The Surface Anatomy of the Pectoral Girdle
The most proximal part of the upper extremity is the shoulder, or pectoral girdle. Its joints allow for a great amount of movement for the arm that’s attached to it. You’ll want to know the anatomy of the pectoral girdle in case a patient has sustained a shoulder injury or suffers from a medical disorder like arthritis (a degenerative disease of the joints).
Pectoral fascia: Covers the pectoralis major and joins the fascia of the abdominal wall
Clavipectoral fascia: Runs from the clavicle to cover the subclavius muscle and pectoralis minor
Suspensory ligament of the axilla: Comes from part of the clavipectoral fascia and supports the axillary fascia, which stems from the pectoral fascia
Cutaneous nerves lie in the subcutaneous layer and innervate the skin of the upper extremity. The cutaneous nerves that supply the shoulder and upper arm come from branches of the cervical plexus, the brachial plexus, and intercostal nerves:
Supraclavicular nerves: Innervate the skin over the clavicle and superiolateral (upper and outer) portion of the pectoralis major
Intercostobrachial nerve: Innervates the skin on the upper medial part of the arm
The following list gives you an idea of where some of the shoulder structures lie under the skin and notes a few surface landmarks to see:
The clavicle is visible and easily palpated just below the neck.
The clavipectoral triangle is a small depression bordered by the clavicle, the clavicular head of the pectoralis major, and the deltoid muscle.
The pectoralis major muscle is seen or palpated on the front of the chest wall.
The deltoid muscle gives the shoulder its shape.
The latissimus dorsi, teres major, and trapezius form the shape of the upper back.
The triangle of auscultation is a small area bordered by the latissimus dorsi inferiorly, the scapula laterally, and the trapezius superiorly. It’s a good spot for listening to breathing sounds with a stethoscope. You can find it by palpating the medial border of the scapula — the triangle of auscultation is an area where the muscles are thinner, between the latissimus dorsi and trapezius muscles.