The pectoralis minor is a thin, triangular muscle, situated at the upper part of the chest

Chest

The chest is a part of the anatomy of humans and various other animals. It is sometimes referred to as the thorax or the bosom.-Chest anatomy - Humans and other hominids:...

, beneath the pectoralis major.

Origin and insertion

It arises from the upper margins and outer surfaces of the third, fourth, and fifth rib

Rib

In vertebrate anatomy, ribs are the long curved bones which form the rib cage. In most vertebrates, ribs surround the chest, enabling the lungs to expand and thus facilitate breathing by expanding the chest cavity. They serve to protect the lungs, heart, and other internal organs of the thorax...

s, near their cartilages

Costal cartilages

The costal cartilages are bars of hyaline cartilage which serve to prolong the ribs forward and contribute very materially to the elasticity of the walls of the thorax.-Differences from 1-12:...

 and from the aponeuroses

Aponeurosis

Aponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, are histologically similar to tendons, and are very sparingly supplied with blood vessels and nerves. When dissected, aponeuroses are papery, and peel off by sections...

 covering the intercostalis.

The fibers pass superior and lateral and converge to form a flat tendon, which is inserted into the medial border and upper surface of the coracoid process of the scapula

Scapula

In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....

.

Special notes

Axillary nodes are classified according to their positions relative to the pectoralis minor muscle. Level 1 are lateral, Level 2 are deep, Level 3 are medial.

Relations

The pectoralis minor muscle is covered anteriorly (superficially) by the clavipectoral fascia

Clavipectoral fascia

The clavipectoral fascia is a strong fascia situated under cover of the clavicular portion of the Pectoralis major....

. The medial pectoral nerve

Medial pectoral nerve

The medial pectoral nerve arises from the medial cord of the brachial plexus and through it from the eighth cervical and first thoracic....

 pierces the pectoralis minor and the clavipectoral fascia.

Actions

The pectoralis minor depresses

Depression (kinesiology)

Depression, in kinesiology, is the anatomical term of motion for movement in an inferior direction.It is the opposite of elevation.This term is often applied to the shoulders Depression, in kinesiology, is the anatomical term of motion for movement in an inferior direction.It is the opposite of...

 the point of the shoulder

Shoulder

The human shoulder is made up of three bones: the clavicle , the scapula , and the humerus as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints. The major joint of the shoulder is the glenohumeral joint, which...

, drawing the scapula

Scapula

In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....

 inferior and medial, towards the thorax

Thorax

The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...

, and throwing its inferior angle posteriorly.

Variations

The origin is from the second, third and fourth or fifth ribs. The tendon of insertion may extend over the coracoid process to the greater tubercle. It may be split into several parts. Absence of this muscle is rare.

External links

• Slide