The posterior compartment of the arm contains the triceps muscle, which has three heads that originate on the scapula and humerus and insert into the ulna. The triceps is innervated by the radial nerve and supplied by the profunda brachii artery. The radial and ulnar nerves pass through the compartment, with the radial nerve giving motor branches to the triceps and the ulnar nerve accompanied by the ulnar collateral arteries.

1. Posterior compartment of Arm
Dr. Mohamed Mahmoud Mosaed

2. Contents of the Posterior Compartment
of the Arm
• Muscle: The triceps muscle
• Nerve supply to the muscle: Radial nerve.
• Blood supply: Profunda brachii and ulnar
collateral arteries
• Structures passing through the compartment
Radial nerve and ulnar nerve

3. Triceps muscle
• Origin:
• Long head: from the infraglenoid tubercle of the scapula.
• Lateral head: from the upper half of the posterior surface of
the shaft of the humerus.
• Medial head: from the lower half of the posterior surface of
the shaft of the humerus
• Insertion:
• Into the upper surface of the olecranon process of the ulna.
• Nerve Supply:
• From the radial nerve.
• Action:
• Extension of the forearm at the elbow joint.

5. Radial Nerve
• The origin of the radial nerve from the posterior
cord of the brachial plexus in the axilla.
• The nerve winds around the back of the arm in the
spiral groove.
• In the spiral groove, the nerve is accompanied by
the profunda vessels, and it lies directly in contact
with the shaft of the humerus.
• It pierces the lateral fascial septum above the
elbow and continues downward into the cubital
fossa in front of the elbow, between the brachialis
and the brachioradialis muscles.

6. Branches of the radial nerve
In the axilla,
• Muscular branches to the long and medial heads of the
triceps
• Posterior cutaneous nerve of the arm.
In the spiral groove
• Muscular branches to the lateral and medial heads of the
triceps and to the anconeus muscle.
• The lower lateral cutaneous nerve of the arm
• The posterior cutaneous nerve of the forearm.
In the anterior compartment of the arm
• Muscular branches to the brachialis, the brachioradialis,
and the extensor carpi radialis longus muscles.
• Articular branches to the elbow joint.

9. Ulnar Nerve
• It is a branch of the medial cord of the brachial plexus
• It pierces the medial fascial septum and descends
behind the septum, covered posteriorly by the medial
head of the triceps.
• The nerve is accompanied by the superior ulnar
collateral vessels.
• At the elbow, it lies behind the medial epicondyle of
the humerus.
• It continues downward to enter the forearm between
the two heads of origin of the flexor carpi ulnaris
Branches
• The ulnar nerve has an articular branch to the elbow
joint

11. Profunda Brachii Artery
• The profunda brachii artery arises from the
brachial artery near its origin.
• It accompanies the radial nerve through the spiral
groove, supplies the triceps muscle, and takes part
in the anastomosis around the elbow joint.
• Superior and Inferior Ulnar Collateral Arteries
• The superior and inferior ulnar collateral arteries
arise from the brachial artery and take part in the
anastomosis around the elbow joint.