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AAAC39 21/5/05 10:48 AM Page 89
The palm of the hand (Fig. 39.1)
adduction is the bringing together of all fingers towards the middle
• Skin: the skin of the palm is bound to underlying fascia by fibrous
finger, abduction is moving them away from the middle finger. The
bands.
dorsal interossei each arise from two metacarpals and insert into the
• Deep fascia: the palmar aponeurosis is a triangular layer which is of the fingers. These movements occur around the middle finger hence
attached to the distal border of the flexor retinaculum. Distally the proximal phalanges so as to provide adduction (P.AD). The dorsal
aponeurosis splits into four slips at the bases of the fingers which blend interossei arise from only one metacarpal and are inserted into the prox-
with the fibrous flexor sheaths (see below). The aponeurosis provides imal phalanges so as to provide abduction (D.AB). Note that the middle
firm attachment of the overlying skin with protection of the underlying finger cannot be adducted (and hence has no palmar interosseous) but
structures. can be abducted in either direction so it has two dorsal interosseous
• Fibrous flexor sheaths: these are fibrous tunnels in which the flexor insertions.
tendons and their synovial sheaths lie. They arise from the metacarpal
heads and pass to the bases of the distal phalanges on the anterior aspect The dorsum of the hand
of the digits. They insert into the sides of the phalanges. These sheaths • Skin: unlike the palm of the hand the skin is thin and freely mobile
are lax over the joints and thick over the phalanges and hence do not over the underlying tendons.
restrict flexion. • Long extensor tendons: the four tendons of extensor digitorum
• Synovial flexor sheaths: these are sheaths that limit friction between (ED) pass under the extensor retinaculum. On the dorsum of the hand
the flexor tendons and the carpal tunnel and fibrous flexor sheaths. the ED tendon to the index finger is accompanied by the tendon of ex-
• Long flexor tendons: the tendons of flexor digitorum superficialis tensor indicis. The ED tendon to the little finger is accompanied by the
(FDS) divide into two halves at the level of the proximal phalanx and double tendon of extensor digiti minimi. The ED tendons of the little,
pass around flexor digitorum profundus (FDP) where they reunite. At ring and middle fingers are connected to each other by fibrous slips. On
this point they then split again to insert into the sides of the middle pha- the posterior surface of each finger the extensor tendon spreads to form
lanx. FDP continues along its path to insert into the distal phalanx. a dorsal digital expansion. This expansion is triangular shaped and at its
Flexor pollicis longus (FPL) passes through the carpal tunnel in its own apex splits into three parts: a middle slip which is attached to the base of
synovial sheath and inserts into the distal phalanx. The tendons of the middle phalanx; and two lateral slips which converge to attach to
flexor carpi radialis, palmaris longus and flexor carpi ulnaris pass the base of the distal phalanx. The base of the expansion receives the
through the forearm and also insert in the proximal hand (see Muscle appropriate interossei and lumbricals. The tendons of abductor pollicis
index, p. 162). longus, extensor pollicis brevis and longus form the boundaries of the
anatomical snuffbox and proceed to insert into the thumb.
Muscles of the hand (Fig. 39.1)
• The thenar muscles: these are the short muscles of the thumb. They Neurovascular structures of the hand (Fig. 39.3)
include: abductor pollicis brevis, flexor pollicis brevis, opponens pol- See chapters on upper limb: arteries, nerves, veins and lymphatics.
licis and adductor pollicis.
• The hypothenar muscles: these are the short muscles of the little Movements of the fingers and thumb
finger. They include abductor digiti minimi, flexor digiti minimi and The hand is required to perform a versatile range of movement extend-
opponens digiti minimi. ing from a firm grasp, such as that needed to carry heavy bags, to preci-
• Lumbricals: these four muscles arise from the tendons of flexor digi- sion gripping such as that required to hold a pencil. For precision grips
torum profundus. They insert into the radial side of each of the prox- the thumb is used to oppose the index finger in which the interpha-
imal phalanges and into the dorsal extensor expansions. The lumbricals langeal joint is extended and the metacarpophalangeal joint is flexed.
serve to flex the metacarpophalangeal joints without flexing the inter- The thumb opposition is carried out mainly by opponens pollicis whilst
phalangeal joints. the lumbricals and interossei are responsible for maintaining flexion at
• The interosseous muscles (Fig. 39.2): these comprise eight muscles the metacarpophalangeal joints and extension at the interphalangeal
which arise from the shafts of the metacarpals. They are responsible for joints. Since the thumb is at right angles to the plane of the fingers,
flexion at the metacarpophalangeal joints and extension of the interpha- abduction of the thumb is a movement away from the plane of the palm.
langeal joints. They also perform abduction and adduction movements This is used in testing the integrity of the median nerve (abductor pollicis).

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