Anatomy
Summary
The brachial plexus is part of the peripheral nervous system, carrying somatic motor and sensory fibers that innervate the shoulder and upper extremity. This plexus is organized from proximal to distal into five segments: roots, trunks, divisions, cords, and terminal branches. The roots of the brachial plexus are the ventral rami of the spinal nerves C5 through T1, which merge to form the superior, middle and inferior trunks. The trunks further divide into anterior and posterior divisions as they exit the neck and pass between the first rib and the clavicle.
These divisions subsequently form three cords, which are named based on their position relative to the axillary artery: lateral, medial, and posterior. The cords further continue as five terminal branches comprising the musculocutaneous, axillary, radial, median, and ulnar nerves. In addition to these primary terminal branches, the brachial plexus also gives rise to eleven preterminal branches.
Lesson Outline
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FAQs
The brachial plexus is a complex network of nerves that originates from the ventral rami of the middle to lower cervical and first thoracic spinal nerves in the neck (C5 through T1). As part of the peripheral nervous system, it forms a conduit for nerve signals between the brain and the upper extremities including the shoulder, arm, forearm, and hand.
The brachial plexus is divided into five primary segments: roots, trunks, divisions, cords, and terminal branches. The roots join together to form three trunks, which then further divide into anterior and posterior divisions. Three cords arise from these divisions, which continue on to give off the terminal branches. There are also 11 preterminal branches.
The cords of the brachial plexus are named based on their position in relation to the axillary artery: the lateral cord is situated to the lateral side, the posterior cord is situated posteriorly, and the medial cord is situated medially.
The roots merge to become three trunks. C5 and C6 form the superior trunk, C7 continues as the middle trunk, and C8 and T1 make up the inferior trunk.
