Prematurity and pre-natal medicine Flashcards
How much of the respiratory system has developed by weeks 5-6 of gestation?
- Mainstem bronchi
- Secondary bronchi
- Development of caudal growth
- Tertiary bronchi
When is the pseudoglandular period?
6 - 16 weeks
What occurs during the pseudoglandular period?
14 generations of branching terminal bronchioles formed
NO respiratory bronchioles
Co-branching of pulmonary arteries
When is the canilicular period?
16 - 26 weeks
What occurs during the canilicular period?
- Terminal bronchioles divide into respiratory bronchioles
2. Alveolar ducts
When is the saccular period?
28 - 36 weeks
What occurs during the saccular period?
- Terminal sacs form
2. Capillaries in close contact with primitive alveoli
What do the terminal sacs give rise to?
Alveoli
When is the alveolar period?
8 months to childhood
What occurs during the alveolar period?
Maturation of alveoli
How many terminal sacs are there at birth?
20-70 million
How long does terminal sac formation continue for?
Until about 8 years old
How many terminal sacs are there in the mature lung?
300-400 million
How does the blood-air barrier change at 8-9 months?
Sac lining cells (type I pneumocytes) are thinner
Capillaries protrude into alveolar sacs
Increasing contact points for gas exchange
When does surfactant start being produced?
End of 6th month when type II pneumocytes appaer