this region, including heightened susceptibility to skin cancers such as melanoma, squamous cell carcinoma and basal-cell carcinoma. Medical professionals advise safer alternatives, including mindfulness and relaxation techniques.