1. GROSS ANATOMY OF THE FOREARM
A CAL package designed by-
Pratik Sinha
Revision Guide for second year Medical Students
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2. Main Menu Bones of the forearm.
Superficial muscles of the anterior compartment.
Deep muscles of the anterior compartment.
Arteries and nerves of the anterior compartment.
Superficial muscles of the posterior compartment.
Deep muscles of the posterior compartment.
Arteries and nerves of the posterior compartment.
Acknowledgements

3. Acknowledgements Supervision Dr John Humpherson
Anatomy Dissection Pictures Gosling , Harris, Humpherson, Whitmore, Willan Atlas of Human Anatomy, Gower Publishing, 1985
Anatomy Drawings Richard Neave & Medical Illustration
Technical Help Tony Bentley, Mike Mahon
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4. Bones of the forearm
The radius proximally articulates with the humerus at the elbow joint. Distally it articulates with the scaphoid and lunate bones of the carpus, and with the ulna at the distal radioulnar joint.
The ulna is the more medial of the two bones. Its proximal end articulates with the humerus at the elbow joint. Distally it articulates with the radius. It is excluded from the wrist joint by the articular disc.
The interosseous membrane bind the radius and the ulna together.
Humerus
Head
Tuberosity of radius
Ulna
Interosseous membrane
Radius
Head
Fig 1. Anterior view of bones of the forearm.
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5. Superficial muscles of the anterior compartment. Title page.
The superficial muscles of the anterior compartment include pronator teres, flexor carpi radialis, palmaris longus, and flexor carpi ulnaris. Also included in this group is flexor digitorum superficialis. The superficial group of muscles all have the same origin, which is attached to the medial epicondyle of the humerus. 1 2
Brachio-
radialis 3
FOR FURTHER DETAILS CLICK ON EACH INDIVIDUAL MUSCLE BELOW.
Pronator teres
Flexor carpi radialis
Flexor carpi ulnaris
Flexor digitorum superficialis
Palmaris longus (not included in the diagram). 4
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Fig 2. Showing superficial muscles of the posterior compartment.

6. Pronator Teres Return to title page
The pronator teres has two heads, the humeral head and the ulnar head. The median nerve enters the forearm between the two heads.
Origin :-
Humeral head- Medial epicondyle of the humerus.
Ulnar head- Medial border of the coronoid process of the ulna.
Insertion :-
Lateral aspect of the shaft of the radius.
Nerve supply :- Median nerve, C6 and C7.
Action :- Pronation of the forearm.
Flexion of the forearm.
Pronator teres
Radius
Fig 3. Pronator teres.
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7. Flexor carpi radialis, palmaris longus, and flexor carpi ulnaris
Origin:- Medial epicondyle of the humerus.
Insertion:- Base of the second and third metacarpal bones.
Nerve supply:- Median nerve, C6 and C7.
Action:- Flexes the hand at the wrist joint.
Abducts the hand at the wrist joint.
Palmaris longus
Insertion:- Flexor retinaculum and palmar aponeurosis.
Nerve supply:- Median nerve, C7 and C8
Action:- Flexes the hand at wrist joint.
Flexor carpi ulnaris.
Origin:-
Humeral head- Medial epicondyle of the humerus.
Ulnar head- Medial aspect of the olecranon process of the ulna and the posterior border of the ulna.
Insertion:- Pisiform bone, hook of the hamate, and base of the fifth metacarpal bone.
Nerve supply:- The ulnar nerve, C7, C8, and T1.
Adducts the hand at wrist joint
Palmaris longus
Pronator teres
Flexor carpi ulnaris
Flexor carpi radialis
Fig 4. Flexor carpi radialis and ulnaris and palmaris longus
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8. Flexor digitorum superficialis.
Origin:-
Humeroulnar head: Medial epicondyle of the humerus and the medial margin of the coronoid process of the ulna.
Radial head: Rising from the oblique line on the anterior surface of the shaft of the radius.
Insertion:- The muscle belly gives rise to four tendons distally. Each of the tendon attaches to the sides of the middle phalanx of the four medial finger.
Nerve supply:- Median nerve, C8 and T1.
Action:- Flexes the middle phalanx of fingers.
Flexes the proximal phalanx of fingers (weak).
Flexes the wrist.
Flexor digitorum superficialis.
