2. Anatomy of chest wall and mechanics of breathing Flashcards
What does Boyle’s Law state?
The pressure exerted by a gas is inversely proportional to its volume
What does Dalton’s Law state?
The total pressure of a gas mixture is the sum of the pressures of the individual gases
What does Charles’ Law state?
The volume occupied by a gas is directly related to the absolute temperature
What does Henry’s Law state?
The amount of gas dissolved in a liquid is determined by the pressure of the gas and its solubility in the liquid
Describe the direction of movement of gases.
Move from areas of high pressure to areas of low pressure
How are the lungs divided?
- Right lung contains 3 lobes
- Left lung contains 2 lobes
What are the lobes of the right lung?
- Superior lobe
- Middle lobe
- Inferior lobe
What are the lobes of the left lung?
- Superior lobe
- Inferior lobe
What are the 2 components of the pleural membrane?
- Parietal pleural membrane
- Visceral pleural membrane
What does the pleural fluid do?
- Acts as a lubricant
- Anchors the visceral and pleural membranes which sticks the lungs and ribs together
What is pleurisy?
Inflammation of the pleura
What does the visceral pleural membrane do?
Coats the outer surface of the lungs
What does the parietal pleural membrane do?
Coats the inner surface of the ribs
What passes through the thorax between the pleural sacs?
The eosaphagus and the aorta
What is found between the surfaces of the pleural membranes?
Intrapleural fluid
Why are the lungs effectively stuck to the ribcage?
Through the relationship of the pleural membranes
What is the normal value for intrapleural pressure?
-3 mmHg
What muscles are involved in inspiration?
- External intercostal muscles
- Diaphragm
- Sternocleidomastoids
- Scalenes
What muscles are involved in expiration?
It is passive at rest but during severe respiratory load the internal intercostal muscles and abdominal muscles can be used
What do the external intercostal muscles do?
Pull the ribs up and out to increase the space of the thoracic cavity
What do the internal intercostal muscles do?
Pull the ribs down and in to decrease the space of the thoracic cavity
What dimension of the rib cage does the pump-handle motion increase?
Anterior-posterior
What dimension of the ribcage does the bucket handle motion increase?
Lateral dimension
What is asthma cause by?
The over-reactive constriction of bronchial smooth muscle which increases resistance and makes expiration difficult
What happens during pneumothorax?
If the sealed pleural cavity is opened to the atmosphere, air flows in which causes the lung to collapse to upstretched size
What is the intra-thoracic (alveolar) pressure (Pa)?
- Pressure inside the thoracic cavity.
- May be negative or positive compared to atmospheric pressure
What is the intra-pleural pressure (Pip)?
- Pressure inside the pleural cavity
- ALWAYS negative
What is the trans pulmonary pressure (Pt)?
- Difference between alveolar pressure and intra-pleural pressure.
- ALWAYS positive
What is the bulk flow of air between the atmosphere and alveoli proportional and inversely proportional to?
- Proportional to the difference between the atmospheric and alveolar pressures
- Inversely proportional to the airway resistance
How is a subatmospheric intrapleural pressure and hence a transpulmonary pressure that opposes the force of elastic recoil established?
- Between breaths at the end of an unforced expiration there is no air flowing and the dimensions of the lungs and thoracic cage are stable as the result of opposing elastic forces.
- The lungs are stretched and are attempting to recoil whereas the chest wall is compressed and attempting to move outward.
What determines airway resistance?
Radii of airways
What determines how much air flows into the lungs at any given pressure difference between atmosphere and alveoli?
Airway resistance
