The document summarizes the important structures of the hand, including bones, joints, ligaments, tendons, muscles, nerves, blood vessels. It describes the muscles in the hand in detail, dividing them into intrinsic muscles (thenar, hypothenar, interossei, lumbricals) and extrinsic muscles that originate in the forearm. For each group of muscles, it provides information on origin, insertion, innervation and function. It also describes structures like the palmar aponeurosis, extensor hoods and tendons.

1. The HandDr M Idris Siddiqui
PART 2
IMPORTANT STRUCTURES

2. IMPORTANT STRUCTURES
• The important structures of the hand can be
divided into several categories. These include
• Bones and joints
• Ligaments and tendons
• Muscles
• Nerves
• Blood vessels
• The front, or palm-side, of the hand is referred to as
the palmar side. The back of the hand is called
the dorsal side.

3. Palm of the hand
• The skin of the palm is characterized by flexure
reases the li es of the pal a d papillar ridges,
which occupy the whole of the flexor surface, those
on the digits being responsible for fingerprints.
• The ridges serve to improve the grip and they
increase the surface area.
• Sweat glands abound, but there are no sebaceous
glands.
• The little palmaris brevis muscle is attached to the
dermis. It lies across the base of the hypothenar
eminence.

4. Dorsum of the hand
• The skin of the dorsum is thin, lax and
can be picked up from the underlying
deep fascia and tendons and moved
freely over them.
• There is usually little subcutaneous
fat here.
–It provides potential space for oedema.

5. The Palmar Aponeurosis
• The palmar aponeurosis is strong fibrous sheath, triangular and
occupies the central area of the palm.
• The apex is attached to the distal border of the flexor
retinaculum and receives the insertion of the palmaris longus
tendon.
• The base divides at the bases of the fingers into four slips.
– Each slip divides into two bands(components):
– One superficial, the other deep.
– The superficial one passes to the skin. The deep component divides into
two, which diverge around the flexor tendons and finally fuse with the
fibrous flexor sheath and the deep transverse ligaments.
• The medial and lateral borders of the palmar aponeurosis are
continuous with the thinner deep fascia covering the hypothenar
and thenar muscles. From each of these borders, fibrous septa
pass posteriorly into the palm and take part in the formation of
the palmar fascial spaces.
– The palmar aponeurosis has longitudinal & transverse fibres.

6. The palmar aponeurosis

8. Dupuytren's contracture
• The function of the palmar aponeurosis is to give
firm attachment to the overlying skin and so
improve the grip and to protect the underlying
tendons.
• Dupuytren's contracture is a localized thickening
and contracture of the palmar aponeurosis.
– It commonly starts near the root of the ring finger and
draws that finger into the palm, flexing it at the
metacarpophalangeal joint.
– Later, the condition involves the little finger in the same
manner.

9. Muscles of hand
• Muscles acting on the hand can be divided into two
groups:
• The extrinsic muscles : located in
the anterior and posterior compartments of the
forearm.
– They control crude movements and produce a forceful
grip po er grip .
• The intrinsic muscles: located within the hand itself.
– They are responsible for the fine motor functions of the
hand.i.e. the execution of precise movement with the
fi gers a d thu pre isio grip .

11. The intrinsic muscles
• They consist of:
–Palmar brevis,
–Adductor pollicis,
–Thenar muscles,
–Hypothenar muscles,
–Interossei ,
–Lumbrical muscles.
• The intrinsic muscles of the hand are innervated by the deep
branch of the ulnar nerve, except for the two lumbrical and
three thenar muscles that are innervated by the median nerve.

12. The extrinsic muscles
• The extrinsic muscles are long
flexor and extensor muscles of
the hand.
• These are muscles that originate
in the forearm and attach in the
hand.

15. The thenar muscles
• The thenar muscles are three short muscles
located at the base of the thumb. The muscle
bellies produce a bulge, known as the thenar
eminence.
• Opponens pollicis
• Abductor pollicis brevis
• Flexor pollicis brevis
• They are responsible for the fine movements
of the thumb.
–The median nerve innervates all the thenar
muscles.

