Gas Exchange 1 Flashcards
What is in the air
78% Nitrogen
21% Oxygen
0.9% Argon
0.037% CO2
What is an important variable in respiratory gas exchange
Rate of diffusion
Diffusion of gas is influenced by: (5 items)
Solubility of the gas in the medium (water, air) Partial pressure gradient Temperature Distance for diffusion Surface area for diffusion
What is the Fick equation?
Rate of diffusion = Diffusion coefficient * SArea * Pressure gradient
Rate of diffusion is smallest when ___
The distance is at its smallest
What is the diffusion coefficient
Index of ease of diffusion of a particular substance through a given medium
The diffusion coefficient depends on what
Temperature and solubility
The pressure of the gas is a measure of ____
the thermodynamic activity of the gas molecules
Dalton’s Law of Pressures
Each gas exerts its own partial pressure. The sum of the partial pressures = total pressure and is proportional to the total number of gas molecules
What is the Ideal gas law?
PV=nRT
What is P equivalent to in the Ideal gas law?
P=(nRT)/V
Partial pressure depends on ___
Temperature of the gas
If the temperature increases and volume is not constant, what will happen?
The volume will increase & pressure stays constant & concentration of gas decreases
If temperature increases and volume is constant, what will happen?
Pressure increases & concentration of gas stays the same
What does a gas need to do before it diffuses into a cell?
Dissolve into the liquid
The amount of gas that will dissolve in a liquid is dependent on ___
Partial pressure in air & solubility in the liquid
What is Henry’s Law
Concentration of gas dissolved in liquid = Partial pressure of gas in atmosphere * Solubility of gas in liquid
What has a large effect on solubility of gases in liquids?
Temperature & salinity
What is Graham’s Law
Diffusion of a gas in a liquid is proportional to its solubility & inversely proportional to the square root of its molecular weight
Which diffuses faster in air: O2 or CO2
O2 is 1.2 faster to diffuse than CO2
Which is more soluble in water: O2 or CO2
CO2 is 24 times more soluble in water than O2
Which is more soluble in air: O2 or CO2
Same
Which has higher molecular weight: O2 or CO2
CO2
What is the diffusion rate for oxygen in water vs. air
Diffusion rate for O2 in water is 300,000 times more slower than air
What direction is O2 gradient in terms of the body
Into the body
What direction is the CO2 gradient in terms of the body
Out of the body
Characteristics of gas exchange organs
Must be moist so that gases can dissolve into liquid
How does the body compensate for slow O2 diffusion rates in liquid
Circulatory system & O2 transport molecules & O2 binding molecules
What is hemoglobin
O2 transport molecule
What is myoglobin
O2 binding molecule
Why is medium (air or water) flow over respiratory surfaces greater in water breathing than in air breathing animals
Because water has a much lower concentration of O2 than air
What is dessication
When the respiratory surface becomes dry
What are problems for water breathing animals
Have to expend more energy to move more medium (water) over the gas exchange organ
What are problems for air breathing animals
Have to keep respiratory surfaces moist to prevent dessication. Water is lost by evaporation
How can you deliver O2 directly to internal cells and tissues
Bulk flow of water or air
3 types of ventilation
- Nondirectional ventilation (wave gills in medium)
- Tidal ventilation (lungs)
- Unidirectional ventilation (fish gills)
What happens in tidal ventilation
- Bidirectional movement
- As Po2 in blood increases, Po2 of medium decreases
- Not the most efficient, but prevents dessication
Why is unidirectional ventilation good
Makes greater exchange efficiency because blood is always exposed to O2-rich medium
The fish gill is an example of what type of flow
Countercurrent (best exchange efficiency)
What is special about Teleost fish
They combine directional flow with concurrent exchange
How do birds maximize gas exchange
They implement a crosscurrent mechanism
What gas exchange organ do birds have
Stiff, hexagonal lungs and air sacs
What flow type do bird respiratory systems implement
Unidirectional & continuous flow
Where do the lungs end
Alveoli
Two types of cells in alveoli
Type I & Type 2
What do Type 1 cells do
Mainly for gas exchange
What do Type 2 cells do
Release surfactant
How is ventilation controlled in mammals
Contraction & relaxation of the diaphragm
Diaphragm contracts when ___
You breath in
Diaphragm relaxes when ___
You breath out
What is tidal volume
The volume of air inhaled/exhaled with each breath
How much is average tidal volume
500 mL
What is vital capacity
Maximum tidal volume during forced breathing
What is the vital capacity for females and males, respectively
3.4 L & 4.8 L
Why don’t the alveoli in the lung collapse
Residual volume & Surfactant
What is residual volume
Air that remains in the lungs after exhalation. The lungs hold more air than the vital capacity
What is surfactant
A detergent (mixture of phospholipids and proteins) secreted by alveolar epithelium.
What does surfactant do
Reduces surface tension in the liquid coating the alveolar surface
What does surfactant increase
Compliance of alveoli
What stimulates surfactant production
Corticosteroids
