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Flashcards in MSK: Week 1 Deck (126):
1

What are 7 purposes of the skeleton

- Raises us from the ground AGAINST GRAVITY
- Determines basic body SHAPE
- Transmits body WEIGHT
- Forms jointed lever system for MOVEMENT
- Protects vital structures from DAMAGE
- Houses bone marrow
- Mineral storage (ca2+ and phosphates)

Remember:
Gary Saw Will Moving Donkey Meek Mills

G - Gravity
S - Shape
W - Weight
M - Movement
D - Damage
M - Marrow
M - Mineral storage

2

How many bones are there in the body

206

3

What are long bones

Tubular shapes with hollow shaft and expanded ends for articulation with other bones

4

What are short bones

Cuboidal shaped

5

What are flat bones

Plates of bones that are needed for protection

6

What are seasmoid bones

Round, oval nodules in a tendon

7

What is a cortical structure of a bone

Cortical = Compact

Cortical parts of a bone from the outer shell (cortex) of the bone

8

What are four roles of the cortical layer of a bone

Protect organs
Support whole body weight
Provide levels for movement
Storage of calcium

9

What is the trabecular part of the bone

Trabecular = SPONGY

Trabecular parts of the bone form the medulla of the bone at the ends, proximal to the joints

10

What are Two characteristics of the trabeculated part of bones

Trabeculated
Many Holes

11

Where are osteoclasts located

In spaces called Lacunae

12

What are the two microstructures of the bone

Woven and Lamellar bone

13

Woven Bone vs Lamellar Bones

Woven vs Lamella:

Made Quickly vs Made Slowly
Disorganised vs Organised
No clear feature vs Layered
More flexible vs Less flexible
Weaker vs Stronger
More osteocytes vs Less Osteocytes

14

What is the role of the wide end of the bone

Spreads load over weak, low frictioned surface

15

What is the role of the hollow long bone

Keeps mass away from neutral axis - minimises deformation

16

Role of the trabecula part of the bone

Gives structural support while minimising mass

17

What is the role of the flat bone

Protective

18

Bone composition

50-70% minerals
20-40% organic matrix
5-10% water

19

What is the mineral part of the bone made of

Hydroxyapatite - crystalline form of calcium phosphate

20

What is the organic matrix made of

Type I collagen - 90% of all proteins present
Non-collagenous protein - 10% of all proteins

21

Describe the arrangement of collagen fibres in the extracellular matrix

The collagen molecules are arranged in 'staggered' form with mineral crystals situated in gaps between them

22

Why do we need minerals in our bones

Provides Stiffness

23

Why do we need collagen in our bones

Provides elasticity

24

Describe the origin of osteoblasts

Mesenchymal stem cells -> Progenitors ->
Adipocytes
Osteoblasts
Chondrocytes
Myoblasts
Fibroblasts

25

What cells are inter-differentiating

Adipocytes -> Osteoblasts (vice versa)

Osteoblasts -> Chondrocytes (Vice Versa)

26

What are osteoids

Unmineralised parts of the bone matrix

27

What cell produces osteoids

Osteoblasts

28

Why are osteoids needed

to form bone tissue

29

What happens to osteoids when they are mineralised

It and adjacent bone cells will develop into new bone tissue

30

How do osteoblasts mineralise the matrix

Depositing crystals with collagen fibrils into the matrix

31

What collagen do osteoblasts produce

Type I

32

What factor affects the level of activity of the enzyme alkaline phosphatase

When bones are growing or bone cells are active

33

What two other substances do osteoblasts secrete

- Non collagenous proteins
- Factors that regulate osteoclasts (RANKL)

34

Describe the origin of osteoclasts

Haematopoietic stem cells -> Determination -> Proliferation -> Differentiation -> Attachment

35

What enzyme causes proliferation

M-CSF

36

What is the role of OCG

Inhibits osteoclast production

37

What cell produces OCG

Osteoblasts

38

Define resorption

Absorption into the circulatory system of cells

39

What are four roles of osteoclasts

Resorb bone
Dissolve mineralised matrix
Breakdown collagen in bone
HIgh expression of TRAP + Cathepsin K

