Pectoralis Minor

Shoulder & Scapula · Upper Limb

Located in the Shoulder & Scapula of the Upper Limb, the Pectoralis Minor is a key muscle for anatomy study. Its origin is Ribs 3–5, near their costal cartilages, and it inserts onto Coracoid process of scapula. It is responsible for several movements: Depresses and protracts scapula; elevates ribs in forced inspiration. Innervation is provided by the Medial pectoral nerve (C8, T1).

Origin, Insertion, Action & Nerve

Origin

Ribs 3–5, near their costal cartilages

Insertion

Coracoid process of scapula

Action

Depresses and protracts scapula; elevates ribs in forced inspiration

Nerve

Medial pectoral nerve (C8, T1)

Attachments explained

The Pectoralis Minor is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.

Origin

Ribs 3–5, near their costal cartilages

Insertion

Coracoid process of scapula

Action & function

When the Pectoralis Minor contracts, it produces the following movements: Depresses and protracts scapula; elevates ribs in forced inspiration.

As part of the Shoulder & Scapula group of the Upper Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.

Nerve supply & clinical relevance

The Pectoralis Minor receives its nerve supply from the Medial pectoral nerve (C8, T1). This nerve carries fibres from spinal segment(s) C8, T1.

Because a muscle can only contract when its nerve is intact, injury to the Medial pectoral nerve or to its spinal roots (C8, T1) can weaken or paralyse the Pectoralis Minor, impairing the movements it normally produces (depresses and protracts scapula). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Pectoralis Minor (the OIANS method)

OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Pectoralis Minor, work through them in order: picture its origin, trace the muscle to its insertion, reason out the action that shortening between those two points must create, then add the nerve that drives it.

Most students remember the Pectoralis Minor fastest by linking its action back to its attachments rather than memorising each fact in isolation. Once the origin and insertion make sense, the action usually follows logically.