The nerves

A nerve is a sort of two-way power cable from the spinal cord and the brain.

It allows at the level of a member to:

control the muscles to perform movements (motor role);

to report various information to the brain such as sensation (sensory role), pain (nociceptive role), position in limb space (proprioceptive role);

also to control the cutaneous heat, the circulation of the blood by means of micro-vessels (vegetative role);

And many other things ! …

Some nerves are mixed (motor and sensory control), pure motor or purely sensory

We will confine ourselves here to the main nerves of the shoulder after having briefly evoked their origin, namely the brachial plexus.

Rapports du plexus brachial avec le squelette de l’épaule et les vaisseaux du membre supérieur
plexus brachial

The axillary nerve is an end branch of the posterior (and therefore secondary) branch of the brachial plexus.

His former name is circumflex nerve because presents a circular path.

It is a relatively short nerve since it bypasses the humerus at the level of its surgical collar.

It has relationships with the lower region of the glenohumeral joint, lower articular capsule and lower edge of the subscapular muscle and tendon.

Once the humerus is bypassed from the back, it travels to the deep surface of the Deltoid muscle that it innervates and contributes to the sensitivity of the shoulder stump of the lateral aspect of the arm.

His traumatic pathology is met with in certain dislocations of the shoulder since the nerve accompanies the humerus during its displacement, in the accidents of the road (motorcycle in particular).

The pathology will be further detailed in one chapter (pathology -> other -> neurological shoulder).

The musculocutaneous nerve is an end branch of the lateral (secondary) trunk.

Its course is also close to the shoulder area since it is internal, close to the coracoid along the origin of the coraco-biceps tendon.

He keeps intimate contact with the coraco-brachial, biceps and brachial muscles to which he distributes nervous twigs.

It is therefore the nerve of the flexion of the forearm on the arm through these muscles.

Its terminating branch is sensitive anterior aspect of the forearm and outer edge of the wrist (inconstant).

The supra-scapular nerve is one of the main nerves of the rotator cuff.

The supra-scapular nerve originates from the upper (primary) trunk consisting of the union of the C5 and C6 roots.

he quickly joins the scapula (scapula) near the coracoid process which he crosses medially through a tunnel under the transverse ligament at the level of the coracoidal exchanger.

He then joins the posterior face of the scapula to the deep surface of the supraspinous muscles and then, near his passage from the spine of the infra-spinous scapula, he innervates these 2 muscles (pure motor nerve)

He thus participates in the abduction of the arm (especially in the first third of the movement by the supraspinous) and the external rotation (by the infraspinous).

The nerve has fixed points at the level of the coracoid notch and passage of the spine of the scapula near the posterior surface of the glenoid (‘spino-glenoid’ notch).