The document discusses the anatomy of the upper limb, brachial plexus, and scapular region. The brachial plexus is formed by the lower cervical and upper thoracic spinal nerves and provides motor and sensory innervation to the upper limb. It is located in the axilla and gives rise to the major nerves of the arm. The axillary artery originates from the subclavian artery and gives rise to vessels that supply the upper limb before terminating as the brachial artery in the arm. Veins in the upper limb drain into the axillary and brachial veins. Key muscles of the scapular region include the deltoid, teres major, triceps brachii

1. Anatomy of the upper limb
• Introduction
• General considerations
• Brachial plexus

24. ANATOMY
UPPER LIMB
BRACHIAL PLEXUS

26. The spinal nerves from C5 to C8, together with the T1 thoracic spinal
nerve, join together to form
the brachial plexus.
The nerve elements
combine,
divide
and combine again to
mix together the various
components that lead into the major nerves of the
shoulder, arm and hand.

27. A nerve plexus is an area where nerves branch
and rejoin.
The brachial plexus is a group of nerves in the cervical spine
from C5 to C8-T1.
This includes the lower half of the cervical nerve roots and the
nerve root from the first thoracic vertebra.

36. Brachial Plexus
1 Ventral root of C5
2 Ventral root of C6
3 Ventral root of C7
4 Ventral root of C8
5 Ventral root of T1
6 Ulnar
7 Radial
8 Median
9 Musculocutaneous
10 Cords
a Medial
b Posterior
c Lateral
11 Posterior divisions
12 Anterior divisions
a Inferior
b Middle
c Superior
13 Inferior trunk
14 Middle trunk
15 Superior trunk

38. Erb’s paralysis
• C5 - C6
• Birth injury
• Arm hangs by the side+Rotate medially
• Forearm pronated + extended
• Flexed wrist + fingers
• deltoid – supraspinatus – infraspinatus –
biceps - brachialis

39. Klumpke’s paralysis
/kloomp’kz/
• C8 – T1
• Intrinsic muscles of the hand + long flexors of
the hand ------ paralysis
• Claw hand = extension at MPJ + flexion at IPJ
• Cervical rib can cause paralysis similar to
Klumpke’s paralysis with post-fixed T2
contribution

40. Winging of the scapula
• Injury to the long thoracic nerve
• Paralysis of serratus anterior muscle
Humeral fracture
At the surgical neck ---------- injury to the
axillary nerve ---- loss of abduction

42. Arterial blood supply
of the upper limb

43. Axillary artery
•Continuation of subclavian artery
•Runs from lateral border of first rib to lower border of teres major
•Pectoralis minor crosses anterior to it and divides it into three parts
•First part
• Highest thoracic artery (also called supreme or superior)
•Second part
• Lateral thoracic artery
• Thoracoacromial artery
•Third part
• Subscapular artery
• Anterior circumflex humeral artery
• Posterior circumflex humeral artery
•Collateral circulation around the scapula
•Branches of first part of Subclavian artery anastomose with branches of the
third part of axillary artery

44. The axillary artery begins at the lateral border
of the first rib as a continuation of the
subclavian artery.
It changes its name to brachial artery at lower
(inferior) border of the teres major muscle.
For purposes of description, it is broken up into
three parts by its relation to the pectoralis
minor muscle.
The first part is between the lateral border of
the first rib and the medial border of the
pectoralis minor,
the second part is behind the pectoralis minor
and the
third part is between the lateral border of the
pectoralis minor and the inferior border of the
teres major

45. Brachial artery
Continuation of the axillary artery
Runs from lower border of teres major to neck of radius
Ends by dividing into radial and ulnar arteries
Branches of the brachial artery
Profunda brachi which travels in the radial groove of humerus
Superior ulnar collateral artery o Inferior ulnar collateral artery
Nutrient artery to humerus
Terminal branches are radial and ulnar arteries
Relations
Median nerve crosses anterior to it from lateral to medial side at the level of
mid arm

46. 1 superior thoracic a.
(supreme thoracic a.)
(highest thoracic a.)
2 thoracoacromial a.
3 lateral thoracic a.
4 subscapular a.
5 anterior humeral circumflex a.
6 posterior humeral circumflex a.

47. Ulnar artery
Gives rise to common interosseous artery
Continues as the superficial palmar arch in the hand
Radial artery
Continues as the deep palmar arch in the hand
Median artery Vestigial in adult life
Arises from the anterior interosseous branch of common
interosseous artery
Provides nutrition to Median nerve
Chief source of blood supply to the upper limb in foetal life
Passes anterior to carpal tunnel

48. The diagram also shows that the brachial artery
terminates just below the elbow joint as the radial
and ulnar arteries, to be covered in the forearm

49. 1 brachial
2 radial
3 radial recurrent
4 superficial radial
5 deep radial
6 ulnar
7 anterior ulnar recurrent
7 posterior ulnar recurrent
8 common interosseous
9 posterior interosseous
10 anterior interosseous
11 superficial branch
12 deep branch

51. The superficial arterial arch is formed mainly from the ulnar artery and is
completed by the superficial branch of the radial. This completion is not always
present or may be extremely small.
The deep arterial arch is formed mainly by the deep branch of the radial artery and
is finished by the deep branch of the ulnar artery.

52. Upper limb
Venous drainage

53. cephalic v.
Tributaries
lateral side of the dorsal venous arch of the hand;
superficial veins of the forearm
Drains Into
axillary vein
Regions Drained
superficial parts of the lateral hand and lateral
forearm
Notes
median cubital vein usually shunts some of the blood collected by the
cephalic v. to the basilic v. (Latin/Greek, kephale = head)

55. The axillary vein lies along the medial
side of the artery and is a continuation
of the basilic vein.
It begins at the inferior border of the
teres major m. and ends at the lateral
border of the first rib, where it
becomes the subclavian v.
It receives tributaries that parallel the branches of the axillary artery.

56. The cephalic v. joins the axillary v. just before it becomes the subclavian.
Penetrating wounds in the larger upper part are serious because air might enter into
the venous system.

