Bones Types & Functione Flashcards
1
Q
what happens in osteoarthiritis
A
cartilage wears away
bone rubs on bone
2
Q
what happens in rheumatoid arthiritis
A
swollen inflamed synovial membrane
3
Q
function of the skeletal system
A
storage protection movement haemotpoesis support mineral storage balance body weight stores bone marrow
4
Q
how many bones do we have
A
206
5
Q
types of bones
A
long short flat irregular sesamoid
6
Q
long bones structure and example
A
tubular shape with hollow shaft
Humerus
7
Q
short bones and eg
A
cuboidal on shape
Carpals , tarsals
8
Q
flat bones and eg
A
plates of bone, often curved, protective function
Sternum ribs
9
Q
irregular bones and eg
A
various shapes
Vertebrae
10
Q
sesamoid bones and eg
A
- round, oval nodules in a tendon
Patella
11
Q
types of bone by structure
A
Primary ( woven)
Secondary ( lamellar )
Cortical
Trabecular (spongy)
12
Q
what is cortical bone structure
A
Dense, solid, only spaces are for cells and blood vessels.
13
Q
what is trabecular structure
A
Network of bony struts (trabeculae), looks like sponge, many holes filled with bone marrow. Cells reside in trabeculae and blood vessels in holes
14
Q
Woven structure ?
A
Made quick
Disorganised
No clear structure
15
Q
Lamellar structure
A
Made slow
Organised
Layered
16
Q
Role of hollow bones
A
Keeps mass away from neutral axis
Minimise deformation
17
Q
Role of trabecular bone
A
Gives structural support whilst minimising mass
18
Q
Role of wide ends
A
Spread of load
19
Q
Up to 10% of an adult bone is made from
A
Water
💧
20
Q
Majority of adult bone is made from
A
Mineral
( hydroxyapatite) type of calcium phosphate
21
Q
What provides stiffness to bone
A
Minerals
22
Q
Cells of bone
A
Osteoclast - multinucleated
Osteoblast - plump cuboidal
Osteocyte - stellate
Bone lining cell - flattened lining the bone
23
Q
Which bone cell type makes bone
A
Osteoblast
24
Q
Most abundant bone cell type
A
Osteocyte
25
Function of osteoclast
Resorb bone
Dissolve the mineralised matrix
Breakdown of collagen in bone
High expression of TRAP and cathepsin K
26
What is modelling and remodelling
Remodel- all bone is altered
| Model- gross shape is altered , bone added or taken away
27
Primary bone cancer
Ademantemona
28
What does calcium provide
Stiffness
29
What does collagen provide
Elasticity
30
What is interstitial growth
Growth from within
31
Appositional growth
Growth from outside
32
What is endochondral ossification
Bone forms from a hyaline cartilage precursor
During foetal development
33
What is ossification
Bone formation
34
what is intramembranous ossification
Bone forms directly from mesenchyme.
| Occurs during foetal development to form flat and irregular bones.
35
process of endochondral ossification
Chondrocytes produce a cartilaginous precursor
Primary ossification centre is formed as osteoblasts lay bone onto the cartilage
Osteoclasts break down the cartilage
POC is vascularised as blood vessels invade
Periosteum collar is formed outside the bone as perichondrium is broken down
Parts of the spongy bone making up the POC are broken down to form the medullary cavity
Process repeats at ends of long bones to form secondary ossification centre
Some layers of cartilage remain between the SOC and POC, known as the epiphyseal (growth) plate
36
process of intramembranous ossification
Mesenchymal stem cells replicate, forming clusters called nidus
Stem cells in nidus become osteoprogenitor cells
Osteoprogenitor cells differentiate into osteoblasts
Osteoblasts produces extracellular matrix containing T1 Collagen fibres
Some osteoblasts become trapped in matrix, forming osteocytes
Bone spicules form via mineralisation
Spicules grow and fuse to form trabeculae, around which periosteum is now formed
37
what is epiphyseal plate
Growth plate allowing continued growth of long bones in childhood and adolescence.
38
how does the growth plate increase
Size of growth plate increases with constant chondrocyte division
Some chondrocytes simultaneously degenerate - they are then ossified by osteoblasts
39
where do osteocytes live
lacunae
40
process of bone remodelling
osteoblast detect cracks in bone and release RANK l
bind to receptors on monocytes to release osteoclasts which resorb bone
they release lysosymes , digest collagen and produce hcl
to stop the process osteoblasts release osteoprotegrin
binds to rank l preventing osteoclast activation
41
why does bone remodelling occur
```
Forming bone shape
Replacing woven bone with lamellar
Reorientation of fibrils and trabeculae to reinforce mechanical strength
Response to load
Calcium release
Damage repair
```
42
what is wolfs law
In a healthy individual, bone will adapt to the loads under which it is placed
43
effect of parathyroid hormone on calcium homeostasis and vit d
PTH released in response to low blood calcium levels
PTH increases bone remodelling rates and calcium RESORPTION
Presence of PTH leads to conversion of 25-hydroxyvitamin D (calcidiol) to the active 1,25-dihydroxyvitamin D (calcitriol)
Combined effect lead to increase in serum Ca2+ levels
44
Role of Phosphate
```
ATP
DNA
Cyclic AMP
Cell membrane
Post-translational protein modification Kinases – phosphorylate Phosphatases – dephosphorylate
Bone mineral - calcium hydroxyapatite
```
45
Normal Phosphate Status
Whole body phosphate 500 - 800g
Serum phosphate 0.8 – 1.5 mmol/l
46
High phosphate causes....
