L64: Gas Exchange Flashcards
In alveoli and capillaries, what gradient do gases move from?
Down a concentration/ pressure gradient
Airways branch into smaller and more numerous bronchioles until terminating to a group of alveoli, describe the respiratory tree:
Trachea > Bronchi > Nonrespiratory bronchioles > Respiratory bronchioles > Alveoli
What happens through each division of the respiratory tree?
- Increase in number of units;
- Decrease in diameter;
- Increase in SA.
What is a conducting airway?
Bronchi containing cartilage and non-respiratory bronchioles
What is a respiratory airway?
Bronchi with alveoli where gas exchange occurs
What is a respiratory unit?
The physiological unit of the lung, a gas exchanging unit
What is the difference between a terminal and respiratory bronchiole?
A respiratory bronchiole has alveoli
How many alveolar sacs do adults typically have?
~300-400 million
What is the diameter of alveoli? (polygonal in shape)
~250μm
What type of cells do alveolar epithelium comprise of?
Type I and type II (septal) cells
What is the most dominant type of alveolar epithelial cell?
Type I, these cover 97% of the surface area
What is the primary function of type I alveolar epithelial cells?
Site of gas exchange
What is the primary function of type II alveolar epithelial cells?
To produce pulmonary surfactant, this reduces surface tension
What is the primary function of alveolar macrophages?
Removal of debris
How are alveoli specialised to carry out their function?
- Large surface area (~100m^2);
- Thin walls (~0.5μm);
- Good diffusion characteristics.
What are the blood supplies for the lung?
- Pulmonary Circulation (heart and lungs);
- Bronchial Circulation (O2 to parenchyma)
What does the lymphatic system do?
Supports the body from pathogens through supporting the immune response and removes lymph fluid
What is the total volume of blood in pulmonary circulation ?
500mLs
At rest, how much blood is in the alveolar-capillary network?
75mLs
During exercise, how much blood is in the alveolar-capillary network?
150-200mLs, through recruitment of more capillaries
How are alveolar capillaries specialised to perform their function?
- Thin-walled;
- Highly compliant;
- Larger diameter
- Lower resistance than in systemic circulation.
Describe the alveolar-capillary network:
- Network for gas exchange;
- Dense, mesh-like network of capillaries, alveoli and rbc;
- 1-2μm between alveoli and rbc;
- abc pass through capillaries in <1 second, sufficient for gas exchange.
In pulmonary circulation, X gas enters and Y gas leaves
X: Oxygen, Y: Carbon Dioxide
In systemic circulation, X gas enters and Y gas leaves
X: Carbon Dioxide, Y: Oxygen
What are the pressures of O2 and CO2 in pulmonary circulation?
O2 (venous blood): 40
O2 (alveolar air): 100
[air to blood]
CO2 (venous blood): 46
CO2 (alveolar air): 40
[blood to air]
What are the pressures of O2 and CO2 in systemic circulation?
O2 (arterial blood): 100
O2 (tissues): 40
[blood to tissues]
CO2 (arterial blood): 40
CO2 (tissues): 46
[tissues to blood]
