Sept29 M1-Developmental anomalies of the respiratory system Flashcards
what allows first bifurcation of two lung buds
caudal endoderm of trachea bifurcates in mesenchyme (which will be pleura)
name of mesenchyme surrounding all endoderm of resp and what will provide
splanchnic mesenchyme, will form CT and cartilage around trachea + smooth muscle
how trachea develops (2)
Overgrowth of cells in lumen
Amniotic fluid flows in there for recanalization and budding
characteristic of lungs budding
asymmetric. right lung more aligned with trachea
what azygos vein normally does and what can do (abnormal) when lung develops
supposed to go over right bronchus. sometimes indents in right upper lobe (still lsurrounded by parietal pleura)
name of result when azygos vein goes through right upper lobe
azygous lobe
how many times one lung bud branches
22
how early diaphragm movements contribute to lung formation
help amniotic fluid circulation
initial lung buds: mesenchyme in contact, something in particular
fibroblast and mesenchyme have receptors for GFs for proliferation at these tips
lung epithelium description at embryo. when branching starts
pseudostratified
how lung epithelium changes with budding
becomes thinner and eventually cuboidal
lung epithelium closer to mesenchyme: description + what phase
end budding phase: squamous and in direct contact with vessels and capillaries in mesenchyme
what proliferation of mesenchyme at initial budding alloes
further bifurcations and thinning of mesenchyme, more ducts
2 factors expressed at endodermal tips and role
Fibroblast GF and Shh (sonic hedgehog) : proliferation
when production of blood vessels stimulated in lung and how
at cuboidal epith phase. VEGF produced and angioblasts (precursors) stimulated
time of end of lung development where gas exchange capability is possible
24-26 weeks
terminal sac phase (26 weeks to birth) what happens in lungs
- ducts bud into resp bronchioles in mesenchyme + angiogenesis
- endoderm: pneumocyte type 1 (surface) and type 2
post alveolar phase (lung dev after birth) what happens
terminal sacs further divided by secondary mesenchymal septa (alveoli form)
from 70M at birht to 300M at 8 years
first genetic defect possible in lung formation
defective gene expression during endodermal-mesenchyme interaction (trachea sep from esophagus + budding)
genetic defect possible in lung formation at budding step + consequence (2)
defective shh expression. affects tracheo-esophageal septum dev + lung branching
ultimate consequence of shh defect
lung hypoplasia
defective apoptosis consequence on lung dev (gut too)
no recanalization of gut and trachea (atresia)
how gut atresia can affect lung dev
leads to abnormal amniotic fluid turnover, affects branching of lung
cause of atresia
failure of normal mesenchyme-endodermal interaction that would facilitate apoptosis of lumen endodermal cells
atresia excess consequence
endodermal cells degenerate : segment of agenesis
how BP affects lung dev
defective vasculature so hypoplasia and maybe atresia of gut: bad amniotic fluid circul to lung
consequence of incomplete apoptosis on gut wall
mesenchyme can project in and cause doubling of gut tube
mesenchyme overgrowth consequence
smooth muscle hypertrophy: stenosis of lumen
stenosis def + 2 causes
narrowing of gut lumen. reduced endodermal cell prolif or excessive mesenchyme prolif
esophageal atresia def + consequence
top and bottom of esophagus not linked: vomiting
esophago-tracheal (or TO) fistula def +consequence
esophagus links to trachea. most food goes in bronchi
trachea atresia def
top and bottom of trachea not linked
OT fistula + atresia of esophagus consequence
regurgitation and trachea linked to bottom of esophagus so air in stomach
one fatal error in esophagus and tracheal dev
failure of TO septum to separate (fatal)
polyhydramnios def
excess amniotic fluid
polyhydramnios one cause
gut atresia
oligohydramnios def
deficit of amniotic fluid
give 1 cause of oligohydramnios + consequence + syndrome name
kidney agenesis (essential to produce amniotic fluid) - hypoplasia of the lung - death at birth - Potters syndrome
