External integument and subcutaneous structures
The study of anatomy begins with the superficial layers. The skin of the perineum has several characteristic features: it is notably thin and significantly pigmented. An important histological feature is that the skin in this zone is extremely rich in both sweat and sebaceous glands, which determines the specifics of care and susceptibility to certain dermatological conditions.
Subcutaneous adipose tissue lies beneath the skin. Its main topographical feature is its extremely uneven development across various areas of the perineum.
Perineal fascia
The fascial apparatus plays a key role in the spatial organization of tissues. Traditionally in anatomy, two main connective tissue layers are distinguished:
- Superficial perineal fascia (fascia perinei superficialis)
- Deep perineal fascia
It is the slit-like space between these two fascial layers that is of paramount practical importance: blood vessels and nerve trunks supplying and innervating this region travel through it.
Muscular apparatus of the urogenital region
The muscles of the anterior perineum (urogenital region) are topographically divided into superficial and deep layers.
The superficial muscles group includes three main structures:
- Ischiocavernosus muscle (m. ischiocavernosus)
- Bulbospongiosus muscle (m. bulbospongiosus)
- Superficial transverse perineal muscle (m. transversus perinei superficialis)
The deeper layer forms the so-called urogenital diaphragm. The deep transverse perineal muscle (m. transversus perinei profundus) belongs to this muscle complex. It creates a solid foundation for the anterior triangle.
Anal region and perineal body
In the posterior section, or anal region, lie the structures ensuring the function of the terminal part of the digestive tract. The key muscular element here is the external anal sphincter (m. sphincter ani externus). Next to it is the ischioanal fossa (fossa ischioanalis), an important anatomical space densely filled with adipose tissue.
The connecting link of the entire perineum is the perineal body (centrum tendineum perinei). This dense fibrous formation, located strictly in the center, functions as a universal anchor—it is precisely where the fibers of the perineal muscles converge and intertwine.
Blood supply and innervation
Trophics and sensitivity of perineal tissues are provided by a single neurovascular complex:
- Blood supply to the entire region is carried out by branches of the internal pudendal artery (a. pudenda interna).
- Innervation of the structures, including the muscular apparatus and skin, is provided by branches of the pudendal nerve (n. pudendus).
Briefly: answers to topical 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. The muscle bundles of the deep transverse perineal muscle enclose the membranous part of the 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 muscle and the coccygeus muscle. The levator ani muscle includes the pubococcygeus muscle, iliococcygeus muscle, and puborectalis muscle.
Specifically, which muscles insert into the perineal body?
The fibers of the superficial transverse perineal muscle, bulbospongiosus muscle, and external anal sphincter insert and cross in the perineal body.
What is the content of the ischioanal fossa (fossa ischioanalis)?
The ischioanal fossa in the anal region is filled with adipose tissue.
What branches does the internal pudendal artery give off to supply the perineum?
The key branches of the internal pudendal artery for the perineum are the inferior rectal arteries, the perineal artery (which gives off posterior scrotal or labial branches), and the artery of the bulb of the penis or vestibule of the vagina.
To memorize the superficial muscles of the urogenital region, use the acronym IBP: Ischiocavernosus, Bulbospongiosus, Superficial transverse perineal.
Class and exam questions
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 run in the space between the superficial and deep perineal fascia.
Which artery and nerve are responsible for the blood supply and innervation of the region?
Blood supply is provided by branches of the internal pudendal artery (a. pudenda interna), and innervation by branches of the pudendal nerve (n. pudendus).
What is the perineal body?
This is the central fibrous structure (centrum tendineum perinei) where the perineal muscles converge and anchor.
What else to study on this topic
- Histological structure of the perineal skin and distribution of glands
- Detailed topography of the ischiocavernosus and bulbospongiosus muscles
- Boundaries and contents of the ischioanal fossa (fossa ischioanalis)
- Course and branching of the internal pudendal artery
- Zones of innervation of the pudendal nerve
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