Human Anatomy Vol 1

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UPPER LIMB

The medial branch supplies the medial side of the
little finger.
The lateral branch is a common palmar digital nerve.
It divides into two proper palmar digital nerves for the
adjoining sides of the ring and little fingers.
The common palmar digital nerve communicates
with the median nerve.

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1 Muscular branches:
a. At its origin, the deep branch supplies three
muscles of hypothenar eminence (Fig. 9.73b).
b. As the nerve crosses the palm, it supplies the
medial two lumbricals and eight interossei.
c. The deep branch terminates by supplying the
adductor pollicis, and occasionally the deep head
of the flexor pollicis brevis.
2 An articular branch supplies the wrist joint.

spared: This causes marked flexion of the
terminal phalanges (action of paradox).
b. Sensory loss is confined to the medial one-third
of thepalmand the medial one and ahalf fingers
including their nail beds (Figs 9.40a and b).
Medial half of dorsum of hand also shows
sensory loss.
c, Vasomotor changes: The skin areas with sensory
loss is warmer due to arteriolar dilatation; it is
also drier due to absence of sweating because
of loss of sympathetic supply.
d. Trophic changes: Long-standing cases of
paralysis lead to dry and scaly skin. The nails
crack easily with atrophy of the pulp of fingers.
e. The patient is unable to spread out the fingers
due to paralysis of the dorsal interossei. The
power of adduction of the thumb, and flexion
of the ring and little fingers are lost. It should
be noted that median nerve lesions are more
disabling. In contrast, ulnar nerve lesions leave
a relatively efficient hand.

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The ulnar nerve is also known as the 'musician's
nerve'because it controls fine movements of the
fingers (Fig.9.3a).
The ul::rar nerve is commonly injured at the elbow,
(Fig. 9.35) behind the medial epicondyle or distal
to elbow as it passes between two heads of flexor
carpi ulnaris (cubital tururel) or at the wrist in front
of the flexor retinaculum.
Ulnar nerae injury at the elbow: Flexor carpi ulnaris
and the medial half of the flexor digitorum
profundus are paralysed.
Due to this paralysis, the medial border of the
forearmbecomes flattened (Fig. 9.36). An attempt
to produce flexion at the wrist result in abduction
of the hand. The tendon of the flexor carpi ulnaris
does not tighten on making a fist. Flexion of the
terminal phalanges of the ring and little fingers is
lost (Figs 9.37 and9.38).
The ul:rar nerve controls fine movements of the
fingers through its extensive motor distribution
to the short muscles of the hand.
Ulnar neroe lesion at the wrist: Produces 'ulnar claw-
hand'.
Ulnar clazu-hand is characterised by the following
signs.
a. Hyperextension at the metacarpophalangeal
joints and flexion at the interphalangeal joints,
involving the ring and little fingers-more than
the index and middle fingers (Fig.9.39). The
Iittle finger is held in extension by extensor
muscles. The intermetacarpal spaces are
hollowed out due to wasting of the interosseous
muscles. Claw-hand deformity is more obvious
in wrist lesions as the profundus muscle is

Behind medial
epicondyle
Cubiial tunnel

At wrist

Fig. 9.35: Sites of ulnar nerve injury

MEDIAN NERVE
The median nerve is important because of its role in
controlling the movements of the thumb which are
crucial in the mechanism of gripping by the hand.

Course
Median nerve lies deep to flexor retinaculum in the
carpal tunnel and enters the palm (Fig. 9.15). Soon it
terminates by dividing into muscular and cutaneous
branches.

Relolions
1 The median nerve enters the palm by passing deep
to the flexor retinaculum where it lies in the narrow
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