z Dr Abeera Sarfraz Dr Muhammad Zubair Nerves

z Dr Abeera Sarfraz/ Dr Muhammad Zubair Nerves of Posterior Abdominal Wall

z § Components of both the somatic and autonomic (visceral) nervous systems are associated with the posterior abdominal wall. § The subcostal nerves (anterior rami of T 12) arise in the thorax, pass posterior to the lateral arcuate ligaments into the abdomen, and run inferolaterally on the anterior surface of the quadratus lumborum. They pass through the transversus abdominis and internal oblique muscles to supply the external oblique and skin of the anterolateral abdominal wall.

z § The lumbar spinal nerves (L 1–L 5) pass from the spinal cord through the IV foramina inferior to the corresponding vertebrae, where they divide into posterior and anterior rami. Each ramus contains sensory and motor fibers. The posterior rami pass posteriorly to supply the muscles of the back and overlying skin, whereas the anterior rami pass laterally and inferiorly, to supply the skin and muscles of the inferior most trunk and lower limb. The initial portions of the anterior rami of the L 1, L 2, and occasionally L 3 spinal nerves give rise to white communicating branches (L. rami communicantes), which convey presynaptic sympathetic fibers to the lumbar sympathetic trunks.

z § The abdominal part of the sympathetic trunks (lumbar sympathetic trunks), consisting of four lumbar paravertebral sympathetic ganglia and the interganglionic branches that connect them, is continuous with the thoracic part of the trunks deep to the medial arcuate ligaments of the diaphragm. The lumbar trunks descend on the anterolateral aspects of the bodies of the lumbar vertebrae in a groove formed by the adjacent psoas major. Inferiorly, they cross the sacral promontory and continue inferiorly into the pelvis as the sacral part of the trunks. § For the innervation of the abdominal wall and lower limbs, synapses between the presynaptic and postsynaptic fibers occur in the sympathetic trunks. Postsynaptic sympathetic fibers travel from the lateral aspect of the trunks via gray communicating branches to the anterior rami. They become thoracoabdominal and subcostal nerves and the lumbar plexus (somatic nerves) that stimulate vasomotion, sudomotion, and pilomotion in the lowermost trunk and lower limb. Lumbar splanchnic nerves arising from the medial aspect of the lumbar sympathetic trunks convey presynaptic sympathetic fibers for the innervation of pelvic viscera.

z LUMBAR PLEXUS § The anterior rami of the upper four lumbar nerves form the lumbar plexus (one of the main nervous pathways supplying the lower limb) in the psoas muscle. The anterior rami give off gray rami communicantes to the sympathetic trunk, and the upper two give receive white rami communicantes from the sympathetic trunk. The branches of the plexus emerge from the lateral and medial borders of the muscle and from its anterior surface. ). It also receives a contribution from the T 12 (subcostal) nerve. § Branches of the lumbar plexus include the iliohypogastric, ilio -inguinal, genitofemoral, lateral cutaneous nerve of thigh (lateral femoral cutaneous), femoral, and obturator nerves. The lumbar plexus forms in the substance of the psoas major muscle anterior to its attachment to the transverse processes of the lumbar vertebrae

z Branches & Distribution § Iliohypogastric and ilio-inguinal nerves (L 1) § The iliohypogastric and ilio-inguinal nerves arise as a single trunk from the anterior ramus of nerve L 1. Either before or soon after emerging from the lateral border of the psoas major muscle, this single trunk divides into the iliohypogastric and the ilio-inguinal nerves. § Iliohypogastric nerve § The iliohypogastric nerve passes across the anterior surface of the quadratus lumborum muscle, posterior to the kidney. It pierces the transversus abdominis muscle and continues anteriorly around the body between the transversus abdominis and internal oblique muscles. Above the iliac crest, a lateral cutaneous branch pierces the internal and external oblique muscles to supply the posterolateral gluteal skin The remaining part of the iliohypogastric nerve (the anterior cutaneous branch) continues in an anterior direction, piercing the internal oblique just medial to the anterior superior iliac spine as it continues in an obliquely downward and medial direction. Becoming cutaneous, just above the superficial inguinal ring, after piercing the aponeurosis of the external oblique, it distributes to the skin in the pubic region. Throughout its course, it also supplies branches to the abdominal musculature.

