Anatomy of chest wall and mechanics of breathing Flashcards
Boyle’s Law
Pressure exerted by a gas is inversely proportional to its volume
Dalton’s Law
Total pressure of a gas mixture = the sum of the pressures of the individual gases
Charles’ Law
The volume occupied by a gas is directly related to absolute temperature
Henry’s Law
That the amount of gas dissolved in a liquid is determined by the pressure of the gas and it’s solubility in the liquid
Pleural cavities are filled with
Intrapleural fluid
Inflammation of the pleura is?
Pleurisy
Intrapleural pressure is?
Sub-atmospheric - lower than normal atmospheric pressure (-3mmHg)
Elastic recoil of the chest tries to?
Pull the chest wall outward
Elastic recoil of the lungs…
Creates an inward pull
When the sealed pleural cavity is punctured, why does the lung collapse?
Since the intrapleural pressure is sub-atmospheric, when the cavity is punctured, air rushes in and fills it, also the inward pull of the lung causes it to collapse and the outward pull of the chest cause the rib cage to expand slightly
According to Boyle’s law, as the volume of gas increases, the pressure…
Decreases
What muscles are used during inspiration?
External intercostals Diaphragm
Sternocleidomastoid
Scalenes
Is expiration passive at rest or does it also use muscles?
Passive at rest
When does expiration use muscles and what muscles are used?
During severe respiratory load
Internal intercostals and abdominal muscles
When the diaphragm contracts, the thoracic cavity…?
Increases by moving down
What nerve innervates the diaphragm and how?
Phrenic nerve
From underneath
What causes asthma?
Over-reactive constriction of bronchial smooth muscle which increases resistance making expiration difficult
A pneumothorax is…
An abnormal collection of air/gases in the pleural space
A pneumothorax causes…
The uncoupling of the lung from the chest wall (lung collapse)
What is alveolar pressure/intra-thoracic pressure (Pa)? When is it negative or positive?
Pressure inside the thoracic cavity/alveoli. At rest after a normal expiration it will be equal to atmospheric pressure.
On inspiration, as the thoracic cavity increases in volume the pressure in alveoli goes negative so air rushes in easier from atmosphere
On expiration, when inspiratory muscles relax, the alveolar air is compressed raising Pa to above atmospheric levels pushing air out.
What is the intra-pleural pressure (Pip)? Positive or Negative?
Pressure inside the pleural cavity and is always negative in healthy lungs
What is transpulmonary pressure (Pt)? Is it negative or positive?
Difference between alveolar pressure and intra-pleural pressure. ALWAYS positive in healthy individuals.
Why is the transpulmonary pressure always positive?
Because since the Pip is always negative the PT = Pa – Pip. Which will become a +.
Pip is always move negative than Pa so even if both are negative it will still turn out to be a positive for the Pt
Transpulmonary pressure opposes forces of…
Elastic recoil
The bulk flow of air between the atmosphere and alveoli is proportional to ____ and inversely proportional to _____
1) The difference between atmospheric and alveolar pressures
2) Airway resistance
Major determinant of the resistance of airways?
Radii of airways