Fig 5. Flexor digitorum superficialis.
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9. Deep Muscles of the anterior compartment. Title page
Brachio-radialis (cut)
The deep muscles of the forearm comprise of the flexor pollicis longus, flexor digitorum profundus and pronator quadratus.
For further details click on each of the individual muscles.
1. Flexor digitorum profundus.
2. Flexor pollicis longus.
Pronator quadratus not shown. 1 2 1
Tendon of carpi flexor radialis (cut)
Fig 6. Deep muscles of the anterior compartment.
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10. Flexor digitorum profundus and flexor pollicis longus
Origin:- Middle of the anterior surface of the shaft of the radius and from the adjoining part of the interosseous membrane.
Insertion:- The tendon passes distally through the carpal tunnel and attaches to the distal phalanx of the thumb.
Nerve supply:- The anterior interosseous branch of the median nerve.
Action:- Flexes the phalanges of the thumb.
Flexor digitorum profundus
Origin:- Upper three-quarters of the anteriomedial shaft of the ulna.
Insertion:- The muscle divides into four tendons just prior to traversing the carpal tunnel. They attach to the distal phalanx of the four fingers.
Nerve supply:- The medial part is supplied by the ulnar nerve, the lateral portion is supplied by the anterior interosseous branch of the median nerve, C8 and T1.
Action:- Flexes the finger. Exclusive flexor of the distal phalanx. Weak flexor of the wrist.
Flexor digitorum profundus
Flexor pollicis longus
Pronator quadratus
Fig 7. Flexor digitorum profundus and flexor pollicis longus.
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11. Pronator Quadratus
Flexor pollicis longus
Origin:- Lower quarter of the anterior surface of the shaft of the ulna.
Insertion:- Lower quarter of the anterior surface of the shaft of the radius.
Nerve supply:- The anterior interosseous branch of the median nerve.
Action:- Pronates the forearm.
Flexor digitorum profundus
Pronator quadratus
Flexor carpi radialis (cut)
Flexor carpi ulnaris (cut)
Fig 8. Pronator quadratus.
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12. Arteries and Nerves of the anterior compartment. Title page
Ulnar artery:- Larger than the radial artery. It passes between the arch formed by the radial and ulnar attachment of the flexor digitorum superficialis and descends through the anterior compartment. It enters the palm of the hand in front of the flexor retinaculum, and promptly divides in superficial and deep palmer branches.
Branches-
Muscular branches- to the muscles of the anterior compartment.
Recurrent branches- to the anastomosis around the wrist joint
Branches to the anastomosis around the wrist joint
Common interosseous artery- arises in the upper part of the ulnar artery and then divides in the anterior and posterior interosseous arteries.
Anterior interosseous artery:- arises from the common interosseous artery and descends in the anterior compartment to eventually join the anastomosis around the wrist joint. It supplies the deep flexor muscles, and gives off nutrient branches to the the radius and ulna.
Brachial artery
Median nerve
Ulnar nerve
Radial nerve
Ulnar artery
Fig 9. Arteries and nerves of the anterior compartment.
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13. Arteries and Nerves of the anterior compartment.
Radial nerve
Brachial artery
Posterior interosseous artery- arises from the common interosseous artery and and enters the posterior compartment.
Radial artery:- It begins in the cubital fossa when the brachial artery divides into the radial and ulna artery. It passes distally, travels under the brachioradialis, resting on the deep flexor muscles. The artery briefly travels on the lateral side of the radius, before travelling over the anterior surface of the radius. The artery then winds around the lateral aspect of the wrist, before entering the palm of the hand to form the deep palmer arch.
Branches-
Muscular branches: to the neighbouring muscles.
Branches to the anastomosis around the wrist and elbow joint.
Superficial palmer joint: arises just above the wrist, frequently joins the ulnar artery to give rise to the superficial palmer arch.
Median nerve
Superficial radial nerve
Ulnar nerve
Ulnar artery
Radial artery
Median nerve
Fig 10. Arteries and nerves of the anterior compartment.
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14. Nerves of the anterior compartment
Median Nerve (fig 9, fig 10)
The median nerve leaves the cubital fossa in between the two heads of the pronator teres. It descends between the superficial and deep flexor muscles. At the wrist it lies superficially, before entering the palm behind the flexor retinaculum.
Branches:-
Muscular branch:- all the superficial muscles of the anterior compartment except flexor carpi ulnaris.