16. Thenar Muscles
• Opponens Pollicis
• The opponens pollicis is the largest of the thenar
muscles, and lies underneath the other two.
• Abductor Pollicis Brevis
• This muscle is found anteriorly to the opponens
pollicis and proximal to the flexor pollicis brevis.
• Flexor Pollicis Brevis
• The most distal of the thenar muscles.
–Innervated by Median nerve. Sometime also
innervated by the deep branch of
the ulnar nerve.

18. Thenar muscles
Muscles Origin Insertion Innervation Function
Opponens
pollicis
Tubercle of
trapezium and
flexor
retinaculum
Lateral margin
and adjacent
palmar surface
of metacarpal I
Recurrent
branch of
median nerve
[C8,T1]
Medially rotates
thumb
Abductor
pollicis brevis
Tubercles of
scaphoid and
trapezium and
adjacent flexor
Proximal
phalanx and
extensor hood
of thumb
Recurrent
branch of
median nerve
[C8,T1]
Abducts thumb
at
metacarpophala
ngeal joint
Flexor pollicis
brevis
Tubercle of the
trapezium and
flexor
retinaculum
Proximal
phalanx of the
thumb
Recurrent
branch of
median nerve
[C8,T1]
flexes the
metacarpophala
ngeal joint of
the thumb

20. Hypothenar Muscles
• The hypothenar muscles produce the hypothenar
eminence – a muscular protrusion on the medial side
of the palm, at the base of the little finger. These
muscles are similar to the thenar muscles in both name
and organisation.
– The ulnar nerve innervates the muscles of the hypothenar
eminence.
• Opponens Digiti Minimi
– The opponens digit minimi lies deep to the other hypothenar
muscles.
• Abductor Digiti Minimi
– The most superficial of the hypothenar muscles.
• Flexor Digiti Minimi Brevis
– This muscles lies laterally to the abductor digiti minimi.

21. Hypothenar muscles
Muscles Origin Insertion Innervation Function
Opponens digiti
minimi
Hook of hamate
and flexor
retinaculum
Medial aspect of
metacarpal V
Deep branch of
ulnar nerve
[C8,T1]
Laterally rotates
metacarpal V
Abductor digiti
minimi
Pisiform, the
pisohamate
ligament, and
tendon of flexor
carpi ulnaris
Proximal
phalanx of little
finger
Deep branch of
ulnar nerve
[C8,T1]
Abducts little
finger at
metacarpophala
ngeal joint
Flexor digiti
minimi brevis
Hook of the
hamate and
flexor
retinaculum
Proximal
phalanx of little
finger
Deep branch of
ulnar nerve
[C8,T1]
Flexes little
finger at
metacarpophala
ngeal joint

23. Interossei
• The interossei muscles are located between the
metacarpals.
– In addition to their actions of abduction (dorsal interossei) and adduction
(palmar interossei) of the fingers, the interossei also assist the lumbricals in
flexion and MCP joints and extension at the IP joints.
• Dorsal Interossei
– The most superficial of all dorsal muscles, these can be palpated
on the dorsum of the hand. There are four dorsal interossei
muscles.
• Palmar Interossei
– These are located anteriorly on the hand. There are three palmar
interossei muscles – although some texts report a fourth muscle
at the base of the proximal phalanx of the thumb.

24. Interossei
DAB
PAD

25. Interossei
Muscles Origin Insertion Innervation Function
Dorsal interossei
(four muscles)
Adjacent sides of
metacarpals
Extensor hood
and base of
proximal
phalanges of
index, middle, and
ring fingers
Deep branch of
ulnar nerve
[C8,T1]
Abduction of
index, middle, and
ring fingers at the
metacarpophalan
geal joints
Palmar interossei
(four muscles)
Sides of
metacarpals
Extensor hoods of
the thumb, index,
ring, and little
fingers and the
proximal phalanx
of thumb
Deep branch of
ulnar nerve
[C8,T1]
Adduction of the
thumb, index,
ring, and little
fingers at the
metacarpophalan
geal joints
DAB
PAD

27. Palmar
interossei

28. Dorsal
interossei

29. Lumbricals
• These are four lumbricals in the hand,
each associated with a finger. They are
very crucial to finger movement, linking
the extensor tendons to the flexor
tendons.
• Denerveration of these muscles is the
basis for the ulnar claw and hand of
benediction.

