The respiratory system Flashcards
Respiratory membrane
Thin air blood barrier
Surfactant prevents drying out
Pleura
Each lung is suspeed in its own pleural cavity
What stops lungs from collapsing?
- Surfactant - reduces surface tension of alveolar fluid
- Pleural fluid - between the parietal and visceral pleura - sticks the lungs to inner wall of thoracic cavity
- Elasticity of the chest walls pulls the thorax outwards while the elastic recoil of the lungs creates an inward pull
Resistance (BF)
Opposition to blood flow
Due to friction between the air
Vasoconstriction, vasodilation
Can lead to obstructive diseases
Compliance )BF)
Measure of the ability of the lungs to expand stretch and enable inhalation
Depends on lung elasticity, alveolar surface tension, flexibility of muscles and joints of thoracic wall
Can lead to restrictive disease
Alveolar surface tension
Surface tension between water molecule in alveolar fluid
Can make alveolar smaller or larger
Can lead to respiratory disease
Diffusion of o2 and CO2 across respiratory membrane is influenced by
- Partial pressure for each gas
- How soluble the gas is in alveolar fluid/plasma
- Matching alveolar ventilation and perfusion of pulmonary arterioles / capillaries
- Structural characteristic of respiratory membrane
Ventilation - perfusion coupling
Efficient gas exchange requires matching gas flow (ventilation) with blood flow (perfusion
Equation
CO2 + H2O —- H2CO3 — H+ + HCO3-
Carbon dioxide + water — carbonic acid — hydrogen + bicarbonate ion
If CO2 or pH rises
CO2 increase, H ions falls (high pH), RHS, more carbonic acid, more hydrogen ions and bicarbonate ions are released and ph decreases
If CO2 or pH falls
CO2 decrease, H ions increase (low pH), LHS, carbonic acid becomes CO2 and H2O, less hydrogen ions and ph increases
Neural control
Chemoreceptors - detect change in CO2, H and O2
Information sent to respiratory centre
