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Histopath. (PATH2000) > Bone > Flashcards

Bone Flashcards

1
Q

3 types of cartilage

A
  • Hyaline cartilage: spacious in b/w cells
  • Elastic cartilage: like hyaline but w/ dense elastic fibres (dark staining)
  • Fibrocartilage: collagen fibres in rows (//) >shock absorber *No perichondrium
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2
Q

List the components in CT

A
  • Cells: produce & secrete extracellular matrix (ECM)
  • Fibres (F): support
  • Ground substance (GS): “fills” space b/w cells & fibres
  • ECM = GS + F + fluid (water)
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3
Q

2 types of chondrogenic growth

A
  1. Appositional: new cartilage forms @ surface of existing cartilage
  2. Interstitial: new cartilage forms w/in existing cartilage
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4
Q

Describe Appositional growth

A
  1. new cells derived from inner perichondrium
  2. resemble fibroblast
  3. produce type I collagen
  4. differentiate into chondroblast & secrete matrix
  5. matrix increase cartilage mass
  6. new fibroblasts produced to maintain cell population of perichondrium
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5
Q

Describe interstitial growth

A
  1. new cells arise from division of cells w/in lacunae
  2. chondrocytes retain ability to divide & surrounding matrix is distensible (stretched) => further secretory activity
  3. lots of daughter cells in lacunae but later matrix separates them
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6
Q

Ca2+ required for:

A
  • enzyme activity
  • muscle contraction
  • mediate cell adhesion & movement
  • exocytosis
  • membrane permeability
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7
Q

What do bones store?

A
  • Ca2+: stored as hydroxyapatite crystals

- (& phosphate)

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8
Q

What 2 hormones control Ca2+ levels in blood?

A
  1. Parathyroid hormone (PTH): Lo -> Hi by stimulating osteocytes & osteoclasts; Increase absorption in SI; reduce loss in kidneys
  2. Calcitonin: Hi -> Lo. Inhibit PTH on esteoclast (= Inhibit bone resorption)
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9
Q

4 types of Bone cell

A
  1. Osteogenic (stem) cell
  2. Osteoblast
  3. Osteocyte
  4. Osteoclast: (lots of nuclei)
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10
Q

Why is decalcification necessary before sectioning tissue?

A

remove calcium bc blades blunt quickly or poor sections produced.

  • Done by Ca2+ chelators (EDTA): slow & gentle
  • or acids (nitric, formic): fast but harsh on tissue
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11
Q

5 zones of epiphyseal plate & add brief description of each

A
  1. Zone of reserved cartilage: give cells
  2. … proliferation: cells proliferates = tiss. become longer
  3. … hypertrophy: tiss. rapidly grow in size
  4. … calcified cartilage: Ca2+ fixed in by osteoblasts
  5. … ossification: hard bone, vascular & neural supply develop
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12
Q

Explain how cartilage becomes bone (in long bones)

A
  1. Proliferation: of chondrocyte
  2. Condensation: contain prehypertonic chondrocyte
  3. Hypertrophy: contain hypertrophic chondrocyte, BV, progenitor
  4. Bone marrow: osteoclast make bones smoother, & precursor cells -> osteoblast + …clast
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13
Q

Describe the steps to thickening bone

A
  1. Initial core is broken down/resorb by osteoclast

2. Osteoblast deposits in the middle = middle gets larger

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14
Q

Cells in bone include

A

osteocytes, progenitor cells, osteoblasts, bone-lining celss, osteoclasts

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15
Q

Mineralised (bone) matrix consist of… & provides…

A

a) mineral (hydroxyapetite crystals); collagen (Type I); ground substance
b) support & protection

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16
Q

Summarise bone repair process

A
  1. hematoma forms (when bone + BV broken) => inflammation
  2. Soft callus takes away clot & replaces w/ fibrous tiss.
  3. Hard callus forms
  4. Bone remodelled (bone strength back to normal)
17
Q

3 types of ground substances (GS) and function of each (5)

A
  1. Proteoglycan macromolecules > compressive strenght & bind to growth factors
  2. Multi-adhesive glycoproteins > attach bone cells & collagen fibres to mineralised GS
  3. Factors:
    - Osteocalcin > captures Caa2+ from blood, attract & stimulate osteoclast
    - Sclerostin > inhibits further bone formation by osteocytes
    - Bone morphogenic proteins (BMPs) > mesynchymal cells -> osteoblasts
18
Q

Functions of osteoblast

A

> secrete bone matrix
secrete osteoid (unmineralised bone): Type I collagen, bone matrix proteins (BMPS), ALP
calcification if bone matrix (add Ca2+)

19
Q

What is the clinical marker that indicate if osteoblasts are active?

A

Osteocalcin & alkaline phosphatase (ALP)

20
Q

What is the osteoprogenitor cells?

A
  • Osteoblast precursor cells derived from mesenchymal cells (in bone marrow)
  • found in internal & external bone surfaces & microvasculature
  • make (diff. into) periosteal & endosteal cells
21
Q

Role of osteoprogenitor cells?

A

required for osteogenesis (new bone formation)

22
Q

What are osteocytes ?

A
  • mature osteoblast- surrounded by osteoid/bone matrix. In lacunae
  • smaller than osteoblast bc reduced perinuclear cytoplasm
  • has cytoplasmic processes through canaliculi = contact other cells
23
Q

Role of osteoblast

A

> maintain bone matrix

> can synthesise new matrix & carry out matrix degeneration

24
Q

What are bone lining cells?

A
  • periosteal & endoosteal derived from esteoblast

- flat cells: reduced cytoplasm

25
Q

Role of bone lining cells

A

> cover bone not remodelling (by osteoclast)
maintain and support nutrition of osteocytes
regulate movement of Ca & PO4 in & out of bone

26
Q

Role of osteoclast

A

> bone resorption (break down): by releasing protons (H+) & lysosomal hydrolases

27
Q

Clinical marker of osteoclast activity

A

tartrate-resistant acid phosphatase (TRAP)

28
Q

Formation of osteoclast (according to cell stages)

A
  1. Hematopoietic stem cell
  2. Monocyte/macrophage
  3. preosteoclast
  4. osteoclast
29
Q

Formation of osteocyte (according to cells stages)

A
  1. mesenchymal stem cell
  2. Pre-osteoblast
  3. osteoblast
  4. osteocyte
30
Q

when decalcifying w/ chelators (EDTA)

A
  • EDTA in pH 7-7.5 is used as the agent
  • Process is very slow: 6-8 weeks
  • Preserves the enzymes
31
Q

factors that influence decalcification process

A

- temp (25ºC)

32
Q

test used to check if Ca2+ present in tissue (after decalcification)

A

Ca oxalate test using ammonium oxalate (after neutralised w/ NH4OH

33
Q

Intramembranous vs endochondral ossification

A
  • Intramembranous: ossification w/in CT membranes in flat bones. spongey appearance
  • Endochondral: ossification w/in hyaline cartilage template in long bones. Has 1º & 2º ossification
34
Q

State the location of type I & II collagen

A

I: fibrocartilage
II: Hyaline, elastic

35
Q

Types of decalcifying agents

A
  • Strong mineral acids
  • Weak inorganic acids
  • chelating agents
36
Q

What is bone fixed w/ & the duration?

A

Neutral buffered formalin for 12-24hrs

Histopath. (PATH2000) (8 decks)

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