Respiratory System Development
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Introduction
Canalicular phase
- 16-25 weeks
- Walls of air spaces start to thin
- Vascularityincreases
- Each terminal bronchiole has 2+ respiratory bronchioles with terminal sacs present
- Type 2 cells emerging
- Respiration possible
Terminal sac phase
(25-40 weeks)
- Gradual flattening of the air space lining
- Type 2 pneumocytedifferentiation/ surfactant production starts
- Capillaries bulge into terminal sacs
First Breath
Alveolar stage
(birth-eight years)
- Terminal sac epithelium thins further
- Surfactant production mature
Resources and References
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