Lung development Flashcards
What is primary ciliary dyskinesia?
AR mutation (45 known) that impacts on ciliary function; dynein arms are absent, causing cilia to become static so mucous is not moved and cleared; will get bronchiectasis and respiratory failure
What are congenital bronchial cartilage defects?
Normally incomplete rings with irregular plates, but can be malacic (floppy) in generalised or localised (occur due to other developmental issue) fashion - always check CVD status
What is Laryngomalacia?
Omega shaped epiglottis with folds that collapse on inspiration - severe airway obstruction
What is lung aplasia?
Bling ending bronchus with no lung or vessel.
What is Lung hypoplasia?
Bronchus and rudimentary lung present but all elements reduced in size and number; relatively common and 2/2 other (physical) factors such as lack of space intra/extrathoracically - can be corrected with in utero surgery
What is cystic pulmonary airway malformation?
1:8,000-1:35,000 mostly diagnosed on antenatal ultrasound; lethal don’t survive but usually seen well; normal blood supply with defect in pulmonary mesenchyma causing abnormal differentiation in early weeks
What is congenital lobar emphysema?
Progressive lobar overexpansion, expanding over midline and squashing other lobes due to weak cartilage or one way valve effects - association with CHD
What is intralobal sequestration?
Lower lobes usually affected and have aberrant blood supply that do not ventilate - no communication with tracheobronchial tree.
What are the four phases of lung development, and at which weeks do they occur?
Embryonic 0-7 weeks
Pseudoglandular phase 5-17 weeks
Canalicular phase 16-27 weeks
Saccular/Alveolar phase 28-40 weeks
What is the embryonic phase?
Lung buds and main bronchi form
Asymmetric branching occurs to produce 3 lobes on the right and 2 on the left
What is the pseudoglandular phase?
Conducting airways and bronchi/bronchioli form
Branching morphogenesis of airways to the mesenchyme, with pre-acinar airways all present by 17 weeks; development of cartilage, glands and smooth muscle continues to canalicular phase
What is the Canalicular phase?
Respiratory airways and blood gas barrier forms
Peripheral airspaces enlarge, with thinning of epithelium by underlying capillaries to allow gas exchange, but forming blood gas barrier required in post-natal life; epithelium differentiates to type I (thin)/II (surfactant - surface tension and allows re-expansion) cells and surfactant detectable at 24-25 weeks - babies become viable at 24 weeks gestation due to surfactant
What is the Saccular/alveolar phase?
Alveolar walls form first as saccule walls with double capillary networks, before forming secondary septa then alveolar walls as the capillaries coalesce to form one sheet, with elastin in the wall produce by myofibroblasts
What are the factors driving morphogenesis?
Lung buds drive process, with progenitor multipotent cells at the tip that differentiate to a range of lung cells based on chemical environment, physical activity and growth factors; communication between the mesenchyme leads to balanced growth factor production
What are Inductive factors?
FGF (morphogenesis) and EGF (epithelial proliferation and differentiation)