57. The veins that run with their
corresponding arteries are
frequently multiple
(2 or 3 interconnected veins).
This interconnected venous
network is called the vena
commitantes

60. Axilla, Pectoral and
scapular regions

61. Anatomically,
the boundaries of the axilla are
medially: serratus anterior and by the ribcage
anteriorly: by the pectoralis major, minor, and subclavius (see also anterior axillary fold)
posteriorly: by the subscapularis above, and teres major and latissimus dorsi below(see
also posterior axillary fold)
laterally: by the intertubercular sulcus (coracobrachialis and the short head of the biceps
brachii are in the axilla.)
superiorly: by the outer border of first rib, superior border of scapula, and posterior
border of clavicle
floor/base: by the skin (visible surface of armpit

62. Deep muscles of the chest and front of the arm, with the boundaries of the axilla.

63. Artery axillary artery
Vein axillary vein
axillary nerve,
medial cord,
Nerve posterior
cord, lateral
cord
axillary lymph
Lymph
nodes

65. Lymphatics
Structure Location Afferents from Efferents to Regions drained Notes
axillary nodes axilla cubital nodes; efferents vessels upper limb, most axillary nodes
lymphatic vessels form the of the mammary number from 20
from the upper subclavian trunk, gland, some of the to 30 and are
limb, thoracic wall some drainage to anterolateral chest organized in five
and subscapular inferior deep wall, posterior groups based on
region cervical nodes thoracic wall and their position
scapular region within the axilla:
1) pectoral nodes,
along the lateral
border of the
pectoralis major
m.; 2) lateral
nodes, located
along the distal
axillary v.; 3)
central nodes,
centrally located
along axillary v.; 4)
subscapular
nodes, located
along the
subscapular v. and
its tributaries; 5)
apical nodes,
located at the
apex of axilla

66. There are some 15 to 20 nodes usually arranged into
to five groups. The groups consist of:
A pectoral (anterior)
L lateral
P posterior
C central
Ap apical

67. Muscles of Axilla and the
Pectoral region

69. Pectoralis major
Origin medial 1/2 of the clavicle, manubrium & body of sternum, costal
cartilages of ribs 2-6, sometimes from the rectus sheath of the upper
abdominal w
Insertion crest of the greater tubercle of the humerus
Action flexes and adducts the arm, medially rotates the arm
Nerve supply medial and lateral pectoral nerves (C5-T1)
Arterial blood supply pectoral branch of the thoracoacromial trunk
the deep fascia on its anterior surface should not be fused to the fascia of the mammary gland - if it is, this is an important clinical
sign indicating breast disease (Latin, pectus = breast bone)

70. Pectoralis minor
origin ribs 3-5
Insertion coracoid process of the scapula
Action draws the scapula forward, medialward,
and downward
Nerve supply medial pectoral nerve (C8, T1)
arterial supply pectoral branch of the
thoracoacromial trunk
Notes; branches of medial pectoral nerve usually pierce pectoralis minor to
reach the pectoralis major muscle .

71. serratus anterior
Origin ribs 1-8 or 9
Insertion medial border of the scapula on its costal (deep)
surface
Action it draws the scapula forward; the inferior fibers rotate
the scapula superiorly
Nerve supply long thoracic nerve (from ventral rami C5-C7)
Arterial supply
lateral thoracic a.
a lesion of long thoracic nerve will cause winging of the scapula (i.e., the medial border
of the scapula falls away from the posterior chest wall and looks like an angel's wing)
(Latin, serratus = to saw)

72. Topographical Anatomy of the Thorax
Structure/Space Description/Boundaries Significance
midaxillary line an imaginary vertical line used as a surface landmark
passing through the middle for descriptive purposes
of the axilla
midclavicular line an imaginary vertical line used as a surface landmark
passing through the for descriptive purposes
midshaft of the clavicle

73. deltopectoral triangle
a triangle in the upper chest region that is bounded medially by the clavicle,
superiorly by the deltoid m.,
and inferiorly by the pectoralis major m.
the deltopectoral triangle
is pierced by the cephalic vein on its course from the upper limb to join the axillary vein in
the axilla

74. nipple located superficial to the 4th location of the left nipple may be
intercostal space in the male and used to help locate the apex of heart,
prepuberal female; areola is dark ring which is approximately 8 cm from
surrounding nipple the midline in the left 5th intercostal
space; a surface landmark used to
place the stethoscope for
auscultation of the bicuspid valve
suprasternal notch the notch located at the superior also known as: jugular notch
border of the manubrium of the
sternum, between the sternal ends
of the clavicles

75. parasternal nodes lateral border of anterior phrenic nodes, larger lymphatic medial side of the parasternal nodes
sternum, along the lymphatic vessels from vessels in the root of mammary gland; constitute an
course of the internal the anterior thoracic the neck medial part of the important drainage
thoracic vessels wall anterior chest wall and pattern in cases of
muscles cancer of the
mammary gland; one
or two parasternal
nodes may be found in
the anterior end of
intercostal spaces 1-6;
also known as: sternal
nodes
pectoral nodes along the lateral lymphatic vessels from central axillary nodes anterolateral thoracic an important group of
border of the the mammary gland wall and muscles; most nodes to examine
pectoralis major m. and anterolateral of the mammary gland during a breast
along the course of the thoracic wall physical exam; also
lateral thoracic vessels known as: anterior
axillary nodes

76. SCAPULAR REGION

77. Muscles of the Scapular Region
Muscle Origin Insertion Action Innervation Artery Notes
deltoid lateral one-third of deltoid tuberosity abducts arm; axillary nerve
posterior the deltoid muscle
the clavicle, of the humerus anterior fibers flex (C5,6) from the
circumflex humeral is the principle
acromion, the & medially rotate posterior cord of
a. abductor of the
lower lip of the the arm; posterior the brachial plexus arm but due to
crest of the spine fibers extend & poor mechanical
of the scapula laterally rotate the advantage it
arm cannot initiate this
action; it is assisted
by the
supraspinatus m.
teres major dorsal surface of crest of the lesser adducts the arm, lower subscapular circumflex scapular teres major inserts
the inferior angle tubercle of the medially rotates nerve (C5,6) from a. beside the tendon
of the scapula humerus the arm, assists in the posterior cord of latissimus dorsi,
arm extension of the brachial and assists
plexus latissimus in its
actions
triceps brachii long head: olecranon process extends the radial nerve deep brachial long head of the
infraglenoid of the ulna forearm; the long (profunda brachii) triceps separates
tubercle of the head extends and a. the triangular and
scapula; lateral adducts arm quadrangular
head: spaces (teres
posterolateral major, teres minor
humerus & lateral and the humerus
intermuscular are the other
septum; medial boundaries); all
head: three heads of
posteromedial origin insert by a
surface of the common tendon
inferior 1/2 of the
humerus

