Human Anatomy and Physiology - I. V. Gaivoronsky 2011

Anatomy of the Reproductive System. Human Reproductive Function and Development
Perineum

The Perineum is a complex of soft Tissues that closes the outlet of the lesser pelvis (Fig. 11.12). It is bounded by the following structures: anteriorly, by the Inferior surface of the Pubic Symphysis; posteriorly, by the tip of the coccyx; and laterally, by the ischial tuberosities. The perineal region contains the external genitalia and the anus. Subcutaneous adipose tissue lies beneath the Skin of the perineum, followed by Muscles covered on both sides by fascia. In obstetric, gynecological, and andrological practice, the perineum (in the narrow sense of the term) refers to the portion of the pelvic outlet region lying between the external genitalia and the anus. In women, it is situated between the urogenital cleft and the anterior margin of the anus; in men, between the posterior margin of the Scrotum and the anal opening.

By means of an imaginary line connecting the ischial tuberosities (linea biischiadica), the perineum is divided into the urogenital and anal regions.

The urogenital region contains the paired deep transverse perineal Muscle and the external urethral sphincter, covered by the superior and inferior pelvic fasciae, which support the Organs of the Urogenital System and form the urogenital Diaphragm. More superficially in the urogenital region lie the following muscles: the ischiocavernosus, the superficial transverse perineal muscle, and the bulbospongiosus. The latter facilitates the expulsion of urine and semen from the Urethra in men, whereas in women it constricts the Vagina and compresses the Veins OF THE Penis or Clitoris, contributing to their erection. Passing through the urogenital diaphragm are the membranous part of the urethra in men, and both the urethra and the vagina in women.

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Fig. 11.12. Female perineum:

1 — ischiocavernosus muscle; 2 — deep transverse perineal muscle; 3 — superficial transverse perineal muscle; 4 — anal opening; 5 — external anal sphincter; 6 — sacrotuberous ligament; 7 — obturator internus muscle; 8 — sacrospinous ligament; 9 — levator ani muscle; 10 — gluteus maximus muscle; 11 — bulbospongiosus muscle; 12 — vaginal opening; 13 — deep perineal fascia; 14 — external urethral orifice; 15 — clitoris

All the Muscles of the anal region and their fasciae form the pelvic floor, which is constituted by the levator ani muscle, the coccygeus muscle, the external anal sphincter, and the fasciae covering them. This diaphragm has the shape of a downward-projecting dome. The depression between the pelvic floor and the ischial tuberosity on each side is called the ischioanal fossa. It contains adipose tissue through which Vessels and nerves pass. The terminal portion of the rectum, ending in the anal opening, passes through the pelvic floor.