31. Lumbricals

32. Lumbricals
Muscles Origin Insertion Innervation Function
Lumbricals (four
muscles)
Tendons of
flexor digitorum
profundus
Extensor hoods
of index, ring,
middle, and
little fingers
Medial two by
the deep branch
of the ulnar
nerve; lateral
two by digital
branches of the
median nerve
Flex
metacarpophala
ngeal joints
while extending
interphalangeal
joints

36. Other Muscles in the Palm
• There are two other muscles in the palm that are not
lumbricals or interossei and do not fit in the hypothenar or
thenar compartments:
• Palmaris Brevis
• This is a small, thin muscle, found very superficially in the
subcutaneous tissue of the hypothenar eminence.
• Adductor Pollicis
• This is large triangular muscle with two heads. The radial
artery passes anteriorly through the space between the
two heads, forming the deep palmar arch.

38. Muscles Origin Insertion Innervation Function
Palmaris brevis Palmar aponeurosis and
flexor retinaculum
Dermis of skin on the
medial margin of the
hand
Superficial branch of
the ulnar nerve [C8,T1]
Improves grip
Adductor pollicis Transverse head-
metacarpal III; oblique
head-capitate and bases
of metacarpals II and III
Base of proximal
phalanx and extensor
hood of thumb
Deep branch of ulnar
nerve [C8,T1]
Adducts thumb
Other Muscles in the Palm

40. Long tendons of the thumb
• On the flexor aspect there is only one tendon, that of flexor
Pollicis longus invested by its synovial sheath as it passes to
the distal phalanx.
• On the extensor surface the tendons of extensor pollicis
brevis and longus are each inserted separately into the
proximal and distal phalanx respectively.
• Extensor hood in thumb is controversial among
anatomists.
• These expansions serve to hold the long extensor tendon
in place on the dorsum of the thumb.

43. The tendons of the extensor digiti minimi(in little finger),
extensor indicis(in index finger) muscles join these hoods.

45. The corners of the hoods attach mainly to the deep transverse metacarpal ligaments

47. Extensor hoods
or 'dorsal digital expansions
or'Dorsal digital e te sor apparatus
• Parts:
• each expansion divides into
–A median slip, which passes to the base of
the middle phalanx,
–Two lateral slips(formed by the tendons of
interossei & lumbricals converge over
middle phalynx and unite) to insert on the
base of the distal phalanx .

49. 'Extensor expansions
• In addition to other attachments, many of the intrinsic
muscles of the hand insert into the free margin of the
hood on each side.
• By inserting into the extensor hood, these intrinsic
muscles are responsible for complex delicate
movements of the digits that could not be
accomplished with the long flexor and extensor
tendons alone.
• In the index, middle, ring, and little fingers, the
lumbrical, interossei, and abductor digiti minimi
muscles attach to the extensor hoods.
• In the thumb, the adductor pollicis and abductor
pollicis brevis muscles insert into and anchor the
extensor hood.

52. Flexor tendon sheaths
•Synovial
– To minimize friction
•Fibrous
–To place tendons in position during
flexion.
–At each of the crease the skin is adherent
to fibrous flexor sheath.

55. Fibrous Flexor Sheaths
• Strong fibrous sheath that is attached to the sides of the
phalanges in the anterior surface of each finger, from the
head of the metacarpal to the base of the distal phalanx.
• The proximal end: is open.
• The distal end: is closed and is attached to the base of the
distal phalanx.
• The sheath and the bones form a blind tunnel in which the
flexor tendons of the finger lie.
• In the thumb: contains the tendon of the flexor pollicis
longus.
• In the four medial fingers: the tendons of the flexor
digitorum superficialis and profundus
– Thick over the phalanges but thin over the joints

56. Synovial Flexor Sheaths
• In the hand, the tendons of the flexor digitorum
superficialis and profundus muscles invaginate a
common synovial sheath from the lateral side.
• The medial part of this common sheath extends distally
without interruption on the tendons of the little finger.
• The lateral part of the sheath stops abruptly on the
middle of the palm.
• The distal ends of the long flexor tendons of the index,
the middle, and the ring fingers acquire digital synovial
sheaths as they enter the fingers.
• The flexor pollicis longus tendon has its own synovial
sheath that passes into the thumb.

