Muscles of the perineum. Urogenital diaphragm.

The perineum (perineum) is a structure that covers the exit from the pelvic cavity. It has a rhomboid shape and has the following borders: the pubic symphysis anteriorly, the apex of the coccyx inferiorly, the lower branches of the pubis and ischium bones, as well as ischial tuberosities bilaterally.

In the center of the perineum, the so-called central tendon of the perineum (centrum tendineum) is located.

The median perineal raphe (raphe perinei) runs along the perineum in the anteroposterior direction.

The structure of the perineum includes a fairly large number of muscles. The line that connects the ischial tuberosities divides the perineum into two important zones:

The urogenital diaphragm (regio urogenitalis)

The pelvic diaphragm / anal triangle (region analis)

Now let’s cover the muscles of the urogenital diaphragm. In men, the urethra passes through it, and in women, the urethra and vagina pass through it.

The muscles of the urogenital diaphragm are divided into superficial and deep.

The superficial muscles include:

The superficial transverse perineal muscle (m. transversus perinei superficialis)

The superficial transverse perineal muscle
(m. transversus perinei superficialis)

Origin: ischial tuberosity

Insertion: perineal body

Function: strengthens the perineal body, supporting the internal organs

Innervation: pudendal nerve (S2-S4)

Blood supply: perineal artery

The ischiocavernosus muscle (m. ischiocavernosus)

The ischiocavernosus muscle
(m. ischiocavernosus)

Origin: ramus of the ischium muscle

Insertion: corpus cavernosum penis (clitoris)

Function: maintains the erection of the penis / clitoris by “pumping” them with blood

Innervation: pudendal nerve (S2-S4)

Blood supply: perineal artery

The bulbospongiosus muscle (m. bulbospongiosus)

The sulbospongiosus muscle
(m. bulbospongiosus)

Origin:

In men: on the lower surface of the bulb of the penis

In women: on the perineal body and the external anal sphincter

Insertion:

In men: corpus spongiosum penis, superficial fascia

In women: dorsal surface of the clitoris

Function:

In men, it provides compression of the bulb of the penis, promoting urination / ejaculation

In women, it narrows the vaginal opening, promotes compression of the greater vestibular gland and the bulb of the vestibule

Innervation: pudendal nerve (S2-S4)

Blood supply: perineal artery

The deep muscles include:

The deep transverse perineal muscle (m. transversus perinei profundus)

The deep transverse perineal muscle
(m. transversus perinei profundus)

Origin: ischium ramus, inferior pubic ramus

Insertion: right and left muscles cross, forming the perineal body

Function: strengthens the central tendon, compresses the urethra in men, and both urethra and vagina in women

Innervation: pudendal nerve (S2-S4)

Blood supply: perineal artery

The sphincter of the urethra (m. sphincter urethrae externus)

The sphincter of the urethra
(m. sphincter urethrae externus)

Origin:

In men: circular fibers surround the membranous urethra, radial fibers are woven into the capsule of the prostate gland

In women: circular fibers surround the urethra and vagina, radial fibers are woven into the vaginal wall

Function: compresses the urethra (as well as the vagina in women), promoting the retention of urine, and radial fasciculi, on the contrary, dilate the urethra

Innervation: pudendal nerve (S2-S4)

Blood supply: perineal artery

Dictionary