Respiratory physiology 1 Flashcards
How does air flow in the lungs
Pressure difference between mouth and alveoli
Moves from more positive to more negative
What do the pleura do?
Visceral connects chest wall
Parietal connected to lung tissue itself
What is PiP?
Intrapleural pressure
What is Palv?
Alveolar pressure
What is Ptp?
Transpulmonary pressure (Palv-pip)
What is Boyle’s law?
Changing space without changing volume decreases pressure
What happens when you inhale?
- Inspiratory muscles contract (diaphragm flattens), ribs come up and out
- This leads to increase in size of thoracic cavity
- Parietal membrane pulls out
- Water tension means visceral membrane pulls out slightly
- Pip becomes more negative - pressure has reduced
- Increases difference between Palv and Pip to increase Ptp
- Larger Ptp means greater distension of alveolar wall
- Alveolar volume increases, Palv decreases, difference created between atmosphere and alveoli
What happens when you exhale?
- Chest wall recoils
- Space between membranes is smaller
- Pressure is more positive
- Differences between alveolar and intra-pleural pressure is smaller
- Alveolar volume decreased
- Palv increases
- Difference between alv and atm
- Fibres inside lung recoil and make lung normal size
What is alveolar interdependence?
As the parietal membrane moves out with the chest, the visceral layer follows
This pulls on outer layer of alveoli
This pulls on the next row of alveoli
All the way until the inner lung
What is a pneumothorax?
- Pleural seal broken
- Pathway either inwards through lung tissue or outwards through chest wall
- negative pressure isn’t generated - ventilation ineffective
- Natural tendency of lung to collapse now unopposed
- Elastic recoil of alveoli
What does fibrosis do to lungs?
Decreases compliance - low expandability of lungs
Disease causing high compliance
Emphysema
What do obstructive diseases do?
Increase resistance
What do restrictive diseases do?
Decrease compliance
What is Poiseuille’s law?
Resistance is directly proportional to the viscosity of the fluid and the length if the tube and inversely proportional to the fourth power of the radius of the tube
