Muscle - Pectoral Region

Question 1

Pectoralis Major

Answer 1

Consists of a sternal head and clavicular head.

Origin (sternal) - anterior surface of sternum, superior six costal cartilages, aponeurosis of the external oblique muscle.

Origin (clavicular) - anterior surface of medial clavicular bone.

Insertion - intertubercular sulcus of humerus

Functions:
1) Adduction of the upper limb

2) Medial rotation of the upper limb
3) Draws scapular anteroinferiorly
4) Clavicular head assists to flex upper limb.

Innervation - medial and lateral pectoral nerves

Question 2

Pectoralis minor

Answer 2

Forms anterior wall of axilla region. Lies beneath the pectoris major.

Origin - 3rd-5th ribs

Insertion - Coracoid process of scapula

Innervation - Medial pectoral nerve

Function - stablises scapula by drawing it anteroinferiorly to the thoracic wall.

Question 3

Serratus Anterior

Answer 3

More laterally of the chest wall. Forms the medial border of the axilla.

Origin - lateral aspect of ribs 1-8.

Insertion - costal surface of the medial border of the scapula.

Function - rotates scapula, so that arm can be raised over 90 degrees. Holds scapular against ribcage.

Innervation - long thoracic nerve.

Question 4

Subclavius

Answer 4

Located beneath the clavicle, running horizontally. Can afford some minor protection to neurovascular structures.

Origin - junction of first rib and its costal cartilage.

Insertion - inferior surface of the middle third of the clavicle

Function - Anchors and depresses clavicle

Innervation - nerve to subclavius.

Question 5

Clinical relevance: winging of scapula

Answer 5

Occurs when the long thoracic nerve is damaged.

Scapula is no longer held against the ribcage and protrudes out of the back - ‘winged appearance’.

Aetiology - traction injuries - where the upper limb is stretched violently.