Excessive formation of hydroxyapatite
Deposition in tissues other than bone
Femoral artery calcification
Tumoral calcinosis
47
Low phosphate....
Poor bone mineralisation
Rickets or osteomalacia
Pain, fractures
48
Dietary sources of phosphate
```
Protein
Animal
Dairy
Soy
Seeds and nuts
Daily recommened intake 700mg
```
49
Gut absorption of phosphate
In small intestine
Passive diffusion – at high concentrations
Active transport (Na-dependent) - at lower concentrations
Fractional absorption increases at lower concentrations
50
Regulation of phosphate metabolism
Parathyroid hormone
1,25 dihydroxyvitamin D
FGF-23 - most important
51
Parathyroid hormone functions
```
Main function is regulation of calcium
Also affects phosphate
Increases 1,25 vitamin D
Increases active gut absorption
Decreases tubular reabsorption of phosphate
Increases renal excretion
```
52
FGF 23 is released in response to
```
Produced by osteocytes
In response to:
Rise in phosphate levels
Dietary phosphate loading
PTH
1,25 Vitamin D
```
53
Autosomal dominant rickets ADR
```
Presents in childhood or adulthood
Bone pain, deformity, fracture
Low bone density
Low serum phosphate
High urine phosphate
```
54
Summary of phosphate homeostasis
Increased phosphate - FGF-23
55
Common pathways with calcium regulation
Calcium mostly regulated by hormones that increase serum calcium:
PTH, vitamin D
Phosphate mostly regulated by hormones that decrease serum phosphate:
FGF-23, PTH
56
Klotho ... what is it?
Transmembrane protein
Associated with longevity
Klotho is one of the three Fates in Greek mythology – chose the time of life and death
Klotho is necessary for the function of FGF-23
Makes the non-specific FGF receptor bind FGF-23
Klotho knock-out mice have tumoral calcinosis
57
Osteoblasts
Builds bone
| B for builder
58
Regulation of bone turnover (remodelling)
Coupling
-Bone formation occurs at sites of previous bone resorption
Balance
-Amount of bone removed by osteoclasts should be replaced by osteoblastic activity
59
Derivation of osteoclasts
Macrophages
| Osteoclasts are specialised macrophages
60
Inflammatory mediators eg and mechanism
Cytokines:
A group of proteins and peptides that are used to allow one cell to communicate with another.
Released by many types of cells (both haemopoietic and non-haemopoietic)
61
Autocrine
If cytokine acts on the cell that secretes it
62
Paracrine
If action is restricted to the immediate vicinity of a cytokine's secretion
63
Endocrine
if the cytokine diffuses to distant regions of the body (carried by blood or plasma) to affect different tissues.
64
Osteoprotegerin (OPG)
Also known as osteoclastogenesis inhibitory factor (OCIF)
A member of the tumour necrosis factor (TNF) receptor superfamily.
Inhibits the differentiation of myeloid precursors into osteoclasts
Decreases resorption by osteoclasts in vitro and in vivo.
Works by binding to RANK-ligand, thus blocking the RANK-RANK ligand interaction between Osteoblast/Stromal cells and Osteoclast precursors
65
FGF- 23 actions
```
Decreases expression of Na transporter in the renal tubule
Increases renal excretion of phosphate
Decreases 1α-hydroxylation of vitamin D
Decreases gut absorption of phosphate
Decreases whole body phosphate
```
66
3 ways pth responds to low calcium conc in blood
Efflux of calcium from bone
Decreased loss of calcium in urine
Enhances absorption of calcium in gi tract
67
Vitamin d pathway
Uvb rays from sun turn 7 dehydroxycholestrol into cholecalciferol vit d3
Cholecalciferol is converted to 25 OH VIT D ( calcidiol) in the liver via 25 hydroxylase
Calcidiol is converted to 1-25 hydroxy vit d ( calcicitrol) in the presence of PTH
68
What is the active form of vit d
Calcicitrol
69
functions of skeletal muscles
Produce movement of body parts
support soft tissues
Maintain posture and body position:
Communication:
Control of openings and passageways:
Maintain body temperature
70
universal characteristics of muscles
