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Semester 2 > MSK Session 3 > Flashcards

MSK Session 3 Flashcards

0
Q

How are somites formed?

A

Paraxial mesoderm aggregates into pairs of blocks either side of the neural tube

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1
Q

What is the origin of the musculoskeletal system?

A

Somites and lateral plate mesoderm

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2
Q

How are somites further organised after formation?

A

Into bone, muscle and skin precursors within the somite

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3
Q

Why does development of the MSK system not take place until relatively late, in the fourth week of development?

A

It is not necessary for the developing embryo like the CVS or NS

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4
Q

Where do the limb buds appear?

A

On the ventral-lateral body wall

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5
Q

Why is the UL always more developed than the LL?

A

It appears ~2 days before

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6
Q

What is the structure of a limb bud?

A

Core of proliferating mesenchymal cells which are similar to CT cells
Proliferate at a greater rate than the surrounding cells which form the bud

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7
Q

Describe the development of limb buds.

A

Somatic layer of lateral plate mesoderm
Activation of mesenchyme w/in lateral mesoderm layer
Flexible mesenchyme core proliferates to elongate limb bud
Apical ectodermal ridge regulates elongation

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8
Q

What is the entire embryo covered by?

A

Endoderm

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9
Q

What does the limb bud need to grow?

A

Thickening of endoderm at apex

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10
Q

What is the function of the apical ectodermal ridge?

A

Orchestrate proximal to distal limb development
Ensure limb develops to required length
Regression for proper digit growth
Marks dorsal-ventral limb boundary

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11
Q

What is the final stage of limb development?

A

Appearance of paddles

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12
Q

What is the function of the dorsal/ventral ectoderm?

A

Exert dorsalising and ventralising influences over mesenchyme core

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13
Q

What are the corresponding postnatal axes to the embryonic axes of limb development?

A 
Anterior (head) = superior
Dorsal = posterior
Proximal = proximal
Posterior (tail) = inferior
Ventral (belly) = anterior
Distal = distal
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14
Q

What are the three degrees of symmetry in the embryo?

A

Side to side
Front and back
Top and bottom

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15
Q

Where is the anrterio-posterio axis of the developing limb?

A

From the 1st digit to 5th

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16
Q

What makes up the dorsal aspect of the developing limb?

A

Back of hand and top of foot

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17
Q

What makes up the ventral aspect of the developing limb?

A

Palm of hand and sole of foot

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18
Q

Where is the proximo-distal axis of the developing limb?

A

Base of limb to tips of digits

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19
Q

What is the function of the AER as the limb elongates?

A

Secretes signalling molecules to the underlying mesenchymal cells to prevent their differentiation and continue proliferation

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20
Q

What happens to the proximal mesenchyme as the limb elongates?

A

Stops receiving signals from AER so it differentiates into constituent tissues

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21
Q

How does the zone of polarising activity generate asymmetry in the limbs?

A

Determines the anterior-posterior axis

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22
Q

What effect does the ZPA have on the hands and feet?

A

Ensures they are mirror images of each other

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23
Q

Where is the ZPA located?

A

Posterior base of the limb bud

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24
Q

What controls patterning as well as maintaining the AER?

A

ZPA

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25
Q

What are the controllers of axial specification?

A 
Anterio-posterio = ZPA
Proximal-distal = AER
Dorsal-ventral = ectoderm
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26
Q

How are hands and feet formed?

A

Limb buds flatten and flare into digital rays

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27
Q

What are digital rays?

A

Mesenchyme condensations w/in plates

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28
Q

Describe the formation and subsequent sculpture of hand and foot plates.

A

Flattening and flaring of limb buds –> digital rays form –> AER regresses so only on apexes of digital rays –> interdigital spaces progressively sculpted by programmed cell death

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29
Q

Why is the AER only maintained at the tips of the digital rays?

A

To allow for their elongation

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30
Q

What can be seen postnatally between the fingers?

