Upper limb and back: antebrachium (extensors)

Question 1

What are the three extensor muscles going to the thumb?

Answer 1

-Abductor pollicis longus m.
-Extensor pollicis longus m.
-Extensor pollicis brevis m.

Question 2

What is the action and innervation of the abductor pollicis longus muscle?

Answer 2

ACTION
-Abducts the carpometacarpal joint of the thumb.
INNERVATION
-Radial n (posterior interosseous n.)

Question 3

What is the action and innervation of the extensor pollicis brevis muscle?

Answer 3

ACTION
-Extends the metacarpophalangeal and carpometacarpal joints of the thumb.
INNERVATION
-Radial n. (post. interosseous n.)

Question 4

What is the origin, insertion, action and innervation of the extensor pollicis longus muscle?

Answer 4

ORIGIN
-Post. surface of ulna and interosseous membrane.
INSERTION
-Base of distal phalanx of the thumb.
ACTION
-Extends the interphalangeal joints of the thumb.
-Can also extend the carpometacarpal and metacarpophalangeal joints of the thumb.
INNERVATION
-Radial n. (post. interosseous n.)

Question 5

What are the three muscles going to the wrist?

Answer 5

-Brachioradialis m.
-Extensor carpi radialis longus m.
-Extensor carpi radialis brevis m.

Question 6

What is the origin, insertion, action and innervation of the brachioradialis muscle?

Answer 6

ORIGIN
-Lateral supracondylar ridge of the humerus.
INSERTION
-Lateral surface of the distal end of radius.
ACTION
-Accessory flexor of arm at elbow joint when the forearm is mid-pronated.
INNERVATION
-Radial n. (before dividing)

Question 7

What is the origin, insertion, action and innervation of the extensor carpi radialis longus muscle?

Answer 7

ORIGIN
-Lateral supracondylar ridge of the humerus.
INSERTION
-Dorsal surface of the base of metacarpal 2.
ACTION
-Abduction and extension of the wrist.
INNERVATION
-Radial n. (before dividing)

Question 8

What is the origin, insertion, action and innervation of the extensor carpi radialis brevis muscle?

Answer 8

ORIGIN
-Lateral epicondyle of humerus.
INSERTION
-Dorsal surface of the base of metacarpals 2 and 3.
ACTION
-Extension and abduction of the wrist.
INNERVATION
-Radial n. (deep branch).

Question 9

What are the three muscles going to the fingers?

Answer 9

-Extensor digitorium m.
-Extensor indicis m.
-Extensor digiti minimi m.

Question 10

What is the origin, insertion, action and innervation of the extensor digitorium muscle?

Answer 10

ORIGIN
-Lateral epicondyle of humerus.
INSERTION
-Base of the middle and distal phalanx of the medial 4 fingers.
ACTION
-Extensor of the medial four fingers.
-Can also extends the wrist.
INNERVATION
-Radial n. (posterior interosseous n.)

Question 11

What is the origin, insertion, action and innervation of the extensor indicis muscle?

Answer 11

ORIGIN
-Post. surface of ulna and interosseous membrane.
INSERTION
-Extensor hood of index finger.
ACTION
-Extensor of index finger.
INNERVATION
-Radial n. (post. interosseous membrane)

Question 12

What is the origin, insertion, action and innervation of the extensor digiti minimi muscle?

Answer 12

ORIGIN
-Lateral epicondyle of humerus.
INSERTION
-Extensor hood of little finger.
ACTION
-Extensor of little finger.
INNERVATION
Radial n. (post. interosseous n.)

Question 13

What are the three other extensor muscles?

Answer 13

-Extensor carpi ulnaris m.
-Anconeus m.
-Supinator m.

Question 14

What is the origin, insertion, action and innervation of the extensor carpi ulnaris muscle?

Answer 14

ORIGIN
-Lateral epicondyle of humerus.
INSERTION
-Base of metacarpal V.
ACTION
-Adduction and extension of wrist.
INNERVATION
-Radial n. (post. interosseous n.)

Question 15

What is the origin, insertion, action and innervation of the anconeus muscle?

Answer 15

ORIGIN
-Lateral epicondyle of humerus
INSERTION
-Olecranon and proximal post. surface of ulna.
ACTION
-Accessory extension of forearm at elbow joint.
-Assists in pronation.
INNERVATION
-Radial n.

Question 16

What is the origin, insertion, action and innervation of the supinator muscle?

Answer 16

ORIGIN
-Superficial: Lateral epicondyle of humerus.
-Deep: supinator crest of ulna.
INSERTION
-Supinator fossa
ACTION
-Supination
INNERVATION
-Radial n. (deep radial n.)

Question 17

What are the borders of the anatomical snuffbox?

Answer 17

Medail: Extensor pollicis longs tendon.
Lateral: Extensor pollicis brevis tendon.

Question 18

What are the constituents of the floor of the anatomical snuffbox?

Answer 18

Scaphoid and trapezium bones.
Extensor carpi radialis longus and brevis tendons

Question 19

What are the contents of the anatomical snuffbox?

Answer 19

Cephalic vein
Radial artery
Superficial radial nerve