Answer
The abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis muscles are part of the deep posterior compartment of the forearm. These muscles play important roles in extending and abducting the thumb and extending the index and other fingers. Here's some information about each of these muscles:
1. **Abductor Pollicis Longus**:
- **Origin**: It originates from the posterior surfaces of the ulna and radius, as well as the interosseous membrane.
- **Insertion**: It inserts into the base of the first metacarpal bone.
- **Action**: The primary function of this muscle is to abduct the thumb (move it away from the palm) and assist in extending the thumb at the carpometacarpal joint.
- **Innervation**: It is innervated by the radial nerve.
2. **Extensor Pollicis Brevis**:
- **Origin**: It originates from the posterior surfaces of the radius and the adjacent interosseous membrane.
- **Insertion**: It inserts into the base of the proximal phalanx of the thumb.
- **Action**: This muscle primarily extends the thumb at the metacarpophalangeal joint and assists in extending the wrist.
- **Innervation**: It is innervated by the radial nerve.
3. **Extensor Pollicis Longus**:
- **Origin**: It originates from the middle third of the posterior surface of the ulna and the interosseous membrane.
- **Insertion**: It inserts into the base of the distal phalanx of the thumb.
- **Action**: The main function of this muscle is to extend the thumb at the interphalangeal joint and assist in extending the wrist.
- **Innervation**: It is innervated by the radial nerve.
4. **Extensor Indicis**:
- **Origin**: It originates from the posterior surface of the ulna, distal to the extensor pollicis longus.
- **Insertion**: It inserts into the extensor expansion of the index finger.
- **Action**: This muscle extends the index finger and assists in extending the wrist.
- **Innervation**: It is innervated by the radial nerve.
These muscles collectively contribute to the fine motor control and strength of the hand and wrist, allowing for precise movements of the thumb and index finger, which are important for activities such as grasping objects, pinching, and performing intricate tasks with the hand.
Work Step by Step
The abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis muscles are part of the deep posterior compartment of the forearm. These muscles play important roles in extending and abducting the thumb and extending the index and other fingers. Here's some information about each of these muscles:
1. **Abductor Pollicis Longus**:
- **Origin**: It originates from the posterior surfaces of the ulna and radius, as well as the interosseous membrane.
- **Insertion**: It inserts into the base of the first metacarpal bone.
- **Action**: The primary function of this muscle is to abduct the thumb (move it away from the palm) and assist in extending the thumb at the carpometacarpal joint.
- **Innervation**: It is innervated by the radial nerve.
2. **Extensor Pollicis Brevis**:
- **Origin**: It originates from the posterior surfaces of the radius and the adjacent interosseous membrane.
- **Insertion**: It inserts into the base of the proximal phalanx of the thumb.
- **Action**: This muscle primarily extends the thumb at the metacarpophalangeal joint and assists in extending the wrist.
- **Innervation**: It is innervated by the radial nerve.
3. **Extensor Pollicis Longus**:
- **Origin**: It originates from the middle third of the posterior surface of the ulna and the interosseous membrane.
- **Insertion**: It inserts into the base of the distal phalanx of the thumb.
- **Action**: The main function of this muscle is to extend the thumb at the interphalangeal joint and assist in extending the wrist.
- **Innervation**: It is innervated by the radial nerve.
4. **Extensor Indicis**:
- **Origin**: It originates from the posterior surface of the ulna, distal to the extensor pollicis longus.
- **Insertion**: It inserts into the extensor expansion of the index finger.
- **Action**: This muscle extends the index finger and assists in extending the wrist.
- **Innervation**: It is innervated by the radial nerve.
These muscles collectively contribute to the fine motor control and strength of the hand and wrist, allowing for precise movements of the thumb and index finger, which are important for activities such as grasping objects, pinching, and performing intricate tasks with the hand.