Which muscles form the deep layer of the urogenital diaphragm?

The deep layer of the urogenital diaphragm is formed by the deep transverse perineal muscle. Muscle fibers of the deep transverse perineal muscle encircle the membranous urethra, forming a sphincter.

Which muscles form the pelvic diaphragm in the anal region?

The pelvic diaphragm in the anal region is formed by paired muscles consisting of the levator ani and coccygeus. The levator ani includes the pubococcygeus, iliococcygeus, and puborectalis muscles.

Which specific muscles insert into the perineal body?

Fibers of the superficial transverse perineal muscle, bulbospongiosus muscle, and external anal sphincter intersect and blend within the perineal body.

What fills the ischioanal fossa (fossa ischioanalis)?

The ischioanal fossa in the anal region is filled with adipose tissue (fat).

What branches does the internal pudendal artery give off to supply the perineum?

Key branches of the internal pudendal artery supplying the perineum include the inferior rectal arteries, the perineal artery (giving rise to posterior scrotal or labial branches), and the artery of the bulb of the penis or vestibule.

Which muscles form the urogenital diaphragm?

The urogenital diaphragm includes the deep transverse perineal muscle (m. transversus perinei profundus).

Where are the vessels and nerves of the perineum located?

Blood vessels and nerves travel within the space between the superficial and deep perineal fascia.

Which artery and nerve supply this region?

Blood supply is provided by branches of the internal pudendal artery (a. pudenda interna), and innervation is supplied by branches of the pudendal nerve (n. pudendus).

What is the perineal body?

It is a central fibrous node (centrum tendineum perinei) where multiple perineal muscles converge and anchor.

Home › Human Anatomy › Perineum: Anatomy, Muscles, and Fascia

Perineum

For medical students2 min readUpdated 2026-10-10

The perineum is a complex soft-tissue structure that forms the inferior boundary of the torso and seals the pelvic outlet. Its components create a robust musculo-fascial framework that provides vital support to the pelvic viscera and regulates sphincter function.

Integumentary tissuesSkin is thin, pigmented, and rich in glands

Fascial layersNeurovascular bundles run strictly between fascial planes

Perineal bodyA central fixation point where multiple muscle fibers converge

Blood supplyProvided by branches of the internal pudendal artery

Surface Anatomy and Subcutaneous Structures

The study of perineal anatomy begins with the superficial layers. The skin of the perineum exhibits distinct characteristics: it is markedly thin and heavily pigmented. A crucial histological feature is that the integument in this region is exceptionally rich in both sweat and sebaceous glands, accounting for its specialized care requirements and susceptibility to specific dermatological conditions.

Beneath the skin lies the subcutaneous adipose tissue. Its primary topographical feature is its highly uneven distribution across various regions of the perineum.

Perineal Fascia

The fascial apparatus plays a pivotal role in the spatial organization of tissues. Classically, anatomy recognizes two main connective tissue layers:

Superficial perineal fascia (fascia perinei superficialis)
Deep perineal fascia

The slit-like space between these two fascial layers holds immense clinical and practical significance: it serves as the conduit for blood vessels and nerve trunks that nourish and innervate the region.

Musculature of the Urogenital Region

The muscles of the anterior perineum (urogenital region) are topographically divided into superficial and deep layers.

The superficial muscle group comprises three main structures:

Ischiocavernosus muscle (m. ischiocavernosus)
Bulbospongiosus muscle (m. bulbospongiosus)
Superficial transverse perineal muscle (m. transversus perinei superficialis)

The deeper layer forms the urogenital diaphragm. Belonging to this muscular complex is the deep transverse perineal muscle (m. transversus perinei profundus), which forms a sturdy foundation for the anterior triangle.

Anal Region and the Perineal Body

The posterior division, or anal region, contains structures responsible for the function of the terminal gastrointestinal tract. The key muscular element here is the external anal sphincter (m. sphincter ani externus). Adjacent to it is the ischioanal fossa (fossa ischioanalis), a critical anatomical space densely packed with adipose tissue.

The central coordinating hub of the entire perineum is the perineal body (centrum tendineum perinei). This dense fibrous structure, located strictly at the center, acts as a universal anchor where the fibers of various perineal muscles converge and interlace.

Blood Supply and Innervation

Trophic support and sensory innervation of the perineum are delivered by a unified neurovascular complex:

Blood supply to the entire region is derived from branches of the internal pudendal artery (a. pudenda interna).
Innervation of all structures, including the muscular framework and skin, is supplied by branches of the pudendal nerve (n. pudendus).

Mnemonic

To memorize the superficial muscles of the urogenital region, use the mnemonic I-B-S: Ischiocavernosus, Bulbospongiosus, Superficial transverse perineal.

Frequently asked questions

Which muscles form the deep layer of the urogenital diaphragm?: The deep layer of the urogenital diaphragm is formed by the deep transverse perineal muscle. Muscle fibers of the deep transverse perineal muscle encircle the membranous urethra, forming a sphincter.
Which muscles form the pelvic diaphragm in the anal region?: The pelvic diaphragm in the anal region is formed by paired muscles consisting of the levator ani and coccygeus. The levator ani includes the pubococcygeus, iliococcygeus, and puborectalis muscles.
Which specific muscles insert into the perineal body?: Fibers of the superficial transverse perineal muscle, bulbospongiosus muscle, and external anal sphincter intersect and blend within the perineal body.
What fills the ischioanal fossa (fossa ischioanalis)?: The ischioanal fossa in the anal region is filled with adipose tissue (fat).
What branches does the internal pudendal artery give off to supply the perineum?: Key branches of the internal pudendal artery supplying the perineum include the inferior rectal arteries, the perineal artery (giving rise to posterior scrotal or labial branches), and the artery of the bulb of the penis or vestibule.
Which muscles form the urogenital diaphragm?: The urogenital diaphragm includes the deep transverse perineal muscle (m. transversus perinei profundus).
Where are the vessels and nerves of the perineum located?: Blood vessels and nerves travel within the space between the superficial and deep perineal fascia.
Which artery and nerve supply this region?: Blood supply is provided by branches of the internal pudendal artery (a. pudenda interna), and innervation is supplied by branches of the pudendal nerve (n. pudendus).
What is the perineal body?: It is a central fibrous node (centrum tendineum perinei) where multiple perineal muscles converge and anchor.

Go deeper

Histology of perineal skin and gland distribution
Detailed topography of the ischiocavernosus and bulbospongiosus muscles
Boundaries and contents of the ischioanal fossa
Course and branching pattern of the internal pudendal artery
Sensory and motor distribution of the pudendal nerve