VAN 121: Veterinary Gross Anatomy-II (2+2)

MUSCLES OF THE ARM

This group consists of muscles, which are grouped around the humerus. Some arise from the scapula and others from the humerus and all are inserted to the forearm. They are as follows

• Biceps brachii
• Triceps brachii
  • Long head (Caput longum tricipitis)
  • Lateral head (Caput parvum tricipitis)
  • Medial head (Caput medium tricipitis)
• Tensor fascia antibrachii
• Brachialis
• Anconeus

( Note the musculature in arm medial )

Biceps brachii

• It is a long, fusiform muscle situated on the anterior face of the humerus passing obliquely downwards, backwards and inwards. It is thick at its middle and bifid at its insertion
• Origin: Tuber scapulae (view image)
• Insertion:
  • Radial tuberosity and
  • Ulna
• Action: To flex the elbow joint
• Blood supply: Anterior circumflex and a direct branch from the brachial artery
• Nerve supply: Musculo-cutaneous nerve

Triceps brachii

• This is a large muscle, which fills up the space between the scapula and olecranon process of the ulna. It is made up of three heads
• Long head (Caput longum tricipitis)
  • It is the largest head and is visible on both the lateral and medial faces
  • Origin: Posterior border of scapula and the humerus(view image)
  • Insertion: The lateral, posterior and medial parts of the summit of the olecranon
  • Action: To flex the shoulder and extend the elbow joint(view image)
• Lateral head (Caput parvum tricipitis)
  • It is quadrilateral in shape and lies on the lateral surface of the arm below the long head.
  • Origin: The curved line extending from the deltoid tuberosity to the neck of the humerus.
  • Insertion: Tendon of long head and lateral aspect of the olecranon.
  • Action: To extend the elbow joint.
• Medial head (Caput medium tricipitis)
  • It is the smallest and is situated on the medial surface of the humerus below the insertion of coracobrachialis.
  • Origin: The upper third of the medial face of the shaft of the humerus.
  • Insertion: Anterior and medial parts of summit of the olecranon process.
  • Action: To extend the elbow.
  • Blood supply: Posterior circumflex and deep brachial arteries.
  • Nerve supply: Radial nerve.

Tensor fascia antibrachii

• This is a long, thin and very narrow muscle extending on the postero-medial face of the long head of triceps.
• Origin: Latissimus dorsi.
• Insertion: Tendon of long head.
• Action: To extend the elbow and tense the fascia of the forearm.
• Blood supply: Posterior circumflex and deep brachial arteries.
• Nerve supply: Radial nerve.

Brachialis

• This is a curved muscle lodged in the musculo-spiral groove of the humerus.
• Origin: Posterior surface of the humerus.
• Insertion: Upper part of the medial surface of the radius below the bicipital tuberosity and the ulna.
• Action: To flex the elbow joint.
• Blood supply: Posterior circumflex and deep brachial arteries.
• Nerve supply: Musculo-cutaneous branch of the median nerve.

Anconeus

• This is a small, thick and prismatic muscle covering the brim of the olecranon fossa and covered by all the three heads of the triceps brachii.
• Origin: The margins of the olecranon fossa.
• Insertion: The anterior and lateral parts of the olecranon.
• Action: To extend the elbow joint.
• Blood supply: Deep brachial and posterior circumflex arteries.
• Nerve supply: Radial nerve.