58. Ulnar bursa
• Common synovial sheath (ulnar bursa):
–Encloses the tendons of the flexor digitorum
superficialis and profundus muscles
– The medial part: extends distally without
interruption on the tendons of the little finger.
– The lateral part: stops on the middle of the
palm.
–The distal ends of the long flexor tendons of the
index, the middle, and the ring fingers acquire
digital synovial sheaths as they enter the
fingers.

59. The radial bursa
• The synovial sheath of the flexor pollicis
longus (sometimes referred to as the radial
bursa) communicates with the common
synovial sheath of the superficialis and
profundus tendons (sometimes referred to as
the ulnar bursa) at the level of the wrist in
about 50% of subjects.

60. Anterior view of the palm of the hand showing
the flexor synovial sheaths. Cross section of a
finger is also shown.

61. The vincula
• The vincula longa and brevia are
small vascular folds of synovial
membrane that connect the tendons
to the anterior surface of the
phalanges.
• They resemble a mesentery and
convey blood vessels to the tendons.

62. Fibrous digital sheaths and synovial sheaths of the hand.

63. The retinacular ligaments
• The retinacular ligaments are fibrous bands attached to
the side of the proximal phalanx, with the fibrous flexor
sheath attachment.
• They extend distally to merge with the margins of the
extensor expansion and thereby gain attachment to the
base of the distal phalanx.
– Extension of the proximal joint draws them tight and limits
flexion of the distal joint. Flexion of the proximal joint
slackens them and permits full flexion of the distal joint.

65. The spaces of the hand
The spaces of the hand are of practical significance because
they may become infected and, in consequence, become
distended with pus. The important spaces are:
1. The superficial pulp spaces of the fingers;
2. The synovial tendon sheaths of the 2nd, 3rd and 4th
fingers;
3. The ulnar bursa;
4. The radial bursa;
5. The midpalmar space;
6. The thenar space.

66. The superficial pulp space of the
fingers
The tips of the fingers and thumb are composed entirely of
subcutaneous fat broken up and packed between fibrous
septa, which pass from the skin down to the periosteum of
the terminal phalanx.
The tight packing of this compartment is responsible for the
se ere pai of a septi fi ger —there is little room for the
expansion of inflamed and oedematous tissues.
– The blood vessels to the shaft of the distal phalanx must
traverse this space and may become thrombosed in a severe
pulp infection with resulting necrosis of the diaphysis of the
bone.

68. Spaces deep in the palm
Two spaces deep in the palm of the hand may rarely become distended
with pus; these are the midpalmar and thenar spaces.
The midpalmar space lies behind the flexor tendons and ulnar bursa in
the palm and in front of the 3rd, 4th and 5th metacarpals with their
attached interossei. The 1st and 2nd metacarpals are curtained off from
this space by the adductor pollicis, which arises from the shaft of the
3rd metacarpal and passes as a triangular sheet to the base of the
proximal phalanx of the thumb.
The thenar space is the space superficial to the 2nd and 3rd
metacarpals and the adductor pollicis. It is separated from the
midpalmar space by a fibrous partition.

69. (a) projected on to the
surface of the hand
(b) in transverse section.
◊The midpalmar and thenar spaces:

70. Left palmar spaces
and synovial
sheaths. Infection
in the thenar or
midpalmar spaces
easily breaks
through into the
lumbrical canals
(connective tissue
sheaths of the
lumbrical muscles),
so the canals are
shown in
continuity with the
spaces.

72. Insertion of the Long Flexor Tendons
• Each tendon of the flexor digitorum superficialis
divides into two halves, which pass around the
profundus tendon.
• The superficialis tendon, divides again into two
slips, which are attached to the borders of the
middle phalanx.
• Each tendon of the flexor digitorum profundus,
having passed through the division of the
superficialis tendon, inserted into the anterior
surface of the base of the distal phalanx.