78. rotator cuff
supraspinatus supraspinato greater abducts the suprascapular suprascapular supraspinatus initiates
us fossa tubercle of arm (initiates nerve (C5,6) a. abduction of the arm, then
the humerus abduction) from the the deltoid muscle
(highest superior completes the action; a
facet) trunk of the member of the rotator cuff
brachial group
plexus
infraspinatus infraspinatou greater laterally suprascapular suprascapular infraspinatus, supraspinatus,
s fossa tubercle of rotates the nerve a. teres minor and
the humerus arm subscapularis are the rotator
(middle facet) cuff muscles
teres minor upper 2/3 of greater laterally axillary nerve circumflex fixes the head of the
the lateral tubercle of rotates the (C5,6) from scapular a. humerus in the glenoid fossa
border of the the humerus arm the posterior during abduction & flexion of
scapula (lowest facet) cord of the the arm; a member of the
brachial rotator cuff group
plexus
subscapularis medial two- lesser medially upper and subscapular subscapularis, supraspinatus,
thirds of the tubercle of rotates the lower a. infraspinatus, and teres
costal surface the humerus arm; assists subscapular minor are the rotator cuff
of the scapula extention of nerves (C5,6) muscles
(subscapular the arm
fossa)

79. Nerves of the Scapular Region
Nerve Source Branches Motor Sensory Notes
axillary n. posterior cord of superior lateral deltoid, teres skin of the upper axillary n. is
the brachial brachial minor lateral arm endangered by
plexus cutaneous nerve surgical neck
fractures
lower posterior cord of unnamed subscapularis m., no cutaneous subscapularis
subscapular n. the brachial muscular brs. teres major m. branches and teres major
plexus (C5, C6) are synergists
(medial rotation
of the humerus)
middle posterior cord of unnamed latissimus dorsi no cutaneous also called the
subscapular n. the brachial muscular brs. m. branches thoracodorsal n.
plexus (C7, C8)
suprascapular n. superior trunk of no named supraspinatus no cutaneous suprascapular n.
the brachial branches m., infraspinatus branches passes through
plexus (C5-C6) m. the scapular
notch inferior to
the superior
transverse
scapular
ligament
thoracodorsal n. posterior cord of unnamed latissimus dorsi no cutaneous also called the
the brachial muscular brs. m. branches middle
plexus (C7, C8) subscapular n.
upper posterior cord of unnamed subscapularis m. no cutaneous subscapularis is a
subscapular n. the brachial muscular brs. branches strong medial
plexus (C5, C6) rotator of the
humerus

80. Arteries of the Scapular Region
Artery Source Branches Supply to Notes
anterior circumflex humeral axillary a., 3rd part unnamed muscular branches deltoid m.; arm muscles near anterior circumflex humeral a.
the surgical neck of the anastomoses with the posterior
humerus circumflex humeral a.
posterior circumflex humeral axillary a., 3rd part unnamed muscular branches deltoid; arm muscles near the posterior circumflex humeral a.
surgical neck of the humerus anastomoses with the anterior
circumflex humeral a.; it passes
through the quadrangular
space with the axillary nerve
axillary subclavian a. (axillary a. is the 1st part: superior thoracic a.; pectoral region, shoulder pectoralis minor m. crosses
continuation of the subclavian 2nd part: thoracoacromial a., region and upper limb anterior to the axillary artery
lateral to the 1st rib) lateral thoracic a.; 3rd part: and is used to delineate the 3
anterior humeral circumflex a., parts mentioned at left
posterior humeral circumflex a.,
subscapular a.
circumflex scapular subscapular a. unnamed muscular branches teres major m., teres minor m., circumflex scapular a.
infraspinatus m. anastomoses with the
suprascapular a. and the dorsal
scapular a. to form the scapular
anastomosis
dorsal scapular subclavian a., 3rd part unnamed muscular branches levator scapulae m., dorsal scapular a. anastomoses
rhomboideus major m., with the suprascapular a. and
rhomboideus minor m. the subscapular a. to form the
scapular anastomosis; dorsal
scapular a is a branch of the
transverse cervical a. in ~30%
of cases
subscapular axillary a., 3rd part circumflex scapular a., subscapularis m., teres major the circumflex scapular branch
thoracodorsal a. m., teres minor m., of the subscapular
infraspinatus m. a.anastomoses with the
suprascapular a. and the dorsal
scapular a. in the scapular
anastomosis
suprascapular thyrocervical trunk muscular supraspinatus & infraspinatus, anastomoses with the
shoulder joint circumflex scapular a. and the
dorsal scapular a. to form the
scapular anastomosis
thoracodorsal subscapular a. unnamed muscular branches latissimus dorsi m. thoracodorsal a. accompanies
the thoracodorsal n.

81. Topographic Anatomy of the Scapular Region
Structure/Space Description/Boundaries Significance
quadrangular space the space bounded by the the axillary n. and the
teres minor m. superiorly, posterior circumflex
the teres major m. inferiorly, humeral a. pass through this
the long head of the triceps space
brachii m. medially and the
humerus laterally
triangular interval the interval between the the radial n. passes through
teres major m. superiorly, this interval to get from the
long head of the triceps axilla to the posterior
brachii m. medially and surface of the humerus
humerus laterally
triangular space the space bounded by the the circumflex scapular
teres minor m. superiorly, vessels are located in this
the teres major m. inferiorly space as they pass from the
and the long head of the axilla to the dorsum of the
triceps brachii m. laterally scapula

82. The scapular and circumflex arteries.
(Quadrangular space is visible but not labeled.
Posterior humeral circumflex artery is visible
entering quadrangular space at center right.)

83. Suprascapular and axillary nerves of right side,
seen from behind. Quadrangular space is the
lateral space, labeled in green at center right.
Axillary nerve is visible entering it.

85. Pectoral region
The human breast
(Mammary gland )

87. consists of 10–20 simple glands.
The presence of more than two nipples is
known as polythelia
and the presence of more than two complex
mammary glands as polymastia.

88. I. Introduction/General Information
A. Embryologically: belong to integument
B. Functionally: part of reproductive system
1. Respond to sexual stimulation
2. Feed babies
C. Modified apocrine sweat glands
- apex of cell becomes part of secretion
and breaks off
D. Present in males and females

89. II. Anatomy
A. Position and Attachment
1. Lateral aspect of pectoral region
2. Located between ribs 3 and 6/7
3. Extend form sternum to axilla
4. Surrounded by superficial fascia
5. Rest on deep fascia
6. Fixed to skin & underlying fascia by fibrous C.T. bands
a. Cooper’s (Suspensory) Ligaments
b. Ligaments may retract when breast tumors are present

90. Breast Anatomy

91. Left breast is usually slightly larger
Base is circular, either flattened or concave
Separated from pectoralis major muscle by fascia, retromammary space
B. Structure
1. Outer surface convex, skin covered
2. Nipple:
a. At fourth intercostal space
b. Small conical/cylindrical
prominence below center

92. Nipple location
4th intercostal
space

93. c. Surrounded by areola: pigmented ring of skin
d. Thin skinned region lacking hair, sweat glands
e. Contains areolar glands
3. Areola: contains
dark pigment that intensifies with pregnancy
a. Circular and radial smooth muscle fibers
b. Cause nipple erection

