Daisy Baker Flashcards
What occurs in the 6-17 week period of lung development
Pseudoglandular - branching to form terminal bronchioles
What occurs in the 17-26 week period of lung development
Canalicular - each bronchiole divides into 2+ respiratory bronchioles
What occurs in the 27 week to term period of lung development
Saccular - respiratory bronchioles divide into 3-6 alveolar ducts which then develop terminal sacs and capillaries establish close association
What occurs in the term to childhood period of lung development
Alveoli mature with well developed epithelial-endothelial association
Which growth factors are required for lung development?
Hepatocyte nuclear factor 3beta Fibroblast growth factor-10 Sonic hedgehog Bone morphogenetic protein 4 (BMP4) Gil proteins Vascular endothelial growth factor
What’s the function of hepatocyte nuclear factor 3beta in lung development?
Growth of the foregut
What’s the function of Gli proteins in lung development?
Branching of bronchioles
What’s the function of VEGF in lung development?
Angiogenesis
Which growth factors promote the outgrowth of new end buds in lung development?
Fibroblast growth factor-10, sonic hedgehog and BMP4
When does the majority of alveolar development occur?
Post term, reaching adult numbers by 4 years
When do type I and type II pneumocytes first develop?
22 weeks
What structural pathologies are most likely to occur <16 weeks gestation?
Branching irreversibly affected and potential permanent reduction in the number of alveoli
What structural pathologies are most likely to occur >16 weeks of gestation?
Issues with alveolar numbers
What could cause respiratory structural pathology in the foetus?
Extrinsic restriction
Intrinsic restriction
Malnutrition due to vitamin A deficiency
Smoking
What can cause extrinsic restriction of the lungs in the foetus?
Congenital diaphragmatic hernia (CDH), effusions, thoracic or vertebral abnormalities e.g. scoliosis
What could cause an intrinsic restriction of the lungs in the foetus?
Lung cysts due to cystic adenomatoid malformation
How does the ionic composition of foetal lung liquid compare to amniotic fluid?
More sodium and chloride ions
Few potassium and bicarbonate ions, and protein
How is lung liquid secreted into the lumen of the lungs?
Secondary active transport of chloride ions from interstitial fluid, followed by passive transport of sodium ions and water
What does the secretion of lung liquid into the lumen do?
Allows for a positive pressure of 1cmH2O
When does reabsorption of lung liquid occur?
During labour and delivery, catelochamines are released reducing secretion and stimulating reabsorption. This involves active transport of sodium into the interstitium where it is followed by chloride ions and water. Exposure to postnatal oxygen also increases sodium transport across the pulmonary epithelium, where lung liquid is reabsorbed by the lymphatic system.
Give examples of lung liquid pathologies
Oligohydramnios due to early rupture of the amniotic sac or kidney abnormalities
Foetal breathing abnormalities due to NMD, phrenic nerve agenesis or CDH
Delivery without labour due to an elective Caesarean section - causes transient tachypnoea in the newborn (TTN)
Define oligohydramnios
Low amniotic fluid levels
Which cell is surfactant produced by?
Surfactant phosphatidylcholine (PC) is produced in the endoplasmic reticulum of type II pneumocytes and stored in lamellar bodies
What is the function of surfactant?
Prevents atelectasis by reducing the surface tension of alveoli, therefore reducing the work required to breathe
