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Origins, insertions, innervation and functions of the pectoralis major muscle.
Hey, everyone! It’s Matt from Kenhub, and in this tutorial, we will discuss the pectoralis major muscle.
The pectoralis major muscle is a strong, fan-shaped muscle of the shoulder joint. It decisively shapes the surface anatomy of the chest. It also participates in forming the anterior wall of the axilla.
The innervation is carried by the medial and lateral pectoral nerves (direct branches of the brachial plexus).
The muscle is subdivided in three parts due to its varying points of origin. The clavicular part originates at the medial half of the clavicle, the sternal costal part from the sternum (second to seventh costal cartilages), and the abdominal part in the anterior layer of the rectus sheath.
All fibers insert together at the crest of the greater tubercle located at the proximal humeral shaft.
Due to the different courses of the muscle fibers, the insertion has a recess which is open to the top, preventing the muscle from overstretching.
The triangular depression between the pectoralis major muscle, deltoid muscle, and clavicle is called infraclavicular fossa.
Here, the cephalic vein passes through in the sub-fascia within the deltopectoral groove.
The pectoralis major muscle is the most important muscle for the adduction and anteversion of the shoulder joint, which is why it is also known as the breast stroke muscle. It rotates the upper arm outwards and makes a powerful stroke movement (known as retroversion) when the arms are elevated.
Example: in wood chopping.
If the arms are fixed, the muscle lifts the trunk, which can be helpful in climbing or during inspiration.