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Medical Histology > Bone > Flashcards

Bone Flashcards

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USMLE® Step 1 flashcards
1
Q

names for spongy bone

A

cancellous, trabecular, spongy

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2
Q

names for compact bone

A

cortical, lamellar, compact

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3
Q

where is spongy bone found

A

within epiphyses (but is covered with a layer of compact bone) of long bones, between the thick plates of the skull’s flat bones (diploe)

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4
Q

where is compact bone found?

A

the diaphysis of long bones (but has a thin layer of spongy lining the bone marrow cavity), thin covering surrounding epiphyses, tables/plates of flat bones - always lamellar bone

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5
Q

composition of outer layer of periosteum

A

fibrous layer of dense irregular connective tissue with collagen fibers, fibroblasts, blood vessels, nerves

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6
Q

composition layer of inner layer of periosteum (cellular layer)

A

periosteal (osteoprogenitor cells)

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7
Q

what are sharpey’s fibers

A

collagen fibers that extend into bone and are continuous with collagen fibers of the extracellular matrix - they are the sticky fibers that help connect periosteum to bone

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8
Q

what is the endosteum

A

thin layer of simple epithelium that lines internal marrow cavities and contains osteoblasts and osteoprogenitor cells

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9
Q

what is the periosteum

A

fibrous, vascular, nerve-containing outer layer of collagen bundles and fibroblasts and inner layer of osteoprogenitor cells

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10
Q

circular components of compact boneq

A

osteon, with central or Haversian canal in center

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11
Q

what is within Haversian canals?

A

vasculature, lymph, nerves (neurovascular bundle)

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12
Q

osteon made of

A

concentric lamellae with lacuna that houses the osteocytes

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13
Q

what is canaliculi

A

dendritic processes coming off of the lacuna (where the osteocyte is) that contain gap junctions that allow osteocytes to communicate

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14
Q

what role does the osteocyte play?

A

controls metabolic and remodeling rate of bone

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15
Q

what is a haversian canal

A

central canal in osteon containing neurovasculature, and runs parallel to bone length

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16
Q

waht is a volkman’s canal or perforating canal

A

vascular canal running perpendicular to bone length

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17
Q

what is lacuna

A

an embedded, hollowed out area between lamella that house osteocytes, are filled with canaliculi for cell communication

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18
Q

what is lamaella

A

concentric rings of compact bone that make up osteon rings

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19
Q

how do lamellae maintain strength while keeping a light weight?

A

regular bone remodeling/maintenance provides differing fiber orientations

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20
Q

what are the bony parts between spaces in spongy bone?

A

trabeculae/spicules

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21
Q

where is red bone marrow located and what is the function

A

epiphyses, site of hematopoiesis (synthesizes RBC, WBC, platelets)

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22
Q

where is yellow bone marrow located

A

diaphysis

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23
Q

osteoblasts

A

synthesis of bone matrix, rounded cells forming a simple row along outer edge of bone

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24
Q

osteoclasts

A

bone degeneration/resorption, large and motile and multinucleated cells derived from monocytes
MACROPHAGES THAT SECRETE ACID AND PROTEASES and COLLAGENASE TO BREAK DOWN BONE MATRIX

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25
Q

osteocytes

A

maintain matrix components, flattened and found within lacunae of bone matrix
REGULATE CA AND PO4 (PHOSPHATE)
they also sense mechanical stress and if bones are not used or there is stress, will signal to osteoblasts/clasts

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26
Q

where are osteoblasts derived from

A

osteoprogenitor stem cells (which are themselves derived from mesenchyme)

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27
Q

what is derived from osteoblasts

A

osteocytes and bone lining cells

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28
Q

what is osteoclast derived from

A

hemopoietic stem cells (CFU-GM)

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29
Q

components of bone matrix

A

65% inorganic components

35% organic components

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30
Q

what inorganic components are in bone

A

hydroxyapatite, bicarbonate, citrate, Mg, K, Na, CaPO4, H2O

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31
Q

what organic components in bone

A

type 1 collagen (type one = bONE)

ground substance rich in osteonectin and osteocalcin (for calcium binding, dependent on vitamin k)

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32
Q

why is the composition in bone minerals and type I collagen?

