Extensors of the Forearm Flashcards
What are the layers of the extensors of the forearm?
Superficial layer
Deep layer
What are the groups of muscles of the superficial layer?
Lateral group:
* Brachioradialis (1)
* Extensor carpi radialis longus (2)
* Extensor carpi radialis brevis (3)
* Extensor digitorum (4)
* Extensor digiti minimi (5)
Medial group:
* Extensor carpi ulnaris (6)
* Anconeus (7)
Origin of the brachioradialis
Lateral group
Upper part of lateral supra-condylar ridge of humerus
Insertion of the brachioradialis
Base of styloid process of radius
Action of the brachioradialis
Accessory flexor of elbow joint when forearm is mid-pronated
Nerve supply of the brachioradialis
Radial nerve
Origin of the extensor carpi radialis longus
Lateral group
Lower part of lateral supra-condylar ridge of humerus
Insertion of the extensor carpi radialis longus
Dorsal surface of base of metacarpal 2
Action of extensor carpi radialis longus
Extends and abducts the wrist
Nerve supply of the extensor carpi radialis longus
Radial nerve
Origin of extensor carpi radialis brevis
Lateral group
Lateral epicondyle of humerus
The lateral epicondyle of the humerus in the common extensor origin
Insertion of the extensor carpi radialis brevis
Dorsal surface of base of metacarpal 3
Action of the extensor carpi radialis brevis
Extends and abducts the wrist
Nerve supply of the extensor carpi radialis brevis
Deep branch of the radial nerve
Origin of the extensor digitorum
Lateral group
Lateral epicondyle of humerus
Insertion of extensor digitorum
Four tendons, into the dorsal aspects of the bases of the middle and distal phalanges of the medial 4 fingers
Action of the flexor digitorum
- Extends the inter-phalangeal joints of the medial 4 fingers
- Extends the metacapo-phalangeal joints
- Extends the wrist
Nerve supply of the extensor digitorum
Posterior interosseous branch of radial nerve
Origin of the extensor digiti minimi
Lateral group
Lateral epicondyle of humerus
Insertion of extensor digiti minimi
Extensor expansion of little finger
Action of extensor digiti minimi
Extends the little finger
Nerve supply of the extensor digiti minimi
Posterior interosseous nerve
Origin of extensor carpi ulnaris
(Medial group)
Lateral epicondyle of humerus and posterior border of ulna
Insertion of extensor carpi ulnaris
Base of metacarpal 5
Action of extensor carpi ulnaris
Extends and adducts the wrist
Nerve supply of extensor carpi ulnaris
Posterior interosseous nerve
Origin of anconeous
(Medial group)
Posterior surface of lateral epicondyle of humerus
Insertion of the anconeous
Olecranon and upper posterior surface of ulna
Action of anconeous
- Extensor of the elbow joint
- Abduction of ulna in pronation
Nerve supply of anconeous
Radial nerve
Deep layer muscles in extensor compartment of the forearm
- Supinator
- Abductor pollicis longus
- Extensor pollicis longus
- Extensor pollicis brevis
- Extensor indicis
Origin of supinator
Lateral epicondyle of humerus & supinator crest of the ulna
Insertion of supinator
Lateral surface of radius above the oblique
line
Action of supinator
Supination
Nerve supply of supinator
Posterior interosseous nerve
Origin of abductor pollicis longus
Upper part of posterior surfaces of ulna and radius
Insertion of abductor pollicis longus
Lateral side of base of metacarpal 1
Action of abductor pollicis longus
Abducts carpometacarpal joint of thumb
Nerve supply of abductor pollicis longus
Posterior interosseous nerve
Origin of extensor pollicis brevis
Middle of the posterior surface of radius
Insertion of extensor pollicis brevis
Dorsal surface of base of proximal phalanx of the thumb
Action of extensor pollicis brevis
Extends metacarpo-phalangeal joint of the thumb; also extend the carpo-metacarpal joint of the thumb
Nerve supply of extensor pollicis brevis
Posterior interosseous nerve
Origin of extensor pollicis longus
Middle of the posterior surface of ulna
Insertion of extensor pollicis longus
Dorsal surface of base of distal phalanx of thumb
Action of extensor pollicis longus
Extends inter-phalangeal joint of the thumb
Extends metacarpo-phalangeal joints of the thumb
Extend carpo-metacarpal joints of the thumb
Nerve supply of extensor pollicis longus
Posterior interosseous nerve
Origin of the extensor inidicis
Lower part of posterior surace of ulna
Insertion of extensor inidicis
Extensor expansion of index finger
Action of extensor indicis
Extends index finger
Nerve supply of extensor indicis
Posterior interosseous nerve
What is the extensor retinaculum?
Thickening of the deep fascia on the
dorsum of the wrist
What is the function of the extensor retinaculum?
It holds the long extensor tendons in position
What is the attachment of the extensor retinaculum?
Medially to the triquetrum & pisiform bones and laterally to the lower part of the anterior border of radius