Anatomy of the anterior compartment of the forearm

Question 1

What are the bones of the hand?

Answer 1

Proximal carpal bones articulate with the radius:

1) Scaphoid

2) Lunate

3) Triquetrum (behind the pisiform)

4) Pisiform

Distal row articulates with the metacarpals: each one with its respective metacarpal

5) Trapezium

6) Trapezoid

7) Capitate

8) Hamate

• 5 metacarpals
• 14 phalangees (2 in the thumb, 3 in each finger)

Question 2

What is the wrist joint?

Answer 2

It is a radiocarpal joint (between the radius and carpal bones) as the ulna is separated from the carpal bones by the articular disc

Question 3

Which bone of the hand will only appear in the dorsal view?

Answer 3

Triquetrum

Question 4

What are the superficial muscles of the anterior compartment of the forearm?

Answer 4

1) Pronator teres

2) Flexor carpi radialis longus

3) Palmaris longus

4) Flexor carpi ulnaris

• They all arise from the front of the medial epicondyle
• Flexor means that it belongs to the anterior compartment

Question 5

What is the origin of the superficial muscles of the anterior compartment of the forearm?

Answer 5

They all arise from the front of the medial epicondyle

Question 6

What is the site of insertion of pronator teres?

Answer 6

Lateral side of the radius

Question 7

What is the action of pronator teres?

Answer 7

1) Pronation (rotates the radius)

2) Flexes the elbow joint

Question 8

What is the site of insertion if the flexor carpi radialus longus?

Answer 8

Base of 2nd & 3rd metacarpals

Question 9

What is the function of the flexor carpi radialis longus?

Answer 9

1) Flexion of elbow and wrist

2) Abduction of the wrist joint

Question 10

Where is the palmaris longus muscle inserted?

Answer 10

Palmar aponeurosis

• It might be absent in some individuals

Question 11

What is the action of the palmaris longus?

Answer 11

1) Flexion of the wrist and elbow

2) Tenses the palmar aponeurosis

Question 12

What is the site of insertion of the flexor carpi ulnaris muscle?

Answer 12

The base of the Fifth metacarpal bone

Question 13

What is the action of the flexor carpi ulnaris muscle?

Answer 13

1) Elbow and wrist flexion

2) Adduction of the wrist

• FYI: All ulnaris adduct while all radialis abducts

Question 14

Which muscle is between the superficial muscles and the deep muscles of the anterior compartment of the forearm?

Answer 14

Flexor digitorum superficialis muscle

Question 15

Where is the flexor digitorum superficialis inserted?

Answer 15

To the side of the middle phalanges

Question 16

Where is the origin of the flexor digitorum superficialis?

Answer 16

Front of the medial epicondyle “Common flexor origin”

Question 17

What is the action of the flexor digitorum superficialis?

Answer 17

Partial flexion of the digits

Question 18

What are the deep muscles of the anterior compartment of the forearm?

Answer 18

1) Flexor pollicis longus

2) Flexor digitorum profundus

3) Pronator quadratus

Question 19

What is the origin of the flexor pollicis longus muscle?

Answer 19

1) The majority of the muscle originates from the middle two-thirds of the anterior surface of the radius

2) The remaining part of the muscle originates from the adjacent interosseous membrane

Question 20

Where is the flexor pollicis longus muscle inserted?

Answer 20

The base of the distal phalanx of the thumb

Question 21

What is the action of the flexor pollicis longus muscle?

Answer 21

Flexes the wrist and all thumb joints

Question 22

What is the origin of the flexor digitorum profundas muscle?

Answer 22

• Profundas (big boss)

1) Anterior and middle surface of the ulna

2) Adjacent interosseous membrane

Question 23

Where is the flexor digitorum profundas inserted?

Answer 23

The base of the distal phalanges of the distal four fingers

Question 24

What is the function of the flexor digitorum profundus?

Answer 24

Complete flexion of the fingers

Question 25

What is the origin of the pronator quadratus muscle?

Answer 25

Lower anterior part of the ulna

Question 26

Where is the pronator quadratus inserted?

Answer 26

The lower anterior part of the radius

Question 27

What is the action of the pronator quadratus?

