Arm Muscles: The arm muscles are located between the shoulder and elbow joint. It contains four muscles – three in the anterior compartment, and one in the posterior compartment.
Muscles of the anterior compartment of the arm:
Coracobrachialis
Biceps brachii
Brachialis
Muscles of the posterior compartment of the arm:
Triceps Brachii
The arm is divided into anterior and posterior compartments by extension of deep fascia which is called the medial and lateral intermuscular septa.
Anterior Compartment of the Arm Muscles
Coracobrachialis muscle:
Origin:
The tip of the coracoid process with the short head of the biceps brachii
Insertion:
The middle 5cm of the medial border of the humerus
Nerve supply:
Musculocutaneous nerve (c5-c7)
Action: Flexes the arm at the shoulder joint.
Biceps brachii:
It has two head-Short head & Long head.
Origin:
Short head: coracobrachialis with the tip of the coracoid process
Long head: supraglenoid tubercle of the scapula
Insertion:
Posterior rough part of the radial tuberosity (ulna)
Nerve supply:
Musculocutaneous nerve(c5, c6)
Action:
1.supinator of the forearm
2.flexor of the elbow joint
3. short head is a flexor of the forearm
4. Long head prevents upward displacement of the head of the humerus
Brachialis:
Origin:
The lower half of the front of the humerus including both the anteromedial and anterolateral surface and the anterior border
Insertion:
Coronoid process and ulnar tuberosity
The rough anterior surface of the coronoid process of ulna
Nerve supply:
The musculocutaneous nerve is motor.
The radial nerve is proprioceptive.
Action:
Flexes the forearm at the elbow joint.
Posterior Compartment of the Arm Muscles
Triceps brachii:
It has three head.
Origin:
long head: Infraglenoid tubercle of the scapula
Lateral head:
Above part of the radial( spiral) groove of the humerus
Medial head:
Below part of the radial( spiral) groove of the humerus
Insertion:
The posterior part of the superior surface of the olecranon process of ulna
Nerve supply:
Radial nerve(c7,c8)
Action:
Powerful active extensor of the elbow.
The long head supports the head of the humerus in the abducted position of the arm.