arm muscles

Question 1

What is the nerve supply and actions of the coracobrachialis muscle?

Answer 1

Nerve Supply:
- Musculocutaneous nerve (C5,6,7)

Actions:
- Weak flexor and adductor of the arm

Question 2

What are the attachments, nerve supply and actions of biceps brachii?

Answer 2

Origin
1. short head:tip of coracoid process.
long head: supraglenoid tubercle of scapula.
Insertion :posterior part of the radial tuberosity.

Nerve Supply:
1. Musculocutaneous nerve (C5,6,7)

Actions:
1. Strong supinator of the forearm when elbow is flexed.
2. Powerful flexor of the forearm, when elbow is extended
3. Weak flexor of shoulder joint.

Clinical Aspect:
1. Biceps brachii is tested by asking patient to flex the elbow ainst resistance when the forearm is supinated

3. Biceps Reflex - tap the tendon of biceps brachii,confirms the integrity of musculocutaneous nerve and C5 and C6 spinal segments.

Question 3

What are the attachments, nerve supply and actions of brachialis?

Answer 3

Origin:
lower half of the anterior surface of the humerus.
Insertion: anterior surface of the coronoid process of ulna.

Nerve Supply:
1. Musculocutaneous nerve (C5,6,7)

Actions:
1. Flexes forearm at the elbow joint.

Question 4

What are the attachments, nerve supply and actions of Triceps Brachii?

Answer 4

Origin:
1. lateral head:lateral lip of radial groove
2.long head :infraglenoid tubercle of scapula.
3. medial head: posterior surface of humerus below the radial groove.

Insertion:posterior part of the superior surface of the olecranon process.

Nerve Supply: radial nerve

Action:
1. Powerful extensor of the elbow joint

Clinical Aspects:
1. If there is injury of the radial nerve in the radial groove, the extension of elbow and triceps reflex is not lost. This is because the nerve to the long head arises from the radial nerve in axilla.