Muscles of Axilla

Question 0

pectoralis major

Answer 0

Origin: Clavicular head: Anterior surf of medial 1/2 of clavicle; sternocostal head: anterior surface of the sternum, SUP 6 costal cartilages, aponeurosis of external oblique
Insertion: lateral lip of intertubercular sulcus
Innervation: lateral and medial pectoral nerves,
clavicular head = C5, C6;
sternocostal head = C7, C8, T1
Action: Adducts and medially rotates shoulder joint, draws scapula anterior and inferiorly;
Acting alone: clav head = flexes shoulder; sternocostal head = extends shoulder

Question 1

pectoralis minor

Answer 1

Origin: 3rd-5th ribs near their costal cartilages
Insertion: medial border and superior surface of coracoid process
Innervation: medial pectoral nerve (C8, T1)
Action: stabilizes scapula by drawing it inferiorly and anteriorly against the thoracic wall

Question 2

serratus anterior

Answer 2

Origin: external surfaces of lateral parts of the 1st-8th ribs
Insertion: anterior surface of medial border of the scapula
Innervation: long thoracic nerve (C5, C6, C7)
Action: protracts scapula and holds scap against the thoracic wall; rotates scapula

Question 3

subclavius

Answer 3

Origin: junction of 1st rib and its costal cartilage
Insertion: inferior surface of middle 1/3 of clavicle
Innervation: subclavian nerve (C5, C6)
Action: anchors and depresses clavicle

Question 4

omohyoid

Answer 4

Origin: superior border of scapula near suprascapular notch
Insertion: inferior border of hyoid
Innervation: C1-C3 by a branch of ansa cervicalis
Action: depresses, retracts, and steadies hyoid