51R. Gas Exchange Flashcards
what is anatomical dead space
some inspired air remains in the airways where it is not available for gas exchange
what is the equation and for pulmonary ventilation
PV= tidal volume x respiratory rate
what is pulmonary ventilation
total volume of air that is inhaled and exhaled from the lungs per minute
which is always less? Alveolar Ventilation or Pulmonary Ventilation and why
alveolar ventilation as some of the inspired air stays in the airway/dead space so isnt exchanged
what is alveolar ventilation
the volume of air that actually reaches the alveoli and is available for gas exchange per minute
what is alveolar ventilation equation
AV= (tidal volume - dead space volume) x respiratory rate
what is boyles law
‘Pressure (P) of a gas is inversely proportional to its volume (V)’ (if temperature & number of gas molecules remains constant in a closed system)
Partial pressure of an individual gas in a gas mixture is explained by Dalton’s Law. What does it state?
In a mixture of gases, the total pressure = the sum of the partial pressures of the individual gases
what is atmospheric pressure at sea level
101 kilopascals
in the atmosphere, what are the partial pressures of the gases in percentage
O2 = 20.9%
N2 = 78%
CO2 = 0.03%
gases dissolve and diffuse according to what
their partial pressure and the partial pressure gradient
When Inspired Gases Come in Contact with Body Fluids what happens
they dissolve in liquid
Water molecules from the body fluids can do what
evaporate and enter the air
Water molecules from the body fluids can evaporate and enter the air which creates pressure. What is this pressure called
vapour pressure
At body temperature inhaled air becomes saturated with water vapour in the upper respiratory tract what is this pressure called
Saturated vapour pressure
what is the solubility coefficient
is a constant for the individual gas and the solvent
what is partial pressure
pressure exerted by the dissolved gas in liquid
what is the concentration of dissolved gas
Number of mmol of gas, dissolved in a litre of liquid
What is the total content of gas
= dissolved gas + gas bound to or reacted with a component
( e.g. O2 dissolved plasma + O2 bound to Hb)
how many oxygens can haemoglobin carry
4
what two ways does your blood carry oxygen
on haemoglobin (proteins) and dissolved in plasma
When oxygen (O₂) moves from the alveolar air into the red blood cells (RBCs) in the capillaries, it must cross several layers
5 Cell Membranes:
- Alveolar Epithelial Cell Membrane (entering the epithelial cell).
- Alveolar Epithelial Cell Membrane (exiting the epithelial cell).
- Capillary Endothelial Cell Membrane (entering the endothelial cell).
- Capillary Endothelial Cell Membrane (exiting the endothelial cell).
- Red Blood Cell Membrane (entering the RBC).
3 Layers of Cytoplasm:
- Alveolar Epithelial Cell Cytoplasm.
- Capillary Endothelial Cell Cytoplasm.
- Red Blood Cell Cytoplasm.
2 Layers of Tissue Fluid and Plasma:
Interstitial Fluid (between the alveolus and capillary).
Plasma (the liquid part of the blood).
how thick is the barrier
<0.4 micrometers
what is the surface area of the alveolar capillary membrane
100 m2
what 3 factors affect rate of diffusion - in disease
thickness of membrane
surface area of membrane
diffusion coefficient of the gas
explain the 3 factors affecting rate of diffusion - in disease
Thickness of the Membrane
Oedema: This is like adding extra layers because of fluid buildup.
Lung Fibrosis: This makes the the membrane even thicker because of scarring.
Surface Area of the Membrane
Removing a Lung
Emphysema
Diffusion Coefficient of the Gas
CO₂ (Carbon Dioxide): super fast and can move easily.
O₂ (Oxygen): slower and has a harder time moving.
The V/Q ratio (ventilation/perfusion ratio) should be close to ……..for optimal gas exchange.
1
Your lungs have about ………. million alveoli, and they can have different amounts of ventilation and perfusion.
300
For the best gas exchange, the amount of air (ventilation) and the amount of blood (perfusion) should be ……..
matched
When the oxygen level (pO₂) in the alveoli is low, the blood vessels (pulmonary arterioles) constrict (get smaller).
This process is called….?
hypoxic vasconstriction