z Ilio-inguinal nerve § The ilio-inguinal nerve is smaller than, and inferior to, the iliohypogastric nerve as it crosses the quadratus lumborum muscle. Its course is more oblique than that of the iliohypogastric nerve, and it usually crosses part of the iliacus muscle on its way to the iliac crest. Near the anterior end of the iliac crest, it pierces the transversus abdominis muscle, and then pierces the internal oblique muscle and enters the inguinal canal. § The ilio-inguinal nerve emerges through the superficial inguinal ring, along with the spermatic cord, and provides cutaneous innervation to the upper medial thigh, the root of the penis, and the anterior surface of the scrotum in men, or the mons pubis and labium majus in women. Throughout its course, it also supplies branches to the abdominal musculature.

z Genitofemoral nerve (L 1 and L 2) § The genitofemoral nerve arises from the anterior rami of the nerves L 1 and L 2. It passes downward in the substance of the psoas major muscle until it emerges on the anterior surface of psoas major. It then descends on the surface of the muscle, in a retroperitoneal position, passing posterior to the ureter. It eventually divides into genital and femoral branches. § The genital branch continues downward and enters the inguinal canal through the deep inguinal ring. It continues through the canal and: § in men, innervates the cremasteric muscle and terminates on the skin in the upper anterior part of the scrotum; and § in women, accompanies the round ligament of the uterus and terminates on the skin of the mons pubis and labium majus. § The femoral branch descends on the lateral side of the external iliac artery and passes posterior to the inguinal ligament, entering the femoral sheath lateral to the femoral artery. It pierces the anterior layer of the femoral sheath and the fascia lata to supp ly the skin of the upper anterior thigh

z Lateral cutaneous nerve of thigh (L 2 and L 3) The lateral cutaneous nerve of thigh arises from the anterior rami of nerves L 2 and L 3. It emerges from the lateral border of the psoas major muscle, passing obliquely downward across the iliacus muscle toward the anterior superior iliac spine. It passes posterior to the inguinal ligament and enters the thigh. § The lateral cutaneous nerve of thigh supplies the skin on the anterior and lateral thigh to the level of the knee §

z Obturator nerve (L 2 to L 4) § The obturator nerve arises from the anterior rami of the nerves L 2 to L 4. It descends in the psoas major muscle, emerging from its medial side near the pelvic brim. The obturator nerve continues posterior to the common iliac vessels, passes across the lateral wall of the pelvic cavity, and enters the obturator canal, through which the obturator nerve gains access to the medial compartment of the thigh. § In the area of the obturator canal, the obturator nerve divides into anterior and posterior branches. On entering the medial compartment of the thigh, the two branches are separated by the obturator externus and adductor brevis muscles. Throughout their course through the medial compartment, these two branches supply: § § articular branches to the hip joint; muscular branches to obturator externus, pectineus, adductor longus, gracilis, adductor brevis, and adductor magnus muscles; cutaneous branches to the medial aspect of the thigh; and in association with the saphenous nerve, cutaneous branches to the medial aspect of the upper part of the leg, and articular branches to the knee joint § §

z Femoral nerve (L 2 to L 4) § The femoral nerve arises from the anterior rami of nerves L 2 to L 4. It descends through the substance of the psoas major muscle, emerging from the lower lateral border of the psoas major. Continuing its descent, the femoral nerve lie s between the lateral border of the psoas major and the anterior surface of the iliacus muscle. It is deep to the iliacus fascia and lateral to the femoral artery as it passes posterior to the inguinal ligament and enters the anterior compartment of the thigh. Upon entering the thigh, it immediately divides into multiple branches. § Cutaneous branches of the femoral nerve include: § medial and intermediate cutaneous nerves supplying the skin on the anterior surface of the thigh; and § the saphenous nerve supplying the skin on the medial surface of the leg (Fig. 4. 159). § Muscular branches innervate the iliacus, pectineus, sartorius, rectus femoris, vastus medialis, vastus intermedius, and vastus lateralis muscles. Articular branches supply the hip and knee joints