Muscles of the anterior wall of the axilla

Question 1

Pectoralis major

Answer 1

Origin:

• Clavicular head - anterior surface of medial half of clavicle
• Sternocostal head - anterior surface of sternum; first seven costal cartilages; sternal end of sixth rib; aponeurosis of external oblique

Insertion:

• Lateral lip of intertuberccular sulcus of humerus

Innervation:

• Medial and lateral pectoral nerves; clavicular head (C5, C6); sternocostal head (C6, C7, C8, T1)

Function:

• Flexion, adduction and medial rotation of arm at glenohumeral joint;
• Clavicular head - flexion of extended arm;
• Sternocostal head - extension of flexed arm

Question 2

Subclavius

Answer 2

Origin:

• First rib at junction between rib and costal cartilage

Insertion:

• Groove on inferior surface of middle one third of clavicle

Innervation:

• Nerve to subclavius (C5, C6)

Function:

• Pulls tip of shoulder down; pulls clavicle medially to stabilise sternoclavicular joint

Question 3

Pectoralis minor

Answer 3

Origin:

• Anterior surfaces and superior borders of ribs III to V; and from deep fascia overlying the related intercostal spaces

Insertion:

• Coracoid process of scapula (medial border and upper surface)

Innervation:

• Medial pectoral nerve (C5, C6, C7, C8, T1)

Function:

• Pulls tip of shoulder down, protracts scapula