QuestionSBA
QuestionChoice
This is one of two pea-sized glands found on either side of the vaginal opening.
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b
Bartholin’s gland
QuestionChoice
This is a potential space between the deep fascia of the pelvic floor and perineal membrane.
10014270
c
Deep perineal pouch
QuestionChoice
This is a fibromuscular structure located between the urogenital and anal triangles and acts as a point of attachment for muscle fibres from the pelvic floor and perineum.
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e
Perineal body
QuestionChoice
This is the opening of the anus (medial to the arrowhead). It lies centrally within the anal triangle with the ischioanal fossae on either side.
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d
Anal aperture
QuestionChoice
The external sphincter muscle is one of the contents found within the anal triangle which is the posterior half of the perineum. The other contents of the anal triangle are the anal aperture and the two ischioanal fossae.
10014268
a
External anal sphincter
Concept
Chapter
## Summary

The perineum is a diamond shaped anatomical region located inferior to the pelvic floor. It is found between the thighs. The pelvic outlet forms the peripheral boundary and the pelvic diaphragm formed by the levator ani and the coccygeus muscles forms the ceiling. The walls of the pelvic cavity form the lateral walls inferior to the attachment of the levator ani muscle.


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## Anatomy

The diamond-shaped perineum is divided into an anterior urogenital triangle and the posterior anal triangle by an imaginary line between the ischial tuberosities.

**Borders:**

* Anterior: inferior border of the pubic symphysis
* Posterior: tip of the coccyx
* Lateral: ischiopubic rami and the sacrotuberous ligament
* Roof: levator ani muscles
* Base: skin and fascia

## Urogenital triangle

The urogenital triangle is located anteriorly in the perineum. The borders are:

* Pubic symphysis
* Ischiopubic rami
* Imaginary line between the 2 ischial tuberosities

This triangle is associated with the external genitalia and the urethra. The **perineal membrane** is a fibrous sheet that fills this region. It has a free posterior border and it is anchored by the perineal body.

The **deep perineal pouch** is a structure that is found superior to the perineal membrane. It contains skeletal muscles, neurovascular tissues, external urethral sphincter and structures unique to males and females:

* Females: vagina
* Males: bulbourethral glands and the deep transverse perineal muscles

The **superficial perineal pouch** is located between the perineal membrane and the membranous layer of the superficial fascia. This pouch contains:

*  Erectile structures that join together to form the clitoris in females and penis in males
*  Associated skeletal muscles  that are attached to the perineal membrane and the adjacent bone

The perineal fascia continues from the abdominal fascia and consists of the deep and superficial fascia.

## Anal triangle

The anal triangle is located posteriorly. The borders are:

* Coccyx
* Sacrotuberous ligaments
* Imaginary line between the ischial tuberosities

The anal aperture is located central and it communicates with the ischio-anal fossa on either side. The external anal sphincter is also found in this region (surrounding the anal canal) and consists of 3 parts, from superior to inferior these are: deep, superficial and subcutaneous.

* Deep part - circles the upper part of the anal canal, blends with the fibres of the levator ani muscle
* Superficial part - surrounds the anal canal. Anchored anteriorly to the perineal body and posteriorly to the coccyx and anococcygeal ligament.
* Subcutaneous part - flattened disc of muscle that surrounds the anal aperture under the skin

## Blood supply

The branches of the internal pudenal artery are:

* Inferior rectal artery
* Perineal artery
* Branches to the erectile tissue of the penis/clitoris

There are also other arteries that enter the perineum:

* External pudenal
* Testicular artery
* Cremasteric artery

The veins usually accompany the artery and drain into the internal pudenal vein and joins the internal iliac vein. The deep dorsal vein of the penis/clitoris is the only exception as it connects with a plexus that surrounds the prostate in men and bladder in women.

## Innervation

The major nerve in this region is the pudenal nerve (S2-S4). The major artery is the internal pudenal artery.

The pudenal nerve travels along the lateral wall of the ischio-anal fossa in the pudenal canal. This canal also contains the internal pudenal artery and the associated veins. The pudenal nerve has 3 branches which are accompanied by branches of the internal pudenal artery:

* Inferior rectal nerve
* Perineal nerve
* Dorsal nerve of the penis/clitoris)

## Clinical points

Damage to teh perineal body (e.g. during childbirth) can lead to weakening of the pelvic floor. This can lead to genital prolaspe or stress incontinence.
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Pelvic Anatomy
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Pelvic Anatomy
Identify the annotated structure.

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a