Download Forearm

DEPARTMENT OF ANATOMY
UPPER LIMB
FOREARM
Dr. SREEKANTH
THOTA
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
Flexor
Carpi
Radialis
Flexes and abducts hand
(at the wrist)
Palmarus
Longus
Flexes hand at the wrist and
tightens palmar aponeurosis
Flexor
Carpi
Ulnaris
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
Pronator Quadratus
Flexes 1st digit (thumb)
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

Posterior
view
Brachoradialis






The brachioradialis is a paradoxical muscle. Its origin and
innervation are characteristic of a extensor muscle, but it is
actually a flexor at the elbow.
The muscle is most visible when the forearm is half pronated,
and flexing at the elbow against resistance.
In the distal forearm, the radial artery and nerve are
sandwiched between the brachioradialis and the deep flexor
muscles.
Attachments: Originates from the proximal aspect of the
lateral supraepicondylar ridge of humerus, and attaches to the
distal end of the radius, just before the radial styloid process.
Actions: Flexes Forearm(weak)
Innervation: Radial nerve.
Brachioradialis
Extensor Carpi Radialis Longus and Brevis
The extensor carpi radialis muscles are situated
on the lateral aspect of the posterior forearm.
Due to their position, they are able to produce
abduction as well as extension at the wrist.
 Attachments: The ECRL originates from the
supracondylar ridge, while the ECRB originates
from the lateral epicondyle. Their tendons
attach to metacarpal bones II and III.
 Actions: Extends and abducts the wrist.
 Innervation: Radial nerve.

Extensor carpi radialis longus and
brevis
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.
 Attachments: Originates from the lateral
epicondyle. The tendon continues into in the
distal part of the forearm, where it splits into
four, and inserts into the extensor expansion of
each finger.
 Actions: Extends medial four fingers at the
MCP and IP joints.
 Innervation: Radial nerve.

Extensor digitorum
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.
 Attachments: Originates from the lateral epicondyle
of the humerus. It attaches, with the extensor digitorum
tendon, into the extensor expansion of the little finger.
 Actions: Extends the little finger, and contributes to
extension at the wrist.
 Innervation: Radial nerve.

Extensor digiti minimi
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.
 Attachments: Originates from the lateral
epicondyle of the humerus, and attaches to the
base of metacarpal V.
 Actions: Extension and adduction of wrist.
 Innervation: Radial nerve.

Tennis elbow(Lateral
epicondylitis)


It occurs at
the common
extensor
tendon that
originates from
the lateral
epicondyle.
The acute pain that
a person might feel
occurs as one fully
extends the arm.
Deep layer






Five muscles
1-Supinator
2-Abductor pollicis longus
3-Extensor pollicis brevis
4-Extensor pollicis longus
5-Extensor indicis
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.
 Attachments: It has two heads of origin. One
originates from the lateral epicondyle of the
humerus, the other from the posterior surface
of the ulna. They insert together into the
posterior surface of the radius.
 Actions: Supinates the forearm.
 Innervation: Radial nerve.

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.
 Attachments: Originates from the
interosseous membrane and the adjacent
posterior surfaces of the radius and ulna. It
attaches to the base of 1st metacarpal .
 Actions: Abducts the thumb.
 Innervation: Radial nerve.

Extensor Pollicis Longus & Brevis






The tendon of the Extensor pollicis longus forms the medial
border of the anatomical snuffbox in the hand.
Attachments: Originates from the posterior surface of the
ulna and interosseous membrane. It attaches to the base of
the distal phalanx of the thumb.
Actions: Extends distal phalanx of thumb at IP joint
The Extensor pollicis brevis contributes to the lateral border
of the anatomical snuffbox.
Attachments: Originates from the posterior surface of the
radius and interosseous membrane. It attaches to the base of
the proximal phalanx of the thumb.
Actions: Extends proximal phalanx of thumb at MCP
joint
Innervation for both: Radial nerve.
Extensor Indicis
This muscle allows the index finger to be
independent of the other fingers during
extension.
 Attachments: Originates from the posterior
surface of the ulna and interosseous membrane,
distal to the extensor pollicis longus. Attaches
to the extensor expansion of the index finger.
 Actions: Extends the index finger &helps
extend hand at wrist.
 Innervation: Radial nerve.

Extensor indicis
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
49
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