FORE ARM ANATOMY

1. The Fore am
Dr Kiryowa Haruna

2. Lecture objectives
• To describe the osteology of the forearm
• To outline the cutaneous nerve supply of the
forearm
• To outline the fascial compartments of the
forearm
• To describe the muscles in the different
compartments of the forearm
• To outline the blood supply of the forearm
• To describe the compartment syndrome and
its management in relationship to the forearm

5. Osteology of the forearm

8. Cutaneous nerve supply
• Sensory nerve supply derived from
different sources
• Anterior and posterior branches of
the lateral cutaneous nerve
• Anterior and posterior branches of
the medial cutaneous nerve
• Posterior cutaneous nerve of the
forearm

9. Cutaneous nerve supply of
forearm

12. Superficial veins of the
forearm
• These lie in superficial fascia
• Important in intravenous application
of fluids and drugs
• Include the cephalic vein, median
cubital vein and basilic vein

13. Veins of the forearm

14. Cephalic vein
• Arises from the lateral side of the dorsal
venous arch at the back of the hand
• Winds around the lateral border of the forearm
• Ascends in the cubital fossa
• Continues on the lateral side of the biceps
brachii in the arm
• Pierces the deltopectoral groove and enters
the axillary vein
• Receives a number of tributaries from the
lateral and posterior surfaces of the upper limb

15. Veins of the forearm

16. Median cubital vein
• Tributary of the cephalic vein in the
cubital fossa
• Runs upwards and medially and joins
the basilic vein
• Crosses the brachial artery and
median nerve but separated from
them by the bicipital aponeurosis

17. Veins of the forearm

18. Basilic vein
• Arises from the medial side of the dorsal
venous arch on the back of the hand
• Winds around the medial border of the forearm
• Ascends in the cubital fossa
• Continues in the arm on the medial side of
biceps
• Terminates by joining the venae commitantes
of the brachial artery to form the axillary vein
• Receives a number of tributaries from the
medial and posterior aspect of the forearm

19. Veins of the forearm

20. Fascial compartments of the fore
arm
• Enclosed by deep fascia
• Attached to the posterior subcutaneous
bordery of the ulna
• Together with the interossoeus
membrane and fibrous intermuscular
septa, divide the forearm into anterior,
lateral and posterior compartment
• Each has its own nerves, muscles and
blood vessels

21. Compartment syndrome

22. Compartment syndrome
• Due to soft tissue injury
• Because of the many structures in each
compartment, no space for expansion
• Hence edema causes vascular compression
initially of the thin veins, and later arteries
• Signs include altered skin sensation, then
pain on muscle movement, tenderness of the
skin and later lack of capillary refill
• Treatment if fascioctomy to decompress the
affected compartment

23. Compartment syndrome

25. Interosseous membrane
• Thin strong membrane running
between the radius and ulna
• Fibers run obliquely downwards and
medially from the radius to the ulna,
hence a fall on an outstretched hand
will transmit the forces from the
radius, to the humerus and finally
scapula

27. Flexor retinaculum
• A thickening of deep fascia infront of the wrist
• Its upper border corresponds to the distal transverse
skin crease infront of the wrist
• It is continous with deep fascia of the fore arm
• Lower border is attached to the palmar aponeurosis
• Fxn is to hold long flexor tendons in position
• Also provides insertion for palmaris longus
• Converts the carpal bones into a tunnel for passage
of the median nerve, flexor pollicis longus, flexor
digitorum superficialis and profundus tendons

28. • Medial attachment is to pisiform and
hook of hamate
• Lateral attachment is scaphoid and
trapezium
• Attachments to trapezium thro the
superficial and deep parts creates a
tunnel for passage of flexor carpi
radialis

29. Deep group

30. Extensor retinaculum
• Thickening of deep fascia located at the back of
the wrist
• Holds long extensors in position
• Attached medially to pisiform and hook of
hamate, and laterally to styloid process of radius
• Grooves the posterior surface of radius and ulna
into 6 separated synovial lined channels for
passage of the long extensors of the forearm
• Tunnels separated from each other by fibrous
septa

31. Anterior compartment of the
forearm
• There are many muscles in the forearm. In
the anterior compartment, they are split
into three categories; superficial,
intermediate and deep
• Function: flexion at the wrist and fingers,
and pronation.
• Nerve supply: median nerve except
FCU(ulnar nerve) and FDP(ulnar and median
nerves)
• Blood supply: radial and ulnar arteries

