362
UNIT 2
Covering, Support, and Movement of the Body
10
MUSCLE
DESCRIPTION
ORIGIN (O) AND
INSERTION (I)
ACTION
NERVE
SUPPLY
MIDPALMAR MUSCLES
Lumbricals
(lum
9
brı˘-klz)
(
lumbric
5
earthworm)
Four worm-shaped muscles
in palm, one to each finger
(except thumb); unusual
because they originate
from the tendons of
another muscle
O—lateral side of
each tendon of flexor
digitorum profundus in
palm
I—lateral edge of
extensor expansion on
proximal phalanx of
fingers 2–5
Flex fingers at
metacarpophalangeal
joints but extend fingers
at interphalangeal joints
Median nerve (lateral
two) and ulnar nerve
(medial two)
Palmar interossei
(in
0
ter-os
9
e-i)
(
interossei
5
between bones)
Four long, cone-shaped
muscles in the spaces
between the metacarpals;
lie ventral to the dorsal
interossei
O—the side of each
metacarpal that faces
the midaxis of the hand
(metacarpal III) but ab-
sent from metacarpal III
I—extensor expansion
on first phalanx of each
finger (except finger 3),
on side facing midaxis
of hand
Adduct fingers
: pull
fingers in toward third
digit; act with lumbricals
to extend fingers at
interphalangeal joints
and flex them at
metacarpophalangeal
joints
Ulnar nerve
Dorsal interossei
Four bipennate muscles
filling spaces between the
metacarpals; deepest palm
muscles, also visible on
dorsal side of hand
(Figure 10.17b)
O—sides of metacarpals
I—extensor expansion
over proximal phalanx
of fingers 2–4 on side
opposite midaxis of hand
(finger 3), but on
both
sides of finger 3
Abduct (diverge)
fingers
; extend fingers
at interphalangeal
joints and flex them at
metacarpophalangeal
joints
Ulnar nerve
MUSCLE GALLERY
Table 10.13
Intrinsic Muscles of the Hand: Fine Movements of the Fingers
(Figure 10.19)
(continued)
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