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21 fall: histology > lecture 5: bone > Flashcards

lecture 5: bone Flashcards

1
Q

bone is hypocellular meaning

A

has few cells

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2
Q

bone stains pink because

A

it is eosinophilic

most ECM is made from collagen, which is positive

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3
Q

compare cartilage and bone

A
  • *Cartilage**
  • large, rounded cells found in clusters
  • texture: firm but gel-like, elastic
  • avascular
  • low metabolic rate
  • ECM Type II collagen and Aggrecan (sulfated PG) (negative purple)
  • permeable
  • continued growth
  • *Bone**
  • ellipsoid, isolated cells encased in mineral, hypocellular
  • mineralized, hard
  • vascularized
  • high metabolic rate
  • ECM: type I collagen, small PGs, glycoproteins
  • impermeable
  • complex structure with capacity for remodeling
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4
Q

ECM of cartilage vs bone

A

cartilage: type II collagen and aggrecan (sulfated PG) (make negative- purple stain)

bone: type I collagen, small PGs, glycoproteins (areas to bind calcium, positive- pink stain)

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5
Q

compare texture of cartilage and bone:

A

cartilage: firm, gel like, high tensile strength, elastic
bone: mineralized hard

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6
Q

compare cells in cartilage and bone

A

cartilage: large, rounded cells, often in clusters, encased in ECM
bone: ellipsoid, isolated cells encased in mineral, more hypocellular

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7
Q

compare metabolic rate and growth in cartilage and bone

A

cartilage: low metabolic rate, avascular, capacity for continued growth

bone: high metabolic rate, highly vascularized, complex structure with capacity for remodeling

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8
Q

% make up of ECM of bone

A

inorganic : 75% of bone

mineral hydroxyapatite

organic: 25 %

type 1 collagen: 90%

small proteoglycans and glycoproteins: 10%

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9
Q

type 1 collagen fibril

A

type 1 collagen molecules form head to tail and have spaces in between that form “hole zone”, gives stripped appearance

hole zones are where calcium deposits

“quarter staggered”

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10
Q

hole zones in bone is where ___

A

calcium and phosphate deposits

this brings more calcium and phosphate which allows minerals to grow and fill space in between type 1 collagen molecules

collagen molecules do not mineralize, only space in between that is why bone is at most 50-75% mineralized

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11
Q

Why is bone at most 50-75% mineralized

A

collagen molecules do not mineralize, only space in between that is why bone is at most 50-75% mineralized

allows some bending of bones

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12
Q

two type of bone formation

A

endochondral ossification

intramembranous ossification

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13
Q

endochondral ossification is found in what type of bones

A

axial and appendicular skeleton, some facial bones

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14
Q

where does intramembranous ossification take place

A

most cranial bones, periosteal bones

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15
Q

endochondral ossification

simple explanation

A

mesenchyme undergo chondrogenesis form

cartilage

cartilage undergoes hypertrophy and degradation and is replaced by trabecular bone (on inside), and bone marrow cavity

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16
Q

intramembranous ossification

simple explanation

A

mesenchyme

compact bone (no marrow)

happens on outside of long bones and skull bones

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17
Q

steps of endochondral ossification

A

mixed process of endochondral and intramembranous ossification

  1. hylan cartilage blueprint
  2. perichondrium replaced with periosteum (compact bone- intramembranous ossification )
  3. cartilage cells undergo proliferation and hypertrophy, during hypertrophy cartilage cells produce different ECM (matrix that can mineralize)
  4. vessels invade bring cells to breakdown cartilage and make bone
  5. cartilage is broken down by chondroclasts leaving hypertrophic ECM backbone
  6. bone is deposited by osteoblasts onto this hypertrophic ECM backbone
  7. same process happens at ends of bones, growth plate in between
  8. continues until bone fully formed and two sites of ossification fuse
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18
Q

how does perichondrium change to periosteum

A

progenitor cells in the perichondrium differentiate into osteoblasts instead of chondroblasts

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19
Q

how is matrix produced by hypertrophic cartilage cells different

A

can mineralize

matrix can be invaded by blood vessels (periostial blood)

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20
Q

what kind of cells are brought into the bone during endochondral ossification

A

clasts, that eat cartilage cells (chondrocytes) and ECM matrix

osteoprogenitor cells- (differentiate into osteoblasts that make bone)

stem cells that form marrow environment

stem cells that form hematopoetic lineages

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21
Q

where does cartilage remain after bones are finished growing

what is different about this cartilage?