32. Superficial group
• Have a common origin, the common flexor
tendon attached on the medial epicondyle
of the humerous
• Include pronator teres, flexor carpi radialis,
palmaris longus and flexor carpi ulnaris
• The 1st and last have two heads with
pronator teres arising from the coronoid
process of the ulnar and FCU arising from
olecranon process abd posterior surface of
the ulna

35. Pronator Teres
• The lateral border of the pronator teres forms
the medial border of the cubital fossa, an
anatomical triangle located over the elbow.
Attachments: It has two
• Origins: medial epicondyle of the humerus, and
the coronoid process of the ulna.
• Insertion: laterally to the mid-shaft of the radius.
• Actions: Pronation of the forearm.
• Innervation: Median nerve.

37. Flexor Carpi Radialis
• Origin: medial epicondyle
• Insertion: bases of the 2nd
and 3rd
of
metacarpals
• Actions: Flexion and abduction at the
wrist.
• Innervation: Median nerve.

39. Palmaris Longus
• This muscle is absent is about 15% of the
population.
• Origin: medial epicondyle
• Insertion: the flexor retinaculum of the wrist.
• Action: Flexion at the wrist.
• Innervation: Median nerve
• Dissection Tip: Just distal to the wrist, if you
reflect back the palmaris longus, you will find
the median nerve immediately underneath it

40. Flexor Carpi Ulnaris
• Origin: medial epicondyle with the other
superficial flexors. It also has a long
origin from the olecranon process and
posterior aspect of the ulna.
• Insertion: to the pisiform carpal bone.
• Actions: Flexion and adduction at the
wrist.
• Innervation: Ulnar nerve.

42. Intermediate Compartment
•The flexor digitorum superficialis is the only muscle of the intermediate
compartment. It can sometimes be classed as a superficial muscle, but in most
cadavers it lies between the deep and superficial muscle layers.
•The muscle is a good anatomical landmark in the forearm – the median nerve
and ulnar artery pass between its two heads, and then travel posteriorly.
•Origin: It has two heads – one originates from the medial epicondyle of the
humerus, the other from the radius.
•Insertion: The muscle splits into four tendons at the wrist, which travel through
the carpal tunnel, and attach to the middle phalanges of the four fingers.
• Actions: Flexes the metacarpophalangeal joints and proximal interphalangeal
joints at the 4 fingers, and flexes at the wrist.
• Innervation: Median nerve.

44. Deep Compartment of the fore arm.
• There are three muscles in the deep anterior forearm; flexor digitorum
profundus, flexor pollicis longus, and pronator quadratus.
• Flexor Digitorum Profundus
• Attachments: Originates from the ulna and associated interosseous
membrane.
• Insertion: At the wrist, it splits into four tendons, that pass through the
carpal tunnel and attach to the distal phalanges of the four fingers.
• Actions: It is the only muscle that can flex the distal interphalangeal
joints of the fingers. It also flexes at metacarpophalangeal joints and at
the wrist.
• Innervation: The medial half (acts on the little and ring fingers) is
innervated by the ulnar nerve. The lateral half (acts on the middle and
index fingers) is innervated by the medial nerve.

46. Flexor Pollicis Longus ( deep group)
• This muscle lies laterally to the FDP.
• Origin: from the anterior surface of the
radius, and surrounding interosseous
membrane.
• Insertion: Attaches to the base of the distal
phalanx of the thumb.
• Actions: Flexes the interphalangeal joint and
metacarpophalangeal joint of the thumb.
• Innervation: Median Nerve.

48. Pronator Quadratus ( deep group)
• A square shaped muscle, found deep to
the tendons of the FDP and FPL.
• Origin: from the anterior surface of the
ulna
• Insertion: to the anterior surface of the
radius.
• Actions: Pronates the forearm.
• Innervation: Median Nerve.