94. Lobes and Lobules

95. 5. Excretory (lactiferous) ducts converge
toward areola
a. Form ampullae (collection sites of lactiferous sinuses)
b. Ducts become contracted at base of nipple
6. Secretory epithelium
a. Changes with hormonal signals
b. Onset of menstruation
c. Pregnancy (glands begin to enlarge at 2nd month)
d. After birth, 1st secretion is colostrom (contain antibodies

96. 7. “Tail of Spence” = axillary tail
a. prolongation of upper, outer quadrant in axillary direction
b. Passes under axillary fascia
c. May be mistaken for axillary lymph nodes
8. Fatty Tissue: surrounds surface, fills
spaces between lobes
a. Determines form & size of breast
b. No fatty deposit under nipple & areola

97. “Tail of Spence”
Axillary Tail

98. Breast: Fatty Tissue

99. Vessels & nerves
1. Arteries: derived from thoracic
branches of three pairs of arteries
a. Axillary arteries
continuous with subclavian a.
gives rise to external mammary ( = lateral thoracic) artery

100. b. Internal mammary (thoracic) arteries
1) first descending branch of subclavian artery
2) supply intercostal spaces & breast
3) used for coronary bypass surgery
c. Intercostal arteries:
1) numerous branches from internal
& external mammary arteries
2) supply intercostal spaces & breast
Veins:
a. form a ring around the base of the nipple (“circulus
venosus”)
b. Large veins pass from circulus venosus to circumference
Of mammary gland, then to
c. External mammary v to axillary v or
d. Internal mammary v to subclavian v

101. Arterial Supply to the Breast
Subclavian a.
Axillary a. Internal
mammary
(thoracic) a.
External
mammary
(thoracic) a.

102. Veins draining the Breast
Subclavian vein
External
mammary vein

103. Innervation: derived from:
a. anterior & lateral cutaneous nerves of thorax
b. spinal segments T3 – T6
Lymphatics: clinically significant!
a. Glandular lymphatics drain into
anterior axillary (pectoral) nodes 
central axillary nodes 
apical nodes 
deep cervical nodes subclavicular (subclavian) nodes
b. Medial quadrants drain into parasternal nodes
c. Superficial regions of skin, areola, nipples: -form large channels & drain into
pectoral nodes
d. NOTE: axillary nodes also drain lymph from arm

104. Lymph Nodes of the Breast
Subclavian
nodes
Axillary
nodes
Parasternal
Lateral nodes
pectoral
nodes

105. Lymph Nodes and Lymph Drainage
Axillary
Nodes

106. Routes of Metastasis
• From medial lymphatics to parasternal nodes
– Then to mediastinal nodes
• Across the sternum in lymphatics to
opposite side via cross-mammary pathways
– Then to contralateral breast
• From subdiaphragmatic lymphatics to nodes in
abdomen
– Then to liver, ovaries, peritoneum

107. Major Routes of Metastasis
Channels to Contralateral Breast
Axillary Lymph Channels
Subdiaphragmatic Lymph Channels

108. The arteries supplying the mammæ are derived from the
thoracic branches of the axillary,
the intercostals,
and the internal mammary.
The veins describe
anastomotic circle around the base of the papilla,
called by Haller the circulus venosus.
From this, large branches transmit the blood to
the circumference of the gland, and end in the
axillary and internal mammary veins.
The arteries supplying the mammæ are derived from the thoracic
branches of the axillary,
the intercostals,
and the internal mammary.

109. Muscles of the upper limb

111. ORIGIN
CORACOBRACHIALIS
Coracoid process of scapula
with biceps brachii
INSERTION
Upper half medial border of
humerus
ACTION
Flexes and weakly adducts
arm
NERVE
Musculocutaneous nerve (C5,
6, 7) (from lateral cord)

112. Latin musculus brachialis
Gray's subject #124 444
Origin anterior surface of the
humerus, particularly the
distal half of this bone
Insertion coronoid process and the
tuberosity of the ulna
Artery radial recurrent artery
Nerve musculocutaneous nerve
Actions flexion at elbow joint

114. The biceps is tri-articulate,
meaning that it works across
three joints. The most
important of these functions
are to supinate the forearm
and flex the elbow.
These joints and the
associated actions are listed
as follows in order of
importance
Proximal radioulnar joint
Humeroulnar joint
Glenohumeral joint

115. Latin musculus biceps brachii
Gray's subject #124 443
Origin short head: coracoid process of the
scapula. long head: supraglenoid
tubercle
Insertion radial tuberosity and bicipittal
aponeurosis into deep fascia on medial
part of forearm
Artery brachial artery
Nerve Musculocutaneous nerve (C5–C7)
Actions flexes elbow and supinates forearm
Antagonist Triceps brachii muscle

117. Anterior compartment
Muscle Origin Insertion Artery Nerve Action Antagonist
coracobrachialis coracoid process of medial humerus brachial artery musculocutaneous adducts humerus
scapula nerve
biceps brachii short head: coracoid radial tuberosity brachial artery Musculocutaneous flexes elbow and supinates Triceps brachii
process of the scapula. nerve (Lateral cord: forearm muscle
long head: supraglenoid C5, C6, C7)
tubercle
brachialis anterior surface of the coronoid process and the radial recurrent musculocutaneous flexion at elbow joint
humerus, particularly the tuberosity of the ulna artery nerve
distal half of this bone

119. POSTERIOR COMPARTMENT
• TRICEPS MUSCLE

120. Schematic drawing with
measurements indicating
the relationship of the
radial nerve to osseous
landmarks.
Note the course of the
radial nerve along the
posterior humerus and its
relationship to the distal
deltoid tuberosity and
lateral epicondyle

121. MUSCLES THAT ACT ON ANTERIOR FOREARM:
•BICEPS BRACHII
•BRACHIALIS
•BRACHIORADIALIS
•PRONATOR TERES
MUSCLES THAT ACT ON POSTERIOR FOREARM:
•TRICEPS BRACHII - LONG HEAD
•TRICEPS BRACHII - MEDIAL HEAD
•TRICEPS BRACHII - LATERAL HEAD
•ANCONEUS

122. Posterior compartment
Antagoni
Muscle Origin Insertion Artery Nerve Action
st
triceps long head: olecranon Profunda radial extends Biceps
brachii scapula process of brachii nerve forearm, caput brachii
lateral head: ulna longum adducts muscle
posterior shoulder
humerus
medial
head:
posterior
humerus
anconeu Lateral lateral Profunda radial partly blended
s epicondyle surface of brachii, nerve in with the
of the the recurrent (C7, C8, triceps, which it
humerus olecranon interosse and T1) assists in
process and ous extension of the
the superior artery forearm.
part of the Stabilises the
posterior elbow and
ulna abducts the
ulna during
pronation.