Articular branches: to the elbow joint
Anterior interosseous nerve: arises from the median nerve as it emerges from the two heads of the pronator teres. (see below)
Palmer cutaneous Branch: Distributed to the skin over the lateral part of the palm.
Anterior interosseous nerve
It arises from the median nerve (see above) and then descends down the anterior surface of the interosseous membrane.
Branches-
Muscular branches: all the muscles of deep flexion in the anterior compartment except the medial part of digitorum profundus.
Articular branches: to the wrist joint, the distal radioulnar joint, and the joints of the carpus.
Ulnar Nerve(fig9, fig 10)
The ulnar nerve passes behind the medial epicondyle and enters the forearm between the two heads of flexor carpi ulnaris. It descends between the flexor carpi ulnaris and the flexor digitorum profundus. The ulnar nerve becomes superficial at the wrist, before entering the palm in front of the flexor retinaculum.
Muscular branches: to the flexor carpi ulnaris and to the medial half of the flexor digitorum profundus.
Articular branches: to the elbow joint.
Palmar cutaneous branch: arises in the middle of the forearm, Supplies skin over the thenar eminence.
Dorsal cutaneous branch: arises in the distal third of the of the forearm, and passes medially to the dorsum of the hand.
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15. Superficial muscles of the posterior compartment. Title page
The superficial muscles of the anterior compartment are mainly concerned with the extension at wrist joint and of the digit. The muscles in this group comprise of the Extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, and the two more lateral lying brachioradialis and extensor carpi radialis longus.
NB- The anconeus also lies in the posterior compartment but is functionally very different to the rest of the muscles in this group. Its action are to aid the triceps in extension at the elbow joint.
Click below on each of the muscles for further detail about each of the individual muscles.
1. Extensor carpi radialis longus
2. Extensor digitorum
3. Extensor carpi ulnaris
4. Extensor digiti minimi
Brachioradialis and extensor carpi brevis are not included in the figure.
Anconeus 3 2 1 2 4
Fig 11. Superficial muscles of the posterior compartment.
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16. Extensor carpi radialis longus and brevis, and extensor carpi ulnaris
Origin:- From the lower third of the lateral supracondylar ridge of the humerus.
Insertion:- Posterior surface of the base of the second metacarpal bone.
Nerve supply:- Radial nerve, C6 and C7.
Action:- Extends and abducts the hand at the wrist joint.
Extensor carpi radialis brevis
Origin:- From the common tendon attached to the lateral epicondyle of the humerus.
Insertion:- Posterior surface of the base of the third metacarpal bone.
Nerve supply:- Posterior interosseous nerve, C7 and C8.
Extensor carpi ulnaris
Insertion:- Posterior surface of the base of the fifth metacarpal bone.
Nerve supply:- Posterior interosseous nerve, C7 and C8
Action:- Extends and adducts the hand at wrist joint.
Extensor carpi radialis longus
Extensor carpi radialis brevis
Extensor carpi ulnaris
Fig 12. Extensor carpi radialis brevis and longus and extensor carpi ulnaris.
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17. Extensor digitorum and extensor digiti minimi
Origin:- From the common tendon attached to the lateral epicondyle of the humerus.
Insertion:- The muscle divides into four tendons which pass to the fingers and form the dorsal expansion. On the dorsum of the hand these are interconnected by fibrous tissue. Near the proximal interphalangeal joint of each finger the expansions divide into the central part, which inserts into base of the middle phalanx, and the two lateral parts, which insert into the base of the distal phalanx.
Nerve supply:- Posterior interosseous nerve, C7 and C8
Action:- Mainly it extends the metacarpophalangeal joint, but it also assists in extending the proximal and distal interphalangeal joint and the arm.
Extensor digiti minimi
Insertion:- Via two tendons to the dorsal expansion for the little finger.
Action:- Assists in the extension of the little finger.
Extensor digitorum
Extensor digiti minimi
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Fig 13. Extensor digitorum and extensor digiti minimi.

18. Brachioradialis
Origin:- From the upper twp thirds of the lateral supracondylar ridge of the humerus.
Insertion:- Base of the styloid process of the radius.
Nerve supply:- Radial nerve, C5 and C6.
Action:- It flexes the forearm (despite being being served by an ‘extensor’ nerve), assists in rotating or restoring the arm into midprone position, depending on the initial position.
