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HC1218 - Physiology, Pathophysiology and Exercise > Bones structure and function > Flashcards

Bones structure and function Flashcards

1
Q

through which two processes do bones change their structure?

A

modeling & remodeling

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2
Q

why do bones undergo modeling?

A

to adapt to changing biomechanical forces

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3
Q

why do bones undergo remodeling?

A

to remove old, microdamaged bone & replace it with new bone

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4
Q

what are the 4 general categories of bone?

A

long bone, short bone, flat bone & irregular bone

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5
Q

what are 2 examples of long bones?

A

tibia & femur

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6
Q

what are 2 examples of short bones?

A

patella & tarsals

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7
Q

what are 2 examples of flat bones?

A

ribs & scapulae

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8
Q

what are 2 examples of irregular bones?

A

vertebrae & coccyx

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9
Q

Name the 6 functions of the skeleton

A

structural support
permits movement - bones act as levers for muscles
organ protection
maintain mineral homeostasis & acid-base balance
bones act as a reservoir for growth factors and cytokines
environment for haematopoiesis

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10
Q

what type of formation do long bones undergo?

A

membranous and endochondral

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11
Q

what type of formation do flat bones undergo?

A

membranous

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12
Q

describe the composition of long bones

A

diaphysis - hollow shaft of thick cortical bone
trabecular meshwork covered in thin cortical shell above growth plates (rounded epiphyses) and below growth plates (cone-shaped metaphyses)

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13
Q

What are the physical properties of cortical bone?

A

It is dense and solid and is made up of haversian systems.

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14
Q

What does cortical bone surround?

A

Marrow space.

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15
Q

What is the haversian system wall made of?

A

Concentric lamellae.

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16
Q

Which is more metabolically active - cortical bone or trabecular bone?

A

Trabecular bone.

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17
Q

Name the outer surface of cortical bone and its function.

A

The periosteal - for growth and fracture repair.

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18
Q

Name the inner surface of cortical bone and its function.

A

The Endosteal - has higher remodelling activity than periosteal due to more strain and cytokine exposure.

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19
Q

Describe the structure of trabecular bone.

A

Honeycomb-like network of trabecular plates and rods.

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20
Q

Where is trabecular bone found?

A

Interspersed in bone marrow.

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21
Q

What structures are made from lamellar patterns?

A

Cortical and trabecular bone.

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22
Q

What is a lamellar pattern?

A

Collagen fibrils laid down in alternating patterns.

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23
Q

How is the structure of the Lamella pattern related to its function?

A

The alternating orientation of collagen fibrils makes the structure extremely strong.

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24
Q

Describe the structure of woven bone.

A

There is no lamellar pattern. The collagen is disorganised.

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25
Q

Is woven bone strong or weak?

A

weak

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26
Q

What is woven bone?

A

The form of primary bone.

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27
Q

What is the periosteum?

A

The fibrous connective tissues surrounding the cortical exterior.

28
Q

What is the function of the periosteum?

A

It contains blood vessels, nerve fibres, osteoblasts and osteoclasts.

29
Q

What is the endosteum?

A

The membrane of the inner cortical and trabecular bone and Volkmann canals.

30
Q

What is the function of the endosteum?

A

Contains vessels, osteoblasts and osteoclasts.

31
Q

Name the three ways in which bones change their shape and structure.

A

Growth modelling and remodelling.

32
Q

In which two ways can bone growth occur?

A

The longitudinally and radially.

33
Q

When does bone growth occur?

A

During childhood

34
Q

Describe the process of longitudinal growth.

A

Cartilage proliferates in epiphyseal and metaphyseal. It becomes mineralized and forms primary new bone. occurs at the growth plates.

35
Q

What is modelling?

A

When bones change shape due to physiologic influences or mechanical forces - the gradual adjustment of the skeleton to the forces it encounters.

36
Q

Why do bones widen with age?

A

It is the response to periosteal opposition of new bone and endosteal reabsorption of old bone.

36
Q

What is Wolff’s law?

A

Long bones change shape to accommodate stress they’re put under

36
Q

What happens during bone modelling?

A

Bones widen or change axis by adding and removing parts of the bone via osteoblast and osteoclasts.

36
Q

What is more frequent in adults - modelling or remodelling?

A

remodelling.

36
Q

What is remodelling?

A

It is the continuous removal of discrete packets of old bone. It is replaced with new proteinaceous matrix, which is then mineralized form bone.

37
Q

Why is remodelling important?

A

bone is renewed to maintain strength and mineral homeostasis.

38
Q

Why is it important that old bonus reabsorbed?

A

It prevents bone micro damage accumulation.

39
Q

At what stage in life does remodelling occur?

A

At all stages, from birth until death.

40
Q

What does a remodelling unit consist of?

A

A tightly coupled group of osteoclasts and osteoblasts, which reabsorbed and form bone.

41
Q

What is the 4 phase cycle of remodelling?

A

Activation reabsorption reversal and formation.

42
Q

What is meant by bone balance?

A

The difference in old bone reabsorption and new bone formation

43
Q

Describe the bone balance of periosteal.

A

Mildly positive.

44
Q

Describe the bone balance of endosteal.

A

Mildly negative.

45
Q

Describe the bone balance of trabecular bone.

A

Mildly negatives.

46
Q

What is the role of osteoclasts?

A

Osteoclasts reabsorb bone.

47
Q

What is the role of osteoblasts?

A

Osteoblasts synthesise new bone matrix on bone falling surfaces.

48
Q

What are osteocytes?

A

Differentiated osteoblasts located in the Lacunae of mineralised bone.

49
Q

List some of the roles of osteocytes.

A

Support bone structure and metabolism
support protective lining cells that cover surface of quiescent bone.
Can act as phagocytes.
connexion to each other and bone surfaces
mechanosensation.

50
Q

Why can osteocytes act as phagocytes?

A

They contain lysosomes.

51
Q

What are gap junctions?

A

Gap junctions link osteocytes metabolically and electrically and are needed for osteocyte maturation activity and survival.

52
Q

One of the roles of osteocytes is mechanosensation. What is this?

A

They transduced stress signals from bending and stretching bone to biologic activity to allow bone remodelling.

53
Q

how does apoptosis of osteocytes occur and what does this affect?

A

Gap junctions may be disrupted, which leads to less and less remodelling and thus weak bones.

54
Q

Describe bone composition.

A

50 to 70% minerals.
20 to 40% organic matrix
5 to 10% water
< 3% lipids.

55
Q

What is the function of the inorganic matrix in bone?

A

Provides mechanical rigidity.
It gives load-bearing strength.

56
Q

Describe mineralization of the inorganic matrix.

A

Minerals are deposited in hole zones between ends of collagen fibrils .

57
Q

Describe the composition of organic matrix.

A

85 to 90% collagen, 10 to 15% non collagenous.

58
Q

What type of collagens are present in organic matrix?

A

Type 1 type 3 type 5 and FACIT collagens.

59
Q

What is the role of FACIT collagens?

A

They act as molecular bridges to organise and stabilise extracellular matrices.

60
Q

What non-collagenous substances are present in organic matrix?

A

Proteoglycans, glycosylated proteins y-carboxylated proteins.

61
Q

What is the role of non-collagenous substances inorganic matrix?

A

Serve functions like mineral deposition, regulation and bone cell activity.

HC1218 - Physiology, Pathophysiology and Exercise (6 decks)

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