Respiratory 1 Flashcards
Diagram of anatomy of respiratory system
- Air comes in through nose - mouth - trachea
- Splits and goes to left and right lung and branches into bronchi –> bronchioles –> terminal bronchioles and alveolar sacks (very smallest of airways where you have exchange of oxygen and CO2 with blood)
Dead space
- The average inhalation for an average-sized person is 500 ml (approx 150 ml is dead space)
- The air comes in, the lungs expand, but the very last bit of air that goes down the tube is sitting in the bronchus and is not exchanging gases a the alveoli, so it still has the same composition of gases as in the air
- So when you breathe out, the first air to come out of your mouth is dead space air (21% oxygen, almost 0% CO2)
How do we inflate and deflate the lungs if they’re like flimsy bags?
- The chest cavity is sealed off (air-tight), so there’s a vacuum
- When the vacuum inflates the lungs, they stick to the inside of the chest cavity and its the negative pressure between the outside of the lung and the inside of the chest wall that keeps your lungs inflated
What is the natural tendency of the lungs (in relation to their elasticity)?
- Natural tendency to collapse into the chest wall
- If you expand the chest wall, there’s a negative pressure, and the lungs follow
What is the most important muscle involved in breathing?
- The diaphragm
- It separates the thoracic cavity from the abdominal cavity
Diagram explaining negative pressure of lungs
- The inward arrows show that there are elastic properties that cause the lung to collapse
- Because there is a negative in the intrapleural space, the outer wall of the lung is suctioned to the inner wall of the chest cavity
- There’s mucus there so it slides, and there are active transport mechanisms that ensure that there’s no fluid accumulating in it and a negative pressure exists
What would happen if something breaks the seal on the chest wall cavity/lung membrane?
- You could have air accumulate in the intrapleural space, which would cause the lung to collapse
- The lung is no longer adhered by a vacuum to the internal wall of the chest cavity
- This is called pneumothorax
More detail on negative pressure of lungs in chest cavity
Lung at rest = airway open and muscles relaxed. This is the lung volume at the end of “quiet breathing” and it is defined as functional residual capacity (FRC)
- Elastic properties of lung pulls inward
- Recoil of chest wall pulls outward
- Negative pressure in the sealed-off, intrapleural space is a result of this pulling in two different directions
- Pneumothorax – loss of vacuum, opening between atmosphere and intrapleural space, allows lung to collapse and chest wall to expand
Mechanisms of movement of air in the lungs
Lungs are not capable of moving air
- They must be inflated
- They have elastic properties that cause them to collapse, like a balloon.
- Movement of diaphragm (pushes down into abdominal cavity) and intercostal muscles (expanding ribs out) changes volume of chest cavity (thoracic cavity)
Mechanism of breathing during ‘quiet’ and ‘loud’ breathing
Expansion of the thoracic cavity, diaphragm most important, expands lungs out
- Intrapleural space has negative pressure that keeps outer surface of lungs in contact with inner surface of thoracic cavity
- During quiet breathing, intrapleural pressure is negative at rest, more negative during inspiration, less negative during exhalation.
- During “loud” breathing, intrapleural pressure is very negative during inspiration and even positive during expiration (forceful contraction of chest wall and abdomen squeezes air out of lungs through airways that offer resistance, so pressure backs up.
Diaphragmatic breathing
- Inhale - relaxation of abdominal muscles expands the abdominal cavity allowing for expansion of thoracic cavity.
- Exhale - contraction of abdominal muscles pushes abdominal contents up into the thoracic cavity thereby decreasing volume of thoracic cavity.
Is inspiration active or passive?
Active
Is expiration active or passive?
Passive during quiet breathing
What is resistance to air flow proportional to? (usually not a big problem, unless you’re breathing really fast)
Proportional to 1/r^4
Resistance of bronchioles
- Small airways are most impacted by resistance (not the trachea or the large bronchi)
- Could be caused by swelling, inflammation, or fluid accumulation could block the airways and dramatically increase resistance
Explain how resistance changes with lung volume
- When the lung is at a low volume, the elastic walls of the small airways tend to collapse
- The little blue fibers are attached to the outer surface of your lung and to the walls of the airways (diagram)
- When you stretch the outer surface of the lung out, there’s more tension on the elastic fibers and the walls of the small airways are held open at a larger radius
- When your lung is more collapsed at a lower volume, the elastic fibers have slack in them and they’re not pulling the airways open. As you try to exhale, the radius gets smaller.
What is functional residual capacity (FRC)?
- Value of where lung volumes go when you relax all respiratory muscles and open up your airways
- Typically happens at the end of a normal expiration
Diagram showing dead space and alveolar space
- The terminal bronchioles are called respiratory bronchioles here
Diagram of the structure of the bronchi and alveoli
- The capillaries surround the walls of the alveolar sac
- The distance between air inside the alveoli and the capillary surrounding the alveolar wall is maybe 10 micrometers (very close)
- This makes diffusion effective
Close-up diagram of alveolar structure and exchange at the surface of alveoli
- The alveoli are airtight to not allow air to escape
- There is very little extracellular space between the alveolar wall and the endothelial cells lining the capillary (smaller than the thickness of a membrane)
- This decreases the distance for diffusion
Big picture diagram of movement of gases from outside the body to into the alveoli
Respiratory cycle diagram (dead space)
- 500 ml of air comes in through the mouth and the last 150 (more or less) is dead space so it never reaches a terminal bronchiole or an alveolus
- The first 150 ml to come out of your mouth has 21% oxygen, whereas the last 350 has ~16% and a higher concentration of CO2
- The first 150 ml of air that goes in is the last 150 that you just breathed out (dead space) so it’s stale air (low oxygen, high CO2)
- This highlights a challenge of batch breathing
Equation for tidal volume
Split up into two types of ventilation:
- Alveolar ventilation- allows for exchange of oxygen and CO2
- Dead space ventilation, which does not
- The most important thing is Va (this is what the body regulates)
Total minute ventilation