Flexor carpi radialis
Brachio-radialis
Extensor carpi radialis longus
Extensor carpi radialis brevis
Fig 15. Brachioradialis (anterior view).
Fig 14 Brachioradialis (lateral view).
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19. Deep muscles in the posterior compartment. Title page1
The deep muscles of the fore arm consist of three muscles that act on the thumb, the extensor indicis and supinator. Except for the supinator they all originate from only the forearm bones.
For further details on each of the bones click on the individual muscles.
1. Supinator.
2. Abductor pollicis longus.
3. Extensor pollicis longus.
4. Extensor indicis.
5. Extensor pollicis brevis. 2 3 4 5
Fig 16. Deep muscles of the posterior compartment.
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20. Extensor pollicis longus and brevis, and abductor pollicis longus
Origin:- Middle of the posterior surface of the shaft of the ulna and radius.
Insertion:- Posterior surface of the base of the first metacarpal bone.
Nerve supply:- The posterior interosseous nerve, C7 and C8.
Action:- Abducts and extends the thumb.
Extensor pollicis longus
Origin:- From the posterior surface of the ulna.
Insertion:- Posterior surface of the base of the distal phalanx of the thumb.
Action:- Extends the thumb.
Extensor pollicis brevis
Origin:- Posterior surface of the radius.
Insertion:- Posterior surface of the proximal phalanx of the thumb
Anatomical snuff box: medial boundary is the the tendon of the extensor pollicis longus and the lateral boundary is the tendon of the abductor pollicis longus and extensor pollicis brevis.
Abductor pollicis longus.
Extensor pollicis longus
Extensor pollicis brevis
Fig 17. Abductor pollicis longus, extensor pollicis longus and brevis.
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21. Supinator
Supinator
The supinator consists of oblique and a transverse head.
Origin:-
Oblique head: From the lateral epicondyle of the humerus and collateral ligament of the elbow joint.
Transverse head: Supinator crest of the ulna.
Insertion:- Both heads wind laterally around the proximal part of the radius, attaching to the anterior aspect of the radius.
Nerve supply:- Posterior interosseous nerve, C6 and C7.
Action:- Supinates the forearm (mainly assists as the biceps brachii is main supinator of the forearm).
Transverse head
Oblique head
Fig 18. Supinator muscle (anterior view).
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22. Extensor indicis Origin:- Posterior surface of the ulna.
Insertion:- Dorsal expansion of the index finger
Nerve supply:- Posterior interosseous nerve, C7 and C8.
Action:- Extends the index finger.
Extensor indicis
Fig 19. Extensor pollicis
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23. Arteries and nerves in the posterior compartment. Title page
Posterior interosseous artery:-
As discussed previously, in the cubital fossa, the common interosseous artery divides in the anterior and posterior interosseous muscle. The posterior interosseous artery lies between the superficial and deep extensor muscles. It terminates by anastomosing with the anterior interosseous muscle and taking part in the anastomosis around the wrist joint.
Branches:
Muscular branch- to the neighbouring muscles.
Recurrent branch- takes part in the anastomosis around the wrist joint.
Anterior interosseous artery (discussed earlier):-
Enters the posterior compartment in the distal third of the forearm. Supplies branches to neighbouring muscles.
Radial artery (discussed earlier)
Has branches that supply the muscles in the lateral aspect of compartment.
Oblique head
of supinator (cut)
Posterior
interosseous
nerve
Posterior
interosseous
artery
Extensor carpi
radialis brevis
Extensor
carpi ulnaris
Fig 19. Posterior interosseous artery and nerve.
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24. Arteries and nerves in the posterior compartment
The posterior compartment of the arm is supplied by branches of the radial nerve.
Posterior interosseous nerve (Deep branch):
It arises from the radial nerve just in front of the lateral epicondyle of the humerus. It enters the posterior compartment in between the two heads of the supinator.
Branches:
Muscular branches: To most of the muscles of the posterior compartment (see individual muscles for detail).
Articular branches: To the elbow, wrist and carpal joints.
Radial nerve:
Muscular branches: supply the brachioradialis and the extensor carpi radialis longus.
Articular branches: To the elbow joint.
Posteror
interosseous
nerve
Posteror
interosseous
artery
Fig 20. Posteror interosseous artery and nerve
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