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Middle trunk. Truncus medius. Acontinuation of C7 spinal nerve itself. C

Lower trunk. Truncus inferior. Formed by the union of C8 andT1 spinal nerves; it lies within the scalenus gap posterior to the subclavian artery. C Anterior divisions. Divisiones anteriores. Portions of brachial plexus formed by the anterior branches of the three trunks. They supply the flexor muscles.

Posterior divisions. Divisiones posteriores. Portions of brachial plexus formed by the posterior branches of the three trunks. They unite to form the posterior cord and supply the extensor muscles. Cords. Fasciculi. Three nerve bundles formed by the union of branches (anterior and/or posterior) from the three trunks.

SUPRACLAVICULAR PART. Pars supraclavicularis. Part ofbrachial plexus extending up to the superior margin of the clavicle. C Dorsal scapular nerve. N. dorsalis scapulae. Nerve that arises from C5 directly lateral to the intervertebral foramen, penetrates the scalenus medius and then courses below the levator scapulae and the two rhomboid muscles, which it innervates. C

Long thoracic nerve. N. thoracicus longus. Nerve that arises from C5-7, penetrates the scalenus medius and travels on the serratus anterior, which it supplies. C

Nerve to subclavius. N. subclavius. Slender nerve from the upper trunk with fibers from C4-6 for the subclavius muscle. It frequently sends a branch (11) to the phrenic nerve. C Suprascapular nerve. N. suprascapularis. Nerve that arises from C5-6, passes over the brachial plexus to the scapular notch and then goes under the superior transverse ligament of the scapula to innervate the supra- and infraspinatus muscles. C INFRACLAVICULAR PART. Pars infraclaviculares. Portion of brachial plexus below the clavicle. It extends from the upper margin of the clavicle to the level where the cords divide into the individual nerves. C

Lateral cord. Fasciculus lateralis. Located lateral to the axillary artery, it is formed by the union of the anterior divisions of the upper and middle trunks, thus from C5-7. C Medial cord. Fasciculus medialis. Cord located medial to the axillary artery. It is formed solely by the anterior division of the lower trunk, thus from C8-T1. C

Posterior cord. Fasciculus posterior. Cord located posterior to the axillary artery; it is formed by the union of the posterior divisions of all three trunks, thus from C5-T1. C Medial pectoral nerve. N. pectoralis medialis. Nerve formed by fibers from the medial cord, thus from C8-T1. It supplies the pectoralis major and minor muscles. C

Lateral pectoral nerve. N. pectoralis lateralis. Fibers from C5-7 that supply the two pectoral muscles. C

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Essentials of Human Physiology

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