The Peripheral Nerves of the Neck, Shoulders and Arms

The Peripheral Nerves of the Neck, Shoulders and Arms Many spinal nerves form interlacing nerve networks – the cervical, brachial, lumbar and sacral nerve plexuses. The cervical plexus in the neck involves the upper 4 cervical nerves and forms the phrenic nerve which supplies both sensory and motor innervation to the diaphragm which is important for breathing. The brachial plexus in the neck and armpit (axilla) involves C4-T2 and innervates the upper limb (arm and shoulder). These give rise to the axillary nerve, musculocutaneous nerve, median nerve, ulnar nerve and radial nerve (and a few others). The axillary nerve comes out behind the head of humerus to innervate the shoulder joint and the deltoid and teres minor muscles. The musculocutaneous nerve comes down the anterior arm innervates flexion of the forearm and sensory for the laterally forearm. The median nerve comes all the way down the central anterior arm to innervate the forearm flexor muscles and activate pronation of the forearm, flexion of the wrist and fingers and opposition of the thumb. It receives sensory from the forearm skin and the lateral palm. The ulnar nerve comes down the medial side of the arm, goes behind medial condyle of the elbow, down the medial forearm and innervates muscles of the forearm and fingers for wrist and medial finger flexion, adduction and abduction. It receives sensory from the medial side of the hand. The radial nerve is the largest of the nerves off the brachial plexus. It comes down the posterior arm, then wraps around the anterior aide of the lateral epicondyle of the elbow, then splits into a superficial branch and deep branch. It innervates all the extensor muscles of the upper limb and receives sensory from the skin of the posterior arm. The Peripheral Nerves of the Neck, Shoulders and Arms brachial plexus axillary nerve musculocutaneous nerve median nerve radial nerve ulnar nerve The Cervical Plexus The cervical plexus is deep in the neck and is fed by the ventral rami of C1-C4. It supplies both sensory (afferent) and motor (efferent) fibers to the phrenic nerve which controls the diaphragm - the main muscle that allows breathing movements. The cervical plexus also brings in sensory impulses from the skin of the neck, ears and shoulders. There is some motor for the muscles of the anterior neck as well. accessory nerve (cranial XI) C1 hypoglossal nerve (cranial XII) lesser occipital nerve C2 greater auricular nerve ansa cervicalis transverse cervical C3 C4 supraclavicular nerves phrenic nerve C5 The Cervical Plexus accessory nerve (cranial XI) C1 hypoglossal nerve (cranial XII) lesser occipital nerve C2 greater auricular nerve ansa cervicalis transverse cervical C3 C4 supraclavicular nerves phrenic nerve C5 The Brachial Plexus The brachial plexus is the source of almost all the nerves that innervate the upper limb (arm and shoulder. It lies in the neck and armpit (axilla) and involves nerve fibers from C4 -T2. These give rise to the axillary nerve, musculocutaneous nerve, median nerve, ulnar nerve and radial nerve (and a few others). Below is an illustration of the complex structure of the brachial plexus and it’s source off the cervical and thoracic nerves. From C4 C5 dorsal scapular nerve C6 suprascapular nerve p Up a ter a L Po axillary nerve ulnar nerve C8 rd Co T1 nk Lower Tru ial Med d Cor long thoracic nerve medial pectoral nerve medial nerve radial nerve C7 M d or C l ior r e st k k Trun e l d id lateral pectoral nerve musculocutaneous nerve run T r e medial cutaneus nerves of arm and forearm upper suprascapular nerve thoracodorsal nerve lower suprascapular nerve ulnar nerve radial nerve medial nerve axillary nerve musculocutaneous nerve ior r e st Po ra e t La d or C l medial cutaneus nerves of arm and forearm lateral pectoral nerve suprascapular nerve ord T1 C8 C7 C6 C5 From C4 long thoracic nerve medial pectoral nerve nk Lower Tru unk upper suprascapular nerve thoracodorsal nerve lower suprascapular nerve ial C Med rd Co k e Tr idd l M p Up run T er dorsal scapular nerve The Brachial Plexus The Lumbosacral Plexus (The Peripheral Nerves of the Pelvis, Buttock and Lower Limbs) The lumbosacral plexus is the overlapping of the lumbar and sacral plexuses and innervates the lower limb and parts of the abdomen, pelvis and buttock. The lumbar plexus comes off L1-L4. It innervates the anterior and medial thigh and parts of the abdominal wall and iliopsoas