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MSK PHYSIOLOGYY > Bones Types & Functione > Flashcards

Bones Types & Functione Flashcards

1
Q

what happens in osteoarthiritis

A

cartilage wears away

bone rubs on bone

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2
Q

what happens in rheumatoid arthiritis

A

swollen inflamed synovial membrane

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3
Q

function of the skeletal system

A 
storage
protection
movement
haemotpoesis
support
mineral storage
balance body weight 
stores bone marrow
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4
Q

how many bones do we have

A

206

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5
Q

types of bones

A 
long
short
flat 
irregular
sesamoid
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6
Q

long bones structure and example

A

tubular shape with hollow shaft

Humerus

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7
Q

short bones and eg

A

cuboidal on shape

Carpals , tarsals

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8
Q

flat bones and eg

A

plates of bone, often curved, protective function

Sternum ribs

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9
Q

irregular bones and eg

A

various shapes

Vertebrae

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10
Q

sesamoid bones and eg

A
  • round, oval nodules in a tendon

Patella

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11
Q

types of bone by structure

A

Primary ( woven)
Secondary ( lamellar )
Cortical
Trabecular (spongy)

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12
Q

what is cortical bone structure

A

Dense, solid, only spaces are for cells and blood vessels.

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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

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14
Q

Woven structure ?

A

Made quick
Disorganised
No clear structure

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15
Q

Lamellar structure

A

Made slow
Organised
Layered

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16
Q

Role of hollow bones

A

Keeps mass away from neutral axis

Minimise deformation

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17
Q

Role of trabecular bone

A

Gives structural support whilst minimising mass

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18
Q

Role of wide ends

A

Spread of load

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19
Q

Up to 10% of an adult bone is made from

A

Water

💧

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20
Q

Majority of adult bone is made from

A

Mineral

( hydroxyapatite) type of calcium phosphate

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21
Q

What provides stiffness to bone

A

Minerals

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22
Q

Cells of bone

A

Osteoclast - multinucleated
Osteoblast - plump cuboidal
Osteocyte - stellate
Bone lining cell - flattened lining the bone

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23
Q

Which bone cell type makes bone

A

Osteoblast

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24
Q

Most abundant bone cell type

A

Osteocyte

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25
Q

Function of osteoclast

A

Resorb bone

Dissolve the mineralised matrix

Breakdown of collagen in bone
High expression of TRAP and cathepsin K

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26
Q

What is modelling and remodelling

A

Remodel- all bone is altered

Model- gross shape is altered , bone added or taken away

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27
Q

Primary bone cancer

A

Ademantemona

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28
Q

What does calcium provide

A

Stiffness

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29
Q

What does collagen provide

A

Elasticity

30
Q

What is interstitial growth

A

Growth from within

31
Q

Appositional growth

A

Growth from outside

32
Q

What is endochondral ossification

A

Bone forms from a hyaline cartilage precursor

During foetal development

33
Q

What is ossification

A

Bone formation

34
Q

what is intramembranous ossification

A

Bone forms directly from mesenchyme.

Occurs during foetal development to form flat and irregular bones.

35
Q

process of endochondral ossification

A

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
Q

process of intramembranous ossification

A

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
Q

what is epiphyseal plate

A

Growth plate allowing continued growth of long bones in childhood and adolescence.

38
Q

how does the growth plate increase

A

Size of growth plate increases with constant chondrocyte division
Some chondrocytes simultaneously degenerate - they are then ossified by osteoblasts

39
Q

where do osteocytes live

A

lacunae

40
Q

process of bone remodelling

A

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
Q

why does bone remodelling occur

A 
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
Q

what is wolfs law

A

In a healthy individual, bone will adapt to the loads under which it is placed

43
Q

effect of parathyroid hormone on calcium homeostasis and vit d

A

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
Q

Role of Phosphate

A 
ATP 
DNA 
Cyclic AMP
Cell membrane
Post-translational protein modification  Kinases – phosphorylate  Phosphatases – dephosphorylate
Bone mineral - calcium hydroxyapatite
45
Q

Normal Phosphate Status

A

Whole body phosphate 500 - 800g

Serum phosphate 0.8 – 1.5 mmol/l

46
Q

High phosphate causes….

A

Excessive formation of hydroxyapatite
Deposition in tissues other than bone
Femoral artery calcification
Tumoral calcinosis

47
Q

Low phosphate….

A

Poor bone mineralisation
Rickets or osteomalacia
Pain, fractures

48
Q

Dietary sources of phosphate

A 
Protein
Animal
Dairy
Soy
Seeds and nuts
Daily recommened intake 700mg
49
Q

Gut absorption of phosphate

A

In small intestine

Passive diffusion – at high concentrations

Active transport (Na-dependent) - at lower concentrations

Fractional absorption increases at lower concentrations

50
Q

Regulation of phosphate metabolism

A

Parathyroid hormone
1,25 dihydroxyvitamin D
FGF-23 - most important

51
Q

Parathyroid hormone functions

A 
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
Q

FGF 23 is released in response to

A 
Produced by osteocytes
In response to:
Rise in phosphate levels
Dietary phosphate loading
PTH
1,25 Vitamin D
53
Q

Autosomal dominant rickets ADR

A 
Presents in childhood or adulthood
Bone pain, deformity, fracture
Low bone density
Low serum phosphate
High urine phosphate
54
Q

Summary of phosphate homeostasis

A

Increased phosphate - FGF-23

55
Q

Common pathways with calcium regulation

A

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
Q

Klotho … what is it?

A

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
Q

Osteoblasts

A

Builds bone

B for builder

58
Q

Regulation of bone turnover (remodelling)

A

Coupling
-Bone formation occurs at sites of previous bone resorption

Balance
-Amount of bone removed by osteoclasts should be replaced by osteoblastic activity

59
Q

Derivation of osteoclasts

A

Macrophages

Osteoclasts are specialised macrophages

60
Q

Inflammatory mediators eg and mechanism

A

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
Q

Autocrine

A

If cytokine acts on the cell that secretes it

62
Q

Paracrine

A

If action is restricted to the immediate vicinity of a cytokine’s secretion

63
Q

Endocrine

A

if the cytokine diffuses to distant regions of the body (carried by blood or plasma) to affect different tissues.

64
Q

Osteoprotegerin (OPG)

A

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
Q

FGF- 23 actions

A 
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
Q

3 ways pth responds to low calcium conc in blood

A

Efflux of calcium from bone
Decreased loss of calcium in urine
Enhances absorption of calcium in gi tract

67
Q

Vitamin d pathway

A

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
Q

What is the active form of vit d

A

Calcicitrol

69
Q

functions of skeletal muscles

A

Produce movement of body parts
support soft tissues

Maintain posture and body position:

Communication:

Control of openings and passageways:

Maintain body temperature

70
Q

universal characteristics of muscles

A

MSK PHYSIOLOGYY (3 decks)

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