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Flashcards in MSK Session 3 Deck (170):
0

What is the origin of the musculoskeletal system?

Somites and lateral plate mesoderm

1

How are somites formed?

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

2

How are somites further organised after formation?

Into bone, muscle and skin precursors within the somite

3

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

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

4

Where do the limb buds appear?

On the ventral-lateral body wall

5

Why is the UL always more developed than the LL?

It appears ~2 days before

6

What is the structure of a limb bud?

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

7

Describe the development of limb buds.

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

8

What is the entire embryo covered by?

Endoderm

9

What does the limb bud need to grow?

Thickening of endoderm at apex

10

What is the function of the apical ectodermal ridge?

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

11

What is the final stage of limb development?

Appearance of paddles

12

What is the function of the dorsal/ventral ectoderm?

Exert dorsalising and ventralising influences over mesenchyme core

13

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

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

14

What are the three degrees of symmetry in the embryo?

Side to side
Front and back
Top and bottom

15

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

From the 1st digit to 5th

16

What makes up the dorsal aspect of the developing limb?

Back of hand and top of foot

17

What makes up the ventral aspect of the developing limb?

Palm of hand and sole of foot

18

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

Base of limb to tips of digits

19

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

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

20

What happens to the proximal mesenchyme as the limb elongates?

Stops receiving signals from AER so it differentiates into constituent tissues

21

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

Determines the anterior-posterior axis

22

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

Ensures they are mirror images of each other

23

Where is the ZPA located?

Posterior base of the limb bud

24

What controls patterning as well as maintaining the AER?

ZPA

25

What are the controllers of axial specification?

Anterio-posterio = ZPA
Proximal-distal = AER
Dorsal-ventral = ectoderm

26

How are hands and feet formed?

Limb buds flatten and flare into digital rays

27

What are digital rays?

Mesenchyme condensations w/in plates

28

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

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

29

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

To allow for their elongation

30

What can be seen postnatally between the fingers?

Remnants of interdigital spaces

31

What is amelia?

Complete absence of a limb

32

What is meromelia?

Partial absence of one or more limb structures

33

What is phocomelia?

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

34

What can cause phocomelia?

Thalidomide exposure

35

What is polydactlyly?

Genetic recessive trait causing extra digits

36

What is syndactyly?

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

37

Which limb is more affected by limb defects?

UL

38

What joins the three discrete bones in the hip?

Triadiate cartilage

39

How do myogenic precursors arrive in the limbs?

Migrate from outside limb buds in somites into limbs

40

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

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

41

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

Ventral = flexor
Dorsal = extensor

42

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

Take innervation from somite linked w/spinal cord with them

43

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

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

44

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

Rotation of limbs which affects LL much more

45

How do the limbs rotate after ventral extension?

UL = laterally
LL = medially

46

How doe the limbs compare before and after rotation?

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

47

Why is rotation of the LL not as fixed?

It is more mobile

48

How do the thumb and big toe rotate?

Thumb = laterally
Big toe = medially

49

What are maintained during rotation?

Ventral axial lines

50

What lies on the pre-axial line?

Thumb and big toe

51

What lies on the post-axial line?

Little finger and toe

52

Which spine segments do the upper limb buds appear opposite?

Caudal cervical

53

Which spinal segments do the lower limb buds appear opposite?

Lumbar and sacral

54

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

Needed along with AER for development

55

What is a myotome/dermatome?

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

56

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

Distorted due to loss of symmetry and limb bud rotation

57

What are the ventral axial lines?

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

58

How do muscles become innervated by the brachial plexus?

Muscles are compartmentalised and nerves grow into common muscle masses

59

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

Regroup to form lateral and medial cords to supply the flexors

60

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

Regroup to form posterior cord to supply extensors

61

What forms the superior border of the cubital fossa?

Imaginary line between lateral and medial elicondyles

62

What forms the medial border of the cubital fossa?

Lateral border of the pronator teres

63

What forms the lateral border of the cubital fossa?

Medial border of brachioradialis

64

What is the cubital fossa?

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

65

What forms the floor of ten cubital fossa?

