Arm Muscles: Anatomy, Attachments, Innervation, Function

Arm Muscles: Anatomy, Attachments, Innervation, Function

Question 1. Name the joints at which biceps brachii acts and tell the movements that it produces at these joints.
Answer.

• Biceps brachii acts at three joints: (a) shoulder joint, (b) elbow joint, and (c) superior radioulnar joint.
• Movements produced at these joints are
  • At the shoulder joint: Flexion of the arm (by the short head)
  • At the elbow joint: Flexion of the forearm
  • At the superior radioulnar joint: Supination of the forearm when the forearm is semiflexed in midprone position

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Question 2. Give the origin, insertion, nerve supply, and actions of the coracobrachialis.
Answer.

Coracobrachialis Origin

From the tip of the coracoid process of the scapula, along with the short head of the biceps brachii.

Coracobrachialis Insertion

In the middle of the medial border of the shaft of the humerus.

Coracobrachialis Nerve Supply

Musculocutaneous nerve.

Coracobrachialis Actions

Adducts the arm and flexes the shoulder joint.

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Question 3. Give the origin, insertion, nerve supply, and actions of brachialis.
Answer.

Brachialis Origin

From the lower half of the front of the humerus and the medial and lateral intermuscular septa.

Brachialis Insertion

Into the coronoid process and the tuberosity of the ulna.

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Brachialis Nerve Supply

• Musculocutaneous nerve
• Radial nerve (supplies only a small lateral part)

Brachialis Action

Flexor of the elbow joint.