Download Muscles of the posterior forearm

DEEP MUSCLES
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.
SUPINATOR



The supinator, along with the brachialis
muscle, forms the floor of the cubital
fossa. The deep branch of the radial nerve
lies between the two heads.
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, just proximal to the
attachment of the pronator teres muscle.

Actions: Supinates the forearm

Innervation: Radial Nerve
ABDUCTOR POLLICIS LONGUS
This muscle lies just distal to
the supinator, on the lateral
side of the forearm.
Attachments: Originates from
the interosseous membrane
and the adjacent posterior
surfaces of the radius and
ulna.
Attaches to the lateral side of
the base of metacarpal I,
contributing to the lateral
border of the anatomical
snuffbox
Actions: Abducts the thumb
Innervation: Radial Nerve

EXTENSOR POLLICIS BREVIS
The extensor pollicis brevis
can be found medial and
deep to the abductor
pollicis longus.
Attachments: Originates from
the posterior surface of the
radius and interosseous
membrane.
Attaches to the base of the
proximal phalanx of the
thumb.
Makes up most of the lateral
border of the anatomical
snuffbox
Actions: Extends the MCP and
carpometacparal joints of
the thumb
Innervation: Radial nerve
EXTENSOR POLLICIS LONGUS
The tendon of the extensor
pollicis longus travels
medial to the dorsal
tubercle at the wrist (the
extensor pollicis brevis and
abductor pollicis longus
travel laterally). This allows
the muscle to use the
tubercle as a trochlea,
increasing its force.
Attachments: Originates from
the posterior surface of the
ulna and interosseous
membrane.
Attaches to the distal phalanx
of the thumb
Actions: Extends all joints of
the thumb
Innervation: Radial Nerve
The tendon of the
extensor pollicis longus
lies in a groove on the
medial aspect of the
dorsal tubercle of the
radius.
Inferior to this, digital
twigs of the superficial
branch of the radial
nerve can be felt
crossing the tendon.
When the thumb is
extended, a hollow
known as the anatomical
snuff-box appears
between the tendon of
the extensor pollicis
longus medially and
those of the extensor
pollicis brevis and
abductor pollicis longus
laterally.
Its floor is formed by the
scaphoid and trapezium
bones and is crossed by
the radial artery.
The hollow is limited
superiorly by the styloid
process of the radius.
EXTENSOR INDICIS


This muscles allows the
index finger to be
independant 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 hood of the
index finger

Actions: Extends the index
finger

Innervation: Radial Nerve
RADIAL NERVE
in the forearm, it
branches into a
superficial branch
(primarily sensory)
and a deep branch
(primarily motor).



The superficial branch of the
radial nerve descends in the
forearm under the
brachioradialis.
It crosses brachioradialis to
enter posterior of forearm
near the back of the wrist
and supply dorsum of hand.
It gives nerve supply to
dorsal aspect of thumb
,index finger,and radial side
of middle finger except the
nail beds,which are supplied
by proper digital branches of
median nerve.
The deep branch of the radial nerve
has a muscular and articular
distribution.
It winds laterally between the
superficial and deep layers of the
supinator and often makes direct
contact with the radius, being
vulnerable in fractures.
At the lower border of the
supinator, it meets the
posterior interosseous
vessels.
For the rest of its course, the
deep branch of the radial
nerve is then termed the
posterior interosseous
nerve, a name that is
sometimes applied to the
entire course of the deep
branch.
The posterior interosseous
nerve reaches the
interosseous membrane
distally and ends in an
enlargement from which
twigs are distributed to
adjacent joints
The superficial
branch of the
radial nerve
provides sensory
innervation to
much of the back
of the hand,
including the web
of skin between
the thumb and
index finger.
The radial nerve (and
its deep branch)
provides motor
innervation to the
muscles in the
posterior
compartment of
the arm and
forearm, which are
mostly extensors.
The superficial branch is the continuation of the
radial nerve, and its distribution is cutaneous and
articular.

It accompanies the radial artery, lying lateral to it,
and then winds dorsally deep to the brachioradialis,
to become subcutaneous and supply the lateral
part of the dorsum of the hand.
Its terminal branches usually supply two and a half
fingers but generally reach no further than the
proximal phalanges of the index and middle fingers.
(The dorsal innervation here is completed by digital
branches of the median nerve.)
Several cutaneous branches of the radial nerve can
be felt by stroking a fingernail down the taut tendon
of the extensor pollicis longus
The radial nerve
innervates the
muscles that
extend at the wrist,
and these are
paralysed. The
flexor muscles are
innervated by the
median nerve, and
are unaffected. The
wrist undergoes
unopposed flexion,
and wristdrop
results
ARTERIES OF POST.FASCIAL
COMPARTMENT
POST INTEROSSEOUS A.
It passes backward
above the upper
margin of the
interosseous
membrane between
the radius and the
ulna.
It then pass down ward
between the
supinator and
abductor pollicis
longus and reach the
interval betweenn the
superficial and deep
group of muscles .
Branches:
1-muscular branches
2-recurrent branch takes
part in the
anastomosis around
the elbow.
It ends by anastomosis
with the ANTERIOR
INTEROSSEIOUS
arteryand taking part
in the anastomosis
around the wrist joint.
ANT. INTEROSSEOUS A.
It descend in the front of interosseous
membrane and pierces it in the lower
third of the membrane to reach the
post.compartment