4 major nerve plexuses are found, which - together with their peripheral nerves -
- arises from the ventral rami of C1 - C5
- supplies muscles of the shoulder and neck
- major motor branch is the phrenic nerve
- innervates the diaphragm
"The primary danger of a 'broken neck' is that the phrenic nerve may have been severed, leading to paralysis, cessation of breathing and death ..."
- arises from ventral rami of C5 - C8, and T1
- subdivides into 5 major peripheral nerves which are:
- serves the muscles and skin of the shoulder, e.g. deltoid muscle
- damage causes paralysis and atrophy of deltoid
- large peripheral nerve which innervates all extensor muscles of the arm, forearm and hand; and all the skin along the way;
- e.g. triceps brachialis
- damage causes wrist drop and inability to extend hand at wrist;
- runs down anterior of the arm
- supplies most of the flexor muscles in the forearm and several muscles in the lateral part of the hand;
- damage causes inability to pick up small objects due to decrease ability to flex and abduct thumb and index finger;
4. Musculocutaneous nerve
- innervates the arm muscles that flex the forearm and of the skin of the lateral surface of the forarm;
- damage leads to decreased ability to flex the forearm;
- runs down along the postero-medial surface of the arm;
- supplies the flexor carpi ulnaris muscle and all intrinsic muscles of the hand not served by the median nerve;
- damage causes typical "clawhand" with inability to spread fingers apart;
- arises from the central rami of L1 - L4;
- innervates the lower abdominal region and the anteromedial thigh;
- the largest nerve of this plexus is the femoral nerve;
- innervates the anterior thigh muscles, lower abdomen, buttocks, and the skin of the anteromedial leg and thigh;
- damage causes inability to extend leg and to flex the hip;
- another important nerve associated with this plexus is the obturator nerve;
- innervates the adductor muscles of the medial thigh and small hip muscles; also serves the skin of the medial thigh and hip joint;
- damage leads to inability to adduct the thigh;
- peripheral nerves of this plexus innervate the buttock, the posterior thigh and virtually all of the leg and foot;
- the major nerve of this plexus is the sciatic nerve;
- it is the largest nerve of the human body!
- travels through the greater sciatic notch of the hip bone down to the posterior thigh;
- innervates the lower trunk and the posterior surface of thigh and leg;
- damage leads to inability to extend hip and to flex the knee --> "sciatica"
- divides in the popliteal region into the:
- innervates the lateral aspect of the leg and foot;
- damage leads to inability to dorsiflex the foot --> "footdrop"
- innervates the posterior aspect of the leg and foot;
- damage leads to inability to plantar flex and invert the foot --> "shuffling gait";
- another important nerve of this plexus is the superior and inferior gluteal nerve;
- innervates the gluteal muscles of the hip;