Anatomy of Chest Wall and Mechanics of Breathing Flashcards
What is meant by Boyle’s law?
Boyle’s Law states that the pressure exerted by a gas is inversely proportional to to its volume (P a 1/V). Note that gases (singly or in mixtures) move from areas of high pressure to areas of low pressure.
What is Dalton’s law?
Dalton’s Law states that the total pressure of a gas mixture is the sum of the pressures of the individual gases.
What is Charle’s Law?
Charles Law states that the volume occupied by a gas is directly related to the absolute temperature (v a T)
What is Henry’s law?
Henry’s Law states that the amount of gas dissolved in a liquid is determined by the pressure of the gas and it’s solubility in the liquid.
Where does the esophagus and the aorta pass through the thorax?
Between the pleural sacs
Where does the parietal membrane fold back on itself?
At the lung hilux?
What type of fluid exists in the pleural cavity?
Intrapleural fluid
What is the function of pleural fluid?
Lubrication, two membranes can glide across each other. Fluid holds the two membranes together
What is pleurisy?
Inflammation of the pleura.
How does pressure of intrapleural cavity compare to the atmospheric pressure?
Subatmospheric
What creates the outward pull of the chest?
Elastic recoil of the chest wall
What pulls the lungs inward?
Elastic recoil of lung?
When are inward and outward forces of the lungs equal?
At the end of an expiration
How is boyle’s law applied in breathing?
Thoracic cavity changes in volume. increase volume = decrease pressure decrease volume = increase pressure Gases always move from high pressure to low pressure
What brings about expiration?
Expiration is passive at rest, but uses internal intercostal and abdominal muscles during severe respiratory load
What muscles are used in inspiration?
Sternocleidomastoids, Scalenes, External intercostals, diaphragm
What activates the skeletal muscles?
Alpha motor neurones
What direction do the internal intercostal muscles travel?
Opposite direction to external intercostal muscles
What is the movement of the sternum during inspiration?
Moves outwards and forwards - pump handle movement
What is the movement of the ribs during inspiration?
Moves outwards - bucket handle movement
What is asthma?
Over-reactive constriction of bronchial smooth muscle. Increases resistance, expiration difficult.
Why are airways open during inspiration?
Physical forces of inspiration holds them open
What happens to airways during expiration?
Compressed by physical forces of expiration
What happens when the pleural cavity is opened?
Air flows in since pleural cavity is subatmospheric Lung collapses to unstretched size
What is Intra-thoracic (Alveolar) Pressure (PA)?
Pressure inside the thoracic cavity, (essentially pressure inside the lungs). May be negative or positive compared to atmospheric pressure. During rest it’s zero - since equals atmospheric pressure
What is Intra-pleural Pressure (Pip)?
Pressure inside the pleural cavity, ALWAYS negative (in healthy lungs at least!)
What is Transpulmonary pressure (PT):
Difference between alveolar pressure and intra-pleural pressure. ALWAYS positive (in health) because Pip is always negative. PT = Palv – Pip.
How do these three pressures change during breathing?
What factors influence bulk flow of air between the atmosphere and the alveoli?
The difference between atmospheric pressure and alveolar pressure Airway resistance
What are the features or the lungs during the end of an unforced expiration?
P atmospheric = P alveolar No air is flowing Dimensions of lungs and thoracic cage are stable as a 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. This creates a subatmospheric intrapleural pressure and hence a transpulmonary pressure that opposes the forces of elastic recoil.
What does airway resistance determine?
How much air flows into the lungs at any given pressure difference between atmosphere and alveoli
What is the major determinant of airway resistance?
The radii of the airways
