MSK: Week 1 Flashcards
1
Q
What are 7 purposes of the skeleton
A
- 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
Q
How many bones are there in the body
A
206
3
Q
What are long bones
A
Tubular shapes with hollow shaft and expanded ends for articulation with other bones
4
Q
What are short bones
A
Cuboidal shaped
5
Q
What are flat bones
A
Plates of bones that are needed for protection
6
Q
What are seasmoid bones
A
Round, oval nodules in a tendon
7
Q
What is a cortical structure of a bone
A
Cortical = Compact
Cortical parts of a bone from the outer shell (cortex) of the bone
8
Q
What are four roles of the cortical layer of a bone
A
Protect organs
Support whole body weight
Provide levels for movement
Storage of calcium
9
Q
What is the trabecular part of the bone
A
Trabecular = SPONGY
Trabecular parts of the bone form the medulla of the bone at the ends, proximal to the joints
10
Q
What are Two characteristics of the trabeculated part of bones
A
Trabeculated
Many Holes
11
Q
Where are osteoclasts located
A
In spaces called Lacunae
12
Q
What are the two microstructures of the bone
A
Woven and Lamellar bone
13
Q
Woven Bone vs Lamellar Bones
A
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
Q
What is the role of the wide end of the bone
A
Spreads load over weak, low frictioned surface
15
Q
What is the role of the hollow long bone
A
Keeps mass away from neutral axis - minimises deformation
16
Q
Role of the trabecula part of the bone
A
Gives structural support while minimising mass
17
Q
What is the role of the flat bone
A
Protective
18
Q
Bone composition
A
50-70% minerals
20-40% organic matrix
5-10% water
19
Q
What is the mineral part of the bone made of
A
Hydroxyapatite - crystalline form of calcium phosphate
20
Q
What is the organic matrix made of
A
Type I collagen - 90% of all proteins present
Non-collagenous protein - 10% of all proteins
21
Q
Describe the arrangement of collagen fibres in the extracellular matrix
A
The collagen molecules are arranged in ‘staggered’ form with mineral crystals situated in gaps between them
22
Q
Why do we need minerals in our bones
A
Provides Stiffness
23
Q
Why do we need collagen in our bones
A
Provides elasticity
24
Q
Describe the origin of osteoblasts
A
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
