The deep perineal pouch is bounded by the perineal membrane inferiorly and the superior fascia of the urogenital diaphragm superiorly . The perineal membrane or inferior fascia of the urogenital diaphragm is a layer of dense fibrous tissue. The membrane separates the superficial and deep perineal pouches. Its attachments laterally are the pubic arch, whereas anteriorly it is thickened to form the transverse perineal ligament. Between this ligament and the inferior pubic ligament, the deep dorsal vein of the clitoris passes.
The contents of the deep perineal pouch include the following:
1. The urethra.
2. The vagina.
3. The sphincter urethrae muscle is thin and divisible into a central and a peripheral portion. The central circular fibers surround the urethra, whereas the peripheral, transverse fibers attach to the pubic arch and the perineal membrane. These fibers run anterior and posterior to the urethra. This muscle functions to constrict the urethra and is supplied by the deep perineal nerve. The posterior fibers of the sphincter urethrae muscle are continuous with the deep transverse perineal muscle, which together form the urogenital diaphragm.
4. The deep transverse perineal muscles arise from the ischial rami and perineal membrane. They insert into the perineal body. Their function is to stabilize the perineum, and their nerve supply arises from the deep perineal nerve. The muscles of the urogenital diaphragm also function to constrict the urethra.
5. The internal pudendal artery enters the deep perineal pouch poster¬iorly after leaving the pudendal canal and courses along the pubic arch, terminating as the deep and dorsal arteries of the clitoris. There is also a branch distributed to the bulbocavernosus.
6.The pudendal nerve terminates as the dorsal nerve of the clitoris, entering the deep perineal pouch on the lateral sides of the internal pudendal artery, which is medial to the pubic arch. It functions as a sensory nerve supplying the erectile tissue of the clitoris. The deep perineal nerve, representing a second terminal branch of the pudendal nerve, gives off the posterior labial nerve from the anterior part of the pudendal canal along with several muscular branches to supply all the muscles of the superficial and deep perineal pouches.
The female urogenital diaphragm seen from below. Also illustrated are the swelling bodies or cavernosus bodies. On the right side, the urogenital diaphragm is cut to show the major vestibular gland.
Lymphatic drainage from the inferior perineal structures, which include the inferior anal canal, lower vagina, and distal urethra, drains to the medial superficial inguinal lymph nodes. Superiorly, lymphatic flow is directed to the pelvic lymph nodes.