Physiology 3 Flashcards
Anatomical dead space?
Inspired air that remains in the airways where it is not available for gas exchange
Pulmonary ventilation equation
Pulmonary ventilation (L)= Tidal volume (L/breath) x Respiratory rate (breath/min) under resting conditions
Difference between alveolar ventilation and pulmonary ventilation?
Alveolar ventilation is less due to presence of anatomical dead space
Alveolar ventilation equation?
Alveolar ventilation (L)- Tidal volume- dead space volume) x Respiratory rate under resting conditions
Pulmonary ventilation?
Volume of air breathed in and out per minute
Alveolar ventilation?
Volume of air exchanged between atmosphere and alveoli per minute
Why is alveolar ventilation more important?
Represents new air available for gas exchange within the blood
How to increase pulmonary ventilation?
Depth (TV) and rate of breathing increases
Why is dead anatomical space significant?
To increase pulmonary ventilation t is more advantageous to increase the depth of breathing instead of the rate of breathing (Although both increase)
What does the transfer of gases around the body depend on?
Ventilation
Perfusion
Perfusion
Rate at which blood is passing through the lungs
Ventilation
Rate at which gas is passing through the lungs
When does differing alveolar and arterial partial pressures being different have a significant effect? and what is it due to?
In disease
Blood flow and ventilation varying from the top to the bottom of the lung
What are ventilated alveoli that are nit adequately perfused with blood considered as?
Alveolar dead space
Alveolar dead space in
a) Healthy
b) Diseased
a) Very small and of little importance
b) could increase significantly
Physiological dead space equals
anatomical + alveolar dead space
What leads to accumulation of CO2 in the alveoli?
Increased perfusion
What does accumulation of CO2 in the airway cause?
Decreased airway resistance
Increased airflow
What causes an increase in alveolar O2 concentration?
Increased Ventilation
What does increased concentration of 02 alveolar cause?
Pulmonary vasodilation
Increased blood flow to match larger airflow
O2 decreases in the area? (Perfusion is greater than ventilation)
Constriction of local blood vessels
Blood flow decreases
CO2 decreases in the area? (Ventilation greater than perfusion)
Constriction of local airways
Airflow decrease
Effect of decreased O2 on pulmonary arterioles?
Vasoconstriction
Effect of increased O2 on pulmonary arterioles?
Vasodilation
Effect of
a) Decreased O2
b) Increased O2
on systemic arterioles?
a) Vasodilation
b) Vasoconstriction
4 factors that influence the rate of gas exchange across an alveolar membrane?
Partial pressure gradient of O2 and CO2
Diffusion coefficient for O2 and CO2
Surface area of the alveolar membrane
Thickness of alveolar membrane
Daltons law of partial pressure letter equation?
Ptotal= P1 + P2 +… + Pn
Daltons law of partial pressure word equation?
The total pressure exerted by a gaseous mixture
The sum of the partial pressures of each individual component in the gas mixture
Partial pressure of Gas definition?
The pressure that one gas in a mixture of gases would exert if it were the only gas present in the whole volume occupied by the mixture at a given temperature
Alveolar Gas equation?
PAO2=
PiO2- [PaCO2/0.8]
PAO2=Partial pressure of 02 in alveolar air
PiO2= Partial pressure of O2 in inspired air
PaC02=Partial pressure of CO2 in arterial blood
0.8 is the respiratory exchange ratio (RER) (ratio of CO2 produced/ O2 consumed for someone eating a mixed diet
What does water vapour pressure contribute to to the total pressure of the lungs?
47mmHg
Pressure of inspired air=
Atmospheric pressure - water vapour pressure
760- 47= 713mmHg at sea level
Pi02=
713 x 0.21 v=150mmHg
Which is more soluble in membranes Co2 or O2?
CO2
Diffusion coefficient is 20 times that of 02
Partial pressure gradient of CO2 is much smaller than partial pressure gradient of O2
Diffusion coefficient for gas?
Solubility of gases in membranes
Fick’s Law of Diffusion
The amount of gas that moves across a sheet of tissue in unit time is proportional to the area of the sheet but inversely proportional to its thickness
How do lungs provide a large SA for gas exchange?
+ what is their circulation like
Airways repeatedly divide
Small airways divide into alveoli
Extensive pulmonary capillary network
Fun fact about pulmonary capillary network?
Receives entire cardiac output
Alveoli
Description
Function
Thin walled inflatable sacs
Function in gas exchange
Walls of alveoli
Walls consist of single layer of flattened Type 1 alveolar cells
What encircles each alveolus
Pulmonary capillaries
As partial pressure of CO2/ O2 increases?
Rate of Transfer of gases increases
As the diffusion concentration gradient increases?
Rate of gas transfer increases
SA of alveolar membrane increases?
Rate of gas transfer increases
Thickness of alveolar membrane increases?
Rate of gas transfer decreases
Non respiratory functions of respiratory system?
- Route for water loss and heat elimination
- Enhances venous return (cardiovascular physiology)
- Helps maintain normal acid-base balance (Resp & Renal physiology)
- Enables speech, singing and other vocalizations
- Defends against inhaled foreign matter
- Removes, modified, activates or inactivates various materials passing through the pulmonary circulation
- Nose serves as organ of smell
