Lecture 10: Lung development and surfactant part 1 Flashcards
Lung airways are primarily
endodermal
Parenchyma and pleura are
mesodermal
Embryonic
26 days to 7 weeks
-Lung bud arises as a ventral outpouching of the foregut endoderm. 3x rounds of branching forming the primary bronchi, the lung lobes (secondary & main bronchi) and the bronchoopulmonary segments (tetiary & segmental bronchi)
Pseudo glandular
5 to 17 weeks
-More branching forming bronchi, bronchioles, and terminal bronchioles ~17th branching rounds
Cannilicular
16 to 25 weeks
Each terminal bronchile > 2+ respiratory bronchioles.
Each of these divide into 3-6 alveolar ducts lined by cuboidal (bad) cells. These cells start to become attenuated, capillaries come into mesoderm.
Baby COULD survive but this is rare, and it would struggle due to no surfactant or squamous cells.
Saccular
24weeks to after birth
Alveolar ducts > clusters of thin-walled terminal air sacs (primitive alveoli)
The type-1 squamous alveolar cells are intimately associated with blood and lymph cappillaries.
Type 2 cells develop > surfactant starting to be produced.
Can survive as they don’t have a huge resp requirement.
Foetal/ Alveolar
Late foetal to 8 years
Increased # terminal sacs, alveolar mature (cont. thinning of squamous epithelial lining & more contact with surrounding capillaries)
Increased SA from more septa and walls ‘secondary septation’
During Vaginal birth
-Compression: starts the fluid removal process
After birth
- Occlusion of Umbilical Vein
- Increase in the PCO2, which increase the respiratory drive to breath
- Has to be a huge breath to overcome the atelectasis
- Inflation of brochial tree, fluid drains into BS and lymph
- Reduction of the pulmonary vascular resistance > closure of the foramen ovale and ductus arteriosus
Tracheo-oesophageal fistula
1:3000 live births, more common in males
Blind ending tubes, fluid goes into lungs > choking and coughing
