forearm and cubital fossa

Question 1

what articulations do the radius and ulna make?

Answer 1

The two long bones lie vertically in the forearm, with the radius lateral to the ulna (so the radius is in line with thumb, and the ulna with the pinky)

● The proximal ends of the radius and ulna articulate with the distal end of the humerus to form the elbow joint

● The distal ends of the radius and ulna articulate with the carpal bones to form the wrist joint

Question 2

what are 5 landmarks of the radius?

Answer 2

Head of the radius
● A disk shaped structure
● It articulates with the capitulum of the distal humerus

Neck of radius
● A narrow area of bone between the radial head and radial tuberosity

Radial tuberosity
● A bony projection, where the biceps brachii attaches

Styloid process
● The lateral side projection of the distal end of the shaft

Ulnar notch
● A concavity found on the medial surface of the distal end of the shaft which articulates with the head of the ulna

Question 3

which of the carpals does the radius articulate with?

Answer 3

scaphoid and lunate

Question 4

what are 6 landmarks of the ulna (including their purpose)?

hint - start with olecranon…

Answer 4

Olecranon
● A large projection which extends proximally (up) forming part of the trochlear notch.
● It can be palpated as the ‘tip’ of the elbow
● The triceps brachii muscle attaches to it

Coronoid process
● This ridge of bone projects outwards anteriorly, forming part of the trochlear notch

Trochlear notch
● A wrench shape formed by the olecranon and coronoid process
● It articulates with the trochlea of the humerus

Radial notch
● Located on the lateral surface of the trochlear notch
● This area articulates with the head of the radius to form the proximal radioulnar joint

Tuberosity of ulna
● A roughening immediately distal to the coronoid process
● It is where the brachialis muscle attaches

• styloid process at the distal end, quite small

Question 5

what kind of joint is the elbow, and what is it comprised of?

what movements does it allow?

Answer 5

synovial hinge joint

an articulation between the distal end of the humerus and proximal ends of radius and ulna

flexion and extension of the forearm

Question 6

what kind of joint is the proximal radioulnar joint and what is is comprised of?

what movement does it allow?

Answer 6

synovial pivot joint

under the elbow, it is where the head of the radius and the radial notch of the ulna meet

allows for pronation and supination (along with the distal RU joint)

Question 7

what kind of joint is the distal radioulnar joint and what is it comprised of?

what movement does it allow?

Answer 7

synovial pivot joint, between head of ulna and ulnar notch of the radius (ulna head = at bottom, radius head = at top)

allows for the distal (bottom) end of the radius to move anteromedially over the ulna during pronation. also contributes to allowing supination

Question 8

what is the general role of the muscles of the anterior compartment of the forearm?

where do these muscles originate from?

Answer 8

also known as the flexor compartment, comprised of 8 muscles that flex the wrist and digits

the superficial and intermediate muscles all originate from the medial epicondyle (not the deep muscles)

Question 9

which nerves innervate the anterior compartment of the forearm?

Answer 9

mostly innervated by the median nerve,

except for flexor carpi ulnaris and the medial half of flexor digitorum profundus,

which are innervated by the ulnar nerve

Question 10

what blood vessels supply the anterior compartment of the forearm?

Answer 10

the radial and ulnar artery

Question 11

name the 8 muscles of the anterior compartment of the forearm including ehat layer they are in

Answer 11

superficial -
Pronator teres
Flexor carpi radialis
Palmaris longus
Flexor carpi ulnaris

intermediate -
flexor digitorum superficialis

deep -
flexor pollicis longus
flexor digitorum profundus
pronator quadratus

Question 12

TABLE

Question 13

what is the role of the muscles in the posterior compartment of the forearm?

innervation?

common origin?

Answer 13

the extensor muscles, typically extend the wrist and the digits

all innervated by the radial nerve

most originate from the lateral epicondyle or the supracondylar ridge

Question 14

name the 12 extensor muscles of the posterior compartment of the forearm, and what layer they belong to

Answer 14

superficial -
brachioradialis
extensor carpi radialis longus
extensor carpi radialis brevis
extensor digitorum
extensor digit minimi
extensor carpi ulnaris
anconeus

deep -
supinator
abductor pollicis longus
extensor pollicis brevis
extensor pollicis longus
extensor indicis

Question 15

define the boundaries of the cubital fossa

Answer 15

triangular shaped depression over anterior aspect of the elbow

lateral border = brachioradialis muscle
medial border = pronator teres muscle
superior border = an imaginary line going between the two epicondyles of the humerus

roof = bicipital aponeurosis fascia fat and skin
floor = brachialis proximally and supinator distally

Question 16

from lateral to medial, what are the contents of the cubital fossa?