123. Cubital Fossa
The cubital fossa is the region of the upper
limb in front of the elbow joint.
It is a triangular area with the following
boundaries:
laterally, brachioradialis muscle
medially, pronator teres muscle
superiorly, an imaginary line from the
medial and lateral epicondyles.

124. artery-nerve layer
aponeurotic layer 1 brachial artery
1 bicipital 2 median nerve
aponeurosis
2 biceps tendon
venous layer
1 cephalic vein
2 basilic vein
3 median cubital vein
bony floor
muscular floor 1 humerus
1 supinator 2 radius
2 brachialis 3 ulna
3 biceps tendon

125. Forearm
Anterior compartment

128. flexor carpi radialis
origin
common flexor tendon from the
medial epicondyle of the humerus
insertion
base of the second and third
metacarpals
action
flexes the wrist, abducts the hand
Nerve supply
median nerve

129. flexor carpi ulnaris
Origin
common flexor tendon & (ulnar head) from
medial border of olecranon & upper 2/3 of
the posterior border of the ulna
insertion
pisiform, hook of hamate, and base of
5thmetacarpal
action
Flex the wrist, adducts hand
Nerve supply
ulnar nerve

130. flexor digitorum profundus
origin
posterior border of the ulna,
proximal two-thirds of medial
border of ulna, interosseous
membrane
insertion
base of the distal phalanx of digits
2-5
action
flexes the metacarpophalangeal,
proximal interphalangeal and distal
interphalangeal joints
Nerve supply
median nerve via anterior
interosseous branch (radial one-
half); ulnar nerve (ulnar one-half)

131. flexor digitorum superficialis
origin
humeroulnar head: common flexor
tendon; radial head: middle 1/3 of
radius
insertion
shafts of the middle phalanges of
digits 2-5
action
flexes the metacarpophalangeal
and proximal interphalangeal joints
Nerve supply
median nerve

132. flexor pollicis longus
origin
anterior surface of radius and interosseous
membrane
insertion
base of the distal phalanx of the thumb
action
flexes the metacarpophalangeal and
interphalangeal joints of the thumb
Nerve supply
median nerve via anterior interosseous
branch

133. pronator quadratus
origin
medial side of the anterior surface of the
distal one-fourth of the ulna
insertion
anterior surface of the distal one-fourth of
the radius
action
pronates the forearm
Nerve supply
median nerve via anterior interosseous
branch

134. palmaris longus
origin
medial epicondyle of humerus
insertion
distal half of flexor retinaculum and
palmaris aponeurosis
action
flexes hand (at wrist) and tightens
palmar aponeurosis
Nerve supply
median n. (C7 and C8) ulnar a.

135. pronator teres
origin
common flexor tendon and (deep
or ulnar head) from medial side of
coronoid process of the ulna
inserion
midpoint of the lateral side of the
shaft of the radius
Actio pronates the forearm
Nerve supply
median nerve

136. supinator
origin
lateral epicondyle of the humerus,
supinator crest & fossa of the ulna, radial
collateral ligament, annular ligament
insertion
lateral side of proximal one-third of the
radius
action
supinates the forearm
Nerve supply
deep radial nerve

137. Muscle Origin Insertion Artery Nerve Action Antagonist
pronator humeral head: radius ulnar median pronation of Supinator
teres medial artery and nerve forearm, flexes muscle
epicondyle of radial elbow
humerus artery
(common
flexor tendon)
ulnar head:
coronoid
process of the
ulna
palmaris medial palmar ulnar median wrist flexor Extensor
longus epicondyle of aponeurosis artery nerve carpi
humerus radialis
(common brevis,
flexor tendon) Extensor
carpi
radialis
longus,
Extensor
carpi
ulnaris

138. flexor carpi medial Bases of ulnar artery Median Flexion and Extensor
radialis epicondyle of second and nerve abduction at carpi radialis
humerus third wrist brevis
(common metacarpal muscle,
flexor bones Extensor
tendon) carpi radialis
longus
muscle
flexor carpi medial pisiform ulnar artery muscular flexion of Extensor
ulnaris epicondyle of branches of wrist carpi ulnaris
the humerus ulnar nerve muscle
(common
flexor
tendon)
flexor medial phalanges ulnar artery median nerve flexor of Extensor
digitorum epicondyle of fingers digitorum
superficialis the humerus (primarily at muscle
(common proximal
flexor interphalang
tendon), as eal joints)
well as parts
of the radius
and ulna.

139. Deep
Muscle Origin Insertion Artery Nerve Action Antagonist
pronator medial, anterior lateral, anterior anterior median pronates the forearm Supinator
quadratus surface of the surface of the interosseous nerve muscle
ulna radius artery (anterior
interosseous
nerve)
flexor ulna distal phalanges anterior median flex hand, Extensor
digitorum interosseous (anterior interphalangeal joints digitorum
profundus artery interosseous muscle
), muscular
branches of
ulnar
flexor pollicis The middle 2/4 of The base of the Anterior Anterior Flexion of the thumb Extensor
longus the distal phalanx of interosseous interosseous pollicis
volar [disambiguation the thumb artery nerve longus
needed] surface of (branch of muscle,
the radius and median Extensor
the adjacent nerve) (C8, pollicis
interosseus T1) brevis
membrane. (Also muscle
occasionally a
small origin
slightly on the
medial
epicondyle of the
ulna.)

140. The muscles are largely involved
with flexion and pronation.
The superficial muscles have their
origin on the common flexor tendon.
The Ulna nerve and artery are also
contained within this compartment
@@@@@@@@@@@@@@@@

141. Forearm posterior compartment

142. abductor pollicis longus
origin middle one-third of the posterior
surface of the radius, interosseous
membrane, mid-portion of posterolateral ulna
Insertion radial side of the base of the first
metacarpal
Action abducts the thumb at
carpometacarpal joint
Nerve supply radial nerve, deep branch

143. Brachioradialis
origin upper two-thirds of the lateral
supracondylar ridge of the humerus
Insertion lateral side of the base of the styloid
process of the radius
Action flexes the elbow, assists in pronation &
supination
Nerve supply radial nerve

144. The Brachioradialis, flexor of the forearm, is
unusual in that it is located in the
posterior compartment, but it is actually in the
anterior portion of the forearm.

