Embryonic lung development

Question 1

What is lung surfactant

Answer 1

Lung matures by glucocorticoids

Enables alveolar cells to touch each other without sticking

Surfactant made by type II pneumocytes

Reduces surface tension

Question 2

What are 4 factors that influence lung development

Answer 2

1. Intra-thoracic space
   Size of space for lungs to develop in
   Can be impaired by conditions
   e.g. diaphragmatic hernia – common – diaphragm fails to close & abdominal contents enter thoracic cavity (compresses lungs & impairs growth)
2. Intra-uterine space
   Size of uterus & amount of amniotic fluid
   Can be impaired by lack of amniotic fluid – leads to uterine compression
3. Fetal breathing movements
   Regular activation of respiratory muscles essential for normal development of fetal lungs
4. Lung liquid production
   Lungs need adequate secretion of fluid to maintain appropriate balance of volume & pressure during development

Question 3

What are the 5 stages of lung development

Answer 3

Question 4

What do lungs develop from

Answer 4

Embryonic endoderm constructs lining of 2 tubes
1st tube is digestive tube
2nd is respiratory tube which forms 2 lungs

Lung buds form by process of branching morphogenesis

Regional specificity of mesenchyme determines differentiation of developing respiratory tube
In region of neck grows straight forming trachea
After entering thorax it branches to form 2 bronchi & lungs

Subsequent divisions generate bronchi, bronchioles & alveoli

Most divisions occur in utero

At birth lungs are immature but functional

Question 5

Describe what is happening in the diagram

Answer 5

A. Formation of laryngotracheal tube
Buds into 2 bronchi

B. Further budding may be unequal

C. Final septation distinguishes pharynx from larynx & trachea from esophagus