Topic Overview

Muscles of the Pectoral Region

1. Pectoralis Major

• Origin

  • Clavicular head → anterior surface of medial ½ of clavicle.

  • Sternocostal head → anterior surface of sternum, upper 6 costal cartilages, aponeurosis of external oblique.

• Insertion

  • Lateral lip of intertubercular sulcus (bicipital groove) of humerus.

• Nerve Supply

  • Medial and lateral pectoral nerves (C5–T1).

• Actions

  • Adduction and medial rotation of arm.

  • Clavicular head → flexes arm.

  • Sternocostal head → extends arm from flexed position.

• Clinical

  • Landmark for axillary dissection.

  • Important muscle in breast surgery.

2. Pectoralis Minor

• Origin

  • Ribs 3, 4, 5 near costal cartilages.

• Insertion

  • Coracoid process of scapula.

• Nerve Supply

  • Medial pectoral nerve (C6–C8).

• Actions

  • Draws scapula forward and downward.

  • Helps in forced inspiration.

• Clinical

  • Important landmark: divides axillary artery into 3 parts.

  • Hypertrophy may compress brachial plexus/axillary vessels (thoracic outlet syndrome).

3. Subclavius

• Origin

  • 1st rib and its costal cartilage.

• Insertion

  • Groove on inferior surface of clavicle.

• Nerve Supply

  • Nerve to subclavius (C5, C6).

• Actions

  • Steadies clavicle during shoulder movements.

  • Protects subclavian vessels during clavicle fracture.

• Clinical

  • Can be used in surgical grafting of brachial plexus injuries (nerve to subclavius).

4. Serratus Anterior

• Origin

  • Outer surfaces of upper 8 or 9 ribs.

• Insertion

  • Anterior surface of medial border of scapula.

• Nerve Supply

  • Long thoracic nerve (C5–C7).

• Actions

  • Protracts scapula (pushing/punching movements).

  • Rotates scapula for overhead abduction of arm.

• Clinical

  • Injury to long thoracic nerve → winged scapula.

  • Patient cannot abduct arm above 90°.

Summary of Nerve Supply

• Pectoralis major → medial & lateral pectoral nerves.

• Pectoralis minor → medial pectoral nerve.

• Subclavius → nerve to subclavius.

• Serratus anterior → long thoracic nerve