Pectoralis major is a fan-shaped thick layer situated in the chest area of the human body and composed of a sternal head and a clavicular head. It is located at the top of pectoralis minor that is known smaller muscle of the chest. Pec minor is called its little brother, so both are called pecs. The bulk of the chest is made up of pec major. It is apparent in males as they do some muscle work and invisible in the female. Pecs muscles connect the front walls of the chest to the upper arm and shoulders.
The pectoral region is located on the anterior chest wall, containing four muscles, the pectoralis minor, major, serratus anterior and subclavius. Pectoralis major is active in deep inspiration but not expiration. To know more about this muscle and its anatomy, read this article thoroughly and carefully.
Anatomy of Pectoralis Major:
It consists of two heads, clavicular head, and sternal head. The former originates on the inside part of the collarbone and the second originates from three different regions, outside border of the sternum, costal cartilages of the top six ribs and aponeurosis of the external oblique muscle.
Both calvicular head and sternal head have the same points of insertion. Points of insertion are located on the humerus which is the long bone of the arm. There is another point of insertion that is the deltoid tuberosity, located at the average part of the humerus.
The main function of the pec major is to adduct and medially rotate the humerus and arm and motion of the shoulder joints. It draws the scapula anteriorly and inferiorly. Clavicular head abducts the humerus and sterna head extends it.
It is supplied from the brachial plexus branches of thoracoacrominal artery.
Pectoralis major Innervations:
It is innervated through the lateral and medial pectoral nerves. The clavicular and sterna heads are innervated by C5, C6, C7 and c8 and T1 respectively.