Pectoralis minor: origin, insertion, action and innervation
The pectoralis minor arises from ribs 3–5 and inserts on the coracoid process of the scapula. It draws the scapula forward and downward, helps forced breathing and is supplied by the medial pectoral nerve.
Quick answer
- Latin name
- Musculus pectoralis minor
- Origin
- Outer surfaces of ribs 3–5, near their costal cartilages
- Insertion
- Coracoid process of the scapula
- Action
- Draws the scapula forward and downward and steadies it against the chest; lifts the ribs in forced inspiration
- Innervation
- Medial pectoral nerve (C8–T1), often with fibres from the lateral pectoral nerve
- Blood supply
- Pectoral branch of the thoraco-acromial artery
The pectoralis minor is a thin, triangular muscle that lies entirely under the pectoralis major. Small as it is, it's a key landmark: it divides the axillary artery into its three parts.
Where it is
It runs from the front of the third, fourth and fifth ribs up and outwards to the coracoid process, the hook-like projection at the front of the scapula. Peel away the pectoralis major in the app and it appears immediately underneath.
Origin and insertion
- Origin: the outer surfaces of ribs 3 to 5, near their costal cartilages.
- Insertion: the medial border and upper surface of the coracoid process of the scapula.
What it does
- Draws the scapula forward and downward, and steadies it on the chest wall.
- Accessory muscle of breathing: when the scapula is fixed, it helps lift ribs 3 to 5 during deep, forced inspiration.
Innervation and blood supply
The medial pectoral nerve (C8–T1) supplies it, usually with a contribution from the lateral pectoral nerve. The thoraco-acromial artery supplies its blood.
How to remember it
- Minor: 3, 4, 5 ribs to the coracoid.
- The coracoid process is the meeting point of three muscles: pectoralis minor, coracobrachialis and the short head of the biceps.
Frequently asked questions
Where does the pectoralis minor insert?
On the coracoid process of the scapula.
What does the pectoralis minor do?
It draws the scapula forward and downward, steadies it, and helps lift the ribs in forced breathing.
Which nerve supplies the pectoralis minor?
Mainly the medial pectoral nerve (C8–T1).