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bone structure and growth Flashcards

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1
Q

what are the main roles of the skeleton

A

structural: enable movement, support and form structure and protect internal organs
homeostasis: storehouse for essential minerals and primarily 85% phosphorus and 995 calcium, house the bone marrow (site of hematoposis- makes red blood cells and store white blood cells, site of energy metabolism and endocrine functions

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2
Q

what are the two types of bones

A

-cortical (compact/dense bone): it is the outer ring of our long bones. the ring on the inside is the bone is the marrow space. it makes up 80% of our total bone mass, its 10% porous and provides strength to structure
-cancellous (trabecular/spongy) bone: this is the bone inside. it makes up 205 OF THE TOTAL BONE MASS, HIGHLY POROUS (50-90%). they align in directions of strains to provide extra structural support. it can provide some shock absorption, resistance to strain.

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3
Q

what is the space in the middle of the bone called

A

marrow space.

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4
Q

parts of cortical bone

A
  • Haversian canals: the holes that you see where the nutrients and blood flows through
  • osteons: concentric rings of the bone
  • osteocyte lacunae: embedded in the bone matrix
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5
Q

aside from offering some absorption to show and resistance to strain, what is the trabecular bone especially important for:

A

provides a large bone surface area for mineral exchange. this provides the minerals the chance to release minerals from the matrix to parts of the body that need it.

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6
Q

do trabecular bone have osteons

A

they have osteocytes. they are not as uniformly organised and not as compact.

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7
Q

what is happening to the fibres that make up the extracellular matrix

A

it is composed of collagen fibril, especifically collagen 1. this is in the nanostructure. this is formed by the tropocollagen triple matrix (subnanostructure). the collagen molecules are very densely packed.they are stuck together by sugars

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8
Q

what doe collagen d for the bone

A

it provides elasticity

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9
Q

what are hydroxyapatite crystals

A

they provide rigidity to the matrix. when the matrix is made, collagen is laid down and the cells that make the matrix will mineralise it by releasing these crystals that will embed themselves.

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10
Q

why is itimptnat to balance collagen and hydroxyapatite crystals

A

hyperminineralised- brittle because it does have enough elasticity
under mineralised: too mcc collagen- too bendy it cannot withstand load or provide structure or protect your organs.

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11
Q

why does the body keep remodelling the skeleton

A
  • repair damage to skeleton
  • prevent accumulation of ages tissue/micro damage
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12
Q

how often does the skeleton get remodelled

A

every ten years, you essentially will have a new skeleton.

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13
Q

what are the four structures we can view bone as

A

macrostructure
microstructure
nanostructure
subananostructure

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14
Q

why do we keep remodelling our bones

A

to repair micro tears and prevent fatigue fractures (stress fracture. this is also to supply calcium and phosphorous in the body.

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15
Q

what processes rely on calcium.

A
  • neuromuscular junction
  • muscle contraction
    we need calcium circulating. deficit will make us use the calcium in the bones through remodelling.
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16
Q

what does bone remodelling look like

A

osteocyte:
osteoclast: bone reabsorbing cells. they remodel and resorb our bone tissue
osteoblast: lay down new bone.
bone lining cells: sit on the bone surface.

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17
Q

is the bone marrow space vascular

A

It is -for release of blood cells. its also full of immune cells.

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18
Q

osteocytes:

A
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19
Q

what are the three phases in the remodelling stage of the one

A
  1. quiescent
  2. reabsoption
  3. reversal
  4. formation
  5. mineralisation
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20
Q

what initiates remodelling cycle

A

osteocytes which are embedded in the bone sense there’s damage. they play a key role in sensing mechanical signal and sense disconnection
we need mineral release.

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21
Q

explain the step by step process of bone remodelling.

A

after sensing shy we need to remodel, osteoclasts precursors are released to the bone surface, they fuse together to form multinucelotid osteoclasts that start eating away the old bone. this stimulates the formation of osteoblasts and lay new bone.

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22
Q

explain how osteoblasts lay down new bone

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A

they lay down collagen fibres and they align into osteoid (non minrealised), they mineralise it. they derive from mesenchymal lineage.

23
Q

what happens when there is no more need to lay down new bone

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A

they can terminally differentiate into an osteocyte or return to resting bone lining cell.

24
Q

where do osteocytes come from

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A

osteoblasts that embed themselves.

