Histo - Bone Ossification Flashcards

1
Q

What is ossification?

AKA ____

A

ossification aka osteogenesis

is the development of bone tissue

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2
Q

What are the two steps in ossification (aka osteogenesis)

A
  1. development of primary bone (woven, immature) TEMPORARY

2. primary bone replaced by secondary bone (mature, lamellar) PERMANENT

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3
Q

Bone tissue is a type of ___

A

connective tissue

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4
Q

Bone tissue arises from connective tissue called ____

A

mesenchyme

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5
Q

What are the two types of ossification (osteogenesis)?

A
  1. intramembraneous ossification

2. endochondrial ossificatino

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6
Q

Which type of ossification has a hyaline cartilage model precursor?

A

endochondrial ossifiction

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7
Q

Which type of ossification follows this pattern:

mesenchyme -> bone

A

intramembraneous ossification

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8
Q

Which type of ossification follows this patterm:

mesenchyme -> hyaline -> hyaline cartilage -> bone

A

endochondrial ossification

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9
Q

Intramembraneous ossification leads to the production of which type of bones?

A

flat bones of skull and face

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10
Q

Which type of ossification leads to the production of flat bones of the skull and face?

A

intramembraneous ossification

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11
Q

Endochondrial ossification leads to the production of which type of bones?

A

short and long bones in the body

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12
Q

Which type of ossification leads to the production of short and long bones?

A

endochondrial ossification

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13
Q

When do intramembraneous ossification and endochondrial ossification each begin?

A

intramembraneous begins to occur ~8weeks gestation

endochondrial

  • first hyaline cartilage visible ~6weeks gestation
  • ossification centers are present in all long bones of limbs by 12th week gestation
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14
Q

What are the 4 steps of intramembranous ossification?

A
  1. development of ossification center
  2. calcification
  3. woven bone and periosteum develop
  4. replacement of woven bone
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15
Q

In intramembranous ossification, explain what happens histologically as mesenchymal cells differenate?

A

elongated, pale staining mesenchymal cell clusters differentiate into osteoprogenitor cells

they become more rounded
cytoplasm changes from acidophilic to basophilic

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16
Q

In intramembranous ossification, why does the cytoplasm change from acidophilic to basophilic as mesenchymal cell clusters differentiate into osteoprogenitor cells?

A

addition of rER

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17
Q

In intramembranous ossification, the osteoprogenitor cells differentiate into ____

A

osteoblasts

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18
Q

In intramembranous ossification, clusters of ___ create the ossification center.

these cells secrete ____

A

osteoblasts.

osteoblasts secrete organic ECM (osteoid)

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19
Q

In intramembranous ossification, what do osteoblasts secrete?

A

organic ecm (osteoid)

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20
Q

In intramembranous ossification, describe the calcification step.

A

Calcium and other mineral salts are deposited around the framework of collagen fibers in intramembranous ossification

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21
Q

In intramembranous ossification, during calcification, cells trapped in calcified osteoid are now called ____

A

osteoclasts in lacunae

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22
Q

In intramembranous ossification, when do osteoclasts form? How?

A

osteoclasts are trapped in the calcified osteoid during the calcification step

(calcification step = when calcium and other mineral salts are deposited around framework of collagen fibers)

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23
Q

What is appositional growth?

A

growth along the surface

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24
Q

In intramembranous ossification, how is woven bone produced?

A

produced in small, irregularly shaped pieces or spicules that increase in size by appositional growth

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25
Q

In intramembranous ossification, describe how appositional growth affects how woven bone is formed?

A

appositonal growth allows small patches of bone production to merge together to produce a labrynth of woven bone

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26
Q

In intramembranous ossification, what are spaces between bone spicules of woven bone filled with?

What does that differentiate into?

A

embryonic blood vessels

will differentiate into red bone marrow

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27
Q

In intramembranous ossification, where do embryonic blood vessels go?

What do they differentiate into?

A

between the bone spicules of woven bone development

will differentiate into red bone marrow

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28
Q

In intramembranous ossification, how does periosteum form?

A

mesenchyme at periphery of bone condenses to form periosteum

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29
Q

In intramembranous ossification, mesenchyme at periphery condenses to form ___

A

periosteum

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30
Q

In intramembranous ossification, what is woven bone replaced with?

A

lamellar bone

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31
Q

What are the 6 stages of endochondrial ossification?

A
  1. Development of fetal cartilage model
  2. Bone collar forms and cartilage begins to calcify
  3. Primary ossification center forms in diaphysis
  4. Secondary ossification center forms in epiphysis
  5. Hyaline cartilage retained for articular cartilage & epiphyseal plate
  6. Epiphyseal plate ossifies into line
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32
Q

In endochondrial ossification, mesenchyme differentiates into ____

A

chondroblasts

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33
Q

In endochondrial ossification, chondroblasts (differentiated from ___) secrete what? produces what?

