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Medicine phase 2 limbs and back > week 5 > Flashcards

week 5 Flashcards

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1
Q

cellular differentiation

A

process of one cell type changing to another cell type

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2
Q

how does differentiation affect a cell

A 
size
shape
membrane potential
metabolic activity
responsiveness to signals
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3
Q

when do limbs start to form

A

week 4

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4
Q

mesenchyme

A

connective tissue found in embryo development
arises from mesoderm
contains loosely packed cells which are non specialised
mesenchymal cells are highly migratory

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5
Q

limb development stages

A

at the end of week 4 - limb buds first become visible
upper limb buds appear first as ridges from ventrolateral body wall
lower limb as small bulges
limb morphogenesis takes place between weeks 4 and 8
lower limbs lag slightly behind
no nerves in early limb bud

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6
Q

where is mesenchyme derived from

A

dorsolateral mesoderm cells of the somites

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7
Q

components of mesenchymal connective tissue

A

matrix of collagen fibres
hyaluronic acid
glycoproteins

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8
Q

structure of a limb bud

A

mesenchymal core - from somatic layer of lateral plate mesoderm
covered by a layer of cuboidal ectoderm
apical ectodermal ridge at distal border

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9
Q

what is the AER

A

apical ectodermal ridge
it is thickened ectoderm at the distal border of a limb bud
has an inductive relationship with mesoderm
remains undifferentiated
key signalling centre in limb development - limbs fail to develop without AER

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10
Q

limb development after AER has formed

A

as limb grows, cells furthest from the AER begin to differentiate into cartilage and muscle
limb outgrowth initiated by secretion of FGF10
position of AER corresponds to border between dorsal and ventral ectoderm

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11
Q

role of FGF10 in limb development

A

signalling molecule first seen in the limb bud
paracrine signalling molecule
FGF family known for mitogenic activity - induce a cell to begin division via triggering a signal transduction pathway

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12
Q

where is radical fringe expressed

A

expressed by dorsal ectoderm

its a signalling molecule

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13
Q

what does the ventral ectoderm express

A

transcription factor called engrailed1

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14
Q

function of FGF 4 and 8 in limb development

A

at distal end keep cells undifferentiated

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15
Q

function of engrailed1 and radical fringe in limb development

A

RF - in dorsal limb it restricts AER to the distal tip

engrailed does the same on the ventral side

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16
Q

function of retinoic acid in limb development

A

at the proximal end starts differentiation into prox components - signals from AER to not reach to prox

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17
Q

what are the factors designating UL and LL

A

t-box family TFs
TBX-5 expressed in the UL
TBX-4 expressed in the LL

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18
Q

mesoderm and ectoderm relationship in AER

A

AER is ectoderm and is acting on mesoderm but its own existence is controlled by mesoderm

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19
Q

week 6 of limb development

A

terminal portion of buds becomes flattened - handplates and footplates
seperated from the proxmal segements by constriction (wrist)
second constriction further divides proximal portion into 2 segments (elbow)

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20
Q

3 components of limb in development

A

stylopod - humerus and femur
zeugopod - radius/ulna and tibia/fibia
autopod - carpels, metacarpals, digits, tarsals/metatarsals

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21
Q

function of HOX genes in limb development

A

regulates positioning of limbs along craniocaudal axis
expressed in overlapping patterns
mis expression will alter limb position

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22
Q

polydactylyl

A

extra digits due to a defect in mesoderm - mutation in HOX genes, Shh or Wnt

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23
Q

what happens after cells start to die in AER

A

cell death in AER separates ridges into 5 parts - 5 digits grow out under influence of 5 ridge parts
mesenchyme condense to form cartilaginous digits
by d56, digit separation is complete

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24
Q

describe limb rotation after development

A

LL develops 1-2 days later
limb development over week 7
UL and LL rotate in opposite directions
rotation occurs from from coronal to the parasaggital plane, then along the long axis

