Handa 9781496386441 Full Sample Chap 1

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SECTION I  Preparing for Surgery

I and ischiocavernosus and bulbospongiosus muscles, is called the superficial perineal pouch or compartment (see FIG. 1.13 ). The deep compartment is the region just deep to the perineal membrane; it is discussed later. The erectile bodies (body and crura of the clitoris and bulb of the vestibule) and their associated muscles within the superficial compartment lie on the caudal surface of the perineal membrane. The clitoris is a complex erectile and highly sensitive organ, which is homologous to the penis. It is embryologically derived from the genital tubercle. In contrast to the penis, the clitoris is not func- tionally related to the urethra, and thus, its primary func- tion is in sexual arousal and orgasm. It is composed of a midline body, topped with the glans, and paired crura. The body lies on, and is suspended from, the pubic bones by the subcutaneous suspensory and fundiform liga- ments of the clitoris. The fundiform ligament of the cli- toris is fibrous condensation of the subcutaneous tissue descending from the linea alba above the pubic symphy- sis, which splits and surrounds the body of the clitoris, before fusing with the fascia of the clitoris. Along with the suspensory ligament, it contributes to the support and positioning of the clitoral body. The paired crura of the clitoris bend downward from the body and are firmly attached to the pubic bones, continuing dorsally to lie on the inferior aspects of the ischiopubic rami. They join in midline to form the body of the clitoris. The body of the clitoris consists of paired corpora cavernosa separated in midline by a fibrous septum, appropriately called the septum of corpora cavernosa. Both the corpora cav- ernosa and the paired crura are invested by a layer of fibroconnective tissue called the tunica albuginea. The dorsal nerve and vessels of the clitoris, discussed later, lie outside the tunica albuginea but within the clitoral fascia, which is continuous with the deep portion of the suspensory ligament of the clitoris. The ischiocavernosus muscles originate at the ischial tuberosities and the free surfaces of the crura to insert on the upper crura and often on the body of the clitoris. A few muscle fibers, called the superficial transverse perineal muscles, origi- nate in common with the ischiocavernosus muscle from the ischial tuberosity and course transversely toward the lateral margins of the perineal body. The paired vestibular bulbs are elongated 3- to 4-cm masses of richly vascular spongy erectile tissue that lie immediately under the vestibular skin. They overlie the greater vestibular (Bartholin) glands pos- teriorly, and the bulb from each side join anteriorly at the commissure of the bulbs, where the spongy tissue attaches to the undersurface of the glans and body of the clitoris. The bulbs are partially covered by the bul- bospongiosus muscles, which originate in the perineal body. These muscles, along with the ischiocavernosus muscles, insert into the body of the clitoris and act to pull it downward. All muscles in the superficial peri- neal triangle, bulbospongiosus, ischiocavernosus, and superficial transverse perineal are covered by a layer

of fascia called the perineal fascia, which is continuous with the clitoral fascia. The greater vestibular (Bartholin) gland is found at the tail end of the bulb of the vestibule and is connected to the vestibular mucosa by a duct lined with squamous epithelium. The gland lies on the perineal membrane and beneath the bulbospongiosus muscle (previously referred to as bulbocavernosus). The intimate relation between the enormously vascular tissue of the vestibular bulb and the Bartholin gland is responsible for the risk of hemor- rhage associated with removal of this latter structure. The perineal membrane and perineal body are important to the support of the pelvic organs. They are discussed in the section on the pelvic floor. Pudendal Nerve and Vessels The pudendal nerve is the main sensory and motor nerve of the perineum. Its course and distribution in the perineum parallel the internal pudendal artery and veins that connect with the internal iliac vessels (see FIG. 1.14 ). The course and division of the nerve are described with the understanding that the vascular channels parallel them. The pudendal nerve arises from the sacral plexus (S2–S4), and the associated arteries originate from the anterior division of the internal iliac artery. They leave the pelvis through the greater sciatic foramen by pass- ing behind the sacrospinous ligament, just medial to the ischial spine ( FIG. 1.15 ). They then enter the pudendal (Alcock) canal through the lesser sciatic foramen. The pudendal canal is formed by a splitting of the obturator fascia covering the medial surface of the obturator internus muscle. It roughly expands from the ischial spine proximally to the ischial tuberosity distally. The nerve and vessels have three branches: the clito- ral, perineal, and inferior rectal. The course and distri- bution of each nerve branch is described below with the understanding that vessels follow a similar path. Terminal Branches of Pudendal Nerve The three terminal branches of the pudendal nerve are the dorsal nerve of clitoris, perineal nerve, and inferior anal (rectal) nerves. These nerves provide sensation to the external female genitalia and motor innervation to the superficial perineal muscles, parts of the striated urethral sphincter muscles, and external anal sphincter muscle. Dorsal nerve of clitoris . This nerve is the primarily sensory nerve to the clitoris ( FIG. 1.16 ). After exiting the pudendal canal, this nerve remains within the deep pouch of the anterior perineal triangle firmly adherent to the inner surface of the ischiopubic ramus. It perfo- rates the perineal membrane adjacent to the medial sur- face of the ramus to reach the superficial perineal pouch. Here, it courses on the deep surface of the ischiocaver- nosus muscle and clitoral crus. In this region, the nerve is surrounded by a dense fibrous capsule adherent to the

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