Proximally = brachialis
Distally = supinator

66

What forms the roof of the cubital fossa?

Skin and fascia reinforced by the bicipital aponeurosis

67

What structure does the median cubital vein run through?

Bicipital aponeurosis

68

What are the contents of the cubital fossa?

Radial nerve
Biceps tendon
Brachial artery
Median nerve

69

Where is the radial nerve located in the cubital fossa?

Deep b/w brachioradialis and brachialis

70

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

Deep and superficial branches

71

How is the biceps tendon located in the cubital fossa?

Runs through attaching to radial tuberosity

72

What is the function of the brachial artery?

Supply oxygenated blood to the forearm

73

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

Bifurcates into radial and ulnar arteries

74

Where does the median nerve exit the cubital fossa?

B/w two heads of the pronator teres

75

What does the median nerve innervate the majority of?

Flexor muscles in the forearm

76

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

Closer to the medial side

77

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

Basilic and cephalic veins

78

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

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

79

Where is the brachial pulse felt?

Immediately medial to biceps tendon in cubital fossa

80

Where do you listen for Korotkoff sounds?

Brachial pulse site in cubital fossa

81

What is the function of the intrinsic back muscles?

Hold spine erect
Responsible for posture

82

What are the three groups of extrinsic back muscles?

Superficial
Posterior axio-appendicular
Intermediate

83

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

Attach axial skeleton to appendicular skeleton

84

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

Trapezius
Latissimus dorsi

85

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

Levator scapulae
Rhomboids

86

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

Deltoid
Teres major
4 rotator cuff muscles

87

What are the main actions of the trapezius?

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

88

What innervates the trapezius?

Accessory nerve

89

How is the accessory nerve tested?

Shrug shoulders against resistance

90

What is the main action of the latissimus dorsi?

Adduct arms
Extend arms at shoulder joint
Medial rotation

91

What innervates the latissimus dorsi?

Thoraco-dorsal nerve

92

Where does the thoraco-dorsal nerve originate from?

Posterior cord of brachial plexus

93

What are the main actions of the deltoid?

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

94

What innervates the deltoid?

Axillary nerve

95

What are the main actions of the levator scapulae?

Elevate scapula
Rotate scapula by depressing glenoid cavity

96

What innervates the levator scapulae?

Dorsal scapular and cranial nerves

97

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

Retract scapula
Rotate scapula by depressing glenod cavity

98

What innervates the rhomboids?

Dorsal scapular nerve

99

Where does the dorsal scapular nerve originate?

C5 root of brachial plexus

100

What are the main actions of Teres major?

Addicts arm
Medial rotation

101

What innervates teres major?

Lower subscapular nerve

102

How is rotation of the scapula achieved?

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

103

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

Otherwise acromion obstructs humerus

104

What deepens the glenoid cavity?

Glenoid labrum w/fibrocartilage rim

105

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

Shallow glenoid cavity
Disproportion of articular surfaces
Multiplanar movements
Lax capsule

106

How is stability of the glenohumeral joint achieved?

Muscles of rotator cuff
Surrounding muscles
Ligaments
Capsule

107

What is the capsule of the glenohumeral joint attached to?

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

108

What does the capsule of the glenohumeral joint bridge?

Intertubercular groove

109

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

Small anterior opening of the glenohumeral capsule

110

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

Axillary nerve and post circumflex artery are vulnerable here

111

What are the three intracapsular ligaments in the glenohumeral joint?

Superior, middle and inferior glenohumeral ligaments

112

What are the intracapsular ligaments of the GH joint?

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

113

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

Anteriorly

114

What are the three extracapsular ligaments of the glenohumeral joint?

Coracoacromial
Coracohumeral
Transverse humerus

115

Which is the most important extracapsular ligament?

Coracoacromial

116

Where is the coracoacromial ligament located?

B/w acromion and coracoid process

117

Where is the coracohumeral ligament located?

Base of coracoid process to anterior greater tubercle

118

What is the function of the transverse humeral ligament?

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

119

What forms the coraco acromial arch?

