The muscles of the arm are divided in two regions, anterior or flexor and posterior or extensor, separated from each other by the septa of the brachial fascia.
The brachial fascia, which at the top continues with the axillary fascia and with the fascia covering the pectoral and deltoid muscles, sends the two medial and lateral intermuscular septa to the humerus. They correspond to the two medial and lateral bicipital grooves visible to the arm inspection. 

  • The muscles of the anterior region are the Biceps Brachii (superficial), the Coracobrachialis and the Brachialis, all innervated by branches of the musculocutaneous nerve. 
  • Posteriorly there is the Triceps Brachii muscle, innervated by the radial nerve.