Cartilage and Bone Flashcards

1
Q

3 types of cartilage

A

hyaline

elastic

fibrocartilage

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2
Q

Why doesnt cartilage heal well?

A

Bc it is avascular and have immoble chondrocytes with limited proliferation

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3
Q

Components of the Hyaline cartilage matrix

A

Homogenous amorphous matrix of:

  • type II collagen
  • GAGs
  • proteoglycans
  • glycoproteins
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4
Q

Characteristics of Hyaline Cartilage

A

Chondrocytes located in lacunae

Hyaline cartilage has perichondrium except at articular surfaces

Low friction

Highly hydrated

calcifies with aging

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5
Q

Componets of elastic cartilage matrix

A

Hyaline Matrix:

  • proteoglycan
  • glycoproteins
  • type II collagen
  • GAGs

PLUS elastic fibers and materials

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6
Q

Charcteristics of elastic cartilage

A

elastic properties

doesnt calcify with aging

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7
Q

Components of fibrocartilage

A

Hyaline cartilage PLUS dense regular connective tissue

Chondrocytes, some fibroblasts

Collagen fibers (type I and type II)

No perichondrium

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8
Q

Characteristics of fibrocartilage

A

Resistance to compression and shearing (‘shock absorber’)

Intervertebral discs, symphysis pubis, menisci of knee joint

Calcification of fibrocartilaginous callus during bone repair)

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9
Q

Steps of chondrogenesis

A

mesenchyme generates chondroblasts

chondroblasts secrete matrix, become isolated chondrocytes

chondroblasts replicate creating isogenous groups of chondrocytes

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10
Q

interstitial growth

A

new cartilage formed within existing cartilage

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11
Q

appositional growth

A

new cartilage formed at the surface of existing cartilage

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12
Q

Extracellular matrix of Bone

A

Mineralized with calcium phosphate (hydroxyapatitecrystals)

type I collagen (primarily)

proteoglycans

glycoproteins (osteonectin, osteopontin)

bone-specific Vitamin K-dependent (osteocalcin, protein S)

growth factors & cytokines

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13
Q

functions of bone

A

Structural support

Protection

Calcium regulation

Hemopoiesis

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14
Q

Osteons (Haversian)

A

Cylindrical structural units of bone

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15
Q

5 cell types in bone

A

Osteoprogenitor cells

Osteoblasts

Osteocytes

Bone-lining cells

Osteoclasts

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16
Q

collagen fiber organization within bone

A

Collagen fibers are parallel within a lamella, but run different direction than adjacent lamella

( right → left, then, left → right)

17
Q

The canal in bone contains

A

blood supply

18
Q

Osteoprogenitor cell

Funtion, location

A

Function

Resting’ mesenchymal stem cell

  • CBFA1 (core binding factor alpha-1) triggers differentiation into osteoblast

Location

Localized to external and internal surfaces of bone (periosteal and endosteal cells)

19
Q

Osteoblast

Funtion and location

A

Function

  • bone forming cell
  • secretes matrix = type I collagen (90% protein in bone)
  • secretes vesicles that initiate matrix calcification

Location

  • Single layer of cells opposed to forming bone
  • gap junctions between osteoblasts
20
Q

Steps of bone matrix calcification

A

vesicles exocytosed from the osteoblast - contain alkaline phosphatase and pyrophosphatase → the initial site of mineralization

*elevated local extracellular Ca2+ and PO4 required (osteocalcin)

*crystallization of CaPO4 = hydroxyapatite crystals [Ca10(PO4)6(OH)2]

21
Q

osteocyte

Function and location

A

Maintians bone matrix

Mechanotransduction: sensing physical forces and translating them into biochemical responses

Found completely enclosed by bone matrix

processes extend thtough cannaliculi to connect w/ other osteocytes

22
Q

Bone lining cells

function and location

A

Function

provide nutritional support to help maintain osteoblasts

regulate Ca2+ and PO4 movement

Location

develop from osteoblasts and line external (periosteal cells) and internal (endosteal cells) bone surfaces

gap junctions are found in between

23
Q

Osteoclast

Function and location

A

Function

Bone reabsorption

stimulated by parathyroid hormone and reduced by calcitonin

Location

Arise from fusion of mononuclear hematopoetic cells

24
Q

Steps of Osteoclast resorption

A
  • A clear (sealing) zone adjacent to ruffled border is formed (integrins–actin)
  • Free H+ from Carbonic acid (H2CO3) actively pumped out of cell.
  • Acid environment causes breakdown of Ca10(PO4)6(OH)2 to

Ca2+, PO4, H2O
* Release of lysosomal enzymes (cathepsin K, matrix metalloproteinases) into extracellular space degrade protein component of bone matrix

  • Osteoclasts ‘tunnel’ into existing bone, osteoblasts follow and rebuild