Human Anatomy Vol 1

Tables 9.3 and 9.4. Following are some other points of
importance about these muscles.

Additionol Points oboutlhe Flexor Digitorum Profundus

1 It is the most powerful, and most bulky muscle of
the forearm. It forms the muscular elevation seen and
felt on the posterior surface of the forearm medial to
the subcutaneous posterior border of the ulna
(Fig. e.a).
2 The main gripping power of the hand is provided
by the flexor digitorum profundus.
3 The muscle is supplied by two different nerves. So it
is a hybrid muscle.

Additionol Poinls oboul lhe FIexor Pollicis longus

1 The anterior interosseous nerve and vessels descend
on the anterior surface of the interosseous membrane
between the flexor digitorum profundus and the
flexor pollicis longus (Fig. 9.5).
2 The tendon passes deep to the flexor retinaculum
between the opponens pollicis and the oblique head
of the adductor pollicis, to enter the fibrous flexor
sheath of the thumb. It lies in radial bursa (Fig. 9.6).

FOREARM AND HAND

Synoviol Sheoths of Flexor Tendons

'1, Common

flexor synoaial sheath (ulnar bursa): The long

flexor tendons of the fingers (flexor digitorum

superficialis and profundus), are enclosed in a

corunon synovial sheath while passing deep to the

flexor retinaculum (carpal tunnel). The sheath has a

parietal layer lining the walls of the carpal tunnel,

and a visceral layer closely applied to the tendons

(Fi9.9.7). From the arrangement of the sheath it

appears that the synovial sac has been invaginated by

the tendons from its lateral side. The synovial sheath

extends upwards for 5.0 or 7.5 cm into the forearm

and downwards into the palm up to the middle of

the shafts of the metacarpal bones. It is important to

note that the lower medial end is continuous with

the digital synovial sheath of the little finger.

2 Synouial sheath of the tendon of flexor pollicis longus

(radial bursa): This sheath is separate. Superiorly,

it is coextensive with the common sheath and

inferiorly it extends up to the distal phalarx of the

thumb (Fig.9.6).

3. Digital synozsial sheaths: Tiire sheaths enclose the flexor
   tendons in the fingers and line the fibrous flexor

Table 9.3: Attachments of the deep muscles

2

Muscle

1. FIexor digitorum
   profundus
   (composite or
   hybrid muscle)
   (Figs 9.5 and 9.7)

Flexor pollicis

longus

Pronator

quadratus

Muscle

1. Flexor digitorum
   profundus
   (Figs 9.6 and 9.7)

Upper three{ourths of the anterior surface. The tendon enters the palm by passing deep to the

of the shaft of radius (see Fig. 2.25) flexor retinaculum

Adjoining part of the anterior surface of. lt is inserted into the palmar surface of the distal phalanx

the interosseous membrane of the thumb

Origin from

. Upper three{ourths of the anterior and
medial surface of the shaft of ulna
. Upper three-fourths of the posterior
border of ulna
. Medial surface of the olecranon and
coronoid processes of ulna (see Fig. 2.25)
. Adjoining part of the anterior surface of
the interosseous membrane

Oblique ridge on the lower one{ourth of

anterior surface of the shaft of ulna, and

the area medial to it (see Fi1.2.25\

Nerve supply

. Medial half by ulnar nerve
. Lateral half by anterior
interosseous nerve (C8, T1)
(branch of median nerve)

Anterior interosseous nerve

Anterior interosseous nerve

lnsertion

. The muscle forms 4 tendons for the medial 4 digits
which enter the palm by passing deep to the flexor
retinaculum in ulnar bursa and digital synovial sheaths
. Opposite the proximal phalanx of the corresponding
digit the tendon perforates the tendon of the flexor
digitorum superficialis (Fig. 9.8)
. Each tendon is inserted on the palmar surface of the
base of the distal phalanx

Superficial fibres into the lower one{ourth of the anterior

surface and the anterior border of the radius

Deep fibres into the triangular area above the ulnar notch

Flexor pollicis

longus (Fig. 9.8)

Pronator quadratus

Table 9.4: Nerve supply and actions of the deep muscles

Actions

. Flexor of distal phalanges after the flexor digitorum superficialis
has flexed the middle phalanges
. Secondarily it flexes the other joints of the digits, fingers,

a

and the wrist

It is the chief gripping muscle. lt acts best when the wrist

is extended

Flexes the distal phalanx of the thumb. Continued action

may also flex the proximal joints crossed by the tendon

Supedicial fibres pronate the forearm

Deep fibres bind the lower ends of radius and ulna

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