Brachial plexus
Say it: BRAY-kee-ul PLEK-sus
The brachial plexus is the network of nerves formed from spinal nerves C5 to T1 that supplies movement and feeling to the shoulder, arm and hand.
Also: plexus brachialis
Definition
What is the brachial plexus?
The brachial plexus begins in the neck, where the front branches (anterior rami) of the fifth cervical to first thoracic spinal nerves, C5 to T1, emerge between the scalene muscles. As the fibers pass over the first rib, behind the clavicle and into the armpit, they repeatedly split and merge, so each final nerve carries fibers from several spinal levels. Anatomists describe this in five stages: roots, three trunks (upper, middle and lower), anterior and posterior divisions, three cords (lateral, medial and posterior, named for their position around the axillary artery) and terminal branches. In some people small contributions come from C4 or T2.
The five main terminal branches are the musculocutaneous, axillary, radial, median and ulnar nerves. Together with smaller branches they carry motor commands to almost every muscle of the upper limb and return sensation from its skin and joints.
The plexus is easily injured when the head and shoulder are forced apart, as in motorcycle crashes, falls and difficult births. Damage to the upper roots (Erb's palsy) leaves the arm hanging limp and turned inward, while damage to the lower roots (Klumpke's palsy) mainly weakens the hand. Injuries range from stretching, which often recovers, to rupture of the nerves or avulsion of roots from the spinal cord, which may need nerve surgery.
Word parts
Where does the term “brachial plexus” come from?
- brachi-
- armLatin brachium
- plexus
- braid, networkLatin plexus, from plectere (to weave)
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Terms that go with it
- Spinal cordThe spinal cord is the column of nerve tissue in the vertebral canal that relays signals between the brain and the body and runs many reflexes.
- AxonAn axon is the single long projection of a neuron that carries electrical impulses away from the cell body toward other neurons, muscles or glands.
- NeuronA neuron is a nerve cell, the basic signaling unit of the nervous system, which receives information and passes it on as electrical and chemical signals.
- Skeletal muscleSkeletal muscle is the striated, voluntary muscle tissue attached to bones by tendons that moves the body, holds posture and produces heat.
- MyelinMyelin is the fatty, layered sheath that glial cells wrap around many axons, insulating them so nerve impulses travel faster and more efficiently.
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