What are the functions of the conducting airways?
- passing air
- warm air to body temp
- humidify inspired air
- filter out foreign material
What are the functions of the pleural sac?
- reduces friction
- holds the lungs tight against the thoracic wall
What are the functions of the respiratory system?
- exchange of gases
- regulation of pH
- protection
- vocalization
If alveolar pressure is equal to intrapleural pressure…
there is no air flow
If alveolar pressure is less than intrapleural pressure…
air flows in
If alveolar pressure is more then intrapleural pressure…
air flows out
Work of breathing is increased if
- a greater pressure gradient is needed
- resistance is greater
Factors affecting breathing (lungs)
- compliance
- elasticity
- surfactant
How do surfactants help with lung compliance?
they reduce surface tension of the alveolar fluid which decreases the resistance of the lung to stretch
Why are trachea and bronchi responsible for a majority of the resistance?
Their diameters do not change - resistance is constant
How is resistance regulated?
Bronchioles
Bronchodilation
SNS activity (smooth muscle, beta-2) and paracrines (CO2)
Bronchoconstriction
PNS activity (ACh) and paracrines (histamines and leukotriene)
Vital capacity
VC = Vt + IRV + ERV
Total lung capacity
TLC = VC + IRV
Inspiratory capacity
IC = Vt + IRV
Functional residual capacity
FRC = RV + ERV
Total pulmonary ventilation
ventilation rate x tidal volume
What is alveolar ventilation?
amount of fresh air that reaches the alveoli each minute