75. THE HAND AS A MECHANICAL TOOL
• One of the major functions of the hand is to grip
and manipulate objects. Gripping objects usually
involves flexing the fingers against the thumb.
Depending on the type of grip, muscles in the hand
act to:
– Modify the actions of long tendons that emerge from
the forearm and insert into the digits of the hand.
– Produce combinations of joint movements inside every
digit that a t e ge erated the lo g fle or a d
extensor tendons alone coming from the forearm.

76. THE HAND AS A SENSORY TOOL
• The hand is utilized to discriminate between objects
on the basis of touch.
• The pads on the palmar aspect of the fingers
include a high density of somatic sensory receptors.
• The sensory cortex of the brain devoted to
interpreting info from the hand, particularly from
the thumb, is disproportionately large relative to
that for many other regions of skin.

77. ORIENTATION OF THE THUMB
• The thumb is positioned at right angles to the
orientation of the index, middle, ring, and little fingers.
Because of this, movements of the thumb take place at
right angles to those of the other digits.
– flexion brings the thumb across the palm, on the other hand
abduction moves it far from the fingers at right angles to the
palm.
• Importantly, with the thumb positioned at right angles
to the palm, only a slight rotation of metacarpal I on
the wrist brings the pad of the thumb into a position
directly facing the pads of the other fingers.
– This opposition of the thumb is crucial for normal hand
function.

78. Clinical Notes
Trigger Finger
In trigger finger, there is a palpable and even audible
snapping when a patient is asked to flex and extend
the fingers.
•It is caused by the presence of a localized swelling
of one of the long flexor tendons that catches on a
narrowing of the fibrous flexor sheath anterior to
the metacarpophalangeal joint. It may take place
either in flexion or in extension. A similar condition
occurring in the thumb is called trigger thumb.
•The situation can be relieved surgically by incising the
fibrous flexor sheath.

79. Anterior view of the palm of the
hand. The long flexor tendons
have been removed from the
palm, but their method of
insertion into the fingers is
shown.

80. How to examine the hand
• A resident was asked to carry out a clinical assessment of a
patient's hand.
• He examined the following:
• Musculoskeletal system The musculoskeletal system
includes the bones, joints, muscles, and tendons. The
resident looked for abnormalities and muscle wasting. He
palpated the individual bones and palpated the scaphoid
with the wrist in ulnar deviation. He examined the
movement of joints because they may be restricted by joint
disease or inability of muscular contraction.
• Circulation Palpation of both radial and ulnar pulses is
necessary. The resident looked for capillary return to assess
how well the hand was perfused.
• Examination of the nerves
– The three main nerves to the hand should be tested:

86. Motor function of the median and ulnar nerves in the hand. A. Flexing the metacarpophalangeal
joints and extending the interphalangeal joints: the 'ta-ta' position. B. Grasping an object
between the fingers. C. Grasping an object between the pad of the thumb and pad of the index
finger.

87. Grip• The power grip (palm grasp) refers to forcible motions of the digits acting
against the palm; the fingers are wrapped around an object with
counterpressure from the thumb
– The power grip involves the long flexor muscles to the fingers, the intrinsic
muscles in the palm, extensors of the wrist .
• A hook grip is the posture of the hand that is used when carrying a
briefcase.
– This grip consumes less energy, involving mainly the long flexors of the fingers,
which are flexed to a varying degree, depending on the size of the object that is
grasped.
• The precision handling grip involves a change in the position of a handled
object that requires fine control of the movements of the fingers and
thumbfor example, holding a pencil, manipulating a coin, threading a
needle, or buttoning a shirt .
– In a precision grip, the wrist and fingers are held firmly by the long flexor and
extensor muscles, and the intrinsic hand muscles perform fine movements of
the digits.
• Pinching refers to compression of something between the thumb and the
index fingerre.

88. Boxer 's fracture
• A boxer's fracture involves a
break in the neck of the
metacarpal.
• was described originally in
the fracture of the
metacarpal bone of the little
(small) finger because this is
the most common one to
break when punching an
immovable object.