muscle. It’s largest branch, the femoral nerve, splits into many branches to innervate the anterior thigh muscles for thigh flexion and knee extension. It receives sensory input from the anterior thigh and medial leg between the knee and foot. The obturator nerve innervates the medial thigh adductor muscles. The sacral plexus comes off L4-S4. It’s largest branch is the sciatic nerve, which is made up of the tibial nerve and the common peroneal nerve. The sciatic nerve enters the back of the thigh just medial to the hip joint and gives off branches to innervate the hamstring muscles, which are thigh extensors and knee flexors. Right above the knee it splits into the tibial and common peroneal nerves. The tibial nerve goes behind the knee (called the popliteal fossa) and innervates the posterior calf muscles. It receives sensory from the skin behind the calf and the sole of the foot. It gives off the sural nerve which receives sensory from the posterior-lateral calf and the plantar nerves which innervates the foot. When the common peroneal nerve splits off the sciatic nerve, it wraps around the head of the fibula and splits into the superficial and deep branches which innervate the anterior-lateral calf muscles, which are extensors and dorsiflexors of the foot. It receives sensory from the knee joint, lateral calf and top (dorsum) of the foot. The sacral plexus also gives off the superior and inferior gluteal nerves which innervate the gluteal muscles of the buttock and a lateral muscle of the thigh (tensor fascia lata). It also gives of the pudendal nerve, which innervates structures in the pelvis. Lumbar Plexus Sacral Plexus The Peripheral Nerves of the Pelvis, Buttock and LEGS anterior view inguinal ligament lateral femoral cutaneous nerve femoral nerve posterior view posterior femoral cutaneous nerve obturator nerve sciatic nerve common peroneal nerve saphenous nerve common peroneal nerve tibial nerve superficial peroneal nerve deep peroneal nerve sural nerve sural nerve The Lumbar Plexus The lumbar plexus comes off L1-L4. It innervates the anterior and medial thigh and parts of the abdominal wall and iliopsoas muscle. It’s largest branch, the femoral nerve, splits into many branches to innervate the anterior thigh muscles for thigh flexion and knee extension. It receives sensory input from the anterior thigh and medial leg between the knee and foot. The obturator nerve innervates the medial thigh adductor muscles. L1 L2 iliohypogastric nerve ilioinguinal nerve L3 genitofemoral nerve L4 lateral femoral nerve L5 femoral nerve lumbosacral trunk obturator nerve The Lumbar Plexus L1 L2 iliohypogastric nerve ilioinguinal nerve L3 genitofemoral nerve L4 lateral femoral nerve L5 femoral nerve lumbosacral trunk obturator nerve The Sacral Plexus The sacral plexus comes off L4-S4. It’s largest branch is the sciatic nerve, which is made up of the tibial nerve and the common peroneal nerve. The sciatic nerve enters the back of the thigh just medial to the hip joint and gives off branches to innervate the hamstring muscles, which are thigh extensors and knee flexors. Right above the knee it splits into the tibial and common peroneal nerves. The tibial nerve goes behind the knee (called the popliteal fossa) and innervates the posterior calf muscles. It receives sensory from the skin behind the calf and the sole of the foot. It gives off the sural nerve which receives sensory from the posterior-lateral calf and the plantar nerves which innervates the foot. When the common peroneal nerve splits off the sciatic nerve, it wraps around the head of the fibula and splits into the superficial and deep branches which innervate the anterior-lateral calf muscles, which are extensors and dorsiflexors of the foot. It receives sensory from the knee joint, lateral calf and top (dorsum) of the foot. The sacral plexus also gives off the superior and inferior gluteal nerves which innervate the gluteal muscles of the buttock and a lateral muscle of the thigh (tensor fascia lata). It also gives of the pudendal nerve, which innervates structures in the pelvis. superior gluteal nerve lumbosacral trunk L4 L5 S1 The Sacral Plexus inferior gluteal nerve S2 common peroneal nerve S3 tibial nerve S4 sciatic nerve posterior temporal cutaneous nerve pudendal nerve The Sacral Plexus L4 lumbosacral trunk L5 superior gluteal nerve inferior gluteal nerve S1 S2 common peroneal nerve S3 tibial nerve S4 sciatic nerve posterior temporal cutaneous nerve pudendal nerve