IRDS Flashcards
When does surfactant start to develop in the lung?
24-26 weeks
What is the pseudoglandular stage?
5-17th week of gestation
period of rapid branching of the pulmonary tree - leading to terminal bronchioles
Mucous glands develop
What is the canalicular stage?
16-24 weeks
Capillary bed expands and endothelium thins
Surfactant begins to be produced
Alveolar capillary dysplasia occurs if capillary beds fail to form properly
What is the saccular stage?
24-38th week
Increase in type 2 cell - increases surfactant and surfactant proteins
External factors may lead to deccreased surfactant production (maternal diabetes)
What is the alveolar stage?
36-2years
Marked increase in epithelial cells, 60% type 2
Changes in pulmonary vasculature - decreased smooth muscle, decreased pulmonary vascular resistance
Failure of these changes results in Persistant Pulmonary hypertension - life threatening
What is the function of Betamethasone?
Increases surfactant production
Decreases alveolar division
Decreases bronchial length
Administration to the mother decreases fetal body growth (only two doses are given)
What is VEGF?
Promotes angiogenesis
If blocked - increases alveolar size (similar to emphysema)
Plays important role in developmend of BPD and ROP
What is surfactant protein A?
Most abundant
recycled by the type 2 pneumocyte
Opsonin - important in phagocytosis and killing bacteria and fungi
deficiency = death
What is surfactant protein B?
Small - enhances the spread of surfactant
Required for extra-uterine life
What is surfactant protein C?
Most hydrophobic
must be activated by SPB
Recruit PL to the surface
What is S PD?
Largest
Found in other organs
Main function is innate immunity
What affects surfactant secretion?
Increased - glucocorticoids, estrogen, thyroid hormone
Decreased - high levels of circulating insulin (gestational diabetes)
How is surfactant inactivated?
After deliver, any available surfactant can be used up in certain disease states
Aspiration, meconium, swallowed blood, pneumonia