A

chondroblasts are differentiated from mesenchyme

They secrete matrix (type II collagen)

Produces hyaline cartilage model

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34
Q

In endochondrial ossification, what specifically produces hyaline cartilage?

A

the chondroblasts (differentiated from mesenchyme) secrete matrix (type II collagen) and PRODUCE HYALINE CARTILAGE MODEL

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35
Q

In endochondrial ossification, hyaline cartilage continues to grow via what type of growth?

A

both appositional and interstitial growth.

interstitial growth because chondrocyte activity in lacunae

appositional growth because of chondroblasts activity at surface

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36
Q

In endochondrial ossification, how does hyaline cartilage grow via appositional growth?

A

chondroblast activity at surface

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37
Q

In endochondrial ossification, how does hyaline cartilage grow via interstitial growth?

A

chondrocyte activity in lacunae

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38
Q

In endochondrial ossification, bone collar forms around ___.

A

diaphysis

39
Q

In endochondrial ossification, while the bone collar is forming around the diaphysis, the cartilage of the ___ begins to calcify

A

shaft

40
Q

In endochondrial ossification, progenitor cells from what region differentiate into osteoblasts?

A

progenitor cells from the perichondrium of the midregion of cartilage

differentiate into osteoblasts

41
Q

In endochondrial ossification, progenitor cells from the perichondrium of the midregion of cartilage differentiate into ___

A

osteoblasts

42
Q

In endochondrial ossification, once progenitor cells from midregion perichondrium differentiate into osteoblasts, what is it called?

A

periosteum

43
Q

In endochondrial ossification, when is the periochondrium called the periosteum?

A

once the progenitor cells from the perichondrium from midregion differentiate into osteoblasts

44
Q

In endochondrial ossification, osteoblasts that are produced along the surface of the midregion secrete ___

A

osteoid which is calcified

creates bone collar around midregion of hylaine cartilage model

45
Q

In endochondrial ossification, how is osteoid secreted?

A

from osteoblasts that are produced along the surface of the midregion

46
Q

In endochondrial ossification, what specifically creates the bone collar around the midregion of hyaline cartilage model?

A

the osteoblasts that are produced along the surface of the midregion

47
Q

In endochondrial ossification, the bone collar forms along the ___

A

diaphyseal portion of the bone

48
Q

In endochondrial ossification, what is the first bone seen in ossification?

A

the bone collar

49
Q

In endochondrial ossification, bone collar impedes on ____

A

diffusion of oxygen and other nutrients

50
Q

In endochondrial ossification, what impedes on diffusion of oxygen and nutrients?

A

bone collar

51
Q

In endochondrial ossification, chondrocytes accumular ___ and undergo ____

A

glycogen and undergo hypertrophy

52
Q

In endochondrial ossification, what accumulates glycogen and undergoes hypertrophy?

A

chondrocytes

53
Q

In endochondrial ossification, what produces alkaline phosphatase?

What does this do?

A

chondrocytes produce alkaline phosphatase

this makes the matrix calcify
calcified cartilage is not bone

54
Q

In endochondrial ossification, what does alkaline phosphatase do? What is it from?

A

alkaline phosphatase makes the matrix calcify

it is produced from chondrocytes

55
Q

In endochondrial ossification, what is the difference histologically between calcified cartilage and bone?

A

calcified cartilage is blue/purple

newly formed bone is pink or red

56
Q

In endochondrial ossification, the calcified matrix means that there is no diffusion, so ____ subsequently die.

A

chondrocytes

57
Q

In endochondrial ossification, why do the chondrocytes die?

A

because calcified matrix means no diffusion of oxygen or nutrients to chondrocytes

58
Q

In endochondrial ossification, when chondrocytes die, what does this create?

A

a porous, 3D structure of cartilage is created in shaft of diaphyseal plate

59
Q

In endochondrial ossification, what creates the primary ossification center?

A

capillaries and osteoprogenitor cells from new periosteum penetrate bone collar and grow into disintegrated calcified cartilage center

60
Q

In endochondrial ossification, _____ penetrate the bone collar and grow into disintegrating calcified center to create primary ossification center

A

capillaries and osteoprogenitor cells

61
Q

In endochondrial ossification, capillaries and osteoprogenitor cells penetrate the ____ and grow into _____ to create primary ossification centers

A

penetrate the bone collar and grow into the disintegrated calcified center

62
Q

In endochondrial ossification, the blood vessels brought into primary ossification centers at core of diaphysis will differentiate into ____

A

red bone marrow

63
Q

In endochondrial ossification, osteoprogeitor cells brought into primary ossification centers will differentiate into ___

A

osteoblasts

64
Q

In endochondrial ossification, osteoblasts in primary ossification center begin to deposit ____

A

bone matrix against remnants of calcified cartilage

65
Q

In endochondrial ossification, where is the primary ossification center found? Where is the remaining hyaline cartilge?

A

primary ossification center found in diaphysis

remaining hyaline cartilage at epiphyses of developing bone

66
Q

In endochondrial ossification, how secondary ossification centers develop in comparison to primary ossification centers?

