lung development

Question 1

what is primary ciliary dyskinesia

Answer 1

androgen receptor mutation impacting ciliary function, resulting in absence of dyein arms, causing cilia to become static and fail to clear mucous

Question 2

what does primary ciliary dyskinesia lead to

Answer 2

bronchiecstasis, respiratory failure

Question 3

what are congenital bronchial cartilage defects

Answer 3

normally incomplete rings with irregular plates, with the soft membrane that can become calcified; can be malacic (floppy) in generalised or localised fashion (occuring due to other developmental issue)

Question 4

what is laryngomalacia

Answer 4

omega shaped epiglottis with folds that collapse on inspiration, causing severe airway obstruction

Question 5

what is cystic pulmonary airway malformation

Answer 5

diagnosed on antenatal ultrasound; lethal defect in pulmonary mesenchyma but with a normal blood supply; abnormal differentiation 5-7 weeks; contains multiple small cysts and is associated with kidney, heart and diaphragm defects

Question 6

what is congenital lobar emphysema

Answer 6

progressive lobar overexpansion over midline and squashing other lobes; caused by weak cartilage, extrinsic compression, one way valve effect; associated with congenital heart disease

Question 7

what is intralobal sequestrian

Answer 7

abnormal segment share of visceral pleural, with lower lobes usually affected; no communication to tracheobronchial tree so not ventilating but does have aberrant blood supply

Question 8

what forms during embryonic phase: 0-7 weeks; signifance of right middle lobe

Answer 8

lung buds, main bronchi; asymmetric branching occurs, producing 3 lobes on right and 2 on left (right middle lobe is most vertical and direct lobe for foreign object entry)

Question 9

what forms during pseudoglandular: 5-17 weeks

Answer 9

conducting airways, bronchi and bronchioli

Question 10

vasculogenesis and branching morphogenesis: pseudoglandular phase (5-17 weeks)

Answer 10

branching morphogenesis of airways into mesenchyme; pre-acinar airways present; development of cartilage, glands and smooth tissue

Question 11

factors driving morphogenesis

Answer 11

lung buds drive process, with progenitor multipotent epithelial cells at tips of buds that differentiate based on chemicals, physical activity or growth factors; communication between epithelial cells in lung buds and surrounding mesenchyme leads to balanced growth factor production

Question 12

inductive growth factors

Answer 12

FGF (branching morphogenesis), EGF (epithelial proliferation and differentiation)

Question 13

inhibitory growth factors

Answer 13

TGFB (matrix synthesis, inhibition of epithelium proliferation), retinoic acic (inhibits branching)

Question 14

describe vasculogenesis

Answer 14

airways act as a structural template for capillary networks to form

Question 15

what forms during canalicular: 16-27 weeks

Answer 15

respiratory airways, blood gas barrier

Question 16

what happens during canalicular phase

Answer 16

airspaces at periphery enlarge; epithelium thins to allow gas exchange (blood gas barrier); epithelial differentiation into type I (thin) and II (surfactant)

Question 17

significance of type II cells producing surfactant at week 24

Answer 17

babies become viable

Question 18

what happens during saccular/alveolar: 28-40 weeks

Answer 18

alveoli appear

Question 19

describe formation of alveoli during saccular/alveolar phase

Answer 19

alveolar walls form first as saccule walls with double capillary networks, before forming secondary septa; alveolar walls then form as capillaries coalesce to form one sheet, with elastin in the wall produce by myofibroblasts