A

rigidity and flexibility

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33
Q

steps of mineralization in bone matrix

A
  1. osteoblasts release components as vesicles
  2. the released vesicles interact with collagen, Ca and PO4 in the osteoid layer (soup)
  3. Ca and PO4 start to mineralize around vesicles
  4. matrix becomes confluent between vesicles/mineralizes
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34
Q

what is osteosarcoma and where is it common

A

malignant tumor of osteoblasts, common in children around the knee joint

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35
Q

what is rickets/osteomalacia

A

vitamin D/calcium deficiency of absorption problem that impedes structural stability (decreases strength) of bone (ossification), so there is excess of non-mineralized osteoid

36
Q

how do osteoclasts produce acid

A

proton pump to create acidic environment that dissolves hydroxyapatite

37
Q

what is howship’s lacuna

A

a clear resorption zone within small depressions in the bone matrix adjacent to osteoclasts (ruffled border)

38
Q

what is the ruffled border

A

the surface against the resorbed bone matrix that is folded/irregular to increase surface area for assistance in breaking down border

39
Q

what is marble bone disease?

A

osteopetrosis, a defect in bone resorption causing overgrowth and thickening of bones that is prone to fracture, obliteration of bone marrow cavities and reduction in blood cell production

40
Q

pathology osteopetrosis

A

genetic defect in osteoclast fct with loss of ruffled borders and resorption bays/howships lacunae, usually caused by mutation in ATPase proton pump or chloride channels)

41
Q

what is intramembranous ossification

A
  1. where osteoblasts differentiate from mesenchyme directly and secrete osteoiid
  2. ossification occurs between membranes of embryonic mesenchymal tissue
  3. osteoblasts lay down woven bone which gets remodeled into lamellar bone
42
Q

what is endochondral ossification

A

where the hyaline cartilage precursor is replaced by osteoblasts producing osteoid, usually in long bones

43
Q

what is the 1st type of bone to appear during osteogenesis pathways ?

A

woven/primary bone - less mineralized, darker on xray, higher osteocyte to matrix ratio

44
Q

describe general woven bone

A

forms during embryonic development or after fx

randomly arranged bundle of calcified type I collagen

45
Q

describe general lamellar bone

A

parallel collagen fibers in concentric rings (lamellae)

46
Q

what type of ossification occurs mainly in flat bones?

A

intramembranous ossification, 2 layers of compact bone arise with a central spongy inner layer

47
Q

steps of intramembranous ossification

A
  1. ossification centers arise from WITHIN thickened regions of mesenchme - osteoblasts differentiate, secrete osteoid
  2. osteoid undergoes calcification
  3. woven bone and surrounding periosteum form - around vasculature - periosteum does not undergo minteralization
  4. lamellar bone replaces woven bone, compact and spongy bone form
48
Q

basic steps of endochondral ossification

A
  1. hyaline cartilage model forms through condensation and differentiation of mesenchyme (chondrogenesis)
  2. periosteal bone collar forms through intramembranous ossification
  3. proliferation of chondrocytes - primary ossification center forms in diaphysis
  4. hypertrophy of chondrocytes - secondary ossification center form in epiphyses
  5. calcification of matrix with apoptosis of chondrocytes
  6. primary cavity formation with remnant condrocyte lacunae - developing bone uses lacunae
  7. periosteal bud of blood vessels infiltrate primary marrow cavity
  8. ossification (osteoid deposited, mineralization via osteoblasts
49
Q

what does calcified cartilage look like

A

basophillic - purple, the calcified spicules during growth at the growth plate look purple

50
Q

what does osteoid formation look like

A

eosinophilic - pink/red, ossified bone looks pink

51
Q

how does bone grow around the ossification centers/epiphyseal growth plate? (esp in secondary center)

A

both directions grow toward the growth plate aka toward each other

52
Q

where does cartilage remain in the long bone

A
  1. articular cartilage (caps articulating ends to form joints)
  2. epiphyseal plate (connects epiphysis to diaphysis)
53
Q

5 zones of epiphyseal growth plates

A
  1. resting phase - hyaline cartilage with typical chondrocytes
  2. proliferation phase - cartilage proliferates and form columns
  3. hypertrophic cartilage - chondrocytes swell with glycogen
  4. zone of calcified cartilage - chondrocytes undergo apoptosis and matrix begins calcification
  5. zone of ossification - influx of bone cells, further matrix production within lacunae of apoptosed chondrocytes
54
Q

what is the process of bone fracture repair

A
  1. during week 1: hematoma forms around break and granulation tissue forms (fibroblasts, ECM, small blood vessels infiltrate)
  2. during weeks 2-3: a fibrocartilaginous callus forms from the fibroblasts (fibroblasts form chondroblasts which forms hyaline cartilage, fibroblasts form osteoblasts to form woven bone)
  3. during weeks 4-16: a hard callus forms - hyaline cartilage and woven bone are replaced by trabecular bone
  4. week 17+: bone is remodeled - trabecular bone is replaced by compact bone (using osteoclasts and osteoblasts)
55
Q

what process does bone fracture repair utilize?