A

Remnants of interdigital spaces

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31
Q

What is amelia?

A

Complete absence of a limb

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32
Q

What is meromelia?

A

Partial absence of one or more limb structures

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33
Q

What is phocomelia?

A

Hands or feet close to trunk due to interference w/AER

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34
Q

What can cause phocomelia?

A

Thalidomide exposure

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35
Q

What is polydactlyly?

A

Genetic recessive trait causing extra digits

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36
Q

What is syndactyly?

A

Error in interdigital space formation causing fusion of digits by CT or bone

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37
Q

Which limb is more affected by limb defects?

A

UL

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38
Q

What joins the three discrete bones in the hip?

A

Triadiate cartilage

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39
Q

How do myogenic precursors arrive in the limbs?

A

Migrate from outside limb buds in somites into limbs

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40
Q

What happens to the myogenic precursors after they have migrated into the limb bud?

A

Coalesce into 2 common muscle masses either side of newly formed central skeletal elements

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41
Q

What do the two common muscle masses formed by myogenic precursors give rise to?

A 
Ventral = flexor
Dorsal = extensor
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42
Q

How do individual muscles email innervated once they have split from the common masses?

A

Take innervation from somite linked w/spinal cord with them

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43
Q

How do the flexor and extensor compartments compare in the UL and LL?

A

UL: flexor = anterior, extensor = posterior
LL: flexor = posterior, extensor = anterior

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44
Q

Why do the upper and lower limb have opposite arrangements of flexor and extensor compartments?

A

Rotation of limbs which affects LL much more

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45
Q

How do the limbs rotate after ventral extension?

A 
UL = laterally
LL = medially
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46
Q

How doe the limbs compare before and after rotation?

A 
Before = thumbs up, elbows out, soles facing each other, knees out
After = thumbs out, elbows down, soles down, knees up
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47
Q

Why is rotation of the LL not as fixed?

A

It is more mobile

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48
Q

How do the thumb and big toe rotate?

A

Thumb = laterally

Big toe = medially

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49
Q

What are maintained during rotation?

A

Ventral axial lines

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50
Q

What lies on the pre-axial line?

A

Thumb and big toe

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51
Q

What lies on the post-axial line?

A

Little finger and toe

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52
Q

Which spine segments do the upper limb buds appear opposite?

A

Caudal cervical

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53
Q

Which spinal segments do the lower limb buds appear opposite?

A

Lumbar and sacral

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54
Q

Why do spinal nerves enter the limb bud early in its development?

A

Needed along with AER for development

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55
Q

What is a myotome/dermatome?

A

Strip of skin/muscle-group of muscles supplied by a single nerve which can be examines clinically

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56
Q

Why is the regular organisation of dermatomes and myotomes seen in the embryo not seen later on in development?

A

Distorted due to loss of symmetry and limb bud rotation

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57
Q

What are the ventral axial lines?

A

Mid axillary lines that spilt the arm in half along the longitudinal axis

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58
Q

How do muscles become innervated by the brachial plexus?

A

Muscles are compartmentalised and nerves grow into common muscle masses

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59
Q

What happens to all anterior divisions of the brachial plexus that innervate the flexors?

A

Regroup to form lateral and medial cords to supply the flexors

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60
Q

What happens to the posterior divisions of the brachial plexus that innervate the posterior components?

A

Regroup to form posterior cord to supply extensors

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61
Q

What forms the superior border of the cubital fossa?

A

Imaginary line between lateral and medial elicondyles

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62
Q

What forms the medial border of the cubital fossa?

A

Lateral border of the pronator teres

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63
Q

What forms the lateral border of the cubital fossa?

A

Medial border of brachioradialis

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64
Q

What is the cubital fossa?

A

Depression on the anterior surface of the elbow joint that marks the area of transition between the anatomical arm and forearm

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65
Q

What forms the floor of ten cubital fossa?

