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Anatomy Quarter 2- 2023 > Lecture 8- Histology of Bone > Flashcards

Lecture 8- Histology of Bone Flashcards

1
Q

What are the different bone shapes

A

Long, short, irregular flat

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2
Q

What are the parts of the long bone

A

Epiphysis, metaphysis, diaphysis

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3
Q

What is the epiphysis

A

End of long bone, near articular cartilage

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4
Q

What is the metaphysis

A

Between articular cartilage and shaft

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5
Q

What is the diaphysis

A

Shaft of bone

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6
Q

Classifying bones by density/porosity

A

Compact vs cancellous

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7
Q

What are the functions of the bone

A

Structural framework for support and protection of body organs, levers for muscles to attain movement, house and make blood cells, fat storage, reservoir for minerals= calcium, phosphorus, magnesium, potassium

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8
Q

Bone is inelastic therefore bone is very good at ____ but less good at

A

Resisting tensile forces but less at resisting compressive and shearing forces

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9
Q

Organic component of bone matrix

A

Primarily made of type 1 collagen

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10
Q

Inorganic component of bone matrix

A

Calcium hydroxyapatite- mainly calcium and phosphorus

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11
Q

Periosteum and endosteum

A

Vascularized connective tissue that lines the surface of bone, nourish bone tissue and make bone cells for appositional growth

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12
Q

What does periosteum line

A

External surface of bone

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13
Q

What are the two layers of periosteum

A

Fibrous and inner cellular layer

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14
Q

Fibrous periosteum

A

Outer layer of dense connective tissue

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15
Q

Inner cellular layer

A

Contains osteogenic cells

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16
Q

What does the endosteum linen and do

A

Central cavity, loose CT, has monolayer of osteogenic cells and osteoblasts

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17
Q

Compact bone

A

Provides support to external surfaces of bone and makes up shafts of long bone, made of 4 lamellar systems =- outer circumferential, inner circumferential, osteons, interstitial

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18
Q

What is the outer circumferential lamellae

A

Deep to periosteum, outermost region of diaphysis, contains sharpey’s fibers anchoring periosteum to bone

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19
Q

Inner circumferential lamellae

A

Completely encircle the marrow cavity, trabecullae of spongy bone extend into marrow cavity

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20
Q

Osteons

A

Form bulk of compact bone

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21
Q

Interstitial lamellae

A

Remnants of osteons after osteoclast resorption

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22
Q

Secondary osteons

A

Form as bone remodels- replaces tissue damaged via micro fractures- form concentric lamellae of bone

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23
Q

Central canal

A

Contains blood vessels and nerves

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24
Q

Perforating canal

A

Connect central canals with each other and blood vessels in the periosteum and marrow cavity, perpendicular to central canals

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25
Q

Two different microtextures of bone

A

Woven (immature)and lamellar (mature)

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26
Q

Woven (immature) bone

A

Initial bone formation, fracture repair, poorly organized type I collagen, relatively weak

27
Q

Lamellar (mature) bone

A

Replaces woven bone, very strong; well organized, type I collagen

28
Q

Lamellar bone replaces woven bone during:

A

Formation of primary bone (primary osteons) and remodeling to form secondary bone (secondary osteons)

29
Q

Cancellous (trabecular, spongy) bone

A

Formed by interconnecting bony struts or trabeculae that provide internal support to bones, high surface area that facilitates calcium ion exchange between bone and blood

30
Q

Spaces between trabeculae contain either

A

Red marrow that produces blood cells and yellow marrow made of adipose tissue

31
Q

Osteoblasts function

A

Secrete ECM, lower blood calcium levels

32
Q

Osteocytes

A

Osteoblasts embedded in lacunae

33
Q

What do osteoblasts and osteocytes derive from

A

Osteoprogenitor cells

34
Q

Osteoclasts

A

Resort bone ECM

35
Q

What are osteoclasts derived from

A

Progenitor cells from the monocyte-macrophage lineage located in bone marrow

36
Q

What are inactive osteoblasts called

A

Bone lining cells

37
Q

Identifying factors of osteoblasts

A

Located along surface of bone, extensive rER, golgi, polarized organelles- nucleus located away from secretory activity

