Upper limb 1.4

Question 1

What is the origin of the abductor pollicis longus muscle?

Answer 1

Arises from posterior aspect of the ulna, radius and interosseous membrane

Question 2

What is the insertion of the abductor pollicis longus muscle?

Answer 2

Attaches to the base of the 1st metacarpal bone

Question 3

What is the action of the abductor pollicis longus muscle?

Answer 3

• Abducts
• Extends
• Laterally rotates the thumb at the carpometacarpal joint
• May also contribute to abduction of the wrist

Question 4

What is the abductor pollicis longus muscle innervated by?

Answer 4

• Radial nerve

- Posterior interosseous branch (C7 and C8_

Question 5

What is there anatomical snuffbox?

Answer 5

When the thumb is abducted, the tendon of the abductor pollicis longus becomes prominent and forms the lateral boundary of the “anatomical snuffbox.”

Question 6

How is the abductor pollicis longus muscle tested clinically?

Answer 6

1. the patient supinate the hand (palm up) and extend the forearm at the elbow
2. The examiner places a finger on the lateral aspect of the patient’s extended thumb for resistance and asks the patient to try to move the thumb toward the elbow (abduct).
3. While the patient does this, the examiner looks for the tendon of the muscle running to the base of the thumb’s metacarpal bone.

Question 7

What is the origin of the extensor pollicis brevis muscle?

Answer 7

arises from posterior surface of the radius and the interosseous membrane

Question 8

What is the insertion of the extensor pollicis brevis muscle?

Answer 8

attaches to the base of the proximal phalanx of the thumb

Question 9

What is the action of the extensor pollicis brevis muscle?

Answer 9

• Extends the proximal phalanx of the thumb at the metacarpophalangeal joint
• By its continued action, it also can extend the 1st metacarpal bone at the carpometacarpal joint

Question 10

What is the innervation of the pollicis brevis muscle?

Answer 10

radial nerve (posterior interosseous branch) C7 and C8

Question 11

How does the extensor pollicis brevis muscle form the anatomical snuffbox?

Answer 11

• The extensor pollicis brevis muscle, a short extensor of the thumb, courses with the abductor pollicis longus muscle.
• The tendons of the 2 muscles form part of the lateral boundary of the “anatomical snuffbox.”

Question 12

How do you test the extensor pollicis brevis muscle?

Answer 12

• One can test the extensor pollicis brevis muscle clinically by having the patient supinate the extended hand and then attempt to extend the thumb (the hitchhiking thumb position) against resistance.
• Not only will the strength of the muscle be tested, but the tendon of the muscle should be visible and palpable over the dorsal surface of the thumb’s metacarpophalangeal joint.

Question 13

Where does the extensor pollicis longus muscle arise from?

Answer 13

-Arises from posterior surface of middle third of ulna and the interosseous membrane

Question 14

What is the insertion of the extensor pollicis longus muscle?

Answer 14

Attaches to the base of the distal phalanx of the thumb

Question 15

What is the action of the extensor pollicis longus muscle?

Answer 15

• Extends the distal phalanx of the thumb at the metacarpophalangeal and intephalangeal joint
• Because it runs in an oblique fashion it can contribute to abduction of the thumb

Question 16

What is the innervation of the pollicis longus muscle?

Answer 16

• radial nerve (posterior interosseous branch) C7 and C8

- The tendon of the extensor pollicis longus forms the medial or ulnar border of the “anatomical snuffbox.

Question 17

How is the radial artery and snuffbox damaged?

Answer 17

1. The radial artery can be found within the anatomical snuffbox, and its pulse may be palpated at that point.
2. The anatomical snuffbox is bounded laterally by the tendons of the abductor pollicis longus and extensor pollicis brevis muscles and medially by the extensor pollicis longus tendon.
3. The scaphoid carpal bone lies in the floor of the snuffbox; fracture from a fall on the outstretched hand will present as pain and swelling in the snuffbox (the scaphoid is the most commonly fractured carpal bone).

Question 18

where does the extensor indices muscle arise from?

Answer 18

-Posterior surface of ulna and the interosseous membrane

Question 19

What is the insertion of the extensor indicis muscle?

Answer 19

An extensor expansion of the 2nd digit

Question 20

What is the action of the extensors indicis muscle?

Answer 20

• Extends all the joints of the index finger.

- It can help other extensors extend the wrist

Question 21

What is the innervation of the extensor indicis muscle?

Answer 21

Radial nerve (posterior interosseous branch) (C7 and C8)

Question 22

Why is the extensor indicis muscle special?

Answer 22

• The extensor indicis muscle, a narrow, elongated muscle, lies medial and parallel to the extensor pollicis longus muscle.
• It permits the index finger to extend independently of the other fingers.
• Along with the extensor digitorum muscle, the extensor indicis muscle provides independent extension of the index finger, such that the other digits may be flexed while still extending the index finger (pointing at someone).
• This maneuver is more difficult to do with any of the other fingers.