Answer 27

Pronation

Question 28

Which nerve supplies the muscles of the anterior compartment of the forearm?

Answer 28

All of them are supplied by the median nerve, except flexor carpi ulnaris (supplied by the ulnar nerve), and flexor digitorum profundus where the lateral half is supplied by the median while the medial half is supplied by the ulnar nerve

Question 29

What is the cubital fossa?

Answer 29

Small triangular area located on the anterior surface of the elbow with the apex of the triangle pointing distally

Question 30

What are the borders of the cubital fossa?

Answer 30

• The gate of the forearm

1) Medially: Lateral border of the pronator teres muscle (median cubital vein runs along it)

2) Laterally: medial border of brachioradialis

3) The base is formed by an imaginary line between the two epicondyles

Question 31

What structures form the cubital fossa?

Answer 31

1) Bones:
- Humerus
- Radius
- Ulna

2) Tendons:
- Brachialis
- Bicep tendon
- Bicipital aponeurosis

3) Blood vessels:
- Brachial artery
- Median cubital vein (joins the cephalic and cubital vein)

4) Median nerve

5) Supinator muscle

Question 32

Describe the structures found in the cubital fossa from medial to lateral

Answer 32

Median nerve - brachial artery termination (divides into radial and ulnar) - biceps tendon - radial nerve

Question 33

What is the origin of the medial nerve?

Answer 33

1) Lateral root: from the lateral cord of the brachial plexus

2) Medial root: From the medial cord of the brachial plexus

Question 34

Describe the route of the median nerve

Answer 34

1) Runs downwards lateral to the brachial artery

2) Once it reaches the insertion of the coracobrachialis it crosses in front of the brachial artery from the lateral to the medial side

3) Then it continues downwards on the medial side of the artery as far as the cubital fossa

4) In the cubital fossa it will lie in front of the brachialis medial to the brachial and then ulnar arteries and behind the bicipital aponeurosis

5) It will then enter the forearm between the 2 heads of the pronator teres

6) Pass between the 2 digitorum

7) It is 5cm above the wrist becoming superficial and dangerous

8) It enters the hand deep into the flexor retinaculum

9) Then it will divide into medial and lateral branches

Question 35

What are the branches of the median nerve?

Answer 35

A) In the arm:
No branches

B) In the forearm:
1) Muscular:
- Pronator teres
- Flexor carpi radialis
- Palmaris longus
- Flexor digitorum superficialis

2) Articular

3) Palmar cutaneous branch

4) Anterior interosseous nerve (arises from the median nerve as it passes between the 2 heads of pronator teres, it will descend in front of the interosseous membrane in company with the anterior interosseous artery between the flexor pollicis longus and flexor digitorum profundus

• It gives a muscular branch to:
  1) Flexor pollicis longus
  2) Lateral 1/2 of flexor digitorum profundus
  3) Pronator quadratus
• It gives articular branch to:
  1) Wrist joint
  2) Inferior radio-ulnar joint

Question 36

What is the origin of the ulnar nerve?

Answer 36

• Medial cord of brachial plexus
• No branches in the arm
• Runs medial to the axillary and medial artery
• Lies behind the medial epicondyle
• Forms deep and superficial branches

Question 37

Describe the course of the ulnar nerve

Answer 37

1) Runs downward medial to the brachial artery

2) At the coracobrachialis level of insertion, it pierces the medial intermuscular septum to run into the posterior compartment

3) Descending till the back of the medial epicondyle

In the forearm:

1) Enters the forearm between the two heads of the flexor carpi ulnaris

2) Then it passes between the flexor carpi ulnaris & flexor digitorum profundus

3) Its lower half is only covered by the skin and fascia entering the hand superficial to the flexor retinaculum

4) In the hand it will then divide into superficial and deep terminal branches

Question 38

What are the branches of the ulnar nerve?

Answer 38

A) No branches in the arm

B) In the forearm:
1) Muscular branch:
- Flexor carpi ulnaris
- medial half of the flexor digitorum profundus

2) Articular
3) Dorsal cut branch
4) Palmar cut branch