A 
Proximally = brachialis
Distally = supinator
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66
Q

What forms the roof of the cubital fossa?

A

Skin and fascia reinforced by the bicipital aponeurosis

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67
Q

What structure does the median cubital vein run through?

A

Bicipital aponeurosis

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68
Q

What are the contents of the cubital fossa?

A

Radial nerve
Biceps tendon
Brachial artery
Median nerve

69
Q

Where is the radial nerve located in the cubital fossa?

A

Deep b/w brachioradialis and brachialis

70
Q

What does the radial nerve divide into in the cubital fossa?

A

Deep and superficial branches

71
Q

How is the biceps tendon located in the cubital fossa?

A

Runs through attaching to radial tuberosity

72
Q

What is the function of the brachial artery?

A

Supply oxygenated blood to the forearm

73
Q

What happens to the brachial artery at the alex of the cubital fossa?

A

Bifurcates into radial and ulnar arteries

74
Q

Where does the median nerve exit the cubital fossa?

A

B/w two heads of the pronator teres

75
Q

What does the median nerve innervate the majority of?

A

Flexor muscles in the forearm

76
Q

Where are the tendon, artery and nerve located in the cubital fossa?

A

Closer to the medial side

77
Q

What does the median cubital vein join in the cubital fossa?

A

Basilic and cephalic veins

78
Q

Why is the medial cubital vein a good site for venepuncture?

A

It’s superficial location makes it clearly visible when a tourniquet is applied

79
Q

Where is the brachial pulse felt?

A

Immediately medial to biceps tendon in cubital fossa

80
Q

Where do you listen for Korotkoff sounds?

A

Brachial pulse site in cubital fossa

81
Q

What is the function of the intrinsic back muscles?

A

Hold spine erect

Responsible for posture

82
Q

What are the three groups of extrinsic back muscles?

A

Superficial
Posterior axio-appendicular
Intermediate

83
Q

What is the function of the posterior axio-appendicular muscles?

A

Attach axial skeleton to appendicular skeleton

84
Q

Which muscles make up the superficial group of the posterior axio-appendicular-appendicular back muscles?

A

Trapezius

Latissimus dorsi

85
Q

Which muscles make up the deep group of posterior axio-appendicular back muscles?

A

Levator scapulae

Rhomboids

86
Q

Which muscles make up the scapulo-humeral group of the posterior axio-appendicular back muscles?

A

Deltoid
Teres major
4 rotator cuff muscles

87
Q

What are the main actions of the trapezius?

A

Superior part: elevation of clavicle
Middle part: retraction of scapula
Inferior part: depression of scapula

88
Q

What innervates the trapezius?

A

Accessory nerve

89
Q

How is the accessory nerve tested?

A

Shrug shoulders against resistance

90
Q

What is the main action of the latissimus dorsi?

A

Adduct arms
Extend arms at shoulder joint
Medial rotation

91
Q

What innervates the latissimus dorsi?

A

Thoraco-dorsal nerve

92
Q

Where does the thoraco-dorsal nerve originate from?

A

Posterior cord of brachial plexus

93
Q

What are the main actions of the deltoid?

A

Anterior fibres = flexion
Middle fibres = abduction from 15-90 degrees
Posterior fibres = extension

94
Q

What innervates the deltoid?

A

Axillary nerve

95
Q

What are the main actions of the levator scapulae?

A

Elevate scapula

Rotate scapula by depressing glenoid cavity

96
Q

What innervates the levator scapulae?

A

Dorsal scapular and cranial nerves

97
Q

What are the main actions of the Rhomboids major and minor?

A

Retract scapula

Rotate scapula by depressing glenod cavity

98
Q

What innervates the rhomboids?

A

Dorsal scapular nerve

99
Q

Where does the dorsal scapular nerve originate?

A

C5 root of brachial plexus

100
Q

What are the main actions of Teres major?

A

Addicts arm

Medial rotation

101
Q

What innervates teres major?