Coracoacromial ligament
Acromion
Coracoid process

120

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

Strong osseoligamentous structure overlies humeral head

121

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

Fracture of humeral head

122

What are the two bursae found in the glenohumeral joint?

Subscapular
Sub acromial

123

What is the function of the subscapular bursa?

Facilitate movement of the tendon of subscapularis muscle over scapula

124

What does the subscapular bursa communicate with?

Joint cavity

125

What does the subacromial bursa facilitate?

Movement of supraspinatus tendon under the CA
Movement of deltoid muscle over shoulder joint capsule and greater tubercle of humerus

126

What does inflammation of the subacromial bursa cause?

Painful arc syndrome

127

What is the rotator cuff?

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

128

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

Rotator cuff

129

Which four muscles make up the rotator cuff?

Supraspinatus
Infraspinatus
Teres minor
Subscapularis

130

Which three rotator cuff muscles attach to the greater tubercle?

Supraspinatus
Infraspinatus
Teres minor

131

What is subscapularis attached to on the humerus?

Lesser tubercle

132

How is the cuff of the rotator cuff formed?

Tendons of the muscles blend together

133

What part of the rotator cuff strengthens the GH joint?

Tendinous cuff fusing with the capsule

134

What holds the humeral head close to the glenoid cavity?

Tone in rotator cuff muscles

135

What is the main action of supraspinatus?

Initiation and first 15 degrees of abduction

136

What innervates supraspinatus?

Suprascapular nerve

137

What is the main action of infraspinatus?

Lateral rotation of the arm

138

What innervates infraspinatus?

Suprascapular nerve

139

What is the main action of teres minor?

Lateral rotation of the arm
Weak adduction

140

What innervates teres minor?

Axillary nerve

141

What is the main action of subscapularis?

Medial rotation of the arm

142

What innervates subscapularis?

Upper and lower subscapular nerves

143

Which muscles are used in flexion of the GH joint?

Pec. major
Anterior fibres of deltoid
Corachobrachialis
Biceps brachii

144

Which muscles are used in extension of the GH joint?

Posterior fibres of deltoid
Latissimus dorsi
Teres major

145

Which muscles are used for abduction of the GH joint?

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

146

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

Rotation of scapula

147

Which muscles are used in adduction of the GH joint?

Pec. major
Latissimus dorsi
Teres major

148

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

Subscapularis
Teres major
Pec. major
Latissimus dorsi

149

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

Infraspinatus
Teres minor

150

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

Flexion

151

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

Pronator teres
Flexor carpi radialis
Palmaris longus
Flexor carpi ulnaris

152

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

Flexor digitorum superficialis

153

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

Flexor pollicus longus
Flexor digitorum profundus
Pronator quadratus

154

What is the main action of pronator teres?

Pronation and flexion of the forearm at the elbow

155

What innervates pronator teres?

Median nerve

156

What is the main action of flexor carpi radialis?

Flex and abduct hand at wrist

157

What innervates flexor carpi radialis?

Median nerve

158

What is the main action of palmaris longus?

Flex hand at wrist
Tense palmar aponeuorsis

159

What innervates palmaris longus?

Median nerve

160

What is the main action of flexor carpi ulnaris?

Flexes and addicts hand at wrist

161

What innervates flexor carpi ulnaris?

Ulnar nerve

162

What is the main action of flexor digitorum superficialis?

Flex middle 4 phalanges at proximal interphalangeal joints
Flex proximal phalanges at metacarpophalangeal joints

163

What innervates flexor digitorum superficialis?

Median nerve

164

What is the main action of flexor digitorum profundus?

Flex distal 2-5 digits at distal interphalangeal joints

165

What innervates flexor digitorum profundus?

Ulnar nerve

166

What is the main action of flexor pollcis longus?

Flex phalanges of first digit

167

What innervates flexor pollicis longus?

Anterior interosseous nerve from median nerve

168

What is the main action of pronator quadratus?

Promate forearm
Deep fibres bind radius and ulna together

169

What innervates pronator quadratus?

Anterior interosseous nerve from median nerve