Lung development and Surfactant Flashcards
What is the first period of lung development?
The embryonic stage, from 26 days to 7 weeks.
The ventral outpouching and the formation of bronchi up to the segmental bronchi
What is the second period of lung development?
Pseudoglandular period, weeks 5-17.
Formation of airways up to terminal bronchioles (generation 17 roughly). Resembles a gland
What is the third period of lung development?
The canalicular period, weeks 16 to 25
Start of respiratory zone, epithelial diffentiation and capillary netwrok forms
What is the fourth period of lung development?
Saccular period, weeks 24 to birth.
Alveoli develop more, surfactant is begun to be formed.
What is the fifth and final stage of lung development?
late foetal to 8 years
The number of terminal alveolar sacs increases by means of more alveolar septa being formed.
What is happening in utero for a babies lungs?
There is breathing practice? and hiccups, the lungs are fluid filled, and the ribs are compressed increasing resistance
What is the composition of surfactant?
95% phospholipid. 5% protein
What do the four surfactant proteins do?
SP-A and SP-D ( large hydrophilic) are associated with lung defense and surface tension reduction. Regulate synthesis.
SP-B and SP-C are small lipophilic. SP-B forms tubular myelin and Sp-C stablises the monolayer.
What is the process of forming the monolayer?
SP-A and SP-B help form the lamellar phospholipids into tubular myelin. Tubular myelin with more surfactant proteins form the monlayer.
How is the bilayer degraded?
Type 2 cells take it up; moves up the airways along surface tension gradient; enzymatic degradation; macrophages; epithelial reabsorption.
What else does surfactant do?
Fluid balance, prevents fluid being sucked into airspace
Host defence: by moving particulate matter and opsonisation.
Reduction of liquid plugs.
