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B5W1 > BUILDING AND MAINTAINING THE SKELETON > Flashcards

BUILDING AND MAINTAINING THE SKELETON Flashcards

1
Q

what are the functions of bones?

A

to protect organs, to provide support and rigidity to limbs, haematopoiesis (marrow), storage of minerals, movements, endocrine regulation

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2
Q

where are the bones of the head derived from embryologically?

A

neural crest

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3
Q

where are the bones of the body derived from embryologically?

A

the mesoderm

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4
Q

where do we find somites?

A

either side of the developing neural tube in the developing embryo

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5
Q

what are somites?

A

blocks of mesoderm that give rise to the cells that form the vertebrae, ribs, the dermis of the dorsal skin, the skeletal muscles of the back, and the skeletal muscles of the body wall and limbs.

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6
Q

what are neural crest cells?

A

multipotent cells at the border of the neural plate that migrate throughout the embryo and later differentiate into multiple cell types

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7
Q

how is the shape of the vertebrae determined?

A

hox genes control regional development of the spine and they control development of limbs and structures throughout the body

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8
Q

describe when and how the limbs form?

A

weeks 4-5
The apical ectodermal ridge which contains a set of cells which release chemical signals which interact with signals from the zone of polarising activity and help with patterning- they determine segments and appropriate cartilaginous precursors for bones

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9
Q

where do we find the apical ectodermal ridge?

A

the distal most part of the limb bud is

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10
Q

what is ossification?

A

the process of developing bones

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11
Q

what is endochondral ossification?

A

The process by which growing cartilage is systematically replaced by bone to form the growing skeleton.

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12
Q

describe the difference between how young and old cartilage grows?

A

young cartilage grows interstitially whilst old cartilage tends to grow from the outside

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13
Q

why do blood vessels invade cartilage when it gets to a certain size?

A

as diffusion can no longer provide the nutrients that the chondrocytes need

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14
Q

where are the 2 ossification centres?

how are they separated?

A

the diaphysis and the epiphysis

by the epiphyseal growth plate

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15
Q

describe simply how bone grows?

A

bone is deposited everywhere within the cartilage but is remodelled to remove bone from the outside and put on the outside to form the medullary cavity

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16
Q

what are the 6 layers of the epiphyseal plate called?

A 
zone of reserve cartilage
zone of proliferation
zone of maturation
zone of hypertrophy
zone of cartilage degeneration
oesteogenic zone
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17
Q

what is within the zone of reserve cartilage in the epiphyseal plate?

A

a thick layer of small, randomly orientated chondrocytes

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18
Q

what is within the zone of proliferation in the epiphyseal plate?

A

cartilaginous cells in stacks. These stacks of cells are the ones driving the two ossification centres apart

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19
Q

what happens in the zone of hypertrophy in the epiphyseal plate?

A

chondrocytes increase in size and minerals begin to deposit into the matrix

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20
Q

what happens in the zone of cartilage degeneration in the epithyseal plate?

A

the chondrocytes are now far from blood vessels and are less able to gain nutrients, so they die leaving behind a fragmented calcified matrix

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21
Q

what happens in the osteogenic zone of the epiphyseal plate?

A

Osteoprogenitor cells and blood vessels from the periosteum invade the fragmented calcified matrix area, proliferate and differentiate into osteoblasts which start to lay down bone matrix.

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22
Q

what is the epiphysis?

A

the end part of a long bone, initially growing separately from the shaft.

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23
Q

what is the physis?

A

the epiphyseal plate

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24
Q

what is the metaphysis?

A

The metaphysis is the neck portion of a long bone between the epiphysis and the diaphysis. It contains the epiphyseal growth plate

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25
Q

what is the diaphysis?

A

the shaft or central part of a long bone

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26
Q

what is all connective tissue comprised of?

A

cells, fibres and ground substance

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27
Q

describe the process of chondroblasts becoming chondrocytes?

A

chondroblasts secrete the extracellular matrix around them and they eventually become trapped in lacunae. they become mature chondrocytes which maintain the cartilage around them.

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28
Q

what is the diaphysis of a bone composed of?

A

compact bone with a central medullary canal containing fatty yellow bone marrow

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29
Q

what is the epiphysis of a bone composed of?

A

an outer covering of compact bone with cancellous (spongy) bone inside

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30
Q

why is cartilage never very thick relative to bone?

A

as they have no blood vessels so rely on diffusion

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31
Q

what is the difference between interstitial growth and appositional growth?

A 
interstitial= growing in all directions (increases length of bone)
appositional= growth at the surface (increases diameter of bone)
32
Q

why does cartilage heal poorly?

A

as it has no blood supply

33
Q

what is bone made of other than connective tissue?

A 
calcium salts (mainly calcium phosphate)
osteoid- mainly collagen fibres
34
Q

describe the microscopic structure of cortical bone?

A

made up of osteons which each have a central canal containing nerves, lymphatics and blood vessels, surrounded by expanding rings-lamellae. each central canal is linked with neighbouring canals by perforating canals. between lamellae are lacunae- within each is an osteocyte. lacunae communicate to each other through canaliculi. between osteons are interstitial lamellae

35
Q

what are interstitial lamellae?

A

the remnants of older systems partially broken down during remodelling or growth of bone

36
Q

what are osteons also called?

A

Haversian systems

37
Q

how are osteons arranged to give bone greater strength?

A

they tend to align the same way that the force us applied to the bone

38
Q

how do lacunae communicate?