A

both intramembranous ossification and endochondral ossification

56
Q

what is meant metabolic role of bone?

A

means that bone remodeling and bone calcium/blood calcium is regulated by hormones

57
Q

what controlls bone turnover equilibrium?

A

osteoblasts (tell osteoclasts what to do)

58
Q

fact about hydroxyapatite

A

bone stores 99% of the body’s total calcium in the crystals of hydroxyapatite

59
Q

what occurs in the event of low blood calcium?

A
  1. parathyroid hormone is released from the parathyroid gland
  2. binds to receptors on osteoblasts
  3. cessation of matrix production and release of osteoclast stimulating factor
  4. increased bone resorption and decreased bone production
60
Q

what happens in the event of high blood calcium?

A
  1. calcitonin is secreted from parafollicular cells in thyroid gland
  2. promotion of calcium incorporation into bone tissue via inhibition of osteoclast activity (blocking bone resorption) and stimulates osteoblast
  3. lowers blood calcium levels
61
Q

relation of growth hormone in bone growth and maintenance

A
  1. anterior pituitary secretes to stimulate bone growth, especially at the epiphyseal plate
62
Q

what is the consequence of deficient GH

A

dwarfism (children)

63
Q

what is the consequence of excess GH

A

gigantism (children), acromegaly (adults)

64
Q

relation of FGFR3 in bone growth and maintenance

A

fibroblast growth factor receptor 3, promotes cartilage growth

65
Q

consequence of FGFR3 mutation

A

inhibition of cartilage growth, dwarfism, achondroplasia

66
Q

what is achondroplasia

A

inhibition of endochondral ossification due to inhibition of precursor cartilage

67
Q

what do androgens and estrogens do for bone growth/maintenance

A

stimulates bone formation and impact timing of ossification center formation and epiphyseal closure

68
Q

why is androgenous steroid use harmful in developing children

A

since it impacts timing of ossification center formation and growth plate closure, growth could be stunted

69
Q

consequence of calcium and vitamin D deficiency

A

incomplete bone matrix calcification, increased bone resorption
(rickets = children)
(osteomalacia = adults)

70
Q

consequence of vitamin C and protein deficiency

A

reduced collagen synthesis, inhibiting bone growth and maintenance, slowing fracture repair
(scurvy)

71
Q

consequence of vitamin A deficiency

A

slow bone growth

72
Q

consequence of Vitamin A excess

A

slow cartilage growth and accelerated ossification causing skeletal deformities and short stature

73
Q

consequence of rickets

A

deformed and slow growing bones caused by Ca deficiency in childhood

74
Q

consequence of osteomalacia

A

deficient calcification and partial decalcification of bone caused by calcium deficiency in adults (weakened bone)

75
Q

consequence of osteoporosis

A

imbalance in bone turnover so that bone resorption exceeds bone formation (weaker bones)

76
Q

consequence of osteopetrosis

A

defective osteoclast function leads to overgrowth, thickening, hardening of bones, obliteration of bone marrow cavities

77
Q

what are diathroses

A

joints that permit free bone movement - usually synovial joints
ex. elbow, knee

78
Q

what are synarthroses

A

limited or no movement permitted

ex. skull sutures, sternoclavicular joint

79
Q

type A synoviocytes

A

macrophage-type cells derived from monocytes

80
Q

type B synoviocytes

A

fibroblast-like cells derived from mesenchyme

81
Q

function of type A synoviocytes

A

on surface of synovial membranes where they line the joint cavity and clear synovial fluid of waste and cellular debris

82
Q

function of type B synoviocytes

A

synthesize hyaluronic acid and other components of ground substance and synovial fluid

83
Q

components of synovial fluid

A

plasma like, rich in hyaluronan and lubricin

84
Q

function of synovial fluid

A
  1. reduces friction (lubricant)
  2. transports nutrients to chondrocytes in the articular cartilage (no perichondrium)
  3. shock absorption due to viscous consistency
85
Q

what is articular cartilage

A

hyaline cartilage that lacks the usual perichondrum covering with the collagen forming arches

Medical Histology (10 decks)

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