A

very similarly, but secondary ossification centers are in the epiphysis of developing bone

67
Q

In endochondrial ossification, where is the hyaline cartilage retained? for what purpose?

A

retained at ends of hyaline cartilage model for articular cartilage

this is for the cushioning of the bone ends participating in joints

68
Q

In endochondrial ossification, the remnant of hyaline cartilage between epiphysis and metaphysis is called what?

what is it responsible for?

A

epiphyseal plate

responsible for lengthwise growth in long bones

69
Q

In endochondrial ossification, the epiphyseal plate is a remnant of what?

Where on a long bone specifically is it located?

A

hyaline cartilage from the hyaline cartilage model

located between epiphysis and metaphysis

70
Q

In endochondrial ossification, when are secondary ossification centers developed?

A

shortly after birth

71
Q

In endochondrial ossification, when does the epiphyseal plate turn into the epiphyseal line?

A

at the end of puberty

which marks the end of growth in terms of height

72
Q

In endochondrial ossification, what causes the epiphyseal plate to become the epiphyseal line?

A

changes in hormone at end of puberty cause the cartilage to be replaced with bone

73
Q

In endochondrial ossification, what is the remnant of the last location of the epiphyseal plate?

A

the epiphyseal line

74
Q

What are the 5 zones of bone growth?

A
1 resting reserve cartilage
2 proliferating cartilage
3 hypertrophic cartilage
4 calcified cartilage
5 ossification
75
Q

Describe zone I:

  • Name?
  • What can we see here?
  • What’s occurring?
A

resting reserve cartilage

closest to epiphysis
can see chondrocytes singular or in small groups

no active ECM production, no mitosis underway

76
Q

Describe zone 2:

  • Name?
  • What can we see?
  • What’s occurring?
A

proliferating cartilage

chondrocytes undergo mitosis (stack like coins) on long axis (stacks are called ISOGENOUS GROUPS) actively produce ecm

this pushes epiphysis away from diaphysis to lengthen

77
Q

Which zone of bone growth are isogenous groups found? what do they do?

A

zone 2: proliferating cartilage

they are stacks of chondrocytes undergoing mitosis and actively producing ECM aka pushing epiphysis away from diaphysis (growing)

78
Q

Zone 3:

  • Name?
  • What can we see?
  • What’s occurring?
A

hypertrophic cartilage

chondrocytes increase in size (hypertrophy) so matrix is compressed/thinned because of cell expansion

cytoplasm if chondrocytes accumulate glycogen

79
Q

Zone 4:

  • Name?
  • What can we see?
  • What’s occurring?
A

Calcified cartilage

(basophilic)
calcified through formation of hydroxyapetite crystals
chondrocytes can no longer recieve nutrients because calcified cartilage… so they die.

80
Q

Zone 5:

  • Name?
  • What can we see>
  • What’s occurring?
A

ossification

next to diaphysis, directly in contact with marrow tissue

blood vessels, osteoprogenitor cells, osteoclasts go into space where chondrocytes were

woven bone is laid down by osteoblasts where cartilage spicules were

primary bone is eroded by osteoclasts to create secondary bone

81
Q

Bone grows width-wise through ___ growth.

A

appositional

82
Q

At what two surfaces does the bone grow width wise?

A

periosteal surface and endosteal surface

83
Q

What is the difference between periosteal appositional growth and endosteal appositional growth?

A

both grow bone width-wise

periosteal surface - osteoblasts secrete bone matrix

endosteal surface - osteoclasts break down bone matrix

84
Q

In terms of bone growing wide, at which surface do osteoblasts secrete matrix? Where do osteclasts breakdown matrix?

A

osteoblasts at periosteal

osteoclasts at endosteal

85
Q

Why should the rate of osteoblast activity equal the rate of ostaclast activity?

A

to keep bones from becoming too heavy or thin

86
Q

What are the two controls impacting bone remodeling?

What do they each control? (Where/When)?

A

Negative feedback loop controls WHEN remodeling occurs
(calcitonin and parathyroid hormone)

Bone’s response to mechanical stress and gravity determines WHEN remodeling occurs

87
Q

If too much calcium is in the blood, ___ secrete ____.

A

parafollicular cells in thyroid gland secrete calcitonin

88
Q

What does calcitonin do?

A

inhibits osteoclasts

encourages calcium to be deposited in ECM, thus increases osteoblast activity

lowers evevated blood Ca levels by removing Ca from blood to put into bone

89
Q

Where is calcitonin released from?

A

parafollicular cells in thyroid gland

90
Q

When is calcitonin released?

A

when there is too much calcium in blood

91
Q

If too little calcium is in the blood, ____ secretes ____

A

parathyroid gland secrete parathyroid hormone

92
Q

What does parathyroid hormone do?

A

stimulates osteoclasts to resorb bone

releases Ca from bone storage to enter bone

raises low blood calcium elvels back to normal

93
Q

Where is parathyroid hormone released from?

A

parathyroid gland