Q33 Pectoralis Major

Question 1

Briefly describe the position of this muscle

Answer 1

Pectoralis major is located on the upper part of the anterior surface of the thoracic wall superficial to pectoralis minor and forming the anterior fold of the axilla.

Question 2

State the attachments of this muscle

Answer 2

The proximal attachments are: for the smaller clavicular fibres the medial half of the anterior surface of the clavicle, sternocostal attachment half of the anterior surface of the manubrium and body of the sternum the anterior surface of the upper 6 costal cartilages. The distal attachment is to the lateral lip of the intertubercular sulcus of the humerus.

Question 3

Give the actions of this muscle

Answer 3

A powerful adductor and medial rotator of the humerus at the shoulder joint, clavicular fibres can flex the humerus to the horizontal, the sternocostal fibres can extend the flexed humerus against resistance. Also with the humerus fixed (for example when gripping the back of a chair) it pulls on the upper ribs to assist in inspiration in respiratory distress.