Brachial region

The brachial region is the part of the thoracic limb located between the shoulder joint (scapulohumeral joint) and the elbow joint (humeroradioulnar joint).

Its only bony support is the humerus, which serves as a lever for locomotion and as an attachment site for numerous muscles.

The muscles of the arm are organized into two main functional compartments.

• The cranial compartment (flexor) contains the biceps brachii and brachialis muscles, whose primary function is flexion of the elbow. These muscles are innervated by the musculocutaneous nerve.

• The caudal compartment (extensor) is mainly composed of the triceps brachii muscle (with its different heads: long, lateral, medial, and accessory in carnivores), the anconeus, and the tensor fasciae antebrachii; it is responsible for extension of the elbow and is innervated by the radial nerve.

This region is traversed by neurovascular structures:

• The radial nerve runs in close contact with the humeral diaphysis in the brachial groove.

• The median nerve and brachial artery descend in the medial groove of the humerus, while the ulnar nerve branches off slightly more distally and laterally to reach the forearm.