Answer 16

radial nerve - travels along lateral side and divides into deep and superficial branches

biceps tendon - passes down the centre, attaching to the radial tuberosity (and gives rise to bicipital aponeurosis)

brachial artery - bifurcates into radial and ulnar artery @ apex of cubital fossa. pulse can be felt

median nerve - travels medially, exiting by passing between the 2 heads of the pronator teres

some superficial veins lie on top of the cubital fossa’s roof…

Question 17

what superficial veins lie on top of the cubital fossa’s roof?

Answer 17

these can be accessed for taking blood (venepuncture)

the median cubital vein, which connects the cephalic and basilic veins

(think this might be in the cubital fossa but) the brachial vein is seen alongside the brachial artery and also branches into ulnar and radial veins

Question 18

pronator teres?

Answer 18

superficial muscle in anterior comp. of forearm

origin = medial epicondyle

insertion = mid-shaft of radius

function = pronates and flexes forearm

Question 19

flexor carpi radialis

Answer 19

superficial muscle in anterior comp. of forearm

O: medial epicondyle
I: base of metacarpals 2-5
F: flexes forearm, flexes hand, abducts hand

Question 20

palmaris longus?

Answer 20

superficial muscle of the anterior comp. of forearm

O:medial epicondyle
I: palmar aponeurosis of the hand
F: flexes forearm and hand

Question 21

flexor carpi ulnaris?

Answer 21

superficial ant. forearm

O:medial epicondyle
I: pisiform, base of metacarpal 5
F: flexes forearm, flexes hand, ADDucts hand

Question 22

flexor digitorum superficialis

Answer 22

intermediate ant. forearm

O: medial epicondyle and radius
I: middle phalanges 2-5
F: flexes proximal interphalangeal joints (hand and forearm

Question 23

flexor pollicis longus?

Answer 23

deep anterior forearm

O: anterior surface of radius and interosseous membrane
I: base of distal phalanx of the thumb
F: flexes thumb

Question 24

flexor digitorum profundus?

Answer 24

deep anterior forearm

O: anterior surface of ulna and interosseous membrane
I: distal phalanges 2-5
F: flexes distal interphalangeal joints, and hand

Question 25

pronator quadratus?

Answer 25

deep anterior forearm

O: distal anterior surface of ulna
I: distal anterior surface of radius
F: pronates forearm

Question 26

brachioradialis?

Answer 26

posterior forearm - superficial

O: lateral supracondylar ridge
I: distal end of radius
F: flexes at the elbow

Question 27

extensor carpi radialis longus?

Answer 27

posterior forearm - superficial

O: lateral supracondylar ridge
I: base of metacarpal 2 (index finger)
F: extends and abducts wrist

Question 28

extensor carpi radialis brevis?

Answer 28

posterior forearm - superficial

O: lateral epicondyle
I: base of metacarpals 2-5
F: extends and abducts wrist

Question 29

extensor digitorum?

Answer 29

posterior forearm - superficial

O: lateral epicondyle
I: base of middle and distal phalanges 2-5 via the extensor hoods
F: Extension of the digits at the interphalangeal and metacarpophalangeal joints

Question 30

extensor digiti minimi?

Answer 30

posterior compartment of forearm - superficial

O: lateral epicondyle
I: dorsal hood of little finger
F: Extends the little finger, and contributes to extension at the wrist

Question 31

extensor carpi ulnaris?

Answer 31

posterior forearm - superficial

O: lateral epicondyle
I: base of metacarpal 5
F: Extension and adduction of wrist

Question 32

anconeus?

Answer 32

posterior forearm - superficial

O: lateral epicondyle
I: olecranon and posterior surface of ulna
F: Extends and stabilises the elbow joint. Abducts the ulna during pronation of the forearm

Question 33

supinator?

Answer 33

deep posterior forearm

O: lateral epicondyle
I: radius
F: supinates the forearm

Question 34

abductor pollicis longus?

Answer 34

posterior compartment of forearm - deep

O: posterior surface of ulna, radius and interosseous membrane
I: base of metacarpal 1
F: abducts the thumb

Question 35

extensor pollicis brevis?

Answer 35

deep posterior forearm

O: posterior surface of radius and interosseous membrane
I: base of proximal phalanx of the thumb
F: extends thumb

Question 36

extensor pollicis longus?

Answer 36

deep posterior forearm

O: posterior surface of ulna and interosseous membrane
I: base of distal phalanx of the thumb
F: extends thumb

Question 37

extensor indicis?

Answer 37

deep posterior forearm

O: posterior surface of ulna and interosseous membrane
I: extensor hood of index finger
F: extends the index finger

Question 38

blood supply of muscles of anterior compartment of forearm vs posterior?

Answer 38

anterior = radial and ulnar arteries

posterior = posterior interosseous artery, a branch of the common interosseus artery, which is a branch of the ulnar artery

Question 39

fractures of the humerus often damage which nerve? why and what problem does this cause?

Answer 39

axillary nerve because it wraps around the surgical neck of the humerus

damage results in loss of shoulder abduction