FOREARM EXTENSORS AND DORSUM OF HAND
I. FOREARM EXTENSORS
A. 11 muscles in posterior forearm
B. Organized into three functional groups
1. Muscles that extend the hand
2. Muscles that extend the medial 4 digits
3. Muscles that extend the thumb
C. Superficial muscles have common extensor tendon from lateral epicondyle and lateral supracondylar ridge of humerus
D. Tendons lie within extensor synovial sheaths - held in place by extensor retinaculum
E. Superficial extensor muscles
1. Brachioradialis - actually a flexor m., but included because of radial nerve innervation
a. Attachments: lateral supracondylar ridge of humerus to lateral styloid process of radius
b. Nerve: radial
c. Artery: radial recurrent
d. Action: flex forearm
2. Extensor carpi radialis longus
a. Attachments: lateral supracondylar ridge of humerus to dorsal surface 2nd metacarpal
d. Nerve: radial
c. Artery: radial, radial recurrent
d. Action: extends wrist, abducts hand = radial deviation = abduction
3. Extensor carpi radialis brevis
a. Attachments: lateral epicondyle of humerus to dorsal part of 3rd metacarpal
b. Nerve: posterior interosseus of radial
c. Artery: radial, radial recurrent
d. Action: extends wrist, abducts hand
4. Extensor digitorum
a. Attachments: lateral epicondyle of humerus to dorsal phalanges of medial 4 digits
b. Nerve: posterior interosseus of radial
c. Artery: posterior interosseus of ulnar
d. Action: extends digits, extends wrist
5. Extensor digiti minimi
a. Attachments: common extensor tendon to dorsum of proximal phalanx D5
b. Nerve: posterior interosseus of radial
c. Artery: posterior interosseus of ulnar
d. Action: extends little finger
6. Extensor carpi ulnaris
a. Attachments: common extensor tendon to base 5th metacarpal
b. Nerve: posterior interosseus of radial
c. Artery: posterior interosseus of ulnar
d. Action: extends wrist, adducts hand = ulnar deviation
7. Anconeus - covered by triceps tendon
a. Attachments: lateral epicondyle to lateral olecranon and posterior ulna
b. Nerve: radial
c. Artery: profunda brachii
d. Action: assists triceps, extends forearm
F. Deep extensor muscles
1. Supinator
a. Attachments: lateral epicondyle, elbow joint, radius and ulna to upper lateral radius – 2 heads
b. Nerve: deep radial (passes through the muscle)
c. Artery: radial recurrent
d. Action: supinates forearm
2. Abductor pollicus longus
a. Attachments: posterior ulna, mid-posterior radius to radial side 1st metacarpal
b. Nerve: posterior interosseus of radial
c. Artery: posterior interosseus of ulnar
d. Action: abducts thumb and wrist
3. Extensor pollicus brevis
a. Attachments: posterior radius to proximal phalanx of thumb
b. Nerve: posterior interosseus of radial
c. Artery: posterior interosseus of ulnar
d. Action: extends thumb
4. Extensor pollicis longus
a. Attachments: mid-posterior ulna to distal phalanx of thumb
b. Nerve: posterior interosseus of radial
c. Artery: posterior interosseus of ulnar
d. Action: extends thumb
5. Extensor indicis
a. Attachments: posterior ulna to proximal phalanx of index finger
b. Nerve: posterior interosseus of radial
c. Artery: posterior interosseus of ulnar
d. Action: extends index finger
G. Posterior nerves of forearm
1. Deep br. of radial nerve
a. superior to elbow divides into superficial and deep branches
b. passes through supinator and emerges as posterior interosseus nerve
c. superficial branch accompanies artery into wrist and branches as digital nerves
H. Posterior arteries of forearm
1. Posterior interosseus artery
a. from common interosseus br. of ulnar artery
b. terminates in dorsal carpal arch
c. interosseus recurrent – anastomoses with middle collateral (from profunda)
I. Anatomical snuff box: space in wrist
1. Roof: superficial radial n. and cephalic vein
2. Lies over scaphoid bone
3. Important site for palpating the radial pulse
4. Borders
a. medial = EPL
b. lateral = EPB and APL
c. apex = metacarpal 1
d. floor = ECRB, ECRL and scaphoid bone
II. DORSUM OF HAND
A. Skin loose and thin
B. Extensor tendons prominent
C. Knuckles produced by heads of metacarpals
D. Prominent dorsal venous arch
E. Extensor retinaculum – forms fibrous tunnels
F. Muscles
1. Dorsal interossei - (DAB = Dorsal ABduct)
a. Attachments: adjacent sides of metacarpals to proximal phalanges D2-D4
b. Nerve: Deep br. ulnar
c. Action: abducts digits
G. Nerves of the dorsum of hand
1. Ulnar nerve
a. dorsal cutaneous br.
b. deep branch - to dorsal interossei mm.
2. Radial nerve
a. superficial br. - lateral 2/3 of hand - begins at elbow
b. lateral branch - thumb, radial side of index finger - branches at wrist
c. medial branch - ulnar side index, radial side middle fingers
3. Median nerve – finger tips D2-4
H. Arteries of the dorsum of hand
1. Radial artery
a. dorsal carpal branch - joins dorsal carpal branch of ulnar and anterior and posterior interossei aa. to form dorsal carpal arch (network, rete)
i. dorsal metacarpal arteries and digital arteries
2. Dorsal digital branch of ulnar artery
I. Veins
1. Dorsal venous network - drains to cephalic and basilic vv.
J. Lymphatics
- drain to axillary and cubital nodes