forearm
DEPARTMENT OF ANATOMY
UPPER LIMB
FOREARM
FOREARM
The forearm is the part of the upper limb that extends between the elbow joint and the wrist joint.
As in the arm, the forearm is divided into anterior and posterior compartments
Compartments of forearm
Muscles in the anterior compartment of the forearm flex the wrist and digits and pronate the hand .
Muscles in the posterior compartment extend the wrist and digits and supinate the hand .
ANTERIOR COMPARTMENT OF
THE FOREARM
Muscles in the anterior (flexor) compartment of the forearm occur in three layers:
1. Superficial
2. Intermediate
3.
Deep
All muscles in the anterior compartment of the forearm are innervated by the median nerve , except for the flexor carpi ulnaris muscle and the medial half of the flexor digitorum profundus muscle, which are innervated by the ulnar nerve .
Superficial layer
Four muscles in the superficial layer-
1.flexor carpi ulnaris
2.palmaris longus
3.flexor carpi radialis
4. pronator teres-
All four muscles have a common origin from the medial epicondyle of the humerus, and, except for pronator teres, extend distally from the forearm into the hand
Intermediate layer
Flexor digitorum superficialis
Deep layer
1.flexor digitorum profundus
2.flexor pollicis longus
3.pronator quadratus
Anterior Forearm
Pronator
Teres
Pronates and flexes forearm at the elbow
Flexes and abducts hand
(at the wrist)
Flexor
Carpi
Radialis
Palmarus
Longus
Flexor
Carpi
Ulnaris
Flexes hand at the wrist and tightens palmar aponeurosis
Flexes and adducts hand at the wrist
Flexor Digitorum Superficialis Flexes middle phalanges at the proximal interphalangeal joints of medial four digits; acting more strongly, it also flexes proximal phalanges at metacarpophalangeal joints and hand[wrist]
Flexor Digitorum Profundus Flexes distal phalanges at distal interphalangeal joints of medial four digits; assist with flexion of hand
Flexor pollicis Longus Flexes 1 st digit (thumb)
Pronator Quadratus Pronates forearm; deep fibers bind radius and ulna together
Arteries of the anterior compartment of the forearm.
At the apex of the cubital fossa, Brachial artery divides into its two major branches, the radial and ulnar arteries.
Radial artery
In the distal forearm, the radial artery can be located using the flexor carpi radialis muscle as a landmark.
Radial artery lies immediately lateral to the large tendon of the flexor carpi radialis muscle.
Radial pulse
The radial pulse can be felt by gently palpating the radial artery against the underlying muscle and bone.
Nerves
Nerves in the anterior compartment of the forearm are the median and ulnar nerves, and the superficial branch of the radial nerve.
Median nerve
The median nerve innervates the muscles in the anterior compartment of the forearm except for the flexor carpi ulnaris and the medial part of the flexor digitorum profundus (ring and little fingers).
It leaves the forearm and enters the palm of the hand by passing through the carpal tunnel deep to the flexor retinaculum.
Branches of median nerve
1. Anterior interosseous nerve: innervates the muscles in the deep layer
2. A small palmar branch originates from the median nerve in the distal forearm immediately proximal to the flexor retinaculum.
Innervates the skin over the base and central palm.
This palmar branch is spared in carpal tunnel syndrome because it passes into the hand superficial to the flexor retinaculum of the wrist.
Cutaneous branches of median and ulnar nerve
Ulnar nerve
In the forearm, the ulnar nerve innervates only the flexor carpi ulnaris muscle and the medial part (ring and little fingers) of the flexor digitorum profundus muscle.
Branches in forearm:
1.Palmar branch originates in the middle of the forearm and passes into the hand to supply skin on the medial side of the palm
Radial nerve
The radial nerve bifurcates into deep and superficial branches under the margin of the brachioradialis muscle in the lateral border of the cubital fossa.
The deep branch is predominantly motor and passes between the two heads of the supinator muscle to access and supply muscles in the posterior compartment of the forearm.
The superficial branch of the radial nerve is sensory.
POSTERIOR COMPARTMENT
OF THE FOREARM
POSTERIOR COMPARTMENT OF
THE FOREARM
Muscles in the posterior compartment of the forearm occur in two layers:
1.Superficial
2.Deep layer
The muscles are associated with:
1.Movement of the wrist joint
2.Extension of the fingers and thumb
3.Supination.
All muscles in the posterior compartment of the forearm are innervated by the radial nerve .
Superficial layer
Seven muscles
1.Brachioradialis
2.Extensor carpi radialis longus
3.Extensor carpi radialis brevis
4.Extensor digitorum
5.Extensor digiti minimi
6.Extensor carpi ulnaris
7.Anconeus
Brachioradialis
Action
Flexes forearm
Extensor carpi radialis longus and brevis
Action
Extends and abducts hand at wrist joint
Extensor digitorum
Action
Extends the medial four digits at metacarpo – phalangeal, IP joint and extends hand at wrist
Extensor digiti minimi
Action
Extends the 5 th digit at the metacarpalphalangeal and interphalangeal joints
Extensor carpi ulnaris
Action
Extends and adducts hand at the wrist
Anconeus
Action accessory extensor of the elbow joint
Deep layer
Five muscles
1-Supinator
2-Abductor pollicis longus
3-Extensor pollicis brevis
4-Extensor pollicis longus
5-Extensor indicis
Supinator
Action
Supinates forearm
Abductor pollicis longus
Action
Abducts thumb
Extensor pollicis longus and brevis
Action
1. Extensor Pollicis
Longus
Extends distal phalanx of thumb
2. Extensor Pollicis
Brevis
Extends proximal phalanx of thumb
Extensor indicis
Action
Extends index finger
ANATOMICAL SNUFFBOX
ANATOMICAL SNUFFBOX
• Boundries
Medially
◦
Extensor pollicis longus tendon
•
Laterally
◦
Abductor pollicis longus tendon
◦
Extensor pollicis brevis tendon
Clinical importance
◦
1- Scaphoid bone
◦
2- Radial pulsation
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Radial nerve
The nerve of the posterior compartment of the forearm is the radial nerve .
In the lateral wall of the cubital fossa, and before dividing into superficial and deep branches , the radial nerve innervates the brachioradialis and extensor carpi radialis longus muscles.
Posterior interosseous nerve supplies the remaining muscles in the posterior compartment.
Posterior interosseous nerve
Radial Nerve Injury in the Forearm
Injury to the deep branch of the radial nerve may occur when wounds of the forearm are deep (penetrating). Severance of the deep branch of the radial nerve results in an inability to extend the thumb and the metacarpophalangeal (MP) joints of the other digits.
Testing the radial nerve
Integrity of the deep radial nerve may be tested by asking the person to extend the MP joints while the examiner provides resistance