A

Lower subscapular nerve

102
Q

How is rotation of the scapula achieved?

A

Superior and inferior parts of trapezius act together elevating GC
Serratus anterior aids upwards rotation
Arm abducted above horizontal

103
Q

Why does the whole unit have to move in the glenohumeral joint to facilitate rotation of the scapula?

A

Otherwise acromion obstructs humerus

104
Q

What deepens the glenoid cavity?

A

Glenoid labrum w/fibrocartilage rim

105
Q

What causes the glenohumeral joint to be the most mobile but least stable?

A

Shallow glenoid cavity
Disproportion of articular surfaces
Multiplanar movements
Lax capsule

106
Q

How is stability of the glenohumeral joint achieved?

A

Muscles of rotator cuff
Surrounding muscles
Ligaments
Capsule

107
Q

What is the capsule of the glenohumeral joint attached to?

A

Glenoid labrum
Margins of glenoid cavity of scapula
Anatomical neck of humerus
Medially to surgical neck

108
Q

What does the capsule of the glenohumeral joint bridge?

A

Intertubercular groove

109
Q

Where does the shoulder joint synovium communicate with the subscapular bursa?

A

Small anterior opening of the glenohumeral capsule

110
Q

Why are intramuscular injections into deltoid given higher than the surgical neck?

A

Axillary nerve and post circumflex artery are vulnerable here

111
Q

What are the three intracapsular ligaments in the glenohumeral joint?

A

Superior, middle and inferior glenohumeral ligaments

112
Q

What are the intracapsular ligaments of the GH joint?

A

3 fibrous bands part of the fibrous capsule b/w glenoid labrum and humerus

113
Q

In which direction do the intracapsular ligaments reinforce the GH joint?

A

Anteriorly

114
Q

What are the three extracapsular ligaments of the glenohumeral joint?

A

Coracoacromial
Coracohumeral
Transverse humerus

115
Q

Which is the most important extracapsular ligament?

A

Coracoacromial

116
Q

Where is the coracoacromial ligament located?

A

B/w acromion and coracoid process

117
Q

Where is the coracohumeral ligament located?

A

Base of coracoid process to anterior greater tubercle

118
Q

What is the function of the transverse humeral ligament?

A

Holds tendon of long head of biceps in place during shoulder movement

119
Q

What forms the coraco acromial arch?

A

Coracoacromial ligament
Acromion
Coracoid process

120
Q

Why does the coraco acromial arch prevent upper displacement of the humeral head?

A

Strong osseoligamentous structure overlies humeral head

121
Q

What will happen before dislocation of the glenohumeral joint due to the coraco acromial arch?

A

Fracture of humeral head

122
Q

What are the two bursae found in the glenohumeral joint?

A

Subscapular

Sub acromial

123
Q

What is the function of the subscapular bursa?

A

Facilitate movement of the tendon of subscapularis muscle over scapula

124
Q

What does the subscapular bursa communicate with?

A

Joint cavity

125
Q

What does the subacromial bursa facilitate?

A

Movement of supraspinatus tendon under the CA

Movement of deltoid muscle over shoulder joint capsule and greater tubercle of humerus

126
Q

What does inflammation of the subacromial bursa cause?

A

Painful arc syndrome

127
Q

What is the rotator cuff?

A

Collective name given to the 4 short muscles closely associated with the glenohumeral joint

128
Q

What is the most important factor in the stability of the glenohumeral joint?

A

Rotator cuff

129
Q

Which four muscles make up the rotator cuff?

A

Supraspinatus
Infraspinatus
Teres minor
Subscapularis

130
Q

Which three rotator cuff muscles attach to the greater tubercle?

A

Supraspinatus
Infraspinatus
Teres minor

131
Q

What is subscapularis attached to on the humerus?

A

Lesser tubercle

132
Q

How is the cuff of the rotator cuff formed?

