6: Physiology III Flashcards
Some inspired air remains in the airways where it is not available for gas exchange. What is this space called?
Anatomical dead space
Give an equation for pulmonary ventilation.
Pulmonary ventilation = Tidal volume x Respiratory rate
What is the average value for pulmonary ventilation (in L/min)?
6 L/min
Why is alveolar ventilation less than pulmonary ventilation?
Because there is anatomical dead space in the airways
Give an equation for alveolar ventilation (in L/min).
Alveolar ventilation = (Tidal volume - Anatomical dead space) x Respiratory rate
What is the average value for alveolar ventilation, in L/min, under resting conditions?
4.2 L/min
What is the definition of pulmonary ventilation?
The volume of air breathed in and out per minute
What is the definition of alveolar ventilation?
The volume of air exchanged between the atmosphere and alveoli per minute
To increase pulmonary ventilation during exercise, the respiratory rate and depth of breathing (tidal volume) increase.
Which increase is most beneficial? Why?
It’s more advantageous to increase the DEPTH of breathing (i.e the tidal volume)
because of anatomical dead space.
The transfer of gases between the body depends on the matching of two factors - what are they?
Ventilation
Perfusion
What is ventilation?
The rate at which gas passes through the lungs
What is perfusion?
The rate at which blood passes through the lungs
What is alveolar dead space?
Ventilated alveoli which are inadequately perfused with blood
What name is given to ventilated alveoli which are inadequately perfused with blood?
Alveolar dead space
Give an equation for physiological dead space.
Physiological dead space = anatomical dead space + alveolar dead space
In disease, alveolar dead spaceis significantly(increased / decreased).
increased
Accumulation of CO2 in alveoli ___ airway resistance leading to ___ airflow.
decreases , increased
What vascular change results from increased alveolar O2 concentration?
Pulmonary vasodilation
Increases blood flow to match ventilation
Why are the pulmonary vascular changes in response to O2 concentration different to those of the systemic circulation?
Pulmonary vasculature aims to maintain V/Q match - alveoli which aren’t being perfused receive less blood flow
What is Dalton’s Law of partial pressures?
The total pressure of a gaseous mixture is = to the sum of the partial pressures of each component gas
What is the partial pressure of a gas?
The pressure that gas would exert if it were the only gas present in the whole volume
Gases move from ___ to ___ partial pressures.
higher , lower
How do you convert mmHg into kPa?
kPa = mmHg / 7.5
Why can CO2 diffuse easily across membranes although its partial pressure gradient is less than that of oxygen?
Diffusion coefficient for CO2 is 20x that of O2
Why do the alveoli increase gas exchange in the lungs?
Thin walled
Large surface area
The lungs have an extensive ___ network.
capillary
Which kind of alveolar cells make up the alveolar walls?
Type 1 alveolar cells
What are the four factors influence rate of gas exchange across the alveolar membrane?
Partial pressure gradient
Diffusion coefficient
Surface area of membrane
Thickness of membrane
The respiratory system also enhances ___ return.
How?
venous
Increased intrathoracic pressure during compresses veins and increases venous return
The respiratory system is also involved in maintaining normal ___-___ balance.
acid-base