25
explain the role of osteoclasts
they degrade bone structure. they are multinucleoteid by fusion of multiple cells. they are fagocitic cells. they bind to the bone surface and create a sealing zone where they can create an acidic environment and deminrelaise the matrix and break it down. they take the mineral out and secrete proteases to break it down.
26
how can we measure how active our osteoclasts and osteoblasts to determine how healthy our bone are.
blood measures because osteoclasts release this during the breakdown of the matrix
26
aside from removing existing bone, what else do osteoclasts do
they release minerals into the circulation that we need like calcium when we have a deficit.
27
role of osteocytes
used to be osteoblasts. they are therefore known as terminally differentiated osteoblasts- they will never change again.
28
how do osteocytes connect
they have little arms that connect them from each other and to the bone surface through gap junctions in little channels called canalicular network that run all the way to the bone matrix
29
why is it important for osteocytes t be connected
by forming a canalicular network , they can communicate to themselves, the bone surface and sense fluid flow and sense mechanical strength. they sense and respond to the load exerted into the skeleton. they can release different things to control what other cells do. eg. RANKL which bind to osteoclasts precursors
30
what is the master regulator of bone remodelling
osteocytes
31
how do bones grow
it uses two approaches to form in utero. we have two different types of ossification/ mineralisation. these are intramembrous ossification and endochondral ossification
32
explain what intramembrous ossification is
this is how our flat bones form. this includes the skull, sternum. scapular on our shoulder.
33
explain how intramembrous ossification work.
it takes place through the stimulation of osteoblasts differenciating and just laying down bone in the middle of some mesechymal tissue condensation. there is no template and simply go off the signal that bone is needed to be laid .they fuse together to form a tubecular network. it is then remodelled with time and we get a collar of periosteal bone that forms on the outside to make the cortical bone.
34
what are the two types of bones
flat and long bone
35
what are the autonomical structures of lone bone
1. epiphysis: sits on either end of the bone. its trabecular 2. diaphysis: the shaft of the one or the stem. its trabecular and cortical 3. epiphyseal line: growth plate. its a line on the epiphysis 4. marrow cavity: in the middle 5. periosteum: outer surface of the bone 6. endosteium: inside surface of the ring in the cortical bone where the marrow is. 7. metaphyis: sits above or below the epiphysis
36
how do long bones form
it forms through the endocondral ossification. they form from a cartilage template (chondrocites) . they start as cartilage tissue then get signals to form periosteum which allows blood vessels to penetrate - important because tissue avascular and have no blood supply here. they bring along with them other cells. we start to see ossification of cartilage cells tis forms the marrow space. the bone continuous to grow and we form the trabecular bone on the inside.we then begin to see changes that occur in postnatally.
37
how do we stop growing
our growth plate closes and means that we have finished longitudinal growth.
37
when do epiphyses ossify
they ossify postnatally
38
why are babies born in breech position need a brace
this is because the epiphyses does not ossify until post natal. the brace will ensure that it ossidifys and prevent hip dysplasia.
39
are growth plates mineralised
no until they close
39
how do we grow bones through endochondral ossification
chondrocytes which hare on top of the growth plate proliferates very quickly. they do this in a columnar manner to achieve length and therefore extend the bone. as chondrocytes move don the growth plate, they will swell and undergo hypertrophy. this means there's less matrix and they're swelling and forcing more space around the nucleus and they again achieve longitudinal growth by opening in a column. they will then calcify/mineralise hypertrophic cartilage and before reaching apoptosis.it acts as a template for osteoblasts to form down new bone.
40
in scientific language. how does long bone grow
- chondrocyte proliferation and hypetrrophy -calcification of hypertrophic cartilage and apoptosis - degradation of transverse septa, vascular invasion - new bone formation on calcified remnants by osteoblasts- primary spongiasa.
41
what is osteoporosis
characterises by compromised structure and strength, leading to an increased change of fracture
42
why is it important to talk osteoporosis
most common bone metabolic disease
43
what age do peak bone mass occur
around age 30, since then, it will begin to degrade
44
why do females have dramatic decrease of bone mass
menopause. loss of oestrogen.
44
what test do you do to determine bone density
blood test and DEXA scan- we focus on hip and invertebrate because we commonly see fractures there.
45
that causes osteoporosis
imbalance in bone remodelling, too much osteoclass and not enough osteoblasts leading to netloss in bone mass
46
main causes for osteoporosis
sex hormones- oestrogen suppresses osteoclasts and increase osteoblast, loss of this leads to imbalance. testosterone- source of eostrogen. age gender height and BMI genetics calcium and protein intake
47
47
why is a sedentary lifestyle detrimental to our skeleton
we lose bone mass, there is no load
48
how to help with bone mass
heavy wight low bearing exercise

human bio (27 decks)

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