145. extensor carpi radialis longus
Origin lower one-third of the lateral
supracondylar ridge of the humerus
Insertion dorsum of the second metacarpal
bone (base)
Action extends the wrist; abducts the hand
Nerve supply radial nerve

146. extensor carpi radialis brevis
origin
common extensor tendon (lateral
epicondyle of humerus)
insertion
dorsum of the third metacarpal bone
(base)
Action extends the wrist; abducts the hand
Nerve supply deep radial nerve

147. extensor carpi ulnaris
origin
common extensor tendon & the middle
one-half of the posterior border of the ulna
insertion
medial side of the base of the 5th
metacarpal
action
extends the wrist; adducts the hand
Nerve supply deep radial nerve

148. extensor digiti minimi
origin
common extensor tendon (lateral
epicondyle of the humerus)
insertion
joins the extensor digitorum tendon to the
5th digit and inserts into the extensor
expansion
action
extends the metacarpophalangeal, proximal
interphalangeal and distal interphalangeal
joints of the 5th digit
Nerve supply deep radial nerve

149. extensor digitorum
origin
common extensor tendon (lateral
epicondyle of the humerus)
insertion
extensor expansion of digits 2-5
action
extends the metacarpophalangeal,
proximal interphalangeal and distal
interphalangeal joints of the 2nd-5th
digits; extends wrist deep
Nerve supply radial nerve

150. extensor indicis
origin
interosseous membrane and the
posterolateral surface of the distal ulna
Insertion
its tendon joins the tendon of the extensor
digitorum to the second digit; both tendons
insert into the extensor expansion
action
extends the index finger at the
metacarpophalangeal, proximal
interphalangeal and distal interphalangeal
joints
Nerve supply deep radial nerve

151. extensor pollicis brevis
origin
interosseous membrane and the posterior
surface of the distal radius
insertion
base of the proximal phalanx of the thumb
action
extends the thumb at the
metacarpophalangeal joint
Nerve supply
deep radial

152. extensor pollicis longus
Origin
interosseous membrane and middle
part of the posterolateral surface of the
ulna
insertion
base of the distal phalanx of the thumb
action
extends the thumb at the
interphalangeal joint
Nerve supply
deep radial nerve

153. Nerves of the upper limbs
Radial nerve
Median nerve
Ulnar nerve

154. RADIAL NERVE
The radial nerve originates as a terminal branch of the posterior cord of the
brachial plexus.
It goes through the arm, first in the posterior compartment of the arm,
and later in the anterior compartment of the arm,
and continues in the posterior compartment of the forearm.

155. In arm
From the brachial plexus, it travels posteriorly through what is often called the
triangular interval (US) or the triangular space of the axilla (UK).
The radial nerve enters the arm behind the axillary artery/brachial artery, and it then
travels posteriorly on the medial side of the arm.
After giving off branches to the long and medial heads of the triceps brachii, it enters
a groove on the humerus, the radial sulcus.
Along with the deep brachial artery, the radial nerve winds around in the groove
(between the medial and lateral heads of the triceps) towards the forearm, running
laterally on the posterior aspect of the humerus.
While in the groove, it gives off a branch to the lateral head of the triceps brachii.
The radial nerve emerges from the groove on the lateral aspect of the humerus.
At this point, it pierces the lateral intermuscular septum and enters the anterior
compartment of the arm.
It continues its journey inferiorly between the brachialis and brachioradialis muscles.
When the radial nerve reaches the distal part of the humerus, it passes anterior to
the lateral epicondyle and continues in the forearm

156. Branches/Innervations
The following are branches/innervations of the radial nerve (including the superficial
branch of the radial nerve and the deep branch of the radial nerve/posterior
interosseous nerve).
Cutaneous
Cutaneous innervation is provided by the following nerves:
Posterior cutaneous nerve of arm (originates in axilla)
Inferior lateral cutaneous nerve of arm (originates in arm)
Posterior cutaneous nerve of forearm (originates in arm)
The superficial branch of the radial nerve provides sensory innervation to much of the
back of the hand, including the web of skin between the thumb and index finger

157. Transverse section across distal ends of radius and ulna.

158. In forearm
In the forearm, it branches into a superficial branch (primarily sensory) and a deep
branch (primarily motor).
The superficial branch of the radial nerve descends in the forearm under the
brachioradialis.
It eventually pierces the deep fascia near the back of the wrist.
The deep branch of the radial nerve pierces the supinator muscle, after which it is
known as the posterior interosseous nerve.

159. Motor
Muscular branches of the radial nerve:
Triceps brachii
Anconeus
Brachioradialis
Extensor carpi radialis longus
Deep branch of the radial nerve:
Extensor carpi radialis brevis
Supinator
Posterior interosseous nerve (a continuation of the deep branch after the
supinator):
Extensor digitorum
Extensor digiti minimi
Extensor carpi ulnaris
Abductor pollicis longus
Extensor pollicis brevis
Extensor pollicis longus
Extensor indicis

162. The Median nerve
is derived from the lateral and medial
cords of the Brachial plexus.
Disk herniations in the Cervical spine
(at the level of C5-C8 and T1) can
cause numbness and/or decreased
grip-strength in the hand

163. the median nerve courses with brachial artery on medial
side of arm between biceps brachii and brachialis.
At first lateral to the artery, it then crosses anteriorly to run
medial to the artery in the distal arm and into the cubital
fossa.

164. The median nerves arises from the cubital fossa and
passes between the two heads of pronator teres.
It then travels between flexor digitorum superficialis and
flexor digitorum profundus
before emerging between flexor digitorum superficialis
and flexor carpi radialis

165. The unbranched portion of the median
nerve innervates muscles of superficial
and intermediate groups of the anterior
compartment except
flexor carpi ulnaris

166. The median nerve does give off two branches as it courses through the forearm:
The anterior interosseous branch courses with the anterior interosseous artery and
innervates all the muscles of the anterior compartment of the forearm except the flexor
carpi ulnaris and the medial (ulnar) half of flexor digitorum profundus.
Its ends with its innervation of pronator quadratus.
The palmar cutaneous branch of the median nerve arises at the distal part of the
forearm. It supplies sensory innervation to the lateral aspect of the skin of the palm (but
not the digits).

167. Distribution
Arm
The median nerve has no voluntary motor or cutaneous function in the (upper)
arm. It gives vascular branches to the wall of the brachial artery. These vascular
branches carry sympathetic fibers.
Forearm
It innervates all of the flexors in the forearm except flexor carpi ulnaris and that
part of flexor digitorum profundus that supplies the medial two digits. The latter
two muscles are supplied by the ulnar nerve (specifically the Muscular branches
of ulnar nerve).
The main portion of the median nerve supplies the following muscles:
Superficial group:
Pronator teres Flexor carpi radialis Palmaris longus
Intermediate group:
Flexor digitorum superficialis muscle
The anterior interosseus branch of the median nerve supplies the following
muscles:
Deep group:
Flexor digitorum profundus (only the lateral half)
Flexor pollicis longus
Pronator quadratus

168. MEDIAN NERVE
Branches in the hand
The median nerve enters the hand through the carpal tunnel, deep to the flexor
retinaculum along with the tendons of flexor digitorum superficialis, flexor
digitorum profundus, and flexor pollicis longus.
From there it sends off several branches:
1. Recurrent branch to muscles of the thenar compartment (the recurrent branch
is also called "the million dollar nerve")[1]
2. Digital cutaneous branches to common palmar digital branch and proper
palmar digital branch of the median nerve which supply the:
a) lateral (radial) three and a half digits on the palmar side
b) index, middle and ring finger on dorsum of the hand
The median nerve supplies motor innervation to the first and second lumbrical
muscles.

