Foetal Respiration

Question 1

What constructs the lining of the 2 tubes during tracheal and lung development?

Answer 1

Embryonic endoderm

Question 2

What does the first tube become?

Answer 2

Digestive tube

Question 3

What does the second tube become?

Answer 3

Respiratory tube

Question 4

How is the trachea formed?

Answer 4

An outgrowth of the foregut at the respiratory diverticulum

Question 5

What are the first few steps in lung bud formation?

Answer 5

Formation of laryngotracheal groove that buds into two bronchi

Question 6

How is lung bud formation influenced by mesenchymal tissue?

Answer 6

• It sends out growth factors
• Left lobe is surrounded by tracheal mesenchyme and becomes straight bronchi
• Right lobe retained by lung mesenchyme and becomes branching of bronchus

Question 7

What are the five stages of lung development?

Answer 7

• Embryonic
• Psuedoglandular
• Canalicular
• Saccular
• Alveolar

Question 8

What happens in the embryonic and psuedoglandular stages?

Answer 8

• Formation of major airways
• Formation of bronchial tree and some respiratory parenchyma
• Brith of acinus

Question 9

What happens in the canalicular stage?

Answer 9

• Last generations of lung periphery formed
• Epithelial differentiation
• Air-blood barrier formed

Question 10

What happens in the saccular stage?

Answer 10

• Expansion of air sacs

- Surfactant is detectable in amnionic fluid

Question 11

What happens in the alveolar stage?

Answer 11

Secondary separation

Question 12

What is the function of surfactant?

Answer 12

Breaks up water molecules and makes lungs more compliant

Question 13

What four factors modulate lung development?

Answer 13

• Intra-thoracic space- size of space for lungs to develop
• Intra-uterine space- size of uterus and amount of amniotic fluid
• Foetal breathing movements- need regular activation of respiratory muscles to ensure normal lung development
• Lung fluid production- need adequate secretion to maintain appropriate balance of volume and pressure

Question 14

How do gluccocorticoids mature the lungs?

Answer 14

• Increase elastin content
• Thin alveolar walls and interstitial tissue
• Differentiation of type II pneumocytes
• Increase surfactant production
• Increase in enzymes of phospholipid synthesis
• Increase in pulmonary beta-andrenoreceptors

Question 15

What produces surfactants?

Answer 15

Type II pneumocytes