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Histo > Bone Development > Flashcards

Bone Development Flashcards

1
Q

What are the 2 types of bone formation mechanisms?

A

Intramembranous and endochondral

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2
Q

What bones are from the intramembraneous mechanism?

A

Flat bones of skull and face (mandible, maxilla)

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3
Q

What bones are from the endochondral mechanism?

A

Long bones, spine, ribs

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4
Q

Intramembraneous bone formation steps

A
  1. Mesenchymal cells proliferate / aggregate into membrane-like structure, then differentiate into osteoprogenitor cells
  2. Osteoprogenitor cells get larger / rounded up, then differentiate into osteoblasts that start producing osteoid
  3. Osteoid processes grow via appositional growth on surface. Trabeculae formation into trabeculae networks then into bone tissue
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5
Q

Where is the primary ossification center?

A

Diaphysis

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6
Q

Where are the secondary ossification centers?

A

Epiphysis

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7
Q

Epiphyseal growth plate

A

Cartilage that remains between the primary and secondary ossification centers

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8
Q

The diaphysis is located at the ___ of long bone.

A

Middle

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9
Q

The epiphysis is located at the ___ of long bone.

A

Ends

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10
Q

Formation of primary ossification center

A
  1. Nutrition supply blocked, chondrocytes hypertrophy and die and the cartilage matrix calcifies
  2. Periosteal buds grow into calcified cartilage, bring osteoclasts and osteoprogenitor cells
  3. Osteoclasts remove the calcified cartilage, making the marrow cavity
  4. Osteoblasts deposit bone matrix on top of calcified cartilage, forming mixed spicules
  5. The mixed spicules (trabeculae) removed later by osteoclasts
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11
Q

Why do the chondrocytes hypertrophy and die?

A

The nutrition supply via diffusion through cartilage matrix (70% water) is blocked by the calcification of the matrix

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12
Q

The formation of secondary ossification centers is by similar processes to the formation of the primary ossification center. T/F

A

True

  1. Chondrocyte hypertrophy and death
  2. Matrix calcification
  3. Blood vessel invasion
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13
Q

Bone collar

A

Compact bone that encases the primary ossification center of the diaphysis, providing structure and support during endochondral bone formation

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14
Q

The perichondrium is replaced with the ___ and chondrogenic cells are replaced with ___.

A

Periosteum, osteoprogenitor cells

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15
Q

Mixed spicules

A

Temporary trabecullae structures of bone matrix (deposited by osteoblasts) on calcified cartilage
Removed later by osteoclasts

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16
Q

Where do the chondrocytes begin to die?

A

Diaphysis, primary ossification center

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17
Q

Formation of mixed spicules

A
  1. Osteoclasts and osteoprogenitor cells migrate in via periosteal buds
  2. Osteoclasts remove calcified cartilage
  3. Osteoblasts form bone (deposit osteoid) on remaining calcified cartilage
18
Q

The mixed spicules are a permanent structure. T/F

A

False, they are transient and are removed by osteoclasts

19
Q

Long bones, spine, and ribs are formed by ___ while flat bones of skull/face are formed by ___.

A

Endochondral bone formation

Intramembraneous bone formation

20
Q

Calcified cartilage is stained ___ and is ___, while bone is stained ___ and contains ___.

A

Basophilic, acellular (chondrocytes have died)

Eosinophilic, osteocytes

21
Q

Metaphysis

A

Cartilage that separates the medullary cavity and epiphysis

22
Q

The epiphyseal plate continues to grow until ___.

A

Puberty

23
Q

What are the 5 zones of the epiphyseal plate?

A
  1. Reserve cartilage
  2. Chondrocyte proliferation
  3. Chondrocyte hypertrophy
  4. Calcified cartilage
  5. Resorption / deposition
24
Q

The epiphyseal plate growth is bidirectional. T/F

A

False, it is unidirectional towards the center.

25
Q

The lengthening in endochondral bone growth occurs from ___, while thickening occurs from ___.

A

Interstitial growth in epiphyseal plate

Appositional growth under periosteum

26
Q

How can you differentiate intramembraneous and endochondral bone formation?

A

Intramembraneous - has same staining color and osteocytes throughout

Endochondral - different staining colors and no osteocytes in CC

27
Q

Describe the 5 zones of the epiphyseal plate. What color is bone? Calcified cartilage?

A

Zone of preservation - chondrocytes at rest

Zone of proliferation - chondrocytes start to stack on top of each other

Zone of hypertrophy - chondrocytes become larger (glycogen accumulation, vacuolation) and die

Zone of calcified cartilage - Cartilage becomes blue/purple

Zone of resorption/deposition - blue CC being removed by osteoclasts, bone (red) forming by osteoblasts

28
Q

The epiphyseal growth can be regulated by growth hormone and nutrition. T/F

A

True

29
Q

What is the function of bone remodeling?

A

To replace immature bone and maintain/change original shape, replaces aging osteons in mature bones

30
Q

Bone remodeling is random resorption an deposition of bone matrix. T/F

A

False, it is selective

31
Q

Bone remodeling begins ___ and ends ___.

A

In utero, at death (throughout life)

32
Q

Bone remodeling units

A

Cutting zone: resorption by osteoclasts

Closing zone: new bone formation by osteoblasts (mature into osteocytes) or bone lining cells (endosteal cells)

33
Q

In bone remodeling units, the cutting zone contains ___, while the closing zone contains ___ or ___.

A

Osteoclasts

Osteoblasts, bone-lining cells

34
Q

Primary / woven bone

A

Formed quickly by osteoblasts, random collagen organization (nonlamellar), more cellular, less mineralized

35
Q

Secondary / lamellar bone

A

Made from remodeling of woven bone

Parallel collagen sheets (lamellae), less osteocytes (organized in osteons), mineralized

36
Q

Calcitonin

A

Inhibits osteoclast activity and bone resorption

37
Q

Parathyroid hormone (PTH)

A

Promotes bone resorption by osteocytes and osteoclasts

38
Q

Estrogen

A

Activates osteoblasts to produce / secrete bone matrix, inhibits osteoclast activation, decreases with age in women (osteoporosis)

39
Q

Bone fracture and repair

A
  1. Granulation tissue: loose CT around injury site from fibroblast and periosteal cell proliferation
  2. Soft callus: dense CT and cartilage for stabilization
  3. Bony callus: cartilage calcifies and cancellous bone forms
  4. Remodeling: cancellous bone remodeled into compact bone, callus removed
40
Q

The soft callus is made from what?

A

Dense CT and cartilage

41
Q

The bony callus is made from what?

A

Calcified cartilage and spongy bone

Histo (10 decks)

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