The musculocutaneous nerve
arises from the lateral cord
of the brachial plexus
, opposite the lower border of the Pectoralis major
, its fibers being derived from C5, C6 and C7.
It penetrates the Coracobrachialis
muscle and passes obliquely between the Biceps brachii
and the Brachialis
, to the lateral side of the arm; a little above the elbow it pierces the deep fascia lateral to the tendon of the Biceps brachii and is continued into the forearm as the lateral cutaneous nerve of the forearm
In its course through the arm it innervates the Coracobrachialis, Biceps brachii, and the greater part of the Brachialis.
- The branch to the Coracobrachialis is given off from the nerve close to its origin, and in some instances as a separate filament from the lateral cord of the plexus; it is derived from the seventh, cervical nerve.
- The branches to the Biceps brachii and Brachialis are given off after the musculocutaneous has pierced the Coracobrachialis; that supplying the Brachialis gives a filament to the elbow-joint.
- The nerve also sends a small branch to the bone, which enters the nutrient foramen with the accompanying artery.
The musculocutaneous nerve presents frequent irregularities.
It may adhere for some distance to the median and then pass outward, beneath the Biceps brachii, instead of through the Coracobrachialis.
Some of the fibers of the median may run for some distance in the musculocutaneous and then leave it to join their proper trunk;... Read More