Embryology of the Respiratory System

Question 1

Describe the formation of lung buds in an foetus

Answer 1

Laryngotracheal groove forms
–>
Develops into the respiratory diverticulum
–>
2 seperate lung buds form
–>
Tracheoesophageal ridges separate the lumens of the trachea and esophagus

Question 2

What is the outcome of a failure of the tracheoesophageal ridges to separate the trachea and oesophagus?

Answer 2

Tracheoesophageal fistula

Question 3

List the stages of lung maturation and the time they occur at

Answer 3

Embryonic Stage:
26 days - 6 weeks

Pseudoglandular Stage:
6 - 16 weeks

Canalicular Stage:
16 - 28 weeks

Saccular Stage:
28 - 36 weeks

Alveolar stage:
36 weeks - early childhood

Question 4

Describe the lungs at the end of the embryonic stage (6 weeks)

Answer 4

• Respiratory diverticulum formed
• ->
• Tertiary bronchi formed
• Lung lobes and segments begin to form

Question 5

Describe the lungs at the end of the pseudoglandular stage (16 weeks)

Answer 5

• Bronchial tree branches

- Terminal bronchioles begin to form

Question 6

Describe the lungs at the end of the canalicular stage (28 weeks)

Answer 6

• Alveolar ducts, sacs partially formed
• Type 1 pneumocyte differentiates
• Capillary bed growth

Question 7

Describe the lungs at the end of the saccular stage (36 weeks)

Answer 7

• Alveolar sacs formed
• Capillary beds develop further
• Surfactant production

Question 8

Describe the lungs at the end of the alveolar stage (early childhood)

Answer 8

Mature alveoli

Question 9

What defect is caused by a lack of surfactant production at birth?

When is this an issue?

Answer 9

• Newborn respiratory distress syndrome

- Arises in premature births