MSK Muscles of the upper arm and hand

Question 1

Name the muscles in the anterior and posterior compartment of the arm

Answer 1

Anterior - BBC
Biceps brachii
Brachialis
Coracobrachialis

Posterior
Triceps brachii

Question 2

What are the attachments and actions of the biceps brachii?

Answer 2

The long head originates from the supraglenoid tubercle
The short head originates from the coracoid process
The biceps attach to the radial tuberosity

Actions:
Main - supination
Flexes arm at elbow and shoulder

Question 3

What happens when the biceps tendon ruptures?

Answer 3

The long head tendon is one of the most common tendons to rupture (although tendon rupture is rare)
Produces popeye sign when the elbow is flexed - a bulge where the muscle belly is
The patient would not notice much weakness due to the action of brachialis and supinator

Question 4

What are the attachments and actions of coracobrachialis?

Answer 4

Originates from the coracoid process
Attaches to the medial humeral shaft at the level of the deltoid tuberosity

Actions:
Flexes the arm at the shoulder

Question 5

What are the attachments and actions of the brachialis?

Answer 5

Originates from medial and lateral surfaces of the humeral shaft
Inserts into the ulna tuberosity

Actions:
Main flexor at the elbow

Question 6

What are the attachments and actions of triceps brachii?

Answer 6

Long head originates from infraglenoid tubercle
Lateral head originates from humerus (superior to radial groove)
Medial head originates from humeral (inferior to radial groove)
They attach to the olecranon of the ulna

Actions:
Extension at the elbow

Question 7

What is the innervation of the 4 arm muscles?

Answer 7

BBC are all innervated by musculocutaneous nerve (although brachialis has some radial nerve innervation)

Triceps innervated by radial nerve

Question 8

What is the difference between intrinsic and extrinsic muscles of the hand?

Answer 8

Extrinsic muscles - located in anterior and posterior forearm and control rude movements and produce grip
Intrinsic muscles - located within the hand and responsible for fine motor movements

Question 9

Name the intrinsic muscles of the hand

Answer 9

Thenar muscles:
Opponens pollicis
Abductor pollicis brevis
Flexor pollicis brevis

Hypothenar muscles:
Opponens digiti minimi
Abductor digiti minimi
Flexor digiti minimi brevis

Lumbricals (1-4)
Interossei - dorsal and palmar
Palmaris brevis
Adductor pollicis

Question 10

What are the attachments and actions of opponens pollicis?

Answer 10

Largest and deepest thenar muscle
Originates from tubercle of the trapezium and inserts into the lateral margin of thumb metacarpal

Actions:
Opposes the thumb

Question 11

What are the attachments and actions of abductor pollicis brevis?

Answer 11

Found proximal to flexor pollicis brevis

Originates from scaphoid and trapezium tubercles and attaches to lateral side of proximal phalanx

Actions:
Abducts the thumb

Question 12

What are the attachments and actions of flexor policies brevis?

Answer 12

Most distal thenar muscle
Originates from tubercle of trapezium and attaches to base of proximal phalanx of the thumb

Actions:
Flexers the thumb

Question 13

What is the innervation of the thenar muscles?

Answer 13

Median nerve

Question 14

What are the attachments and actions of opponens digiti minimi?

Answer 14

Deep to all the hypothenar muscles
Originates from hook of hamate and inserts on the medial margin of metacarpal 5

Actions:
Opposes little finger

Question 15

What are the attachments and actions of abductor digiti minimi?

Answer 15

Most superficial hypothenar
Originates from pisiform and tendon of flexor carpi ulnaris and attaches to base of proximal phalanx

Actions:
Abducts the little finger

Question 16

What are the attachments and actions of flexor digiti minimi brevis?

Answer 16

Originates from hook of hamate and inserts into base of proximal phalanx

Actions:
flexes little finger

Question 17

What is the innervation of the hypothenar muscles?

Answer 17

Ulnar nerve

Question 18

What are the attachments and actions of the lumbricals?

Answer 18

There are 4 lumbricals each associated with a finger
They link the extensor and flexor tendons

Each originates from tendon of flexor digitorum profundus and pass dorsally and laterally around each finger to insert into the extensor hood

Actions:
Flex at the metacarpalphalangeal joint
Extend interphalangeal joints

Question 19

What is the innervation of the lumbricals?

Answer 19

Medial 2 lumbricals (little and ring finger) - ulnar nerve

Lateral 2 lumbricals - median nerve

Question 20

What happens to the fingers if the lumbricals are denervated?

Answer 20

Ulnar claw - damage to ulnar nerve paralyses the lumbricals of the little and ring finger, so they are bent
Hand of benediction - damage to median nerve, occurs when patient asked to make a fist

Question 21

What are the attachments and actions of the dorsal interossei?

Answer 21

Most superficial, there are 4 which sit between the metacarpals

Originate from lateral and medial surface of the metacarpals and attach to extensor hood and proximal phalanx of each finger

Actions:
DAM abducts

Question 22

What are the attachments and actions of the palmar interossei?

Answer 22

There are 3 (the middle finger is missing because it cants adduct anywhere)

Originate from lateral and medial surface of the metacarpals and attach to extensor hood and proximal phalanx of each finger

Actions:
PAM adducts

Question 23

What is the innervation of the interossei?

Answer 23

Ulnar nerve

Question 24

What are the attachments and actions of the palmaris brevis?

Answer 24

A small thin muscle found superficially of hypothenar eminence

Originates from palmar aponeurosis and attaches to skin of the medial margin of hand

Actions:
Wrinkles the skin of the hypothenar eminence to deep curve of hand and improve grip

Question 25

What innervates the palmaris brevis?

Answer 25

Ulnar nerve

Question 26

What are the attachments and actions of the adductor pollicis?

Answer 26

Large triangular muscle with 2 heads - the radial artery passes anteriorly between the 2 heads forming the deep palmar arch

One head originates from metacarpal 3, the other from capitate and metacarpals 2 and 3
Both attach to base of proximal phalanx of thumb

Actions:
Adducts the thumb

Question 27

What is the innervation of adductor pollicis?

Answer 27

Ulnar nerve