169. Hand
In the hand, the median nerve supplies motor
innervation to the 1st and 2nd lumbrical
muscles.
It also supplies the muscles of the thenar
eminence by a recurrent thenar branch.
The rest of the intrinsic muscles of the hand are
supplied by the ulnar nerve.

170. The muscles of the hand supplied by the median nerve can be
remembered using the mnemonic, "LOAF" for
Lumbricals 1 & 2,
Opponens pollicis,
Abductor pollicis brevis
and Flexor pollicis brevis.

172. The median nerve innervates the skin of the palmar side of the
thumb, the
index and
middle finger,
half the ring finger, and the
nail bed of these fingers
The Opponens pollicis muscle is innervated exclusively by the Median nerve
. The inability to firmly hold an object between the index finger and thumb is a
classic sign of Median nerve pathology.

173. The lateral part of the palm is supplied by the palmar
cutaneous branch of the median nerve, which leaves
the nerve proximal to the wrist creases.
This palmar cutaneous branch travels in a separate
fascial groove adjacent to the flexor carpi radialis and
then superficial to the flexor retinaculum.
It is therefore spared in carpal tunnel syndrome.

174. ULNAR NERVE
Arm
The ulnar nerve comes from the medial cord of the brachial plexus, and descends on
the posteromedial aspect of the humerus. It goes behind the medial epicondyle,
through the cubital tunnel, at the elbow
Forearm
It enters the anterior (flexor) compartment of the forearm through the two heads of
flexor carpi ulnaris and runs alongside the ulna. There it supplies one and a half muscles
(flexor carpi ulnaris & medial half of flexor digitorum profundus).
It soon joins with the ulnar artery, and the two travel inferiorly together, deep to the
flexor carpi ulnaris muscle.
In the forearm it gives off the following branches:[2]
Muscular branches of ulnar nerve
Palmar branch of ulnar nerve
Dorsal branch of ulnar nerve

176. Hand
After it travels down the ulna, the ulnar nerve enters the palm of
the hand.
The ulnar nerve and artery pass superficial to the
flexor retinaculum, via the ulnar canal
The course of the ulnar nerve through the wrist contrasts with
that of the median nerve, which travels deep to the flexor retinaculum of the hand and
therefore through the carpal tunnel
In the hand
Ulnar nerve gives
Superficial branch of ulnar nerve
Deep branch of ulnar nerve

177. HAND ANATOMY
AND
THE WRIST

178. Carpal bones
1. scaphoid
Metacarpal bones 2. lunate
9. I 3. triquetrum
10. II 4. pisiform
11. III 5. trapezium
12. IV 6. trapezoid
13. V 7. capitate
8. hamate hook of
hamate
Phalanges
proximal 14
middle 15
distal 16

179. •flexor retinaculum (FR)
•1 scaphoid
•2 trapezium
median nerve •3 pisiform
tendons of flexor digitorum superficialis •4 hamate
tendons of flexor digitorum profundus
tendon of flexor pollicis longus
tendon of flexor carpi radialis

180. Muscles of the Hand From Superficial to Deep
The intrinsic muscles of the hand can be arranged into three groups
according to either to a region or to depth.
Regional groups of muscles are the thenar and hypothenar group.
The thenar muscles are three in number and act on the thumb.
The hypothenar group are three in number and act on the little finger.
The ramainder muscles can be arranged from superficial to deep as
shown in the diagrams below.
Once the palmar aponeurosis is removed, the first layer is made up of
the tendons of the flexor digitorum superficialis. This and the other
layers are shown below.

181. Palmar aponeurosis Lumbricals
Flexor digitorum
superficialis

182. Palmar interossei
Dorsal interossei

185. The superficial arterial arch is formed mainly from the ulnar artery and is
completed by the superficial branch of the radial. This completion is not always
present or may be extremely small.
The deep arterial arch is formed mainly by the deep branch of the radial artery and
is finished by the deep branch of the ulnar artery.

186. The dorsal venous plexus of the hand and the ensuing
cephalic (1) and basilic (2) veins drain the superficial aspects of
the hand.
The cephalic vein ends up in the axillary vein just before it
becomes the subclavian and the basilic vein joins the brachial
vein to become the axillary vein.

187. Dorsum of Hand
posterior antebrachial cutaneous skin of dorsum of wrist
skin of dorsum of thumb and
radial nerve 2 1/2 digits as far as
the distal interphalangeal joint
ulnar 1 1/2 digits and
ulnar nerve
adjacent part of dorsum of hand

188. palm of hand
sensory to skin of ulnar 1 1/2
digits
motor to muscles of
hypothenar eminence
ulnar nerve
motor to ulnar two lumbricals
motor to 7 interossei
motor to adductor pollicis
muscle
sensory to skin of palmar
aspect of thumb and 2 1/2
digits
including the skin on the dorsal
aspect
median nerve
of the distal phalanges
motor to muscles of thenar
eminence
motor to radial two lumbrical
muscles

189. abductor digiti minimi proximal phalanx of little
pisiform ulnar abducts little finger
(hypothenar muscle) finger
flexor digiti minimi flexor retinaculum proximal phalanx of little
ulnar flexes little finger
(hypothenar muscle) hook of hamate finger
opponens digiti minimi flexor retinaculum opposes little finger to
5th metacarpal ulnar
(hypothenar muscle) hook of hamate other digits
medial side of 2nd adducts index finger
palmar interosseus I medial base of index finger ulnar
metacarpal towards middle finger
lateral side of 4th adducts ring finger
interosseous II lateral base of ring finger ulnar
metacarpal towards middle finger
lateral side of 5th adducts little finger
interosseous III medial base of little finger ulnar
metacarpal towards middle finger
adjacent sides of lateral aspect of extensor abducts ring finger away
dorsal interosseous I ulnar
metacarpal bones expansion of ring finger from middle finger
adjacent sides of medial aspect of extensor abducts the middle finger
dorsal interosseous II ulnar
metacarpal bones expansion of middle finger away from its long axis
adjacent sides of lateral aspect of extensor abducts the middle finger
dorsal interosseous III ulnar
metacarpal bones expansion of middle finger away from its long axis
abducts the index finger
adjacent sides of lateral aspect of extensor
dorsal interosseous IV ulnar away from the middle
metacarpal bones expansion of index finger
finger
flex the
tendons of flexor lateral aspect of extensor metacarpophalangeal joint
lumbricals I & II median
digitorum superficialis expansion extend the interphalangeal
joints
flex the
tendons of flexor lateral aspect of extensor metacarpophalangeal joint
lumbricals III & IV ulnar
digitorum superficialis expansion extend the interphalangeal
joints

190. superficial nerves
of palm of hand
deep nerves of palm of hand dorsum of the hand

196. The Interossei dorsales of left hand.
The Interossei volares of left hand.

197. Transverse section across the wrist and digits.

203. Anatomical snuff box
The anatomical snuffbox,
or radial fossa, (in Latin Foveola radialis),
is a triangular deepening on the radial, dorsal aspect of the hand –
at the level of the carpal bones,
specifically, the scaphoid and trapezium bones forming the floor.
The name originates from the use of this surface for placing and then
sniffing powdered tobacco, or “snuff.”