A

the canaliculi allow circulation of interstitial fluid through the bone and direct contact between the osteocytes

39
Q

what are circumferential lamellae?

A

Layers of bone matrix that go all the way around the bone.

40
Q

where do osteoblasts come from?

A

osteoblast precursors in the periosteum

41
Q

what do osteoclasts do?

A

they break down bone by secreting HCL to dissolve thecalcium in the bone and enzymes to digest the collagen fibres

42
Q

how do osteoblasts form new bone?

A

they secret osteoid to gradually replace cartilage and then they lay down calcium and phosphate salts.

43
Q

what type of bone is formed first developmentally?

A

woven bone- mechanically weak because of randomly orientated collagen fibres

44
Q

what type of bone is formed second developmentally?

A

lamellar bone- mechanically strong as collagen fibres are parallel and in layers

45
Q

what is bone remodelling?

A

continuing process of synthesis and destruction that gives bone its mature structure and maintains normal calcium levels in the body.

46
Q

what is the difference between primary and secondary osteons?

A

primary- formed by mineralisation of cartilage when bone is not present
secondary- formed by replacement of existing bone

47
Q

why is the shape of our face different to other primates?

A

surface remodelling- the anterior margins of the face resorb to keep the face vertical

48
Q

what is the function of cancellous bone?

A

contains red bone marrow which produces blood cells

reduces the weight of the skeleton as it is ‘spongy’

49
Q

describe the microscopic structure of cancellous bone?

A

a bony framework formed by trabeculae. the bone tissue is very sparse

50
Q

why do trabeculae form in cancellous bone?

A

as osteoclasts remove bone from the middle of the bone

51
Q

where do we tend to find trabeculae in bone?

A

where we need re-inforcement e.g. at the epiphyses where forces don’t align very well

52
Q

why is skeletal mass lost during breast feeding?

A

as the bones are raided for their calcium

53
Q

why is prevention of osteoporosis better than treatment?

A

as not much can be done to restore bone and drugs just tend to thicken the remaining trabeculae rather than restoring the lost ones

54
Q

which hormones are important in bone growth?

A

growth hormone, thyroxine, triiodothyronine, testosterone, oestrogen, calcitonin. parathyroid hormone

55
Q

why are oestrogen and testosterone important in bone growth?

A

rising levels give the growth spurt of puberty

56
Q

why does menopause increase risk for osteoporosis and fractures?

A

as oestrogen levels drop

57
Q

what does calcitonin do?

A

increase calcium uptake in bone- reduces blood calcium

58
Q

what does parathyroid hormone do?

A

increases blood calcium by decreasing calcium uptake by bone

59
Q

which bones will be remodelled fastest?

A

those subject to high stress e.g. if you life weights

60
Q

what does the bone need from the diet?

A

calcium and vitamins A C D

small amounts of phosphate, iron and manganese

61
Q

what is vitamin A needed for?

A

osteoblast activity

62
Q

what is vitamin C needed for?

A

collagen synthesis

63
Q

what is vitamin D needed for?

A

calcium and phosphate absorption from the intestinal tract

64
Q

what is osteoporosis?

A

a bone disease that occurs when the body loses too much bone, makes too little bone, or both. As a result, bones become weak and may break more easily.

65
Q

what are synarthroses?

A

an immovably fixed joint between bones connected by fibrous tissue

66
Q

what are syndesmoses?

A

a fibrous joint held together by ligaments- found between parallel bones

67
Q

what type of joints are there?

A

synarthroses-immovable
amphiarthroses- slightly movable (cartilaginous)
diarthroses- freely moveable (synovial)

68
Q

what is the structure of a synovial joint?

A

The articular capsule surrounds the joint and is continuous with the periosteum of articulating bones. The articulating surfaces of a synovial joint are covered by a thin layer of hyaline cartilage. there is synovial fluid within the joint cavity

69
Q

what are the 2 functions of articulating cartilage?

A

minimising friction upon joint movement and absorbing shock

70
Q

what is the function of synovial fluid?

A

Lubrication
Nutrient distribution
Shock absorption

71
Q

describe the histology of articular cartilage?

A

the outer layer is here cells align parallel to the surface. the next layer has no orientation to the cells. in the radial layer we find cells in columns. beneath this we find calcifying cartilage and beneath this is bone.

72
Q

what is osteoarthritis?

A

Where the articular cartilages break down through injury or disease or age- wear and tear

73
Q

what is rheumatoid arthritis?

A

If the synovial membrane becomes inflamed through autoimmune disease

74
Q

describe the haematoma formation in bone healing?

A

a collection of clotted blood forms rapidly between the ends of bones and in surrounding tissue. this acute inflammatory response causes swelling and attracts inflammatory cells. this stage is painful as the periosteum has many nerve endings

75
Q

describe the callus formation in bone healing?

A

the haematoma is stabilised with fibrin and becomes the framework for the formation of granulation tissue. fibroblasts migrate to the site to lay down collagen fibres and other repair materials. osteoblasts begin laying down new osteoid and bone ends are joined with soft tissue. macrophages phagocytose dead bone to clear the way for new bone. new capillaries begin to grow with the granulation tissue

76
Q

describe the bony callus formation in bone healing?

A

after about 2 weeks, a bony callus forms as osteoblasts begin to calcify the osteoid. callus is laid down as spongy bone and unites, supports and splints the fracture. the haematoma is being progressively removed

77
Q

describe the recanalisation and remodelling step in bone healing?

A

a period of remodelling converts the external callus to compact bone and reanalyses bone by osteoclasts.

B5W1 (9 decks)

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