Muscles of the Arm

Question 0

Brachialis

Answer 0

Origin: distal 1/2 of anterior surface of humerus
Insertion: coronoid process and tuberosity of ulna
Innervation: musculocutaneous nerve (C5, C6)
Action: flexes elbow joint in all positions

Question 1

Biceps Brachii

Answer 1

Origin: short head: tip of coracoid process of the scapula
long head: supraglenoid tubercle of the scapula
Insertion: tuberosity of radius and fascia of forearm via bicipital aponeurosis
Innervation: musculocutaneous nerve (C5, C6)
Action: supinates forearm, when it is supinated, flexes elbow joint; flexes shoulder joint; short head resists dislocation of shoulder

Question 2

Coracobrachialis

Answer 2

Origin: tip of coracoid process of scapula
Insertion: middle 1/3 of medial surface of humerus
Innervation: musculocutaneous nerve (C5, C6, C7)
Action: helps flex and adduct shoulder joint; resists dislocation of shoulder

Question 3

Triceps Brachii

Answer 3

Origin: long head: infraglenoid tubercle of scapula
Lateral head: posterior surface of humerus, superior to radial groove
Medial Head: posterior surface of humerus, inferior to radial groove
Insertion: proximal end of olecranon of ulna and fascia of forearm
Innervation: radial nerve (C6, C7, C8)
Action: chief extensor of elbow joint; long head extends shoulder joint and resists dislocation of humerus (especially important during abduction)