Anatomy of Chest Wall and Mechanics of Breathing Flashcards
What are the 4 gas laws?
Boyle’s law
Dalton’s law
Charles’ law
Henry’s law
What does Boyle’s law state?
Pressure exerted by a gas is inversely proptional to its volume (P = 1/V)
What does Dalton’s law state?
Total pressure of a gas mixture is the sum of the pressures of the individual gases
What does Charles’ law state?
Volume occupied by a gas is sirected related to the absolute temperature (V directly proportional to T)
What does Henry’s law state?
Amount of gas dissolved in a liquid is determined by the pressure of the gas and its solubility in the liquid
When talking about the pressure and volumes of gas, what does the volume refer to?
The volume of the container that the gas is in
What is core body temperature?
37oC
What is ventilation?
Movement of air in and out of the lungs
In terms of pressure, where does air always move?
From areas of high pressure to areas of low pressure
If the pressure in the lungs is more than the atmosphere, where does the air move?
From the lungs to the atmosphere (out of the body)
What shape is the diaphragm?
Domed shaped

What happens when the diaphragm contracts?
It flattens which increases the volume of the thoracic cavity
How many lobes does the right and left lung have?
Right has 3 lobes
Left has 2 lobes
What are the lobes in the right lung called?
Superior lobe
Middle lobe
Inferior lobe

What are the lobes of the left lung called?
Superior lobe
Inferior lobe

What is the pleural cavity critical for?
Maintaining the inflation state of our lungs
What is A?

Aorta
What is B?

Left lung
What is C?

Pleural membranes
What is D?

Left pleural cavity
What is E?

Pericardial cavity
What is F?

Right pleural cavity
What is G?

Right lung
What is H?

Esophagus
What does the pleural cavity contain?
5mm of pleural fluid
What is the pleural cavity unique to?
Each lung, they do not join
What does the inside and outside of the pleural membrane line?
Ribs and outer tissue of the lungs
What are the 2 pleural membranes called?
Visceral pleural membrane (lines lungs)
Parietal pleural membrane (lines ribs)
What does the visceral pleural membrane line?
Lungs
What does the parietal pleural membrane line?
Ribs
What are some functions of pleural fluid?
Act as lubricant, allowing the two membranes to glide across each other as the lungs expand and contract
Create a force that stops the seperation of the lungs from the rib cage, so when the rib cage moves so does the lungs
What is pleurisy?
Inflammation of pleural membranes
What is inflammation of the pleural membranes called?
Pleurisy
What is the pressure of the pleural cavity when the lungs are at rest?
-3mmHg

Where does the rib cage and lungs naturally want to move?
Rib cage wants to move outwards and the lungs want to recoil inwards
What happens to the intrapleural pressure when the lung is punctured?
Becomes equal to atmospheric pressure and the lung collapses

What is the end of expiration a balance between?
The lung wanting to retract inwards and the ribcage wanting to expand outwards
What creates the negative pressure of the pleural cavity?
Lung wanting to retract inwards and the ribcage wanting to expand outwards
What is intrapleural pressure?
Negative pressure inside the pleural cavity
What gas law is the mechanics of breathing based on?
Boyle’s law
Increase in volume decreases pressure
Decrease in volume increases pressure
What are the mechanics of breathing?
1 ) Thoracic cavity changes volume
2) This changes the pressure (Boyle’s law)
3) Air moves from area of high pressure to low pressure
What muscles does inspiration use?
Intercostal muscles
Diaphragm

What muscles does expiration use?
Is passive at rest, but during severe respiratory load uses:
Internal intercostal muscles
Abdominal muscles

What is A?

Sternocleidomastoids
What is B?

Scalenes
What is C?

External intercostals
What is D?

Diaphragm
What is E?

Abdominal muscles
What is F?

Internal intercostals
Where do external intercostals run between and what happens when they contract?
Ribs
When they contract they lift the rib cage upwards and outwards

Where do internal intercostal muscles run between, and what do they do when they contract?
Ribs
When they contract they lift they pull the ribcage inwards and downwards

What happens when abdominal muscles contract?
They bring abdominal organs upwards, which push agaist the diagragm and decreases thoracic volume

What does the diaphragm do during inspiration?
Contracts and flattens which increases thoracic volume
What does the diaphragm do during expiration?
Relaxes which decreases thoracic volume
What can thoracic volume increasing due to rib movement be compared to?
Bucket handle shows increase in lateral dimensions
Pump handle shows increase in anterior-posterior dimensions

What can the ribs causing an increase in lateral dimensions be compared to?
Bucket handle

What can the ribs causing an increase in anterior-posterior dimensions be compared to?
Pump handle

What is asthma?
Over reactive constriction of bronchial smooth muscle, increasing resistance
Why do asthma sufferers struggle during expiration but not inspiration?
Physical forces pull airways open during inspiration but not expiration
What is pneumothorax?
Collapsed lung, occuring due to air leaking into the pleural cavity and altering the pressure (equal to atmospheric pressure)
What is a collapsed lung called?
Pneumothorax
What happens during pneumothorax?
Rib cage expands slightly and lung collapses to unstretched size due to no longer being attached by the force created by the pleural cavity
Why does a pneumothorax happen?
Punctured pleural cavity causes loss of negative pressure as it becomes equal to the atmosphere
Force that attaches lungs to rib cage is no longer present and so the lung collapses to unstretched size
What are 3 relative pressures?
Intra-thoracic (alveolar) pressure, PA
Intra-pleural pressure, PIP
Transpulmonary pressure, PT
What is intra-thoracic (alveolar) pressure, PA?
Pressure inside the thoracic cavity (inside lungs)
May be negative or positive
What is intra-pleural pressure, PIP?
Pressure inside the pleural cavity
Always negative
What is transpulmonary pressure, PT?
Pressure difference between the alveolar and intra-pleural pressure
PT = PA - PIP
Always positive because intra-pleural pressure is always more negative than alveolar pressure
What is intra-pleural pressure compared to alveolar pressure?
Always more negative
How does pressure change during the respiration cycle?
During inspiration alveolar pressure goes negative then back to 0 and intrapleural pressure goes more negative
During expiration alveolar presure goes positive and then back to 0 and intrapleural pressure goes closer to 0

What formula describes the flow of air?
Directly proportional to the difference between atmospheric and alveolar pressure and inversely proportional to airway resistance:
F = (PATM - PA / R
How does alveolar pressure compare to atmospheric pressure at the end of an unforced expiration?
PATM = PA
Why are the dimensions of the thoracic cage stable after an unforced expiration?
Opposing elastic forces are equal, creating subatmospheric intrapleural pressure and a transpulmonary pressure that opposes the forces of elastic recoil
What is the most important thing affecting airway resistance?
Radii of airway