40

Role of TRAP

Degrades phosphoproteins in skeletal muscles

41

Role of Cathepsin K

A protein that breaks down bone and cartilage

42

Define modelling

Gross shape is altered, bone is added or take away

43

Define remodelling

All bone is altered, new bone replaces old bone

44

How does the bone enlarge during remodelling

Enlarges as cartilage grows

Cartilage is then replaced by bones

45

What are 7 reasons for bone-remodelling

- Form bone shape
- Replace woven bone with lamellar bone
- Reorientate fibrils + Trabecullae to increase mechanical strength
- Repair
- Response to load
- Obtain calcium
- Disease

46

What is the most abundant type of collagen

Type I

47

Describe the structure of type I collagen

Look in book

48

How many alpha chains are present in collagen's helix

Three

So it is called tropocollagen

49

What are collagen strands arranged into

fibrils

50

What are the collagen fibrils arranged into

Collagen Fibres

51

What is the tropocollagen made of (AA wise)

Gly-X-Y tripeptide continuously repeating

52

What is the Y of Gly-X-Y

Usually proline or hydroxyproline

53

What is the X of Gly-X-Y

Any AA

54

What is the purpose of Y in Gly-X-Y

Allows for formation of alpha helix chain

55

What holds the fibril molecules together

By covalent cross-links from lysine/hydroxylysine side-chains

56

What cell guides the formation of fibrils

Fibroblasts

57

Where do covalent cross-links take place in collagen

Between tropocollagen helices and within the triple helices themselves

58

How do cross-links form within the triple helix

Due to 2 hydroxyglycine molecules

59

What enzyme is needed to form cross-links

Lysyl Oxidase

60

What element is required by lysyl oxidase

Copper

61

How do cross-links form between tropocollagen molecules

Between three hydroxylysine molecules

Forms a structure called pyrodinoline

62

What other force is acting in collagen

Hydrogen Bonding

63

How do hydrogen bonds form in collagen

Between two hydroxyproline molecules within tropocollagen

64

What compound is needed to produce hydroxyproline

Vitamin C

65

What needs to happen to type I collagen before it is moved into the extracellular matrix to produce bone

Needs to be processed

66

What happens during processing of tropocollagen

N-terminal peptide (P1NP) and C-terminal peptide (P1CP) need to be removed

67

How can we measure bone formation rate

Checking P1NP + P1CP levels in the blood (usually P1NP) shows us collagen formation rate

68

Why is P1NP the main way we check for bone formation rate

It is more stable than P1CP

69

How do we break down tropocollagen

Cleave N and C telopeptides

70

What two enzymes will go on to break down the rest of the tropocollagen molecule

Colaginase
Cathepsin K

71

Where can NTx (N-terminal telopeptides) be measured

Urine

72

Where can CTx be measured (C-terminal telopeptides)

In the blood

73

Which is a better marker and why (NTx or CTx)

CTx because it is found in the blood

74

When should CTx be measured

During fasting as it increases after a meal

75

What two reasons are there for collagen breakdown

Pathological
Normal repair and replacement

76

What are FACIT collagens

IX, XII, XIV

77

What are Microfibrillar collagens

VI

78

What are short-chain collagen

X + VIII

79

What are basement membrane collagen

IV

80

How can we measure bone formation

P1CP/P1NP

81

How can we measure bone destruction

NTx/CTx

82

What is the action of the iliopsoas muscle

Flexes lower limb at hip joint and assists in lateral rotation of the hip joint

83

What is the iliopsoas innervated by

Psoas major: L1-L3 anterior rami

Iliacus: Femoral Nerve

84

What muscles are the quadriceps femoris made of

Three vastus muscles

A rectus muscle

85

What two structures pass through the adductor canal

Superficial femoral artery
Popliteal vein

86

What does the popliteal vein form as it passes through the adductor canal

Superficial femoral vein

87

What part of the body is the main reservoir for Ca2+

Skeleton = 1200g

88

What are three roles of Ca2+

- Normal Blood Clotting
- Muscle Contractility
- Nerve Function
- Cell signalling

89

What are active metabolites of calcium

Free-floating Ca2+

90

What are inactive metabolites of calcium

Protein-bound calcium in the blood

91

What protein do calcium ions bind to and circulate in the blood with

Albumin

92

How does pH affect albumin binding to calcium

Increased pH = strong binding to calcium

Decreased pH = Weak binding to calcium

93

How does high pH affect ionised calcium and inactive ion conc.

