The document summarizes the gross anatomy of the forearm, including: - The bones of the forearm are the radius and ulna. The radius articulates with the humerus proximally and wrist bones distally. The ulna articulates with the humerus proximally. - The superficial and deep muscles of the anterior compartment are described, including flexor muscles like pronator teres, flexor digitorum superficialis, and flexor digitorum profundus. - The arteries and nerves of the anterior compartment are outlined, including the ulnar artery, radial artery, median nerve, and ulnar nerve. - The superficial muscles of the posterior compartment

1. GROSS ANATOMY OF THE
FOREARM
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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.
Head
Interosseous
membrane
Radius
Humerus
Tuberosity of
radius
Ulna
Head
Fig 1. Anterior view of bones of the forearm. Return to main menu

5. Superficial muscles of the anterior
compartment. Title page.
1
2
3
4
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.
FOR FURTHER DETAILS CLICK ON EACH INDIVIDUAL
MUSCLE BELOW.
1. Pronator teres
2. Flexor carpi radialis
3. Flexor carpi ulnaris
4. Flexor digitorum superficialis
Palmaris longus (not included in the diagram).
Fig 2. Showing superficial muscles of the
posterior compartment.
Brachio-
radialis
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6. Pronator Teres
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.
Return to title page

7. Flexor carpi radialis, palmaris longus, and flexor
carpi ulnaris
Flexor carpi radialis
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
Origin:- Medial epicondyle of the humerus.
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.
Action:- Flexes the hand at wrist joint.
Adducts the hand at wrist joint
Pronator
teres
Flexor
carpi
radialis
Palmaris
longus
Flexor
carpi
ulnaris
Fig 4. Flexor carpi radialis and ulnaris and palmaris longus
Return to title page

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.
Return to title page

9. Deep Muscles of the anterior compartment.
Title page
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
1
2
Brachio-
radialis
(cut)
Tendon of
carpi flexor
radialis (cut)
Fig 6. Deep muscles of the anterior
compartment.
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menu

10. Flexor digitorum profundus and flexor pollicis
longus
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
pollicis
longus
Pronator
quadratus
Flexor
digitorum
profundus
Fig 7. Flexor digitorum profundus and flexor
pollicis longus.
Return to title page

11. Pronator Quadratus
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.
Pronator
quadratus
Flexor
carpi
radialis
(cut)
Flexor
pollicis
longus Flexor
digitorum
profundus
Flexor
carpi
ulnaris
(cut)
Fig 8. Pronator quadratus.
Return to title
page

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.
Next
Return to nerves

13. Arteries and Nerves of the anterior compartment.
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.
Radial
nerve
Superficial
radial nerve
Radial
artery
Brachial
artery
Median
nerve
Ulnar
nerve
Ulnar
artery
Median
nerve
Fig 10. Arteries and nerves of the
anterior compartment. Next
Return to nerves

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.
Branches-
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.
Return to main menu

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.
2
4
Anconeus
2
3
1
Fig 11. Superficial muscles of the posterior
compartment. Return to main menu

16. Extensor carpi radialis longus and brevis, and
extensor carpi ulnaris
Extensor carpi radialis longus
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.
Action:- Extends and abducts the hand at the wrist joint.
Extensor carpi ulnaris
Origin:- From the common tendon attached to the lateral epicondyle
of the humerus.
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.
Return to title
page

17. Extensor digitorum and extensor digiti minimi
Extensor digitorum
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
Origin:- From the common tendon attached to the lateral
epicondyle of the humerus.
Insertion:- Via two tendons to the dorsal expansion for the
little finger.
Nerve supply:- Posterior interosseous nerve, C7 and C8
Action:- Assists in the extension of the little finger.
Extensor
digitorum
Extensor
digiti
minimi
Fig 13. Extensor digitorum and extensor
digiti minimi.
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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.
Brachio-
radialis
Extensor carpi
radialis longus
Extensor carpi
radialis brevis
Flexor carpi
radialis
Fig 15. Brachioradialis (anterior
view).
Fig 14 Brachioradialis (lateral
view). Return to title page

19. Deep muscles in the posterior compartment. Title
page
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.
1
2
4
3
5
Fig 16. Deep muscles of the posterior compartment.
Return to main menu

20. Extensor pollicis longus and brevis, and abductor
pollicis longus
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.
Nerve supply:- The posterior interosseous nerve, C7 and C8.
Action:- Extends the thumb.
Extensor pollicis brevis
Origin:- Posterior surface of the radius.
Insertion:- Posterior surface of the proximal phalanx of the thumb
Nerve supply:- The posterior interosseous nerve, C7 and C8.
Action:- Extends 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
Fig 17. Abductor pollicis longus, extensor
pollicis longus and brevis.
Extensor pollicis
brevis
Return to title page

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). Return to title page

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.
Return to title page
Extensor indicis
Fig 19. Extensor
pollicis

23. Arteries and nerves in the posterior
compartment. Title page
Arteries
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.
Next
Oblique head
of supinator (cut)
Posterior
interosseous
artery
Extensor
carpi ulnaris
Posterior
interosseous
nerve
Extensor carpi
radialis brevis
Fig 19. Posterior interosseous
artery and nerve.

24. Arteries and nerves in the posterior
compartment
Nerves
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:
Branches:
Muscular branches: supply the brachioradialis and
the extensor carpi radialis longus.
Articular branches: To the elbow joint.
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Posteror
interosseous
artery
Posteror
interosseous
nerve
Fig 20. Posteror interosseous
artery and nerve

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