Write The Origin, Insertion Nerve Supply & Action Of Muscles of Front Of Arm. 5 Mark
Reading File
Finding Sources
Finding Sources
Finding Sources
Finding Sources
Reading File
Reading File
Finding Sources
Reading File
Reading File
Loading Image
Here is a complete, exam-ready answer on the Muscles of the Front of the Arm (Anterior Compartment):
Muscles of the Front of the Arm (Anterior Compartment)
The anterior compartment of the arm contains three muscles: Coracobrachialis, Biceps Brachii, and Brachialis. All three are innervated by the musculocutaneous nerve (C5–C7).
1. Coracobrachialis
| Feature | Detail |
|---|---|
| Origin | Apex of the coracoid process of the scapula |
| Insertion | Linear roughening on the mid-shaft of the humerus on its medial side |
| Nerve Supply | Musculocutaneous nerve (C5, C6, C7) — the nerve actually pierces this muscle |
| Action | Flexion and adduction of the arm at the glenohumeral joint |
Note: The musculocutaneous nerve pierces coracobrachialis to enter the anterior compartment of the arm — a useful clinical landmark.
2. Biceps Brachii
| Feature | Detail |
|---|---|
| Origin | Long head — Supraglenoid tubercle of the scapula (tendon passes through the glenohumeral joint and intertubercular sulcus) |
| Short head — Apex of the coracoid process of the scapula (with coracobrachialis) | |
| Insertion | Radial tuberosity; also the deep fascia of the forearm via the bicipital aponeurosis |
| Nerve Supply | Musculocutaneous nerve (C5, C6) — tests the C6 reflex (biceps jerk) |
| Actions | 1. Powerful flexor of the forearm at the elbow joint |
| 2. Most powerful supinator of the forearm (especially when elbow is flexed) | |
| 3. Accessory flexor of the arm at the glenohumeral joint |
The bicipital aponeurosis fans out medially from the distal tendon to blend with deep fascia of the anterior forearm.
3. Brachialis
| Feature | Detail |
|---|---|
| Origin | Anterior surface of the humerus (distal half) — medial and lateral surfaces, and adjacent intermuscular septa |
| Insertion | Tuberosity (coronoid process) of the ulna |
| Nerve Supply | Musculocutaneous nerve (C5, C6) — main supply; small branch from the radial nerve (C7) to the lateral part of the muscle |
| Action | Most powerful flexor of the forearm at the elbow joint (pure flexor — acts regardless of forearm rotation) |
Brachialis is often called the "workhorse" of elbow flexion because, unlike biceps, it cannot supinate. It is the only muscle whose sole action is elbow flexion.
Summary Table
| Muscle | Origin | Insertion | Nerve | Action |
|---|---|---|---|---|
| Coracobrachialis | Coracoid process (apex) | Mid-shaft humerus (medial) | Musculocutaneous (C5–C7) | Flex & adduct arm |
| Biceps Brachii | Long head: supraglenoid tubercle; Short head: coracoid process | Radial tuberosity + bicipital aponeurosis | Musculocutaneous (C5–C6) | Flex forearm, supinate forearm, flex arm |
| Brachialis | Anterior humerus (distal half) + intermuscular septa | Ulnar tuberosity | Musculocutaneous (C5–C6) + Radial nerve (C7, lateral part) | Flex forearm |
Key Point for Exams: All three muscles are supplied by the musculocutaneous nerve (formed from C5, C6, C7 of the medial cord of the brachial plexus). Damage to this nerve causes weakness of elbow flexion and loss of forearm supination.
— Gray's Anatomy for Students, Table 7.8 (Muscles of the Anterior Compartment of the Arm); General Anatomy and Musculoskeletal System, THIEME Atlas
This is a shared conversation. Sign in to Orris to start your own chat.