MS Systems: Bones and Bone Growth Flashcards

1
Q

What are the functions of bones?

A
\+ Protection
\+ Support
\+ Movement
\+ Storage of minerals (Ca, P, Mg)
\+ Blood cell formation
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2
Q

What are the structural features of a long bone?

A

+Epiphysis (head)

+ Diaphysis (shaft)

+ Periosteum

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3
Q

What are features of the Epiphysis?

A

+ Articular surface

+ Covered by hyaline cartilage

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4
Q

What are features of the diaphysis?

A

+ Hollow cylinder
+ Contains bone marrow
+ Nutrient foramen

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5
Q

What are features of the periosteum?

A

Fibrous layer that covers external surfaces. Cells include:

  • fibroblasts: synthesize collagen
  • mesenchymal cells: can differentiate into osteoblasts and chondroblasts
  • osteoclasts
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6
Q

What are the functions/features of osteoclasts?

A

+ Resorb bone matrix by demineralization in response to mechanical stresses and physiological demands

+ Multinucleated

+ Derived from haematopoietic cells

+ Regulated by osteoblasts and hormones

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7
Q

How to osteoclasts resorb bone?

A

+ Form a “sealing zone” on bone

+ Release H+ and hydrolytic enzymes to dissolve the mineral, liberate calcium and break down the extracellular matrix

+ Regulated by osteoblasts and hormones

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8
Q

What are the functions/features of osteoblasts?

A

+ Responsible for bone formation

+ Cuboidal cells, derived from osteoprogenitor cells that line the surface of the bone

+ Deposit the organic matrix, then cause mineralisation

+ Some become entombed during this process, mature into osteocytes

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9
Q

What are the features/functions of osteocytes?

A

+ Mature bone cells; embedded in lacunae, relatively inactive

+ Maintain bone matrix through cell-cell communication: via projections in canaliculi

+ Influence bone remodelling

+ Mechanosensing

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10
Q

What is the structure/function of compact bone?

A

+ Osteons or Haversian systems
+ Very strong, light cylinder that resists compressive (grav.) forces
+ Osteocytes buried alive in the bone matrix

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11
Q

What is the structure of cancellous/trabecular bone?

A

+ Spongy, porous, bone tissue that is filled with red bone marrow

+ Not as strong as cortical bone found in long bones, but very important for producing blood cells

+ Found in ends of long bones and the pelvis, ribs, vertebrae, and skull

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12
Q

What effect does calcitonin have on osteoclast activity and blood calcium levels?

A

It decreases the activity of osteoclasts, therefore decreasing blood Ca++ levels

Favours bone resorption/atrophy

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13
Q

What effect does parathyroid hormone (PTH) have on osteoclast activity and blood calcium levels?

A

It increases the activity of osteoclasts and releases Ca++

Favours bone formation/hypertrophy

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14
Q

What are the steps in the bone remodelling cycle?

A

+ Resorption
+ Reversal
+ Formation
+ Quiescence

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15
Q

How can bone mass and density increase?

A

Excessive mechanical stimulation

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16
Q

How can bone mass and density decrease?

A

+ Non-weight bearing (immobilisation)

+ Sex-hormone deficiency (e.g menopause)

+ Endocrine/nutritional disorders

17
Q

What is Wolff’s law?

A

+ Bone adapts to the load under which it is placed e.g orthodontic braces, head binding

18
Q

How long do fractures of woven bone take to heal?

A

2-4 weeks

- dependent on the severity and position of the fracture and age of the patient

19
Q

What are the steps of bone fracture healing?

A

+ Callus formation

  • osteoblasts quickly form woven bone to bridge the gap
  • woven bone is weak as the collagen fibres are irregular

+ Lamellar bone laid down
- collagen organised in regular sheets to give strength and resilience

Remodelling by osteoclasts to restore original bone shape

20
Q

What is the foetus cartilage model is replaced by?

A

Bone (ossification)

  • endochondrial (long bones)
  • intremembranous (flat bones)

Bone growth begins in the shaft during foetal life

21
Q

What is the foetus cartilage model is replaced by?

A

Bone (ossification)

  • endochondrial (long bones)
  • intremembranous (flat bones)

Bone growth begins in the shaft during foetal life

22
Q

Where is does ossification begin/primary ossification?

23
Q

Where is does ossification begin/primary ossification?

24
Q

Where is the secondary centre of ossification?

A

Epiphysis (epiphyseal plate)

25
What are the zones of the epiphyseal plate?
``` + Ossification (osteogenic) zone + Calcification zone + Hypertrophic zone + Growth (proliferating) zone + Resting zone ```
26
When does fusion of the epiphyseal plate occur?
By the end of puberty
27
What is the chemical composition of bone matrix?
Calcium hydoxyapatite: (Ca5 (PO4)OH)
28
What are features of the medullary cavity?
+ Contains bone marrow supported by cancellous bone | - red bone marrow is one site of haematopoiesis
29
What are features of the resting zone?
On the epiphyseal side of the plate (reserve cells)
30
What occurs at the growth zone?
Cells undergo mitosis (proliferation)
31
What occurs at the maturation zone?
Cartilage cells are transforming and enlarging and the matrix calcifies
32
What occurs at the osteogenic zone?
+ Calcified cartilage removed by osteoclasts + Replaced by bone secreted by osteoblasts