Deltoid Muscle - Anterior and Middle Heads
Pectoralis Major Muscle – Attachment, Action & Innervation
Pectoralis major is a thick, fan-shaped muscle contributing to the thoracobrachial motion. It consists of a clavicular part and a sternal part, both converging to a flat tendon that inserts on the humerus. It’s innervated by both medial and lateral pectoral nerves.
Attachments of Pectoralis Major Muscle: Origin & Insertion
Origin: (proximal attachments)
a. Clavicular head: medial half of the clavicle.
b. Sternal head: sternum, upper costal cartilages (1-6), and the aponeurosis of the external oblique.
Insertion: (distal attachments)
a. Lateral lip of the intertubercular (bicipital) groove of the humerus.
b. Crest of the greater tubercle of the humerus.
Actions of Pectoralis Major Muscle:
Both heads working together:
Innervation of Biceps Brachii:
b. C8 and T1 (medial pectoral nerve to the sternal head).