Chapter 13 - The Peripheral Nervous System and Reflex Activity - Review Questions - Page 522: 20b

Cervical plexus. Spinal nerves involved: C1-C4(C5) Composition : ventral rami of C1-C5 Location: deep in the neck under the sternocleidomastoid muscle Areas served: Sensory branches to skin of neck, ear area back of head and shoulder motor nerves to muscles of anterior neck; the phrenic nerve (C3-C4) provides sensory and motor supply to the daipragm which is the chief muscle of respiration. Brachial Plexus: Spinal nerves involved: C5-T1( +lower half of T2) Composition: Ventral rami of C5-T1 and lower half of T2 Location : under armpit Service area: chest, shoulder, arms and hands Lumbar Plexus Spinal nerves involved: L1-L5( and parts of T12) Composition: ventral rami of L1-L5 Location: within psoas major muscle Service area: abdominal wall muscles, psoas muscle,muscles of anterior and medial thigh, skin of thigh and medial surface of leg from thigh to foot Sacral Plexus Spinal nerves involved: L4-S4 Composition: ventral rami of L4-S4 Location: posterior wall of pelvic cavity Area served: pelvis, buttocks, genitals, thighs, calves , feet.

The four major spinal nerve plexuses are the cervical plexus, the brachial plexus, the lumbar plexus and the sacral. The lumbar and the sacral complexes are often discussed together as the lumbosacral plexus. 1. Cervical Plexus; The cervical plexus id formed by the ventral rami of spinal nerves C1-C4(C5). It is located deep in the neck under the sternocleidomastoid muscle. Some of the sensory nerves that derive from this plexus are: lesser occipital , greater auricular, transverse cervical, supraclavicular. The motor complement includes ansa cervicalis, segmental and the phrenic nerve The phrenic nerve is the sole motor supply to the diaphragm the principal muscle of ventilation. Areas served: Transmits impulses from skin of neck. ear area, back of head, shoulder, . The efferent nerves serve the anterior neck. The phrenic nerve (C3-C4) traverses the anterior thorax and carries sensory and motor fibers to the diaphragm which is the chief muscle of respiration ( ventilation. 2.Brachial Plexus This plexus comprises the ventral rami of C5-T1 (with contributions from T2 It is located partly in the neck and partly under the armpit. . Branches serve the chest, shoulder, arms and hands. This is the largest and most important spinal nerve plexus. some of the nerves that derive from this plexus are,, median, musculocutaneous, , the radial, the ulnar, the axillary, the dorsal scapular, the long thoracis the subscapula and the pectoral Areas served; Axillary :Skin and joint capsule of shoulder; deltoid and teres major muscle Musculocutaneous:: Motor fibers to biceps brachii, brachialis, and coracobrachialis, cutaneous nerves to lateral forearm Median : Skin of forearm, flexor muscles of forearm, intrinsic muscles of forearm, muscles of side of palm, muscles that pronate the forearm, flex the wrist and fingers and oppose the thumb Radial nerve. Largest nerve of the plexus: Supplies posterior skin of upper limbs. extensor muscles of upper limbs, supplies muscles that supinates the forearm, extend the elbow, extend the wrist and fingers, and abduct the thumb. Ulnar nerve: Supplies flexor carpi ulnaris, flexor digitorum profundum, intrinsic muscles of the hand, and skin of hand; flexes, wrist and fingers; adducts and abducts medial fingers. 3. Lumbar Plexus Comprised of ventral roots L1-L4 Areas served: lower limbs; branches supply muscles of abdominal wall, psoas muscle pelvis and buttocks, anterior and medial thigh. Important nerves that derive from this plexus include the femoral ( longest nerve in the body), the obturator, lateral cutaneous cutaneous, the Iliohypogastric, he Ilioinguinal and the genitofemoral. Some Areas served by Lumbar Plexus It serves the anterior thigh muscles( for example , the quadriceps femoris.), the thigh flexors and knee extensors, Cutaneous branches go skin of anterior thigh and medial surface of leg --knee to foot. The obturator nerve : Areas served: adductor muscles of median thigh ( longus, brevis and gracilis), Sensory branches go to skin of medial thigh, hip and knee joint. Lateral femoral cutaneous; supplies skin of lateral thigh. Sensory branches supply the peritoneum. Iliohypogastric: ; Serves skin of lower abdomen and hip. Also supplies muscles of the anterolateral wall of the abdomen--internal oblique and transversus. Ilioinguinal: Supplies skin of external genitalia, medial aspects of the thigh; and inferior abdominal wall. Genitofemoral:Supplies skin of anterior thigh ; also innervates skin of scrotum and the cremaster muscles in males; in females it supplies the labia majora. Sacral Plexus: Includes ventral rami L4-S4 The sacral and the lumbar plexus share some branches. There are 11 sacral nerve branches; Some areas served include buttocka and lower limbs. Motor branches go to the hamstrings and to the adductor major. Some important branches of this plexus are the sciatic--the longest and thickest nerve in the body. It serves most of the lower limbs --except the anteromedial thigh Other important branches of the sacral plexus are tibial, the common fibular and the pudendal. The tibial supplies posterior muscles of the leg, skin of posterior calf, and sole of the foot. The sural branch supplies the supplies the skin of the posterior and lateral leg , while the medial and lateral plantar nerves supply most of the foot. the superior and inferior gluteal supply gluteal muscles of the buttocks and the tensor fasciae latum. Pudendal nerve: Serves muscles o and skin of the perineum . It controls urination and erection. Other nerves of the sacral plexus supply thigh rotators and muscles of the pelvic floor.