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25
which way does UL rotate in development
UL rotates 90 degrees laterally | extensor muscles lie lateral ad posterior side
26
which way does LL rotate in development
rotates 90degrees medially | extensors on anterior surface
27
appositional growth
increase in girth/width | chondroblasts deposit collagen matrix on cartilage beneath the periosteum which initiates growth
28
interstitial growth
increase in length | achieved by growth plate up until puberty - cartilage can do this not bone
29
endochondral ossification
cartilage model laid down as a precursor to bone | mainly in long bones
30
intramembranous ossification
cartilage not involved condensation of mesenchyme which is converted straight to bone see this in flat bones
31
stages of limb bone development | part 1
as external shape is being established, mesenchyme in the buds becomes condensed cells differentiate to chondrocytes - driven by expression of BMPs at week 6 - hyaline cartilage models can be seen areas where chondrogenesis is arrested makes joints - cell proliferation, increased density, differentiation then cell dealth - induced by WNT 14 bones formed by week 8 centres of ossification form in diaphyses and epiphyses primary centres of ossification present in all long bones by week 12 growth plates of cartilage remain
32
stages in limb bone development | part 2
cells in centre of cartilage model proliferate, enlarge, make new kind of matrix - can be calcified calcified cartilage matrix does not allow diffusion of nutrients so cartilage cells die left with spicules of calcified cartilage matrix - acts as a scaffolding on which bone can be deposited periosteum is vascular connective tissue around model where blood vessels grown in - BVs bring in progenitor cells osteoprogenitor cells become osteoblasts - line up on spicules and start producing bone matrix core of calcified cartilage matrix removed by osteoclasts trapped osteoblasts become osteocytes
33
during growth period, what remodels bone to maintain overall shape and proportion
osteoclasts
34
achondroplasia
disorder of bone growth that affects endochondral ossification via cartilage
35
achondroplasia mutation
mutation in FGFR3 - normally down regulates cartilage and bone growth and it inhibits cell proliferation and differentiation mutation in receptor results in permanent expression so protein is overactive - results in reduced chondrocyte activity
36
examples of where hyaline cartilage is located in the body
skeletal - articular, costal, growth plate trachea larynx nose
37
examples of where elastic cartilage is located in the body
ear | epiglottis
38
examples of where fibrocartilage is located in the body
meniscus | IVDs
39
describe articular cartilage
smooth lubricated surface for articulation facilitate load transmission and create low friction environment cells - chondrocytes ECM - collagen, water, proteoglycans/proteins - hyaluronan and aggrecan it is avascular, aneural, non-immunogenic
40
function of chondrocytes and ECM in articular cartilage
c - synthesise and maintain ECM | ECM - protects chondrocytes from loading forces
41
what is involved in the degradation part of cartilage turnover
MMPs - degrade collagen/proteoglycans | TIMPs prevent degradation of MMPs
42
what is involved in the synthesis part of cartilage turnover
collagen, proteoglycans and proteins increase in GFs, IGF-1 and TGF-beta decrease in cytokines
43
issue with cartilage healing
injury must penetrate subchondral bone to allow bleeding - inflammatory cells, platelets, mesenchymal cells to synthesise collagen type I (not as good as II)
44
stages of cartilage healing
inflammation repair remodelling
45
issue with meniscal tears
cant heal as no blood supply
46
composition of fibrocartilage
cells - fibrocartilage | ECM - collagen type I, water, proteoglycans, glycoproteins, elastin
47
acute and chronic cartilage injuries
a - trauma, sports, infection | c - osteoarthritis, previous injury
48
diagnosis of cartilage injury
xray mri arthroscopy
49
treatment of cartilage injury
``` physiotherapy medical - paracetamol, NSAIDs arthroscopy cartilage transplantation joint replacement ```
50
two types of bone
``` mature/lamellar: all cortical and cancellous bone osteoblasts lay bone matrix in sheets - lamellae parallel, organised collagen fibres immature/woven: randomly aligned collagen fibres ```
51
cortical bone
mature bone laid down in concentric rings 80% of the skeleton slow turnover rate/metabolic activity
52
cancellous bone
