Posterior Forearm and Dorsum of the Hand Muscles

Question 1

Brachioradialis

Origin

Answer 1

-Lateral supracondylar ridge of humerus

Question 2

Brachioradialis

Insertion

Answer 2

-Lateral surface of distal radius, proximal to styloid

process

Question 3

Brachioradialis

Innervation

Answer 3

-Radial nerve (C5, C6, C7)

Question 4

Brachioradialis

Action

Answer 4

-Weak flexion of elbow (maximal when forearm in

midpronated position)

Question 5

Extensor Carpi Radialis Longus (ECRL)

Origin

Answer 5

-Lateral supracondylar ridge of humerus

Question 6

Extensor Carpi Radialis Longus (ECRL)

Insertion

Answer 6

-Dorsal aspect of base of 2nd metacarpal

Question 7

Extensor Carpi Radialis Longus (ECRL)

Innervation

Answer 7

-Radial nerve (C6, C7)

Question 8

Extensor Carpi Radialis Longus (ECRL)

Action

Answer 8

-Extends and radially deviates wrist (active

during fist clenching)

Question 9

Extensor Carpi Radialis Brevis (ECRB)

Origin

Answer 9

-Lateral epicondyle of humerus (via common

extensor tendon)

Question 10

Extensor Carpi Radialis Brevis (ECRB)

Insertion

Answer 10

-Dorsal aspect of base of 3rd metacarpal

Question 11

Extensor Carpi Radialis Brevis (ECRB)

Innervation

Answer 11

-Deep branch of radial nerve (C7, C8)

Question 12

Extensor Carpi Radialis Brevis (ECRB)

Action

Answer 12

-Extends and radially deviates wrist (active during fist clenching)

Question 13

Extensor Digitorum (ED)
Origin

Answer 13

-Lateral epicondyle of humerus (via common extensor tendon)

Question 14

Extensor Digitorum (ED)
Insertion

Answer 14

-Extensor expansions of 2nd-5th digits

Question 15

Extensor Digitorum (ED)
Innervation

Answer 15

-Deep branch of radial nerve (C7, C8)

Question 16

Extensor Digitorum (ED)
Action

Answer 16

• -Extends elbow
• extends hand at wrist
• extends 2nd -5th digits (primarily at MCP joint, secondarily at IP joint)

Question 17

Extensor Digiti Minimi (EDM)

Origin

Answer 17

-Lateral epicondyle of humerus (via common

extensor tendon)

Question 18

Extensor Digiti Minimi (EDM)

Insertion

Answer 18

-Extensor expansion of 5th digit

Question 19

Extensor Digiti Minimi (EDM)

Innervation

Answer 19

-Deep branch of radial nerve (C7, C8)

Question 20

Extensor Digiti Minimi (EDM)

Action

Answer 20

• extends 5th digit (primarily at MCP joint, secondarily at IP joint)
• Weak wrist extension

Question 21

Extensor Carpi Ulnaris (ECU)

Origin

Answer 21

-Lateral epicondyle of humerus (via common extensor tendon); posterior border of ulna

Question 22

Extensor Carpi Ulnaris (ECU)

Insertion

Answer 22

-Dorsal aspect of base of 5th metacarpal

Question 23

Extensor Carpi Ulnaris (ECU)

Innervation

Answer 23

-Deep branch of radial nerve (C7, C8)

Question 24

Extensor Carpi Ulnaris (ECU)

Action

Answer 24

-Extends and ulnarly deviates wrist (active during fist clenching)

Question 25

Supinator | Origin

Answer 25

- Lateral epicondyle of humerus (via common extensor tendon) - radial collateral and anular ligaments - supinator fossa; crest of ulna

Question 26

Supinator | Insertion

Answer 26

-Lateral, posterior, and anterior surfaces of proximal third of radius

Question 27

Supinator | Innervation

Answer 27

-Deep branch of radial nerve (C7, C8)

Question 28

Supinator | Action

Answer 28

-Supinates forearm

Question 29

Abductor Pollicis Longus (APL) | Origin

Answer 29

-Posterior surface of proximal halves of ulna, radius, and interosseous membrane

Question 30

Abductor Pollicis Longus (APL) | Insertion

Answer 30

-Base of 1st metacarpal

Question 31

Abductor Pollicis Longus (APL) | Innervation

Answer 31

-Posterior interosseous nerve (C7, C8) (a continuation of deep branch of radial nerve)

Question 32

Abductor Pollicis Longus (APL) | Action

Answer 32

-Abducts and extends thumb at carpometacarpal | (CMC) joint

Question 33

Extensor Pollicis Brevis (EPB) | Origin

Answer 33

-Posterior surface of distal third of radius and | interosseous membrane

Question 34

Extensor Pollicis Brevis (EPB) | Insertion

Answer 34

-Dorsal aspect of base of proximal phalanx of thumb

Question 35

Extensor Pollicis Brevis (EPB) | Innervation

Answer 35

-Posterior interosseous nerve (C7, C8) (a continuation of deep branch of radial nerve)

Question 36

Extensor Pollicis Brevis (EPB) | Action

Answer 36

- -Extends proximal phalanx of thumb at MCP joint | - extends CMC joint

Question 37

Extensor Pollicis Longus (EPL) | Origin

Answer 37

- Posterior surface of middle third of ulna and | interosseous membrane

Question 38

Extensor Pollicis Longus (EPL) | Insertion

Answer 38

-Dorsal aspect of base of distal phalanx of thumb

Question 39

Extensor Pollicis Longus (EPL) | Innervation

Answer 39

-Posterior interosseous nerve (C7, C8) (a | continuation of deep -branch of radial nerve)

Question 40

Extensor Pollicis Longus (EPL) | Action

Answer 40

- -Extends distal phalanx of thumb at IP joint | - extends thumb at MCP and CMC joints

Question 41

Extensor Indicis | Origin

Answer 41

-Posterior surface of distal third of ulna and | interosseous membrane

Question 42

Extensor Indicis | Inseriton

Answer 42

-Extensor expansion of 2nd digit

Question 43

Extensor Indicis | Innervation

Answer 43

-Posterior interosseous nerve (C7, C8) (a continuation of deep branch of radial nerve)

Question 44

Extensor Indicis | Action

Answer 44

-Extends 2nd digit (enabling its independent extension from other digits) -weakly extends hand at wrist