205. Anatomical snuff box
The boundaries
The medial border of the snuffbox is the tendon of the extensor pollicis longus.
The lateral border tendons, of the extensor pollicis brevis and the abductor pollicis
longus.
The proximal border is formed by the styloid process of the radius
The distal border is formed by the approximate apex of the schematic snuffbox
isosceles triangle.
The floor of the snuffbox varies depending on the position of the wrist, but both
the trapezium and primarily the scaphoid can be palpated.

206. Deep to the tendons which form the borders of the anatomical snuff box lies
the radial artery,
which passes through the anatomical snuffbox on its course from the normal radial pulse
detecting area,
to the proximal space in between the first and second metacarpals to contribute
to the superficial and deep palmar arches.
The cephalic vein arises within the anatomical snuffbox,
while the dorsal cutaneous branch of the radial nerve can be palpated by stroking along
the extensor pollicis longus with the dorsal aspect of a fingernail

208. Ligaments Of The Upper Limb
The acromio-clavicular ligament joins the acromion process to the clavicle.
The coraco-clavicular ligament joins the coracoid process to the clavicle.
The coraco-acromial ligament joins the coracoid process to the acromion process.
The ligaments of the shoulder-joint are :
1. Capsular. 3. Gleno-humeral.
2. Coraco-humeral. 4. Glenoid
The ligaments of the elbow are in the form of a capsule which surrounds the joint
on all sides. They are the
(1) External lateral, (3) Anterior,
(2) Internal lateral, (4) Posterior.
The ligaments of the wrist are the
(1) Anterior, (3) Internal lateral,
(2) Posterior, (4) External lateral.
Synovial Membrane.—The pisiform, and the upper metacarpal joint of the thumb,
have each a separate synovial membrane. The other carpal and metacarpal joints
have a single synovial membrane.

215. The 5 flexor tendon zones in the hand are
Zone I consists of the profundus tendon only and is bounded proximally by
the insertion of the superficialis tendons and distally by the insertion of the
FDP tendon into the distal phalanx.
Zone II is often referred to as "Bunnell's no man's land," . Proximal to zone II,
the flexor digitorum superficialis (FDS) tendons lie superficial to the flexor
digitorum profundus (FDP) tendons.
Within zone II and at the level of the proximal third of the proximal
phalanx,
the FDS tendons split into 2 slips, collectively known as Camper chiasma.
These slips then divide around the FDP tendon and reunite on the dorsal
aspect of the FDP, inserting into the distal end of the
middle phalanx
Zone III extends from the distal edge of the carpal ligament to the proximal edge of
the A1 pulley, Within zone III, the lumbrical muscles originate from the FDP tendons.
The distal palmar crease superficially marks the termination of zone III and the
beginning of zone II.
Zone IV includes the carpal tunnel and its contents (ie, the 9 digital flexors and the
median nerve).
Zone V extends from the origin of the flexor tendons at their respective muscle
bellies to the proximal edge of the carpal tunnel.

217. Flexor tendons with attached vincula.
Membranous portion of the flexor tendon Retinacular portion of the flexor tendon
sheath sheath (pulley system).

218. Flexor Muscles of the Digits
The forearm can be divided anatomically into anterior and posterior
compartments.
The anterior compartment contains the flexor-pronator group of muscles,
most of which arise from a common flexor attachment on the medial
epicondyle of the humerus.
The 8 muscles of the anterior compartment may be divided further into 3
distinct functional groups, as follows:
(1) muscles that rotate the radius on the ulna,
(2) (2) muscles that flex the wrist, and
(3) (3) muscles that flex the digits.
The muscles that flex the digits include the flexor digitorum profundus (FDP),
flexor digitorum superficialis (FDS), and the flexor pollicis longus (FPL).

219. Digital Flexor Sheath
The digital flexor sheath is a closed synovial system consisting of both
membranous and retinacular portions.
The membranous portion comprises visceral and parietal layers that invest the
flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) tendons
in the distal aspect of the hand.
The retinacular component consists of tissue condensations arranged in
cruciform, annular, and transverse patterns that overlie the membranous, or
synovial, lining.
The digital flexor sheath has been proposed to have a 3-fold function, as follows:
(1) it facilitates smooth gliding of the tendons;
(2) the retinacular component acts as a fulcrum, adding a mechanical advantage
to flexion;
(3) it is a contained system, or bursa, with synovial fluid bathing the tendons and
aiding in their nutrition.

220. The membranous portion of the sheath appears macroscopically as
a number of cul-de-sacs, or plicae, that interdigitate between both
the tendons and the retinacular tissue condensations.
The first cul-de-sac is located approximately 10-14 mm proximal to
the distal metacarpal head and represents the point of transition
between the parietal and visceral layers of synovium.
This outpouching occurs for each separate tendon, in effect
forming 2 separate plicae.
(Note that this is true only for the middle 3 rays of the hand.
In most instances, both the first- and fifth-digit synovial layers
begin much more proximally at the level of the wrist, and are
referred to as the radial and ulnar bursa, respectively.)

221. Distally, the parietal layer of synovium forms plicae between each of the retinacular
elements of the pulley system.
The synovium ends distally, forming a final single cul-de-sac prior to the insertion of the
FDP tendon on the distal phalanx.

222. Extensor Tendon
Zones of hand.
The dorsum of the hand, wrist, and forearm are
divided into 8 anatomic zones
Zone 1 (distal interphalangeal [DIP] joint)
Zone 2 (middle phalanx)
Zone 3 (proximal interphalangeal [PIP] joint)
Zone 4 (proximal phalanx)
Zone 5 (metacarpophalangeal [MCP] joint)
Zone 6 (dorsum of hand)
Zone 7 (wrist)
Zone 8 (dorsal forearm)