What happens when the bronchioles in the lungs dilate?
They increase their volume and lower the pressure inside the lungs, moving air in
What does the parietal pleura secrete?
What is the purpose of the fluid secreted by the parietal pleua?
The surface tension adheres the two pleural layers together
What is the parietal pleura attached to?
The chest wall
What is the result of the parietal pleura being attached to the chest wall?
When the chest wall expands, the parietal pleura moves wtih it, as does the visceral pleura
What is the visceral pleura attached too?
What is the result of the attachment of the visceral pleura to the lung?
When the chest wall expands, the lung expands
What do the external intercostal muscles do?
Elevate the ribs in a 'bucket handle' type movement
How much of chest expansion is the chest wall responsible for during quiet respiration?
What does the diaphragm do to expand the chest?
Contracts and descends
How much of chest expansion is the diaphragm responsible for during quiet respiration?
What muscles are involved in inhalation during quiet breathing?
- External intercostals
What muscles are involved in exhalation during quiet breathing?
What muscles are involved in inhalation during forced breathing?
- External intercostals
- Pectoralis minor
- Serratus anterior
What muscles are involved in exhalation during forced breathing?
- Internal intercostals
- Innermost intercostals
- Abdominal muscles
What happens to blood flowing through alveolar capillaries?
It picks up oxygen and loses carbon dioxide by diffusion of those gases across the alveolar wall
What is the rate of gas exchange in the alveolar capillaries determined by?
- Area available for gas exchange
- Resistance to diffusion
- Gradient of partial pressure
In a normal lung, what is the exchange area?
What creates the large area for exchange in the lungs?
The huge number of alveoli
In normal lungs, is the area available for exchange a limiting factor on gas exchange?
What provides resistance to diffusion in the alveoli?
Although the diffusion pathway is short, there are several structures between the alveolar as and the alveolar capillary blood
What must the alveolar gas diffuse through to reach the alveolar capillary blood?
- Gas in the alveoli
- The alveolar epithelial cell
- Interstitial fluid
- Capillary endothelial cell
- RBC membrane
5 cell membranes, 3 layers of intracellular fluid and 2 layers of extracellular fluid
How long is the diffusion distance between alveolar gas and alveolar capillary blood?
Less than 1 micron
What gases must diffuse through the barrier between alveolar gas and alveolar blood?
Oxygen and carbon dioxide
What is the rate of diffusion across the alveoli affected by for most of the barrier (the cells, membranes, and fluid)?
Solubility of gas in water
How does the diffusion rate of carbon dioxide differ from that of oxygen?
It diffuses 21 types as fast for a given gradient
Why does carbon dioxide diffuse across the alveoli faster than oxygen?
Because it is more soluble
How much faster than oxygen does carbon dioxide diffuse for a given gradient?
21 times as fast
What is the result on gas exchange at the alveoli of carbon dioxide diffusing much faster than oxygen?
Anything affecting diffusion will only change oxygen transport, as that is limiting (if there is a problem affecting the exchange of gases, oxygen will be affeted first)
What must be true of the partial pressure if the tissues of the body are to be properly supplied with oxygen and carbon dioxide?
The partial pressure of oxygen and carbon dioxide in the alveolar gas must be kept very close to their normal values