A

caps of bone- ends articular surface

no longer has perichrondrium - does not have cells to make cartilage- can not repair or regrow

protects bone

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22
Q

epiphysis

A

end of bones

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23
Q

diaphysis

A

shaft of bone

24
Q

periosteum

A

two layer membrane that covers bone

outer layer: dense irregular connective tissue with blood vessels

inner layer: progenitor cells

25
Q

inner membrane of bone

A

endosteum

26
Q

endosteum

A

inner membrane of bone

branched- has progenitor cells for bone and marrow stroma

27
Q

metaphysis

A

area of bone between epiphysis and diaphysis that contains growth plate and its products (endochondral ossification)- trabecular bone

28
Q

bone formed by endochondral ossification is called

A

trabecular

spongy

cancellous bone

and marrow

29
Q

bone formed by intramembranous ossification is called

A

periosteal

cortical

dense

compact

30
Q

what is this

A

endochondral ossification derived bone:

trabecular bone (spongy bone)(pink with purple center which is remnants of hypertrophic cartilage)

marrow (white with purple red blood cells)

31
Q

intramembranous ossification

A

bone used for structural support

mesenchymal cells (star cells) differentiate into osteoblasts that start to secrete ECM bone matrix (type 1 collagen, small PG and glycoproteins (osteoid)

as the osteoblasts secrete more ECM, ECM starts to mineralize (mineralizing osteoid) osteoblasts get stuck and become osteocytes

occurs in outward fashion, concentric rings

32
Q

matrix of bone that is not yet mineralized

A

osteoid

33
Q

cytoplasmic projections of osteocytes that reach out and touch other osteocytes

A

filopodia

34
Q

tiny canals through which osteocyte connect to each other

A

canaliculi

filopodia reach out and touch/ communicate with each other

35
Q

home of osteocyte

A

lacuna

36
Q

filopodia have calcium sensors and are bathed in interstitial fluid which allows for

A

calcium sensor: monitor EMC and determine if it needs to be broken down or made

interstitial fluid: can detect movement and detect pressure/ force put onto bone

37
Q

cell that breaks down bone

A

osteoclast

(not a connective tissue type- made from hematopoetic cells- similar to macrophage)

secrete hydrochloric acid which demineralizes hydroxyapatite

removed matrix- forms resorption pit -Howship’s lacunae

large amount of lysosomes

38
Q

pit of resorption made by osteoclast

A

howship’s lacunae

39
Q

primary bone is changed to ___

A

secondary bone

primary bone gets eaten and deposited in rings to form osteons

40
Q

IO: primary bone is unorganized, when it is remodeled it forms ___

A

secondary bone which is very organized in ring structures called osteons

41
Q

rings of bone

A

lamellae

42
Q

central canal of osteon

A

haversian canal

43
Q

what lives in haversian canals

A

dense irregular connective tissue

blood vessels

and nerves

44
Q

`mature secondary bone: other name

A

lamellae bone

45
Q

perpendicular canals in bone

connect what to what

A

volkmann’s canals

connect periosteal vessels, to haversian canale vessels and to bone marrow

46
Q

in trabecular bone new bone is formed

A

on outside, follows contour of hypertrophic cartilage underneath

47
Q

in compact bone, bone is remodeled

A

by osteoclasts eaten bones and osteoblasts reform bone in a concentric circle (osteon)

48
Q

flattened, line most bone surfaces, may represent quiescent osteoblasts

A

bone lining cells

49
Q

osteoblasts

A

make bone

50
Q

osteocytes

A

mature bone cells

non-proliferative, encased in mineral, extensive filopodia, monitor calcium levels and communicate with bone forming( osteoblasts) and bone resorbing (osteoclasts) cells

51
Q

osteoclasts

A

break down or resorb bone

large multinucleate, form monocytic lineage, on bone surfaces

52
Q

formation of bone

A

osteogenesis

53
Q

direct differentiation of mesenchymal cells to osteoblasts which secrete bone matrix

A

intramembranous ossification

54
Q

during skeletogenesis

A

bones increase in width and change their shape

primary bone is substituted by secondary

55
Q

during adult life: bone remodeling

A

means for bone to adapt to mechanical pressure

calcium storage and release mechanism

56
Q

during pathology: bone remodeling

A

calcium homeostasis disorders

fracture repair

57
Q

bone remodeling is the balance of ___ and ___ controlled by ___

A

osteoblasts (make bone)

osteoclasts (eat bone)

osteocytes

21 fall: histology (36 decks)

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