38
Q

Osteoblasts communicate via

A

Gap junctions

39
Q

Osteoid

A

Initial organic component synthesized by osteoblasts

Calcify, slowly calcify if low vitamin D

40
Q

Low calcium results in

A

Renal failure

41
Q

What do osteocytes direct

A

Bone remodeling in response to mechanical stimuli, form gap junctions with each other and osteoblasts by sending cell processes through channels in bone called canaliculi

42
Q

Organic portion of bone

A

Mostly type I collagen, histology looks pale before mineralized and called osteoid

43
Q

Inorganic portion of bone

A

Added to to osteoid, made of hydroxyapatite crystals that are mostly calcium ions bound together by multiadhesive glycoproteins. Osteoblasts secrete bone specific alkaline phosphatase an enzyme that aids in hydroxyapatite formation

44
Q

How do osteoclasts increase blood calcium levels

A

Resorb bone, endocytose into ECM, secrete into blood

45
Q

Ruffled border

A

Portion of osteoclast in direct contact with bone

46
Q

Clear zone

A

Ring of cytoplasm around restorative compartment, immediately surrounds ruffled border, lacks organelles

47
Q

Actin ring

A

Inside the clear zone helps create sealing zone isolating subosteoclastic compartment, prevents damage to tissue

48
Q

How is the inorganic portion of bone resorbed

A

Dissolved by pumping H+ ions into the resoprtive cavity. The ruffled border increases surface area for transport

49
Q

How is the organic portion of bone resorbed

A

Degraded by lysosomal enzyme that are secreted into cavity. Clear zone around it forms a seal to prevent secretions from damaging surrounding tissue

50
Q

What are the byproducts of resorption and what happens to them

A

Ca2+ are endocytosed by osteoclast and secreted into blood

51
Q

What are the two hormones that regulate bone ECM resorption

A

Parathyroid hormone and calcitonin

52
Q

Parathyroid hormone

A

Released by parathyroid gland, promotes resorption, increases blood calcium levels, receptors on osteoblasts, osteoblasts produce osteoclast stimulating factor

Effect: stimulate osteoclast to increase bone resorbing activity

53
Q

Calcitonin

A

Secreted by thyroid gland, slow resorption, decrease blood calcium levels, receptors on osteoclasts

Effect: inhibit osteoclast to decease bone resorbing activity

54
Q

What do oxygen levels determine

A

Differentiation of mesenchymal cells to facilitate either cartilage or bone formation

55
Q

What happens in a high O2 environment

A

Mesenchymal cells differentiate into osteoprogenitor cells and osteoblasts that form bone. This process is called intramembranous ossification and requires vascularized mesenchyme to supply O2

56
Q

What happens in low O2 environments

A

Mesenchymal cells differentiate into Chondrogenic cells and chondrocytes that form hyaline cartilage. As blood vessels grow into the cartilage, chondrocytes exposed to high O2 and start acting like bone cells by calcifying ECM. Eventually ECM is replaced with bone. Process called endochondral ossification. It begins in avascular mesenchyme and results in highly vascularized bone

57
Q

Steps in intramembranous ossification

A
  1. Mesenchymal cells near blood vessels differentiate into osteoblasts
  2. Osteoblasts form bone trabeculae. The early sites of bone formation near blood vessels are called ossification centers
  3. Over time, the trabeculae enlarge, fuse and remodel to form bones and marrow cavities internally
58
Q

Steps of endochondral ossification

A
  1. A low O2 environment induced mesenchymal cells to differentiate into chondrocytes that form hyaline cartilage model of the bone
  2. Blood vessels invade the cartilage inducing the formation of ossification centers bone cells migrate and replace the cartilage with bone
  3. Sheet of hyaline cartilage called a growth plate remains between the epiphysis and diaphysis. Growth plate is responsible for longitudinal growth. Growth ends when the growth plates are vascularized and replaced with bone
59
Q

Zone of reserve

A

Directs proliferation

60
Q

Zone of proliferation

A

Chondrocyte mitosis

61
Q

Zone of hypertrophy

A

Chondrocytes enlarge brining in O2

62
Q

Zone of calcification

A

Chondrocytes calcify the ECM

63
Q

Zone of ossification

A

Cartilage is replaced with bone

Anatomy Quarter 2- 2023 (39 decks)

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