Developmental Physiology of the Respiratory System

1. Developmental Physiology
of the
Respiratory System
Mohammad Rezaei
Pediatric Pulmonologist

2. Lung Development
• Prenatal Development
• Postnatal Development and Growth

3. Prenatal Development of the Lung

4. Prenatal Development of the Lung

5. Prenatal Development of the Lung
Embryonic stage

6. Prenatal Development of the Lung
Pseudoglandular stage

7. Prenatal Development of the Lung
Canalicular stage

8. Prenatal Development of the Lung
Saccular stage

9. Prenatal Development of the Lung
Alveolar stage

10. Birth
• Lung Fluid
• Pulmonary Blood Flow

11. Postnatal Development and Growth
of the Lung

12. Postnatal Development of the Lung
Alveolarization Microvascular Maturation

13. Postnatal Growth of the Lung
Postnatal lung growth continue throughout infancy and childhood and
into the adolescent years.

14. Chest Wall & Diaphragm
• Chest wall compliance
• Diaphragm and respiratory muscles (type of fibers)

15. Chest Wall Configuration

16. Chest Wall Configuration

17. Normal values for pulmonary function with age
• predicted values of pulmonary function depend upon age, height,
gender, and race .
• Lung Capacities and flows continue to increase until late adolescence.
(then decrease)
• Lung Volume, Gas exchange surface area, Diffusion capacity,…all
increase in relation of body mass increase.

18. Normal values for pulmonary function with age
Compliance
• Chest wall
• Lung

19. Normal values for pulmonary function with age
Resistance
• Airway diameter (r)
The diameter of airways in infants and children is much smaller than adults, resulting in
increased Raw
• Number of airways
• RR
• Lung Volume
Site of Airway Resistance
• In the infant lung, small peripheral airways may contribute as much
as 50% of the total airway resistance, and this proportion does not
decrease until about 5 years of age.
(Remember small airway diseases such as Bronchiolitis)

20. Normal values for pulmonary function with age
Total Lung Capacity
• Lung volume is linearly related to body length during childhood

21. Normal values for pulmonary function with age
Functional residual capacity
• in the infants predicts a supine FRC of only 10% of TLC, whereas in adults
FRC accounts for approximately 50% of TLC in the upright position.
• In infants, the post inspiratory activity of the inspiratory muscles and the
laryngeal control of expiratory flow ( “grunting” ) modify respiratory
mechanics to maintain the patency of small airways and alveoli.
• Mean values for FRC range from 20-25 mL/kg in infants up to 18 months
of age

22. Normal values for pulmonary function with age
Tidal Volume
Respiratory Rate

23. Normal values for pulmonary function with age
Minute Ventilation
Minute Ventilation = Tidal Volume x Respiratory Rate

24. Normal values
for pulmonary
function with age

25. Thank you