Anatomy of the pectoral and scapular regions

The pectoral and scapular regions consist of various structures that include muscles, blood vessels, and nerves; which all act together to make our upper limbs functional. The muscles of the pectoral region are divided into groups based on their locations.

There are axio-appendicular muscles, which extend between the axial and appendicular skeletons; and the scapulohumeral muscles, which specifically connect the scapula to the humerus.

First, let’s take a look at the axio-appendicular muscles, which are divided into two large groups: the anterior and posterior groups of muscles.

The anterior axio-appendicular group is composed of four muscles: the pectoralis major, pectoralis minor, the subclavius, and the serratus anterior.

The pectoralis major is a relatively flat, fan shaped muscle, which covers the upper half of the thorax.

This muscle has two proximal attachments also called heads. The first one is the clavicular head, which attaches proximally to the medial half of the clavicle.

Below it, there’s another much larger part called the sternocostal head, which attaches proximally to the anterior surface of the sternum and the superior six costal cartilages.

Both the clavicular and the sternocostal heads converge distally and then attach to the lateral lip of the intertubercular groove of the humerus.

Superolaterally, the clavicular head of the pectoralis major lies adjacent to the deltoid muscle.

These muscles don’t come completely together, thus creating a narrow gap between them that’s called the deltopectoral groove, which is where the cephalic vein passes.

Additionally, inferolaterally, the sternocostal head of the pectoralis major twists and forms the anterior axillary fold.

The pectoralis major muscle is innervated by two nerves: the lateral pectoral nerve and the medial pectoral nerve.