Human Anatomy - Kotsan I. Y. 2009

Muscles and fascia of the upper limb
Muscles of the hand
Middle group of hand muscles

The Middle Group of hand Muscles comprises the lumbrical muscles, palmar interossei, and dorsal interossei.

The lumbrical muscles (mm. lumbricales) are four slender, cylindrical structures located beneath the palmar aponeurosis. These muscles extend to all digits except the thumb. They originate from the tendons of the flexor digitorum profundus and insert into the dorsal surface of the bases of the proximal Phalanges of digits 2 through 5, blending into the dorsal digital expansion of the extensor digitorum Muscle. Function: they flex the proximal phalanges and straighten the middle and distal phalanges of the 2nd to 5th digits.

Innervation: the First and Second lumbricals are supplied by the median nerve (C_V-T_hI), while the third and fourth are supplied by the ulnar nerve (C_V-T_hI).

The palmar interossei (mm. interossei palmares), three in number, occupy the interosseous spaces between the 2nd and 5th Metacarpal bones (Fig. 124, 1). Origins: the first arises from the ulnar aspect of the 2nd metacarpal bone; the second and third arise from the radial aspect of the 4th and 5th metacarpal bones, respectively. They insert into the dorsal surface of the proximal phalanges of the 2nd, 4th, and 5th digits. Function: they flex the proximal phalanges and extend the middle and distal phalanges of the 2nd–5th digits, and adduct the 2nd, 4th, and 5th digits toward the 3rd digit.

Innervation: ulnar nerve (C_VII—T_hI).

Class="center">

Fig. 124. Interosseous Muscles of the right hand

1 — palmar interossei, 2 — dorsal interossei

The dorsal interossei (mm. interossei dorsales) are four bipennate muscles that are significantly thicker than the palmar interossei and fill all four spaces between the metacarpal bones (Fig. 124, 2). Each muscle originates by two heads from the facing surfaces of two adjacent metacarpal bones. They insert into the dorsal aponeuroses of digits 2 through 4. The first muscle attaches to the radial side of the proximal phalanx of the 2nd (index) finger; the second muscle attaches to the radial side of the proximal phalanx of the 3rd (middle) finger; the third muscle attaches to the ulnar side of the proximal phalanx of the same 3rd finger; and the fourth muscle attaches to the ulnar side of the proximal phalanx of the 4th finger. Function: they flex the proximal phalanges, extend the middle and distal phalanges, and abduct the fingers away from the middle finger.

Innervation: ulnar nerve (C_VII—T_hI).