Antebrachial region (with transverse section)
The *Antebrachial Region*
Bones of the Antebrachial Region:
1. *Radius*:
- Located on the lateral side (thumb side) of the forearm.
- Its proximal end articulates with the humerus at the elbow and the ulna at the proximal radioulnar joint.
- Its distal end articulates with the carpal bones at the wrist joint and the ulna at the distal radioulnar joint.
2. *Ulna*:
- Located on the medial side (little finger side) of the forearm.
- Proximally, it articulates with the humerus at the elbow (via the olecranon process) and the radius.
- Distally, it is connected to the radius but does not directly articulate with the carpal bones of the wrist.
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### *Muscles of the Antebrachial Region:
The forearm muscles are divided into *anterior (flexor) and posterior (extensor) compartments*, separated by the interosseous membrane and fascia.
Anterior Compartment (Flexors and Pronators):
- Superficial Layer:
1. *Pronator teres*: Pronates the forearm and assists in flexing the elbow.
2. *Flexor carpi radialis*: Flexes and abducts the wrist.
3. *Palmaris longus*: Flexes the wrist (often absent in some individuals).
4. *Flexor carpi ulnaris*: Flexes and adducts the wrist.
- Intermediate Layer:
1. *Flexor digitorum superficialis*: Flexes the middle phalanges of the fingers and aids in wrist flexion.
- Deep Layer:
1. *Flexor digitorum profundus*: Flexes the distal phalanges of the fingers.
2. *Flexor pollicis longus*: Flexes the thumb.
3. *Pronator quadratus*: Pronates the forearm.
Posterior Compartment (Extensors and Supinators):
- *Superficial Layer*:
1. *Brachioradialis*: Flexes the forearm at the elbow.
2. *Extensor carpi radialis longus*: Extends and abducts the wrist.
3. *Extensor carpi radialis brevis*: Extends and abducts the wrist.
4. *Extensor digitorum*: Extends the fingers.
5. *Extensor digiti minimi*: Extends the little finger.
6. *Extensor carpi ulnaris*: Extends and adducts the wrist.
- Deep Layer:
1. *Supinator*: Supinates the forearm.
2. *Abductor pollicis longus*: Abducts the thumb.
3. *Extensor pollicis brevis*: Extends the thumb at the metacarpophalangeal joint.
4. *Extensor pollicis longus*: Extends the thumb at the interphalangeal joint.
5. *Extensor indicis*: Extends the index finger.
Blood Supply:
1. *Brachial artery: Divides into the **radial* and *ulnar arteries* just below the elbow.
- *Radial artery*: Runs along the lateral side of the forearm (near the radius) and supplies the lateral forearm muscles.
- *Ulnar artery*: Runs along the medial side of the forearm (near the ulna) and supplies the medial forearm muscles.
- *Anterior and posterior interosseous arteries*: Branches of the ulnar artery that supply deeper structures in the forearm.
*Nerve Supply:*
1. *Median nerve*:
- Innervates most of the flexor muscles in the forearm (except for flexor carpi ulnaris and the medial part of flexor digitorum profundus).
- Also provides sensory innervation to the lateral palm and first three fingers.
2. *Ulnar nerve*:
- Innervates the flexor carpi ulnaris and the medial half of the flexor digitorum profundus.
- Provides sensory innervation to the medial palm and the fourth and fifth fingers.
3. *Radial nerve*:
- Supplies all the extensor muscles in the posterior compartment of the forearm.
- Provides sensory innervation to the dorsum of the hand and part of the forearm.
Borders and Clinical Projections*:
- *Proximal boundary: Begins at the **cubital fossa*, the anterior elbow depression, bordered by the brachioradialis and pronator teres muscles.
- *Distal boundary*: Ends at the wrist joint.
- *Medial and lateral borders*: The medial border is marked by the ulna, and the lateral border by the radius.
Clinical Relevance:*
- *Fractures: Commonly occur in both the **radius* and *ulna, such as **Colles’ fracture* of the distal radius.
- *Compartment Syndrome*: Increased pressure in the forearm's fascial compartments can lead to tissue ischemia.
- *Tennis Elbow (Lateral Epicondylitis)*: Affects the common extensor tendon at the lateral epicondyle.
- *Golfer’s Elbow (Medial Epicondylitis)*: Affects the common flexor tendon at the medial epicondyle.