Pectoralis minor

From Ganfyd

Pectoralis minor ('pec minor') is a muscle of the anterior chest wall, axilla and upper limb.

Surface Anatomy

Pectoralis minor
System:	Muscle
Function:	Protracts scapula, assists in inspiration
Origin:	Third to fifth ribs
Branches:
Insertion:	Medial and upper surface of the coracoid process of the scapula
Arterial supply:
Venous drainage:
Lymphatic drainage:
Innervation:	Medial pectoral nerve and lateral pectoral nerve (C5 - T1)
Vertebral levels:
Search for Pectoralis minor in Gray's.

Usually masked by the bulk of pectoralis major, pectoralis minor can be felt to contract in the axilla by letting the arm hang loose whilst protracting the scapula.

Shape

Pectoralis minor is situated beneath pectoralis major on the anterior chest wall. Its fibres pass superolaterally to converge into a flat tendon.

Pectoralis minor is a major landmark of the axilla.

Actions

• Protraction of the scapula
• Aids in respiration if the scapula is fixed

Joints Affected

• Shoulder girdle

Origin

• Third, fourth and fifth ribs

Insertion

• Coracoid process of the scapula

Nerve Supply

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

Relations

• See axilla
• Pectoralis major - anteriorly

Variations

• May originate from second rib or any combination of second to fifth
• The tendon may extend superiorly over the coracoid process to the greater tubercle
• May be split into several separate muscles or heads
• Rarely absent
• A separate muscle, pectoralis minimus, may rarely run from the first rib to the coracoid process.