Lower Respiratory System

Definition
The lower respiratory system consists of the parts inside the chest or thoracic cavity including:

• bronchi
• bronchioles
• alveoli
• lungs
• pleura
• diaphragm
• ribs
  

The lower airway changes with growth.

• Alveoli and bronchioles continue to grow after birth increasing from 24 million to 296 million increasing surface area by a factor of 20.
• Chest wall becomes firmer and more oval with growth.
• Infants have fewer central and peripheral chemoreceptors to help control breathing.
  
  

• Fewer alveoli and bronchioles = less surface area for gas exchange.
  
• Child's breathing is less efficient.
• Breath sounds are transmitted throughout all the lung fields in children