Question 23

How are muscles divided in forearm?

Answer 23

1. Muscles in the anterior compartment are largely flexors at the wrist and of the fingers (and 2 are pronators).
   - Median nerve and its branches ( Only the flexor carpi ulnaris and the medial half of the flexor digitorum profundus are innervated by the ulnar nerve and its branches)
2. Muscles in the posterior compartment generally are extensors at the wrist and of the fingers (and 1 is a supinator muscle).
   - Muscles of the posterior compartment of the forearm are innervated by the radial nerve and its branches

Question 24

What is the origin of the abductor pollicis brevis muscle?

Answer 24

arises from flexor retinaculum and the tubercles of the scaphoid and trapezium bones

Question 25

What is the insertion of the abductor pollicis brevis muscle?

Answer 25

inserts into lateral side of the base of the proximal phalanx of the thumb

Question 26

What is the action of the abductor pollicis brevis muscle?

Answer 26

Abducts the thumb t the carpometacarpal and metacarpopharlangeal joints

Question 27

What is the innervation of the abductor pollicis brevis muscle?

Answer 27

Reccurent branch of the median nerve (C8 and T1)

Question 28

What are thenar muscles?

Answer 28

• The abductor pollicis brevis muscle is 1 of the 3 muscles that make up the thenar muscles at the base of the thumb.
• The thenar muscles are all innervated by the recurrent branch of the median nerve.

Question 29

How can you test the pollicis brevis muscle?

Answer 29

1. The abductor pollicis brevis muscle is tested clinically by having the patient abduct the thumb against resistance.
2. Abduction of the thumb involves moving it at right angles to the palm toward the elbow in the supinated position.
   - Look for the bulging of the muscle belly in the thenar eminence.

Question 30

What is the origin of the flexor pollicis brevis muscle?

Answer 30

• 2 heads
  1. Superficial head arises from the flexor retinaculum and the trapezium bone
  2. The deep head arises from the floor of the carapal canal which overlies the trapezoid’s and capitate bones

Question 31

What is the insertion of the flexor pollicis brevis muscle?

Answer 31

• 2 heads of the flexor pollicis brevis muscle join in a common tendon that inserts on the lateral side of the 1st metacarpal bone and base of the proximal phalanx
• The tendon of insertion contains the radial seasmoid bone of the metacarapophalangeal joint

Question 32

What is the action of the flexor pollicis brevis muscle?

Answer 32

-Flexes proximal phalanx of the thumb at the metacapophalangea joint and indirectly rotates the metacarpal bone of the thumb medially at the carpometacarpal joint

Question 33

What is the innervation of the flexor pollicis brevis muscle?

Answer 33

Recurrent branch of median nerve (C8 and T1)

Question 34

Is the flexor pollicis brevis muscle part of the thenar muscles?

Answer 34

• The flexor pollicis brevis muscle is 1 of the 3 muscles that make up the thenar muscles at the base of the thumb.
• The thenar muscles are all innervated by the recurrent branch of the median nerve.

Question 35

Why are lacerations of the hand dangerous?

Answer 35

1. The recurrent branch of the median nerve lies somewhat superficial in the palm before diving into the belly of the flexor pollicis brevis muscle.
2. Lacerations across the palm and thenar eminence may sever this important branch, as it innervates all 3 of the thenar muscles. 3. Therefore, one must carefully test the integrity of these muscles in hand lacerations.

Question 36

What is the origin of the opponens pollicis muscle?

Answer 36

arises from the flexor retinaculum and the trapezium bone

Question 37

Where does the opponenns pollicis muscle insert?

Answer 37

Attaches to the lateral side of the 1st metacarpal bone

Question 38

What is the action of the opponens pollicis muscle?

Answer 38

Pulls and rotates the 1st metacarpal in a medial fashion across the palm, opposing the thumb against the fingers

Question 39

What is the innervation of the opponens pollicis muscle?

Answer 39

Recurrent branch of the median nerve (C8 and T1).

Question 40

Is the opponens pollicis muscle part of the thenar muscles?

Answer 40

The opponens pollicis muscle is 1 of the 3 muscles that make up the thenar muscles at the base of the thumb. The thenar muscles are all innervated by the recurrent branch of the median nerve.

Question 41

How can the opponens pollicis be examined?

Answer 41

asking the patient to touch the base of the little finger with the thumb while resistance is provided to the palmar side of the base of the thumb

Question 42

How can a median nerve injury be dangerous?

Answer 42

• As with all of the thenar muscles, injury in the palm before the origin of the recurrent branch of the median nerve will denervate these muscles
• If the median nerve injury is confined to the wrist and/or hand, then all the forearm muscles innervated by the median nerve should still be functional.