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Kin 1A03 > Bone tissue, Case study 4 > Flashcards

Bone tissue, Case study 4 Flashcards

1
Q

necrosis

A
  • cell or tissue death
  • if blood flow is cut off to femoral head, the bone tissue & marrow will die
  • if blood supply stops for a long period of time, bone tissue and joint structure will degenerate
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2
Q

what is a DEXA scan?

what does it measure?

A

(or DXA) Dual Energy X-ray Absorptiometry
measures mineral component of bone (inorganic) and determines fracture risk
- does not measure info re: levels of organic components (protein) in bone

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3
Q

how does a DEXA scan work?

A

sends x rays through body w 2 energy peaks

  • one peak is absorbed by soft tissue
  • one peak is absorbed by bone and so we can see both
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4
Q

osteoporosis

A
  • a loss of bone density

happens when osteoclast activity is greater than osteoblast activity

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5
Q

some factors affecting osteoporosis

A
  • menopause: loss of estrogen results in lack of osteoblast cells to come build bone
  • calcium and phosphorus levels in the blood: if too low, increases osteoclast activity
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6
Q

why is weight bearing physical activity used to treat/prevent osteoporosis?

A

any force on bone stimulates osteoblast cell activity

resistance exercise is best

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7
Q

what drugs are typically used to treat osteoporosis?

A

bisphosphonate drugs

  • slow resorption (process of breaking down bone tissue)
  • triggers osteoclast cells to undergo apoptosis
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8
Q

functions of the skeletal system

A

support - bone is rigid, cartilage is flexi&strong
movement - muscles attached to bones via tendons
storage - Ca & P in bone. Fat in yellow marrow
protection - cranium, ribs, vertebrae
blood cell production - red bone marrow

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9
Q

red bone marrow

A

produces blood cells and platelets

- replaced by yellow bone marrow as we age

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10
Q

yellow bone marrow

A

a means of fat storage

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11
Q

types of cartilage

A

hyaline cartilage
elastic cartilage
fibrocartilage

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12
Q

hyaline cartilage

A
  • fairly strong
  • present in moveable joints (ie usually synovial)
  • found in nose, trachea (rings)
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13
Q

elastic cartilage

A
  • has elastic fibres in it, along w collagen

- found in external ear

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14
Q

fibrocartilage

A
  • strongest
  • found in weight bearing joints (ex. disks b/w vertebrae, meniscus of knee)
  • no perichondrium therefore very hard to fix, repair
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15
Q

some things about cartilage

A
  • avascular: must get blood supply from outside
  • composed of cartilage cells and matrix
  • matrix composed of 70-85% water, proteins, ground substance
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16
Q

main cell type in cartilage is ? tell me more

A

chondrocyte
located in a cavity called a lacuna
- an immature chondrocyte is called a chondroblast

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17
Q

chondroblast

A
  • produce matrix: collagen, proteoglycans

- produce matrix around them and then get trapped inside the matrix and thus become chondrocytes

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18
Q

perichondrium

A
  • double layer of dense irregular CT that covers most cartilage
  • composed of fibroblasts & gets pushed out as chondroblast layer beneath grows
  • – the blood vessels and nerve supply for cartilage is here so nutrients and such must diffuse from here
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19
Q

articular cartilage

A

a type of hyaline cartilage

- no perichondrium therefore, it must get blood supply from nearby bone tissue

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20
Q

what are the name for which cartilage grows?

A

interstitial growth

appositional growth

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21
Q

interstitial growth

A

growth from within

  • 2 chondrocytes split and secrete matrix between them, this pushed other cells outwards
  • occurs during childhood and into adolescence
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22
Q

appositional growth

A

growth outside of cartilage w chondroblasts

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23
Q

bone composition? what’s it like?

A
  • made of extracellular matrix and bone cells

- bone cells are trapped in matrix, constant breakdown and replacing of old bone matrix

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24
Q

bone matrix

A

55% inorganic; crystallized mineral salts, white portion of bone, what mineralizes our bones
hydroxyapatite=calcium phosphate crystals
– gives compressive, weight bearing strength
45% organic: collagen / proteoglycans, water
– gives flexible strength

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25
Q

osteoblasts

A

build bone

  • produce collagen & proteoglycans (vesicles)
  • form matrix vesicles of hydroxyapatite
    • when these vesicles are released, bone matrix is formed (mineral framework and then add organic)
  • has extensions called processes, inside of one cell is attached to the inside of another blast cell
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26
Q

osteochondral progenitor cells

A

stem cells that can become osteoblasts or chondroblasts

can then turn into osteocytes and chondrocytes

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27
Q

osteocytes

A
  • an osteoblast surrounded by bone matrix, located in a cavity called lacuna
  • considered inactive
28
Q

canaliculi of osteocytes

A

matrix doesn’t form where processes are

- this is where nutrients and oxygen move through towards the cell

29
Q

osteoclasts

A
  • located on inside and/or outside of bone
  • large multinuclear cells, formed by fusion of bone
  • resorption
    • attaches itself to bone and creates a cavity w protein attachments, plasma membrane ruffles and gives surface area to digest bone
30
Q

resorption of bone

A

breakdown of bone

  • acid dissolves minerals ( calcium and phosphate)
  • enzymes digest proteins / proteoglycans
  • fragments of these guys are engulfed and digested
31
Q

classifications of bone

A

woven bone

lamellar bone

32
Q

woven bone

A
  • randomly oriented collagen fibres
  • how bones start out and end up when repaired
  • remodelled to create lamellar bone
33
Q

remodelling of woven bone

A

clast cells break down bone and blast cells rebuild bone into lamellae
- cyte cells are sandwiched between lamellae

34
Q

lamellar bone

A

mature bone organized into sheets/layers/rings called lamellae

35
Q

spongy/cancellous/trabecular bone

A
  • less bone matrix, more space
    more affected by osteoporosis bc of surface area
  • found inside bones: long bones, flat bones, vertebrae
  • makes up ~20% skeletal mass
  • protected by compact bone
  • nutrients rec’d through canaliculi
  • osteoctes sandwiched b/w lamellae
36
Q

why do we need spongy bone?