Decreased ionised calcium ions
Increased inactive ion conc.

94

How is calcium re-absorbed at the intestines

Absorped by intestinal epithelial cells + bound to calbindin

Ca2+ is transferred to the opposite side of the cell without entering the cytosol

95

How is calcium re-absorption controlled at the kidneys

PTH controls the amount of Ca2+ absorped in the intestines

Reduces amount of PO43- reabsorped

96

Why do we need to decrease phosphate ions in the body to increase ionised calcium ion levels

Because phosphate will combine with calcium to form an insoluble salt

An increase phosphate ions conc. reduces amount of calcium ions in the ECF

97

What is the major source of calcium in diet

Dairy Products

98

What are three minor sources of calcium in the diet

Vegetables
Cereals
Oily Fish

99

How much of calcium taken in by our diet is absorbed into the GI tract

30%

100

Where does active absorption of calcium ion take place

Jejunum
Duodenum

101

Where does passive absorption of calcium ion take place

Ileum + Colon

102

What compound mediates absorption of calcium ions in the gut

Calcitriol

103

How does decreased intake of calcium in our diet affect calcitriol levels

Increases them

104

Why does calcitriol increase when calcium intake decreases

To increase the fraction of calcium re-absorped

105

Where can we get 'rapid release' of calcium

From exchangeable calcium on bony surface + decreased excretion at kidneys

106

Where can we get 'slow release' of calcium

From osteoclasts during bone resorption and increased reabsorption at intestines

107

What two factors affect how much calcium is filtered at the glomerulus

GFR
The ultrafiltrable calcium (ionised or in protein complex)

108

Describe calcium/phosphate ion re-absorption along the kidney nephron

Look in book

109

Describe vit D synthesis pathway

7-dehydrocholsterol -> Vit D -> 25(-OH)D
-> 1,25(OH)2D
-> 24,25(OH)2D

1,25(OH)2D -> Intestines or bone

24,25(OH)2D -> Calcitroic Acid

110

What is calcitriol

Active form of vit D

111

Name three roles of phosphates

Intracellular signalling
Activation of protein kinase
Cell membrane component
Post-translational protein modification (Kinases and phosphatases)

112

Role of kinases and phosphatases

Kinases - Add phosphate
Phosphatases - Remove phosphate

113

What are normal levels of phosphates in the body

500 to 800 g

114

What are normal serum levels of the phosphates in the body

0.8 to 1.5 mmol/L

115

What would be the result of excess hydroxyapatite

Deposition in tissues other than bone

116

What would be the result of a lack of hydroxyapatite

Poor bone mineralisation

117

Four dietary sources of phosphates

- Animal
- Dairy
- Soy
- Seeds + Nuts

118

Where does gut absorption of phosphates take place

Small intestines via passive diffusion

When conc. of phosphates decreases this becomes active via NA co-transporters

119

Where is more unbound phosphates re-absorbed

80% at the PCT via Na-cotransporters
10% at the DCT

120

What cell produces FGF-23

Osteocytes

121

What does the osteocyte produce FGF-23 in response to

Increased phosphate levels
PTH
1,25(OH)2D
Dietary PO43- loading

122

Describe FGF-23 action

Decreases expression of NA transporter in the renal tubules

Decreases 1-alpha hydroxylation of vitamin D (so less phosphate is reabsorbed at the gut)

123

What is Klotha

Transmembrane protein

124

What is Klotha needed for

Necessary for the function of FGF-23 as it acts as a receptor.

125

What are the borders that make up the popliteal fossa

Superomedial Border (semimembranous)

Superolateral border (Biceps Femoris)

Inferomedial Border (Medial head of the gastrocnemius)

Inferolateral Border (Lateral head of the gastrocnemius and plantaris)

126

What structures can I find in the popliteal fossa

Tibial nerve
Common fibular nerve
Popliteal nerve
Popliteal artery