A

Tendons of the muscles blend together

133
Q

What part of the rotator cuff strengthens the GH joint?

A

Tendinous cuff fusing with the capsule

134
Q

What holds the humeral head close to the glenoid cavity?

A

Tone in rotator cuff muscles

135
Q

What is the main action of supraspinatus?

A

Initiation and first 15 degrees of abduction

136
Q

What innervates supraspinatus?

A

Suprascapular nerve

137
Q

What is the main action of infraspinatus?

A

Lateral rotation of the arm

138
Q

What innervates infraspinatus?

A

Suprascapular nerve

139
Q

What is the main action of teres minor?

A

Lateral rotation of the arm

Weak adduction

140
Q

What innervates teres minor?

A

Axillary nerve

141
Q

What is the main action of subscapularis?

A

Medial rotation of the arm

142
Q

What innervates subscapularis?

A

Upper and lower subscapular nerves

143
Q

Which muscles are used in flexion of the GH joint?

A

Pec. major
Anterior fibres of deltoid
Corachobrachialis
Biceps brachii

144
Q

Which muscles are used in extension of the GH joint?

A

Posterior fibres of deltoid
Latissimus dorsi
Teres major

145
Q

Which muscles are used for abduction of the GH joint?

A

0-20 degrees = supraspinatus
20-90 degrees = central deltoid fibres
>90 degrees = trapezius, serratus anterior

146
Q

What must happen for adduction of the GH joint above 90 degrees?

A

Rotation of scapula

147
Q

Which muscles are used in adduction of the GH joint?

A

Pec. major
Latissimus dorsi
Teres major

148
Q

Which muscles are used in medial rotation of the GH joint?

A

Subscapularis
Teres major
Pec. major
Latissimus dorsi

149
Q

Which muscles are used for lateral rotation of the GH joint?

A

Infraspinatus

Teres minor

150
Q

What is the general function of muscles in the anterior forearm?

151
Q

What are the muscles of the first layer of the anterior forearm?

A

Pronator teres
Flexor carpi radialis
Palmaris longus
Flexor carpi ulnaris

152
Q

What are the muscles of the second layer of the anterior forearm?

A

Flexor digitorum superficialis

153
Q

What are the muscles of the third layer of the anterior forearm?

A

Flexor pollicus longus
Flexor digitorum profundus
Pronator quadratus

154
Q

What is the main action of pronator teres?

A

Pronation and flexion of the forearm at the elbow

155
Q

What innervates pronator teres?

A

Median nerve

156
Q

What is the main action of flexor carpi radialis?

A

Flex and abduct hand at wrist

157
Q

What innervates flexor carpi radialis?

A

Median nerve

158
Q

What is the main action of palmaris longus?

A

Flex hand at wrist

Tense palmar aponeuorsis

159
Q

What innervates palmaris longus?

A

Median nerve

160
Q

What is the main action of flexor carpi ulnaris?

A

Flexes and addicts hand at wrist

161
Q

What innervates flexor carpi ulnaris?

A

Ulnar nerve

162
Q

What is the main action of flexor digitorum superficialis?

A

Flex middle 4 phalanges at proximal interphalangeal joints

Flex proximal phalanges at metacarpophalangeal joints

163
Q

What innervates flexor digitorum superficialis?

A

Median nerve

164
Q

What is the main action of flexor digitorum profundus?

A

Flex distal 2-5 digits at distal interphalangeal joints

165
Q

What innervates flexor digitorum profundus?

A

Ulnar nerve

166
Q

What is the main action of flexor pollcis longus?

A

Flex phalanges of first digit

167
Q

What innervates flexor pollicis longus?

A

Anterior interosseous nerve from median nerve

168
Q

What is the main action of pronator quadratus?

A

Promate forearm

Deep fibres bind radius and ulna together

169
Q

What innervates pronator quadratus?

A

Anterior interosseous nerve from median nerve

Semester 2 (45 decks)

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