Nerves of the Upper Limb
Advertisements help pay for this website. Thank you for
your support.
The
brachial plexus | Main Anatomy
Index | Arteries of the upper limb
Last updated 30 March 2006
Nerves of the Upper Limb
The
Axillary Nerve
- This nerve passes to the posterior aspect of the arm
through the quadrangular space
in the company of the posterior
circumflex vessels.
- On emerging from the quadrangular space, the axillary
nerve winds around the surgical neck of the humerus to supply the teres minor
and deltoid muscles.
- The axillary nerve ends as the upper
lateral brachial cutaneous nerve.
- It supplies skin over the inferior half of the deltoid
and adjacent areas of the arm.
The
Main Nerves of the Forearm
The
Median Nerve
- Then is continues between the two
flexor digitorum muscles.
Branches
of the Median Nerve
- There are no branches in
the arm.
- Articular branches pass
to the elbow joint as the median nerve passes it.
The
Anterior Interosseous Nerve
The Palmar Cutaneous Branch
- It passes superficial to the flexor retinaculum to supply
skin of the lateral part of the
palm.
Median
Nerve Injury
- Note: occasionally, there are communications between the
median and ulnar nerves in the forearm. Usually, there
are several slender nerves.
- These are clinically important, as even with complete
lesion of the median nerve, some muscles may not be
paralysed.
- This may lead to the erroneous conclusion that the median
nerve has not been damaged.
When Severed at the Elbow Joint
Severed
Proximal to the Flexor Retinaculum (Wrist Slashing)
The
Ulnar Nerve
- In the distal part of the forearm, the ulnar nerve become
relatively superficial covered only by fascia and skin.
- It pieces the deep fascia
and passes superficial to the
flexor retinaculum with the ulnar artery, lateral to the pisiform,
between this bone and the hook of
the hamate.
- This passage for the nerve and artery, covered with a
slip of flexor retinaculum, is referred to clinically as
the canal of Guyon.
Branches
of the Ulnar Nerve
- There are no branches in
the arm.
- Articular branches pass
to the elbow joint,
where the nerve is in the groove between the olecranon of
the ulna and medial
epicondyle of the humerus.
The Palmar Cutaneous Branch
- This arises from the ulnar nerve near
the middle of the forearm.
- It pierces the deep fascia
in its distal 1/3 to supply the skin
on the medial part of the palm.
The Dorsal Cutaneous Branch
- It arises from the ulnar nerve from
the distal half of the forearm.
- It passes posteroinferiorly between the ulna and flexor
carpi ulnaris muscle.
- It supplies the posterior surface
of the medial part of the hand.
The Superficial Branch of the Ulnar Nerve
- This branch supplies the cutaneous
fibres to the anterior
surfaces of the medial
one and a half digits.
The
Deep Branch of the Ulnar Nerve
- The deep branch of the ulnar nerve also supplies several
joints (wrist,
intercarpal, carpometacarpal
and intermetacarpal joints).
- The ulnar nerve is referred to as the nerve
of fine movements.
Ulnar
Nerve Injury
- This commonly occurs where the nerve
passes posterior to the medial
epicondyle of the humerus.
- Often the damage occurs when the elbow hits a hard
surface and the medial epicondyle if fractured.
- There tends to be extensive motor
and sensory loss to the hand.
- Adduction is impaired,
and when an attempt is made to flex the wrist joint, the hand
is drawn to the radial side by the flexor
carpi radialis muscle.
- There is difficulty making a fist
as the distal
interphalangeal joints cannot
be flexed.
- When an effort is made to straighten the fingers, the
hand goes into the position known as "claw hand".
The
Radial Nerve
The Superficial Branch
- In the distal 1/3 of the forearm, the superficial
branch passes posteriorly, deep to the tendon
of the brachioradialis
muscle, and enters the posterior
fascial compartment of the forearm.
- It pierces the deep fascia 3 to 4
cm proximal to the wrist and supplies skin on
the dorsum of the wrist,
hand, thumb,
and the lateral 1 (or 2) and a half
digits.
The
Deep Branch
- This is the larger of the two terminal branches and is entirely muscular and articular
in its distribution.
- On reaching the posterior aspect of the forearm, the deep
branch of the radial nerve gives many branches to the extensor
muscles.
- One of these branches, the posterior
interosseous nerve, accompanies the posterior interosseous artery
and supplies the deep extensor
muscles.
Radial
Nerve Injury
- This may occur in deep wounds of the forearm.
- Severance of the radial nerve results in the inability to extend the thumb
and the metacarpophalangeal
joints of the other digits.
- There is no loss of sensation because the deep branch of
the radial nerve is entirely muscular and articular in
distribution.