The radial nerve is a nerve in the human body that supplies the posterior portion of the upper limb. It innervates the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm and the associated joints and overlying skin.
A spinal nerve is a mixed nerve, which carries motor, sensory, and autonomic signals between the spinal cord and the body. In the human body there are 31 pairs of spinal nerves, one on each side of the vertebral column. These are grouped into the corresponding cervical, thoracic, lumbar, sacral and coccygeal regions of the spine. There are eight pairs of cervical nerves, twelve pairs of thoracic nerves, five pairs of lumbar nerves, five pairs of sacral nerves, and one pair of coccygeal nerves. The spinal nerves are part of the peripheral nervous system.
The ulnar nerve is a nerve that runs near the ulna, one of the two long bones in the forearm. The ulnar collateral ligament of elbow joint is in relation with the ulnar nerve. The nerve is the largest in the human body unprotected by muscle or bone, so injury is common. This nerve is directly connected to the little finger, and the adjacent half of the ring finger, innervating the palmar aspect of these fingers, including both front and back of the tips, perhaps as far back as the fingernail beds.
The cervical plexus is a nerve plexus of the anterior rami of the first four cervical spinal nerves C1-C4. The cervical plexus provides motor innervation to some muscles of the neck, and the diaphragm; it provides sensory innervation to parts of the head, neck, and chest.
A dermatome is an area of skin that is mainly supplied by afferent nerve fibres from the dorsal root of any given spinal nerve. There are 8 cervical nerves , 12 thoracic nerves, 5 lumbar nerves and 5 sacral nerves. Each of these nerves relays sensation from a particular region of skin to the brain.
A nerve plexus is a plexus of intersecting nerves. A nerve plexus is composed of afferent and efferent fibers that arise from the merging of the anterior rami of spinal nerves and blood vessels. There are five spinal nerve plexuses, except in the thoracic region, as well as other forms of autonomic plexuses, many of which are a part of the enteric nervous system. The nerves that arise from the plexuses have both sensory and motor functions. These functions include muscle contraction, the maintenance of body coordination and control, and the reaction to sensations such as heat, cold, pain, and pressure. There are several plexuses in the body, including:
The intercostal nerves are part of the somatic nervous system, and arise from the anterior rami of the thoracic spinal nerves from T1 to T11. The intercostal nerves are distributed chiefly to the thoracic pleura and abdominal peritoneum, and differ from the anterior rami of the other spinal nerves in that each pursues an independent course without plexus formation.
The posterior cutaneous nerve of the thigh is a sensory nerve of the thigh. It is a branch of the sacral plexus. It supplies the skin of the posterior surface of the thigh, leg, buttock, and also the perineum.
The lumbar plexus is a web of nerves in the lumbar region of the body which forms part of the larger lumbosacral plexus. It is formed by the divisions of the first four lumbar nerves (L1-L4) and from contributions of the subcostal nerve (T12), which is the last thoracic nerve. Additionally, the ventral rami of the fourth lumbar nerve pass communicating branches, the lumbosacral trunk, to the sacral plexus. The nerves of the lumbar plexus pass in front of the hip joint and mainly support the anterior part of the thigh.
The lateral cutaneous nerve of the thigh is a cutaneous nerve of the thigh. It originates from the dorsal divisions of the second and third lumbar nerves from the lumbar plexus. It passes under the inguinal ligament to reach the thigh. It supplies sensation to the skin on the lateral part of the thigh by an anterior branch and a posterior branch.
The lateral cutaneous nerve of forearm is a sensory nerve representing the continuation of the musculocutaneous nerve beyond the lateral edge of the tendon of the biceps brachii muscle. The lateral cutaneous nerve provides sensory innervation to the skin of the lateral forearm. It pierces the deep fascia of forearm to enter the subcutaneous compartment before splitting into a volar branch and a dorsal branch.
The medial cutaneous nerve of the forearm is a sensory branch of the medial cord of the brachial plexus derived from the ventral rami of spinal nerves C8-T1. It provides sensory innervation to the skin of the medial forearm and skin overlying the olecranon. It descends through the (upper) arm within the brachial fascia alongside the basilic vein, then divides into an anterior branch and a posterior branch upon emerging from the brachial fascia; the two terminal branches travel as far distally as the wrist.
The medial brachial cutaneous nerve is a sensory branch of the medial cord of the brachial plexus derived from spinal nerves C8-T1. It provides sensory innervation to the medial arm. It descends accompanied by the basilic vein.
The intercostobrachial nerve is the name applied to the lateral cutaneous branch of the second intercostal nerve. It arises anterior to the long thoracic nerve. It provides sensory innervation to the skin of the axilla, and a variable region of the medial side of the upper arm.
The posterior cutaneous nerve of arm is a branch of the radial nerve that provides sensory innervation for much of the skin on the back of the arm. It arises in the axilla.
The cutaneous branch of the obturator nerve is an occasional continuation of the communicating branch to the femoral medial cutaneous branches and saphenous branches of the femoral to the thigh and leg. When present it emerges from beneath the distal/inferior border of the adductor longus muscle and descends along the posterior margin of the sartorius muscle to the medial side of the knee where it pierces the deep fascia and communicates with the saphenous nerve. When present, it provides sensory innervation to the skin of proximal/superior half of the medial side of the leg.
Cutaneous innervation of the lower limbs is the nerve supply to areas of the skin of the lower limbs which are supplied by specific cutaneous nerves.
Cutaneous innervation of the upper limbs is the nerve supply to areas of the skin of the upper limbs which are supplied by specific cutaneous nerves.
The following diagram is provided as an overview of and topical guide to the human nervous system:
