Physiology 3 Flashcards
What name is given to space in the lungs filled with air which is not available for gas exchange?
Anatomical dead space
Give a word equation for pulmonary ventilation.
Pulmonary ventilation = Tidal volume x Respiratory rate (L/min)
Give a word equation for alveolar ventilation.
Alveolar ventilation = (Tidal volume - dead space volume) x Respiratory rate (L/min)
Why is alveolar ventilation LESS than pulmonary ventilation?
Anatomical dead space
What is pulmonary ventilation?
The volume of air breathed in and out per minute
What is alveolar ventilation?
The volume of air exchanged between the atmosphere and alveoli per minute
Why is the value for alveolar ventilation more important than that of pulmonary ventilation?
It represents the new air available for gas exchange with the blood
How does one increase their pulmonary ventilation?
- Increase the depth of breathing (tidal volume)
2. Increase the rate of breathing (respiratory rate)
Because of dead space, it is more advantageous to increase (depth of breathing / respiratory rate).
depth of breathing
What is ventilation?
The rate at which GAS passes through the lungs
What is perfusion?
The rate at which BLOOD passes through the lungs
Arterial partial pressure and alveolar partial pressure are at equilibrium when the ventilation/perfusion ratio is _.
1
In most of the lung, partial pressures (are / are not) the same.
are not
What is alveolar dead space?
Ventilated alveoli which is not adequately perfused with blood
Alveolar dead space increases in ____.
disease
Give a word equation for physiological dead space.
Physiological dead space = anatomical dead space + alveolar dead space
___ ___ acts on the airways and arterioles to match airflow to blood flow.
Smooth muscle
What must be matched in the airways and arterioles?
Airflow and blood flow
Why may carbon dioxide accumulate in the alveoli?
Increased perfusion
What occurs in the airways in response to alveolar carbon dioxide accumulation?
Dilation of airway / decrease in airway resistance –> Increased airflow
Why may oxygen accumulate in the alveoli?
Increased ventilation
What occurs in the pulmonary vessels in response to alveolar oxygen accumulation?
Vasoconstriction / increase in vascular resistance –> Decreased blood flow
What happens to pulmonary arterioles when oxygen concentration of adjacent alveoli decreases?
Vasoconstriction
What happens to pulmonary arterioles when oxygen concentration of adjacent alveoli increases?
Vasodilation
Name four factors influencing the rate of gas exchange across the alveolar membrane.
- Partial pressure gradients of O2 and CO2
- Diffusion Coefficients
- Surface area of alveolar membrane
- Thickness of alveolar membrane
What is Dalton’s Law of Partial Pressures?
The total pressure exerted by a gaseous mixture = The sum of partial pressures of each gaseous component
What is the partial pressure of a gas (e.g Gas X)?
The pressure that Gas X would exert if it alone occupied the total volume
What is the partial pressure gradient?
Gases move from higher to lower partial pressures
What are the two units of measurement for partial pressure?
- kilopascals (kPa)
2. mm Hg (to convert to kPa, divide by 7.5)
What is the diffusion coefficient of a gas?
The solubility of that gas in membranes
The diffusion coefficient of carbon dioxide is __ times that of oxygen.
20
The higher diffusion coefficient of carbon dioxide offsets its smaller ___ ___ ___.
partial pressure gradient
___ amounts of oxygen and carbon dioxide are transferred across the membrane.
Equal
What is Fick’s Law of Diffusion?
The amount of gas which moves across a sheet of tissue per unit time is:
- Directly proportional to the surface area of the sheet
- Inversely proportional to the thickness of the sheet
What are two properties of the lungs which make them favourable for gas exchange?
- Large surface area
2. Thin membranes
The extensive pulmonary capillary network of the lungs receives the entire ___ ___.
cardiac output
The walls of alveoli consist of what type of alveolar cell?
Type I
Which type of alveolar cell produce pulmonary surfactant?
Type II
Alveoli are encircled by ____ ____.
pulmonary capillaries
Name two non-respiratory functions of the respiratory system.
- Water loss and heat elimination
- Enhances venous return
- Maintains acid-base balance
- Enables speech and articulation
- Defence against foreign material
- Nose - function of smell
