Brachial Plexus
The brachial plexus is a network of spinal nerves. Spinal nerves carry information from peripheral sensory receptors to the spinal cord (of the central nervous system), and then carry information back from the central nervous system to effector muscles and glands. The brachial plexus carries out these functions in the pectoral girdle and upper limbs. Specifically, nerves of the brachial plexus aid in innervation of the muscles of the upper limbs (with the exception of the trapezius and the levator scapula. In addition to muscular innervation, these nerves also innervate most of the cutaneous membrane of the upper limb (with the exception of the axilla, a point on the superior portion of the shoulder, and the dorsal scapular area).
The nerves of the brachial plexus originate from each side of the five most inferior cervical vertebrae (C4 – C8) and from the first thoracic vertebra (T1). In connection to the spinal cord, spinal nerves have a ventral root and an anterior root, which join at the spinal nerve. The initial portions of ventral rami are also referred to as ‘roots,’ however these are considered to be roots of the plexus. Moving laterally, the ventral rami of C5 and C6 join to form the portion known as the superior trunk. The root originating from C7 continues laterally to form the middle trunk, and the unification of the ventral rami of C8 and T1 form portion known as the inferior trunk.
Each of the three trunks bisects to form an anterior division, which generally innervates muscles responsible for flexor movement, and a posterior division (which innervates muscles responsible for extension). Moving distally, the anterior portion of the superior and middle trunk combine, forming the lateral cord. The dorsal portion of the inferior trunk then becomes the medial cord, and the posterior portion of all three trunks come together and form the posterior cord.
Moving distally, the cords separate into terminal branches, which attend to both autonomic and
The nerves of the brachial plexus originate from each side of the five most inferior cervical vertebrae (C4 – C8) and from the first thoracic vertebra (T1). In connection to the spinal cord, spinal nerves have a ventral root and an anterior root, which join at the spinal nerve. The initial portions of ventral rami are also referred to as ‘roots,’ however these are considered to be roots of the plexus. Moving laterally, the ventral rami of C5 and C6 join to form the portion known as the superior trunk. The root originating from C7 continues laterally to form the middle trunk, and the unification of the ventral rami of C8 and T1 form portion known as the inferior trunk.
Each of the three trunks bisects to form an anterior division, which generally innervates muscles responsible for flexor movement, and a posterior division (which innervates muscles responsible for extension). Moving distally, the anterior portion of the superior and middle trunk combine, forming the lateral cord. The dorsal portion of the inferior trunk then becomes the medial cord, and the posterior portion of all three trunks come together and form the posterior cord.
Moving distally, the cords separate into terminal branches, which attend to both autonomic and