which nerve of the brachial plexus innervates the serratus anterior muscle
Brachial plexus The five roots are the five anterior rami of the spinal nerves, after they have given off their segmental supply to the muscles of the neck. The brachial plexus emerges at five different levels; C5, C6, C7, C8, and T1. C5 and C6 merge to establish the upper trunk, C7 continuously forms the middle trunk, and C8 and T1 merge to establish the lower trunk. Prefixed or postfixed formations in some cases involve C4 or T2, respectively. The dorsal scapular nerve comes from the superior trunk[2] and innervates the rhomboid muscles which retract the scapula. The subclavian nerve originates in both C5 and C6 and innervates the subclavius, a muscle that involves lifting the first ribs during respiration. The long thoracic nerve arises from C5, C6, and C7. This nerve innervates the serratus anterior, which draws the scapula laterally and is the prime mover in all forward-reaching and pushing actions.
Supraspinatus muscle The supraspinatus muscle performs abduction of the arm, and pulls the head of the humerus medially towards the glenoid cavity.[5] It independently prevents the head of the humerus to slip inferiorly.[5] The supraspinatus works in cooperation with the deltoid muscle to perform abduction, including when the arm is in adducted position.[5] Beyond 15 degrees the deltoid muscle becomes increasingly more effective at abducting the arm and becomes the main propagator of this action.[6]