50. Nerves of the anterior fascial
compartment
• Include median nerve and ulnar nerve
• Median nerve: leaves cubital fossa between the
two heads of pronator teres, continues between
FDS and FDP. At the wrist, it emerges from the
lateral border of FDS, behind tendon of
palmaris longus. Enters the hand behind the
flexor retinaculm
• Brnaches: muscular branches to anterior
compartment, articular branches to the elbow
and anterior interosseous nerve(supplies deep
group and wrist joint)

51. Motor nerve supply

52. • Ulnar nerve: passes behind medial epicondyle,
crosses medial ligament of elbow, enters
forearm between the two heads of FCU, runs btn
FCU and FDP, in distal 1/3, ulnar artery is lateral
to it. Becomes superficial at the wrist, lying
between FCU and FDP. Enters the palm infront of
the flexor retinaculum, medial to the ulna artery
• Branches: muscular, articular (elbow), palmar
cutaneous branch (theaner eminence) and
dorsal posterior cutaneous branch(post aspect of
hand and fingers)

53. Nerves and blood vessels in the
anterior compartment

54. Arteries of anterior
compartment
• Ulnar artery: larger terminal branch of
brachial artery. Starts at neck of radius, in
upper part, its deep to the flexors. Towards
wrist, lies superficial btn FDS and FCU. At
the wrist, lies lateral to the pisiform(site for
ulnar pulse)
• Branches: muscular, recurrent (elbow
anastomosis), common interosseous,
anterior and posterior interosseous(nutrient
arteries to radius and ulna)

55. Anterior compartment: FDS intact

56. Radial artery
• smaller terminal branch of brachial artery.
Starts at the neck of the radius.passes
downwards and laterally behind
brachioradialis, resting on the deep muscles.in
the distal part, its suprficial, lying on the
radius, with brachioradialis tendo on its lateral
side and FCR on its medial side (radial pulse).
Leaves fore arm by curving around lateral
aspect of wrist.
• Branches: muscular, recurrent and superficial
palmar branch

57. Nerves and blood vessels in the
anterior compartment

58. Lateral compartment

59. Lateral compartment
• Has two muscles, Extensor carpi
radialis longus and Brachioradialis
• Have a common origin, the lateral
suoracondylar ridge of the humerus
• Nerve supply: radial nerve
• Blood supply: radial artery

60. Posterior comparment: superficial
group

61. The brachioradialis
• Its origin and innervation are
characteristic of a extensor muscle,
but it is actually a flexor at the elbow.
• Origin: upper 2/3 of lateral
supracondylar ridge of the humerus
• Insertion: radial styloid process.
• Actions: Flexes at the elbow.
• Innervation: Radial nerve.

62. Extensor Carpi Radialis
Longus
• Origin: Lower 1/3 of the lateral
supracondylar ridge of the humerus.
• Insertion: base of 2nd metacarpal
bones
• Actions: Extends and abducts the
wrist.
• Innervation: Radial nerve.

63. Nerves and arteries of lateral
compartment
• Radial nerve: pierces lateral intermuscular septum,
passen down infront of lateral epicondyle, lying between
brachialis and brachioradialis, divides into superficial
and deep branches at level of lateral epicondyle
• Deep branch: runs within supinator to enter posterior
compartment
• Superficial branch: runs deep to brachioradialis, medial
to radial artery, then leaves artery and below tendon of
brachiradialis reaches posterior surface of wrist, then
gives off terminal that supply the posterior surface of
the lateral 31/2 fingers
• Articular branches: elbow joint

64. Nerves of the forearm

65. Neurovascular bundles of
forearm

66. Posterior compartment

67. Posterior compartment
• Composed of two groups: superficial group and
deep group
• Muscles of the superficial group have a common
origin from the common extensor tendon
attached to the lateral epicondyle of the
humerus
• Muscles of the deep group arise from the bones
of the forearm.
• Nerve supply is by deep branch of radial nerve
• Action is extension of wrist and fingers,
supination and abduction

68. Superficial group
Includes
• anconeus
• Extensor carpi radialis brevis
• Extensor digitorum
• Extensor carpi unlnaris
• Extensor digiti minimi

70. Anconeus
• Origin: Lateral epicondyle of the
humerus
• Insertion: olecranon process
• Nerve supply: radial nerve
• Action: extension of the elbow

71. Extensor Carpi Radialis
Brevis
• Origin: Lower 1/3 of the lateral
epicondyle of the humerus.
• Insertion: base of 3rd metacarpal bone
• Actions: Extends and abducts the
hand at the wrist.
• Innervation: Deep branch of radial
nerve.

