Anterior Axioappendicular Muscles

Question 1

Give the Origin, Insertion, Innervation, Action, and Test of:

Pectoralis Major

Answer 1

Origin:
Clavicular head - Medial 1/2 of anterior clavicle
Sternocostal head - Anterior surface of sternum, Costal cartilages of superior 6 ribs, aponeurosis of external oblique muscle.

Insertion:
Lateral lip of Intertubercular groove of humerus

Innervation:
Medial and Lateral Pectoral Nerves (C8,T1 and C5,6,7 respectively)

Action:
Adduct + medially rotate the arm. Also draws the scapula anterior + inferiorly.
(Alone, the clavicular head flexes the humerus and the sternoclavicular-costal head extends it from flexed position)

Test:
Clavicular head - Ask patient to hold arm at 90 degree abduction and move it anteriorly against examiner resistance. Can palpate + see muscle if it is acting normally.
Sternocostal head - Ask patient to hold arm at 60 degree abduction and then try to adduct their arm against examiner resistance. Can see + palpate muscle if it is acting normally.

Question 2

Give the Origin, Insertion, Innervation, Action, and Test of:

Pectoralis Minor

Answer 2

Origin:
Anterior surface of ribs 3-5 (near their costal cartilages)

Insertion:
Medial border + superior surface of Coracoid process of scapula

Innervation:
Medial Pectoral Nerve (C8,T1)

Action:
Stabilises scapula by pulling it anteriorly and inferiorly against thoracic wall. Also helps elevate ribs for deep inspiration (when pectoral girdle is fixed or elevated).

Test:
None listed.

Question 3

Give the Origin, Insertion, Innervation, Action, and Test of:

Subclavius

Answer 3

Origin:
Junction of rib 1 and its costal cartilage

Insertion:
Middle 1/3 of the inferior surface of the clavicle

Innervation:
Nerve to subclavius (C5,6)

Action:
Helps to anchor + depress the clavicle. Also helps to resist the tendency of dislocation at the sternoclavicular joint (eg. In tug of war).

Test:
None listed.

Question 4

Give the Origin, Insertion, Innervation, Action, and Test of:

Serratus Anterior

Answer 4

Origin:
External surfaces of lateral parts of ribs 1-8

Insertion:
Anterior surface of medial border of scapula + inferior angle

Innervation:
Long Thoracic nerve (C5,6,7)

Action:
Protracts (extends forwards and outwards) and holds the scapula against thoracic wall. Also is able to rotate the scapula (to allow arm to be abducted over 90 degrees)

Test:
Ask patient to push out against a wall. If normal, several digitations of the muscles may be seen + palpated and the scapula should NOT wing. Also the test for the long thoracic nerve

Question 5

Name the anterior axioappendicular muscles

Answer 5

Pectoralis Major
Pectoralis Minor
Subclavius
Serratus Anterior