Handa 9781496386441 Full Sample Chap 1

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SECTION I  Preparing for Surgery

bones. Fibers join the dorsal nerve of the clitoris and pro- vide innervation to the corpora cavernosa. In contrast to the dorsal nerve of the clitoris, the cavernous nerve fibers are of very small caliber and their presence can only be confirmed by microscopy. These nerves consist of sym- pathetic and parasympathetic components and are criti- cal to sexual function. Injury to the inferior hypogastric plexus during radical hysterectomy or other extensive pelvic or perineal surgeries can lead to varying degrees of voiding, sexual, and defecatory dysfunction. Anti- incontinence procedures where sutures or trocars are passed through the paraurethral tissue may also disrupt these fibers within the retropubic space. Lymphatic Drainage Injection studies and clinical observation have estab- lished the pattern of the vulvar lymphatic vessels and drainage into the superficial inguinal group of lymph nodes. This anatomy is important to the treatment of vulvar malignancies; an overview of this system is pro- vided here. This area is described and illustrated in more detail in Chapter 23. Tissues external to the hymenal ring are supplied by an anastomotic series of vessels and lymphatics in the super- ficial tissues that coalesce to a few trunks lateral to the clitoris and proceed laterally to the superficial inguinal nodes ( FIG. 1.17 ). The vessels draining the labia majora also run in an anterior direction, lateral to those of the labia minora and vestibule. These lymphatic channels lie medial to the labiocrural fold, establishing it as the lat- eral border of surgical resection for vulvar malignancies. Injection studies of the urethral lymphatics have shown that lymphatic drainage of this region terminates in either the right or left inguinal nodes. The clitoris has been said to have some direct drainage to deep pelvic lymph nodes, bypassing the usual superficial nodes, but the clinical significance of this appears to be minimal. The inguinal lymph nodes are divided into two groups—the superficial and the deep nodes. There are 12 to 20 superficial nodes, and they lie in a T-shaped distri- bution parallel to and 1 cm below the inguinal ligament, with the stem extending down along the saphenous vein. The nodes are often divided into four quadrants, with the center of the division at the saphenous opening (fossa ovalis). The vulvar drainage goes primarily to the medial nodes of the upper quadrant. These nodes lie deep in the adipose layer of the subcutaneous tissues, in the mem- branous layer, just superficial to the fascia lata. The large saphenous vein joins the femoral vein through the saphenous opening. Within 2 cm of the inguinal ligament, several superficial blood vessels branch from the saphenous vein and femoral artery. They include the superficial epigastric vessels that supply the subcutaneous tissues of the lower abdo- men, the superficial circumflex iliac vessels that course laterally to the region of the iliac crest, and the

I periosteum of the ischiopubic ramus. Approximately 2 to 3 cm lateral to the mid pubic symphysis, it emerges from the deep and lateral surface of the crus and then courses toward the dorsal surface of the clitoral body tightly embedded in layers of fibroconnective tissue, including that of the suspensory and fundiform ligaments of the clitoris. In this region, the nerve is consistently 2 to 4 mm in diameter. The nerve from each side then courses along the dorsal surface of the clitoral body, at approximately the 11 o’clock and 1 o’clock positions. It remains deep to the clitoral fascia but superficial to the tunica albuginea layer that surrounds the corpora cavernosa. In this area, it gives off small branches to the skin of the prepuce and to the corpora cavernosa. It ends by perforating the glans of the clitoris to which it provides sensory innervation. The section of this nerve that courses deep within the sus- pensory ligament is covered by vulvar and prepuce skin as well as by their underlying layer of connective tissue. Thus, excisional procedures that extend deep to the sub- cutaneous tissue in this region, pelvic fractures, and some anti-incontinence procedures risk injury to this nerve and can affect clitoral sensation and sexual function. Perineal nerve (see FIG. 1.14 ). The perineal nerve is the largest branch of the pudendal nerve. Branches of this nerve include the posterior labial nerves, which supply the labia minora and all but the anterior part of the labia majora; muscular branches, which provide motor inner- vation to the muscles of the superficial perineal pouch (ischiocavernosus, bulbospongiosus, and superficial trans- verse perineal) and sensory branches to the vestibular bulbs, vestibule, and lower part of the vagina. Although data are limited, branches of perineal nerve may provide innervation to the distal part or the striated urogenital sphincter muscles (compressor urethrae and urethrovagi- nalis), which are found in the deep perineal pouch, supe- rior to the perineal membrane. The dorsal nerve of the clitoris may also contribute branches to these structures. Inferior anal (rectal) nerve (see FIG. 1.14 ). The infe- rior anal nerve innervates the external anal sphincter and perianal skin. Thus, injury to this nerve may lead to fecal incontinence and pain syndromes. The path of the inferior rectal nerve differs from that of the other pudendal nerve branches in that this nerve does not enter the pudendal canal in approximately 50% of specimens examined in cadaver studies. This finding may have clinical implications in certain surgical proce- dures where the ischioanal fossa is entered and during radiographic-guided injections used to manage pain. Autonomic Innervation to Erectile Structures The erectile tissues of the perineum are innervated by the cavernous nerves of the clitoris. These are the dis- tal extensions of the uterovaginal plexus, a component of the inferior hypogastric plexus. These fibers course within the paravaginal and paraurethral connective tissue and reach the perineum by passing under the pubic

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