72. Extensor Digitorum
• The extensor digitorum is the main extensor of the
fingers. To test the function of the muscle, the forearm is
pronated, and the fingers extended against resistance.
• Origin: from the lateral epicondyle.
• Insertion: The tendon continues into in the distal part of
the forearm, where it splits into four, and inserts into the
extensor hood of each finger.
• Actions: Extends medial four fingers at the MCP and IP
joints.
• Innervation: deep branch of Radial nerve.

74. Extensor digiti minimi
• The extensor digiti minimi is thought to originate
from the extensor digitorum muscle. In some people,
these two muscles are fused together. Anatomically,
the extensor digiti minimi lies medially to the
extensor digitorum.
• Origin: Attachments: Originates from the lateral
condyle of the humerus.
• Insertion: It attaches, with the extensor digitorum
tendon, into the extensor hood of the little finger.
• Actions: Extends the little finger, and contributes to
extension at the wrist.
• Innervation: deep branch of radial nerve.

75. Extensor Carpi Ulnaris
• The extensor carpi ulnaris is located on the
medial aspect of the posterior forearm. Due
to its position, it is able to produce adduction
as well as extension at the wrist.
• Origin: from the lateral condyle of the
humerus
• Insertion: extensor expansion of the little
finger.
• Actions: Extension and adduction of wrist.
• Innervation: deep branch of radial nerve.

76. Deep Muscles of the extensor
compartment.
• There are five muscles in the deep
compartment of the posterior forearm – the
supinator, abductor pollicis longus,
extensor pollicis brevis, extensor pollicis
longus and extensor indicis.
• With the exception of the supinator, these
muscles act on the thumb and the index
finger.

78. Supinator
• The supinator lies in the floor of the cubital fossa. It has two
heads, which the deep branch of the radial nerve passes between.
• Origin: It has two heads of origin. One originates from the lateral
epicondyle of the humerus, the other from lateral ligament of the
elbow, annular ligament of the proximal radial ulnar joint, and the
superior crest of the ulna.
• Insertion: neck and posterior surface of the shaft of the radius.
• Actions: Supinates the forearm.
• Innervation: deep branch of radial nerve.

79. Abductor Pollicis Longus
• The abductor pollicis longus is situated
immediately distal to the supinator muscle. In the
hand, its tendon contributes to the lateral border
of the anatomical snuffbox.
• Origin: from the interosseous membrane and the
adjacent posterior surfaces of the radius and ulna.
• Insertion: lateral side of the base of the 1st
metacarpal
• Actions: Abducts the thumb.
• Innervation: Radial nerve.

80. Extensor Pollicis Brevis
• The extensor pollicis brevis can be found medially
and deep to the abductor pollicis longus. In the hand,
its tendon contributes to the lateral border of the
anatomical snuffbox.
• Origin: from the posterior surface of the radius and
interosseous membrane.
• Insertion: base of the proximal phalanx of the thumb.
• Actions: Extends at the metacarpophalangeal and
carpometacarpal joints of the thumb.
• Innervation: deep branch of radial nerve.

81. Extensor Pollicis Longus
• The extensor pollicis longus muscle has a large muscle belly than
the EPB. Its tendon travels medially to the dorsal tubercle at the
wrist, using the tubercle as a ‘pulley’ to increase the force
exerted.
• The tendon of the extensor pollicis longus forms the medial
border of the anatomical snuffbox in the hand.
• Origin: posterior surface of the ulna and interosseous membrane.
• Insertion: distal phalanx of the thumb.
• Actions: Extends all joints of the thumb: carpometacarpal,
metacarpophalangeal and interphalangeal.
• Innervation: deep branch of radial nerve.

82. Extensor Indicis
• This muscles allows the index finger to be
independent of the other fingers during
extension.
• Origin: Originates from the posterior surface
of the ulna and interosseous membrane, distal
to the extensor pollicis longus.
• Insertion: the extensor hood of the index
finger.
• Actions: Extends the metacarpopharyngeal
joint of the index finger.
• Innervation: deep branch of radial nerve.

83. Nerve and blood supply of the
posterior compartment
• Blood supply: anterior and posterior
interosseous arteries, from the
common interosseous artery, a
branch of the ulnar artery
• Nerve supply: deep branch of the
radial nerve(gives off muscular
branches and articular branches to
the wrist and carpal joints)

84. Wrist drop

85. END
THANKS