Lung developmentf Flashcards

1
Q

the lung at birth

A

vol small
related to height
airways present and diff - cartilage, glands, muscle and nerves
blood gas barrier present - less developed and smaller
30% alveoli = GE
most artery and veins present

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2
Q

mechanisms to increase flow after birth

A

expansion of alveoli dilates arteries - physical effect, need big breath
expansion stim release of vasodilator agents NO and PGI1
inhib of vasoconstrictors in foetus - ET - otherwise have pul hypertension
direct effect of O2 on sm

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3
Q

changes in bv at birth

A
decrease in vascular resistance 
10fold rise in flow 
lumer increases in arteries, wall thins 
change in cell shape and cytoskeleton organisation - not loss of cells 
arteries grow and keep thin wall 
low pressure, low resistance
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4
Q

changes in alveoli in childhood

A

number increase to 9-12yrs
increase in size and complexity t0 increase SA x20
bv increase alongside alveoli - cap vol x35

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5
Q

effect of post natal development

A

a lot of development is postnatally
possibility of insult through exposure, infection, genetics
if lung damage to child - bigger chance of lung correcting itself - alveoli are still being layed down

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6
Q

exponential growth of alveoli

A

new born 150million alveoli

adult 300-600million

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7
Q

blood vessel development

A

interaction between bv and airway
vasculogenesis around the framework of the airway
due to physical and chemical pathways
branching morphogenesis
blood gas barrier
alveo and angiogenesis
alveoli not complete when born - but should still have functioning adult system for GE

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8
Q

morphogenesis of the lung

A

asymmetric

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9
Q

pseudoglandular phase

A

5-17 wks
branching morphogenesis of airways into mesochyme
pre-acinar airways present by 17 wks
development of cartilage, gland and sm tissue
driven by lung bud
vessels grow between mesochyme and bud

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10
Q

factors driving branch morphogenesis

A

driven by lung bud
in tip - progenitor multipotent cell - differentiate depending on env
stretch into mesochyme because of growth factors and inhibitors - cause mesochyjme to release more factors
communication between epi cells in distal branching lung buds and surrounding mesochyme

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11
Q

GF in lung development

A

FGF - branching morphogenesis, subtypes in epi and mesenchyme
EGF - epi proliferation and diff
TGFBeta - inhib matrix synth, surfactant production, proliferation of epi and bv
retinoic acid - inhibit branching

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12
Q

endothelial diff in pseudoglandular phas

A

diff in mesenchyme around bud
endo cells coalesce to form capillaries - vasculogeneis
act as structural template
VEGF produced by epi cells stimulates endo diff

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13
Q

Canalicular stage

A

16-27wks
3rd trimester
airspaces at periphery enlarge
thinning of epi by cap allow GE
blood gas barrier required in postnatal is formed
epi diff into T1 - thin and T2 - round make surfactant (reduce surface tension = no collapse)
surfactant at 24-25wks

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14
Q

mechanism of formation of alveolar walls

A

saccule wall- epi on both side, double cap network, myofibroblasts and elastin at intervals along wall
wall forms secondary septa develop from wall led by microfibroblast and elastin, cap line both sides - matrix between
then cap coalesce to form 1 sheet alveolar wall - thinner and longerm less matrix, muscle and elastin at top

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15
Q

blood gas barrier development

A

29wks - septa thick - surfactant exogenously - high pressure = tear and lung damage
8month - thin bed cap in septal - good for GE
term - don’t have to have exogenous surfactant - normal lung development and vasculogenesis

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16
Q

airway epi

A

columnar
goblet produce mucin
ciliated, motile - primary defence mech - clear debris by mucociliary escalator
there are many inherited conditions causing resp ciliopathy

17
Q

inherited ciliary mutations

A

autosomal mutation
45 known inherited
primary ciliary dyskinesia

18
Q

cilia

A

9+2 arrangement
microtubule doublet pairs
hook - ATPase unit - slide 1 pair over the other

19
Q

primary ciliary dyskinesia

A

chronic suppurative lung disease - progressive
get bronchiectasis early
resp failure
dynein arm gone - lose primary defence mech

20
Q

congenital bronchial cartilage defects

A

malacic
generalised - laryngotracheomalcia
localised - malacic segment from external compression
heart can block airways - see pulsation in trachea
have complete tracheal ring - narrow airways, need surgery - tracheostomy until done

21
Q

laryngomalacia

A

omega shaped epiglottis
aryepiglottic folds not sat nicely
breathe in - collapse and occlude vocal cords
in growth fixes itself - tracheostomy until then

22
Q

agenesis

A
complete absence of lung and vessel 
other lung permeate to other side 
diaphragm rise up too 
abnormal flow in 4th wk 
associated with other pathology
mediastinal shift to opaque hemithorax
23
Q

aplasia

A

blind ending bronchus - no lung or vessel

24
Q

hypoplasia

A

bronchus and rudiamentry lung present - all elements reduced in size and numver
lack of space
relativelky common - secondary
from hernia 75-90% - bowel in chest, lung size not improved after correction of hernia
treat in foetus
chest wall pathology - dystrophy - break rib and insert titanium, on ventilator
oligohydramnios - loss of amniotic fluid
lymphatic or cardiac mass eg tumour
appear symmetrical - 1 lobe actually small

25
cystic pulmonary airway malformation
diagnosed with antenatal US - seen in well children defect in pul mesenchyma abnormal differentiation 5-7th wk normal blood supply badly modelled lung associated with renal agenesis, cardiovascular defects, diaphragmatic hernia, syryngomelia bronchiolar epithelium with overgrowth - separated by alveolar tissue that was underdeveloped don't know cause - not contributed to ventilation at risk of infection - pneumonia
26
congenital lobar emphysema
progressive lobar overexpansion after 1st breath caused by: weak cartilage, extrinsic compression, one way valve effect, alveoli expand - not disrupted left upper lobe>right middle> R upper males> females CHD association normally children are fine - if not can remove lobe
27
one way valve effect
air in but not out
28
intralobar sequestration
75% pul sequestrations abnormal segment share visceral pleura covering normal lung aberrant lung supply of blood no communication to tracheobronchial tree - not ventilating lower lobe prediomininance caused by: chronic bronchial obstruction and postobstructive pneumonia
29
blood supply in intralobular sequestration
can go into high flow present with cardiac failure cardiologist embolise vessel - it shrivels and is not used
30
time line of lung development
embryonic phase 0-7 weeks - lung buds and main bronchi psueudoglandular 5-17 wks - conducting airways, bronchi and bronchioles canalicular 16-27 wks - resp airways - blood gas barrier saccular/alveolar 28-40 wks - alveolar appear post-natal - adolescence - alveoli multiply and enlarge until 9-12 yr old
31
land marks in lung development
``` 6wk - lobar airway 16wk - pre-acinar airway 30wk - resp airway, 1st alveoli newborn - 1/3-1/2 adult alveoli 3yr old - most alveoli ```