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Musculoskeletal, Skin > 090314 bone > Flashcards

090314 bone Flashcards

1
Q

how is bone specialized CT?

A

it is CALCIFIED extracellular matrix

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2
Q

what is bone a reservoir of

A

Ca, phosphate

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3
Q

what 3 cell types are in bone?

A

osteoblasts
osteocytes (maintain bone)
osteoclasts (activated by PTH of the parathyroid, inhibited by calcitonin of the thyroid)

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4
Q

what is in the matrix of bone?

A

inorganic stuff is 70%

organic stuff is 30%

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5
Q

what’s in the inorganic stuff of the matrix of bone?

A

Ca + phosphorus = hydroxyapatite

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6
Q

what’s in the organic stuff of the matrix of bone?

A

type I collagen
proteoglycans (less than in cartilage)
glycoproteins (promote hydroxyapatite formation)

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7
Q

what does type I collagen stain

A

acidophilia, red

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8
Q

what is a glycoprotein that is bone specific?

A

osteocalcin

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9
Q

what is the organic matter of the matrix of bone called?

A

the osteoid

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10
Q

why is bone so hard?

A

combined hydroxyapatite AND collagen type I

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11
Q

diff btwn bone and cartilage?

A

bone has 70% hydroxyapatite/mineral content, whereas hyaline cartilage has none

bone is 25% water, hyaline cartilage is 75%

bone has type I collagen, hyaline cartilage has type II (softer) collagen

bone has neuronal and vascular structures, but hyaline cartilage has none

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12
Q

osteoblasts are what kind of cell

A

fibroblast (specialized)

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13
Q

the only osteoblast specific genes

A

Cbfa-1 (master gene transcription factor)

Osteocalcin

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14
Q

what growth factors induce osteoblast differentiation?

A

bone morphogenetic proteins (BMPs)

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15
Q

what do osteoblasts do?

A

make osteoid (type I collagen and glycoproteins)

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16
Q

how is bone formation completed?

A

osteocalcin-mediated deposition of calcium within the osteoid

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17
Q

what do osteocytes occupy

A

lacunae (1 osteocyte per lacuna)

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18
Q

what is the function of osteocytes

A

maintaining bone matrix

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19
Q

what runs in the canaliculi of lacuna?

A

the cytoplasmic processes of osteocytes (they extend to join those of other osteocytes via gap jxns)

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20
Q

role of osteoclasts

A

destroy or remodel bone matrix

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21
Q

what is special about the nucleus of osteoclasts

A

multinuclear-developed from macrophages that fused together

22
Q

where do osteoclasts reside

A

hollow areas of matrix called Howship’s lacunae

23
Q

what does the ruffled border of the osteoclast do?

A

attaches to ECM and provides microenvironment promoting bone resorption

24
Q

how are osteoclasts regulated?

A

by HORMONES (calcitonin, PTH)

25
Q

how does PTH activate an osteoclast

A

lysosomes manufacture cathepsin K, which is secreted into microenvironment; promotes secretion of acid, which activates the Cathepsin K

26
Q

where are cells of bone located

A

osteoblasts-periosteum, with smaller numbers in endosteum

osteocytes-within lacunae of bony matrix between periosteum and endosteum

osteoclasts-mostly attached to bony matrix on endosteal side

27
Q

compact bone

A

also called cortical bone

dense, no cavitation

28
Q

spongy bone

A

also called cancellous, trabecular bone

has cavitations

29
Q

microscopic appearance of compact vs spongy bone

A

identical

30
Q

flat bone

A

2 plates of compact bone surrounding diploe of spongy bone

31
Q

long bones

A

have diaphysis and epiphyses

diaphysis is compact with spongy bone lining marrow

epiphysis has cap of compact bone around spongy bone

32
Q

osteon

A

cylinder in long bone with concentric lamellae

33
Q

what does the innermost lamella in an osteon surround

A

Haversian canal

34
Q

HOw are Haversian canals connected

A

volkmann’s canals

35
Q

primary bone vs secondary bone

A

primary is immature (fetus, or broken bone, or in remodeling process)

secondary is mature/lamellar

36
Q

two ways in which bone develops

A

intramembranous (osteoblasts deposit osteoid onto mesoderm)

endochondral (osteoblasts deposit osteoid onto cartilage)

37
Q

endochondral bone development

A

bone forms on hyaline cartilage

at diaphysis-osteoblasts invade CALCIFIED cartilage–secrete osteoid to get ossification

at the epiphyses-same process as above. articular cartilage remains at ends of bones. epiphyseal plate cartilage remains for growth in length

for fetus development and natural repair of fractures

38
Q

how do long bones get long (part one)

A

sex steroid hormones influence pituitary, which secretes growth hormone (GH/somatotropin), which caues liver to make somatomedin (or IGF-1), which goes to the epiphyseal plate

at epiphyseal plate:
there’s reserve cartilage, and beneath that-there’s a zone of proliferation, which is induced by somatomedin (IGF-1)

39
Q

how do long bones get long (part two)

A

the zone of proliferation has chondrocytes

next is the zone of hypertrophy (20% of fractures)

40
Q

how do long bones get long (part three)

A

next is the zone of calcification (basophilic), where you will find collagen X, not collagen II). This will be calcified cartilage.

next is the zone of ossification, which is eosinophilic due to the deposition of collagen I by osteoblasts

41
Q

how does fracture repair occur?

A

macrophages remove debris

chondroblasts secrete callus of hyaline cartilage

osteoblasts replace cartilaginous callus with bony callus

primary bone replaced by secondary bone

42
Q

what happens with difficult fractures that don’t heal?

A

they require grafting

43
Q

what are therapeutic targets for osteoporosis

A

osteoclasts and osteoblasts

44
Q

how are osteoclasts regulated by PTH?

A

stromal cells in bone marrow are induce by PTH to secrete three factors that regulate osteoclasts

the three factors are: RANKL, OPG, M-CSF

45
Q

role of M-CSF

A

induces macrophage proliferation

46
Q

RANK-L

A

induces macrophage differentiation into osteoclasts

47
Q

OPG

A

osteoprotegerin - it antagonizes RANK-L by binding to its receptor

48
Q

alpha5beta3

A

enalbes attachment of osteoclasts to bone

49
Q

leptin has what action

A

inhibts osteoblasts

50
Q

what is induced by PTH?

A

osteoblasts (when there’s spikes of PTH) and osteoclasts

51
Q

anabolic drugs

A

pro-osteoblast

PTH 1-34 (teriparatide/Forteo)

52
Q

anti resorptive drugs

A

anti-osteoclast

SERMs (raloxifene)
bisphosphonates (ibandronate/Boniva)
calcitonin

Musculoskeletal, Skin (33 decks)

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