spongy or trabecular bone | high turnover rate and undergoes greater remodelling
53
inorganic part of bone matrix
calcium and phosphorus
54
organic part of bone matrix
collagen, mucopolysaccharides, non-collagenous proteins
55
3 blood supplies of bone
periosteum blood supply is most important supply in children nutrient artery enters centre of diaphysis - high pressure vessels enter at metaphysis and epiphysis - communicate with nutrient artery but enter separately
56
two types of fracture healing
indirect and direct
57
indirect fracture healing process
``` haematoma: haemopoetic cells secrete GFs fibroblasts, osteoprogenitor cells, mesenchymal cells, immune cells granulation tissue forms soft callus: 1 week - 1 month 10% strain at failure hard callus: soft callus becomes mineralised disorganised woven bone remodelling: stable bridge with low strain environment osteoclasts go across and dissolve mineralised bone, osteoblasts form new bone ```
58
direct fracture healing
unique 'artificial' surgical situation - forms low strain environment direct formation of bone without formation of callus - via osteoclastic absorption and osteoblastic formation fracture stable - no movement under physiological load relies upon compression of the bone ends - osteoblasts and osteoclasts can cut across gap that has been compressed
59
which fractures are prone to problems with union or necrosis bc of blood supply problems
proximal pole of scaphoid fractures talar neck intracapsular hip surgical neck of humerus
60
inhibition of fracture healing factors
``` increasing age diabetes anaemia malnutrition peripheral vascular disease hypothyroidism smoking alcohol ```
61
why are there increasing numbers of people with a disability
population growth increase in chronic disease medical advances which extend and prolong life
62
a disabled person
someone with a physical or mental impairment that has a long term effect on his/her ability to carry out normal daily activities even if condition is controlled by medication etc it still counts as a disability - except eyesight controlled by glasses
63
impairment
is due to an injury, illness or congenital condition that causes or is likely to cause a loss or difference of physiological or psychological function
64
causes of disability in young people
``` prenatal premature birth injury - cerebral palsy congenital - downs syndrome accident infection - meningitis violence disease ```
65
barriers children with disabilities experience
``` physical disability locomotor disability - movement cosmetic disability sensory eg blind, deaf cognitive impairment ```
66
promoting factors for young disabled people in the work participation
``` male education level parental education level higher level of psychosocial functioning lower scores on depression scales ```
67
hindering factors for young disabled people in the work participation
``` lower educational factors female inpatient treatment - can affect education motor impairment wheelchair use functional limitations multiple health problems low mental health perception, dependent coping strategy ```
68
adjustments to work with a disability
adjustments to equipment, work station - voice activated software support - supervision change in duties modification of hours and place absence due to treatment or rehabilitation may involve moving to lower grade job if that is what they are competent of now
69
embryonic folding
occurs in 2 directions: lateral folding - driven by somites - creates embryo body - creates tube with endoderm in the middle cephalocaudal/head to tail folding - driven by CNS - creates c shape as tube bends the folds happen simultaneously and somatic LPM fuses to close the body wall to create tube like structure
70
what does the dermomyotome form
becomes dermis and skeletal muscle
71
what does the sclerotome form
vertebrae and ribs
72
process of intramembranous ossification
begins with condensation of the mesenchymal stem cells - they undergo proliferation and undergo morphological changes and differentiate into osteoprogenitor cells which will develop into osteoblasts osteogenic cells start to deposit bone matrix which are arranged in bony spicules differentiating osteoblasts arrange themselves along the spicules and begin to secrete more bone matrix as more matrix gets laid down, the spicules increase in size and will fuse together as these grow, they will fuse with more and more spicules and this results in the formation of trabeculae

Medicine phase 2 limbs and back (6 decks)

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