Brachial Plexus

Description

Originating from the anterior rami of C5 to T1, the brachial plexus forms in the lower lateral neck between the anterior and middle scalene muscles before coursing inferolaterally toward the shoulder girdle. Superior, middle, and inferior trunks lie proximal to the clavicle, then divide into anterior and posterior divisions as they pass posterior to the clavicle and over the first rib. Around the axillary artery, the lateral, posterior, and medial cords are arranged by position, then continue distally as the musculocutaneous, median, ulnar, radial, and axillary nerves in relation to the clavicle, scapula, and ribcage. Bony landmarks are crisp. Cervical vertebrae, ribs, sternum, clavicle, and scapula anchor the nerve network spatially, with superficial veins included as blue companions. Course matters here because the plexus is vulnerable where it is tethered, at the interscalene triangle, the costoclavicular space, and beneath pectoralis minor. Traction injuries after shoulder depression or lateral neck flexion classically involve the upper trunk (Erb palsy, C5 to C6), while compression from a cervical rib or scalene hypertrophy can target the lower trunk and medial cord (neurogenic thoracic outlet syndrome) with ulnar-sided paresthesia and intrinsic hand weakness. For anesthetists, the relationship of trunks and cords to the clavicle and first rib frames why an interscalene block spares the ulnar distribution and why infraclavicular approaches better capture the cords. Designed for gross anatomy and neuroanatomy teaching, this plate supports brachial plexus mapping exercises, OSCE prep, and textbook figures explaining trunk versus cord-level deficits. It also fits clinical handouts for orthopedic, sports medicine, and peripheral nerve surgery discussions of thoracic outlet syndrome, clavicle fracture traction neuropathy, and iatrogenic plexopathy after shoulder procedures. Anatomical accuracy verified by SciePro's Medical Advisory Board.