A

bc it allows skeleton to be lighter but still sturdy

37
Q

trabeculae

A

connecting rods/ plates

  • spaces are filled w blood vessels or bone marrow
  • oriented along lines of stress (in direction of muscle pulling)
38
Q

compact/cortical bone

A
  • dense, fewer spaces and only for cells and blood vessels
  • found on outside of all bones and shafts of long bones for strength
  • makes up ~80% of skeletal mass
39
Q

name the diff ways that lamellae are organized in compact bone

A
  • concentric lamellae
  • circumferential lamellae
  • interstitial lamellae
40
Q

blood vessels are found within compact bone organized in which ways?

A

as perforating canals (Volkmann)

and as central canals (Haversian)

41
Q

concentric lamellae

A
  • organized in osteons (osteon is the cylinder of bone tissue)
  • rings form around blood vessels (Haversian)
  • blood gases and nutrients diffuse outwards
42
Q

circumferential lamellae

A
  • lamellae sheets that line of the bone of the bone (around the outside hence, “circumference”)
43
Q

interstitial lamellae

A

columns formed in spaces between osteon circles

- are the leftover remnants of osteons that were broken down previously

44
Q

perforating canal

A

aka Volkmann canal
- carry blood vessels
- run perpendicular to the long axis in bone
think perforating as in they perforate the periosteum

45
Q

central canal

A

Haversian

- blood vessels that run parallel to long axis of bone

46
Q

the layers of periosteum are

A

outer - dense fibrous layer

inner - osteogenic layer

47
Q

dense fibrous layer of periosteum

A

outer layer of periosteum

- contains periosteal arteries and veins (blood supply to bones)

48
Q

inner osteogenic layer of periosteum

A

contains osteoblast, osteoclasts and osteochondral progenitor cells

49
Q

endostenum

A

connective tissue lining all internal surfaces of bones

ex. medullary cavity, spongy tissue, Volkmann’s canals, Haversian canals

50
Q

medullary cavity

A

contains yellow bone marrow

- infants born w red bone marrow here and it is replaced by yellow bone marrow as we age

51
Q

diaphysis

A

shaft of long bone - mostly compact bone

52
Q

epiphysis

A

end of long bone - mostly spongy bone

53
Q

metaphysis

A

the bit between the diaphysis and epiphysis

54
Q

osteogenesis/ossification

A
  • the process of forming bone tissue
  • begins in embryo at 8 weeks, when blood vessels start forming
  • mesenchyme becomes osteochondral progenitor cells
55
Q

types of bone development

A
  • intramembranous ossification
  • endochondral ossification

both ways produce woven bone which gets remodelled into lamellar bone

56
Q

explain the process of intramembranous ossification

A
  • mesenchyme cells create a membrane of connective tissue made of a collagen fibre framework
  • osteochondral progenitor cells become osteoblast cells that start to ossify the membrane at 8 weeks
57
Q

explain the process of endochondral ossification

A
  • mesenchyme cells become osteochindral progenitor cells, turn into chondroblasts that form a hyaline cartilage skeleton
  • blood vessels invade perichondrium of hyaline cartilage, stimulates osteochondral progenitor cells to become osteoblasts
  • perichondrium becomes the periosteum
58
Q

how does bone growth occur

A

appositional growth of bone tissue only: formation of new bone on the surface of old bone at epiphyseal plate w cartilage
- no interstitial growth bc bone matrix is too rigid

59
Q

growth of bone in length

A
  • takes advantage of interstitial growth of cartilage at epiphyseal growth plates
  • from bottom to top (anatomically) we have 4 zones of hyaline cartilage :
    zone of resting cartilage
    zone of proliferating cartilage
    zone of hypertrophic cartilage
    zone of calcified cartilage
60
Q

zone of resting cartilage

A

contains very slowly dividing chondrocytes (interstitial)

- stays connected to epiphysis

61
Q

zone of proliferating cartilage

A

rapidly dividing chondrocytes that divide into what looks like stacks of coins

62
Q

zone of hypertrophic cartilage

A

chondrocytes enlarge and mature, then secrete matrix vessels containing hydroxyapatite which starts to calcify the zone above it

63
Q

zone of calcified cartilage

A

chondrocytes die off and blood vessels and osteoblasts invade into this area from the endosteum

64
Q

growth of bone thickness

A
  1. osteoblasts beneath the periosteum lay down bone matrix and periosteal ridges form around the region where there’s a blood vessel
  2. ridges meet forming a tunnel that pinches off , periosteum becomes endosteum of the tunnel
  3. osteoblasts from the endosteum form new concentric lamellae, (build towards blood vessel)
  4. osteoblasts from periosteum from new circumferential lamellae
65
Q

bone remodelling

A

continuous action of osteoclast and osteoblast activity

  • as we grow w age, we need to increase the size of medullary cavity while thickness of bone remains relatively constant
  • it takes 10 years for entire skeleton to be rebuilt

Kin 1A03 (12 decks)

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