The genital branch of the genitofemoral nerve—this branch enters the inguinal canal with the round ligament and passes through the superficial inguinal ring to the anterior vulva.
3.
The perineal branches of the posterior femoral cutaneous nerve—after leaving the pelvis through the greater sciatic foramen, these branches run in front of the ischial tuberosity to the lateral perineum and labia majora.
4.
Perforating cutaneous branches of the second and third sacral nerves—these branches perforate the sacrotuberous ligament to supply the buttocks and contiguous perineum.
5.
The anococcygeal nerves—these nerves arise from S4 to S5 and also perforate the sacrotuberous ligament to supply the skin overlying the coccyx.
Autonomic Innervation Functionally, the innervation of the pelvic viscera may be divided into an efferent component and an afferent, or sensory, component. In reality, afferent and efferent fibers are closely associated in a complex interlacing network and cannot be separated anatomically.
Efferent fibers of the autonomic nervous system, unlike motor fibers in the somatic system, involve one synapse outside the central nervous system, with two neurons required to carry each impulse. In the sympathetic (thoracolumbar) division, this synapse is generally at some distance from the organ being innervated; conversely, the synapse is on or near the organ of innervation in the parasympathetic (craniosacral) division.
Axons from preganglionic neurons emerge from the spinal cord to make contact with peripheral neurons arranged in aggregates known as autonomic ganglia. Some of these ganglia, along with interconnecting nerve fibers, form a pair of longitudinal cords called the sympathetic trunks. Located lateral to the spinal column from the base of the cranium to the coccyx, the sympathetic trunks lie along the medial border of the psoas muscle from T12 to the sacral prominence and then pass behind the common iliac vessels to continue into the pelvis on the anterior surface of the sacrum. On the anterolateral surface of the aorta, the aortic plexus forms a lacy network of nerve fibers with interspersed ganglia. Rami arising from or traversing the sympathetic trunks join this plexus and its subsidiaries.
Figure 5.9 The presacral nerves.
The ovaries, part of the fallopian tubes, and broad ligament are innervated by the ovarian plexus, a network of nerve fibers accompanying the ovarian vessels and derived from the aortic and renal plexuses. The inferior mesenteric plexus is a subsidiary of the celiac plexus and aortic plexus and is located along the inferior mesenteric artery and its branches, providing innervation to the left colon, sigmoid, and rectum.
The superior hypogastric plexus (presacral nerve) is the continuation of the aortic plexus beneath the peritoneum in front of the terminal aorta, the fifth lumbar vertebra, and the sacral promontory, medial to the ureters (Fig. 5.9). Embedded in loose areolar tissue, the plexus overlies the middle sacral vessels and is usually composed of two or three incompletely fused trunks. It contains preganglionic fibers from lumbar nerves, postganglionic fibers from higher sympathetic ganglia and the sacral sympathetic trunks, and visceral afferent fibers. Just below the sacral promontory, the superior hypogastric plexus divides into two loosely arranged nerve trunks, the hypogastric nerves. These nerves course inferiorly and laterally to connect with the inferior hypogastric plexuses (pelvic plexuses), which are a dense network of nerves and ganglia that lie along the lateral pelvic sidewall overlying branches of the internal iliac vessels (Fig. 5.9).