2 Respiratory System Flashcards
Define gas exchange - external and internal respiration
CO2 and O2 exchange between pulmonary capillaries and alveoli = external respiration
CO2 and O2 exchange between systemic capillaries and surrounding cells = internal respiration
What are the 4 factors affecting EXTERNAL respiration?
Lipid solubility of gases = to allow passing through membranes via simple diffusion
Perfusion and rate of flow = compatible alveolar airflow and pulmonary capillary blood flow
Partial pressure gradients
Surface area, thickness and structure of respiratory membranes
What does it mean to have lipid soluble gases?
They rely on partial pressure gradients to simply diffuse through lipid membrane
How to calculate partial pressure?
Atmospheric pressure (760 mmHg) x fraction of gas in the atmosphere (fixed proportion %)
Explain the connection between atmospheric pressure and partial pressures?
Combined partial pressure of gasses = atmospheric pressure
What happens to partial pressure at high altitude?
Atmospheric pressure decreases
Therefore partial pressure of each gas decreases with increasing altitude
What is Henry’s Law?
How much gas can dissolve in a liquid at a given temperature
Depends on partial pressure and solubility of the gas
What happens to partial pressure in a closed system?
Partial pressure gradient is lost because everything would equilibrate
What occurs when partial pressure is increased in an open system that has reached equilibrium?
At equilibrium, the pressure of oxygen in the air is the same as that in the liquid with equal diffusion in both direction
Increasing partial pressure leads to increase diffusion INTO the liquid until new equilibrium is reached
Why at the same pressure and temperature, does more CO2 dissolve into liquid than O2?
CO2 has greater SOLUBILITY than O2
How does humidification of inhaled air occur?
Air moving along the airways gets humidified
Picks up water molecules and increases the partial pressure of water
If ventilation is decreased, what happens to lung pCO2?
The pCO2 in the lungs will increase so diffusion of CO2 from blood to alveolus would decrease because gradient could reverse
What factors are required for diffusion across alveoli?
Diffusion only occurs if alveoli are
VENTILATED
PERFUSED
Explain pulmonary perfusion
The blood flowing through the capillaries surrounding the alveoli
Gas exchange occurs when blood perfuses capillary
No blood flow = no gas exchange
Why is the rate of blood flow important in gas exchange?
Alveolar gases take time to diffuse and equilibrate with blood
Different gases = different rates
If rate is too fast = not enough time for gas exchange to occur (can occur as exercise)
If rate is too slow = gas exchange stilted
What occurs in the 0.25s buffering time to full oxygenation of blood?
pO2 of blood reaches alveolar pO2 in 0.25s
What happens to the transit time of RBC in capillary during severe exercise?
Decrease the time the RBC is in the capillary
Less time for gas to equilibrate so sometimes blood is not fully oxygenated when exercising
What are the factors affecting INTERNAL respiration?
Metabolic rate of tissue
Rate of blood flow
Partial pressure gradients
Surface area in various tissues
What happens if there is imperfect ventilation-perfusion coupling in the TISSUES?***
pO2 of blood entering systemic capillaries is lower than alveolar
Gas exchange only occurs at the cell-capillary interface when a new equilibrium is reached where O2 is delivered into tissue and CO2 is removed through the blood
What factors are needed for good ventilation?
Good air flow
Space to ventilate
What can cause there to be a decrease in ventilation?
Constricting airway = due to external or allergic reaction
Obstructing airways
Reduced airspace for ventilation = severe pneumonia lungs fulled with debris, mucus, etc
Define pulmonary ventilation
Process of air exchange between lungs and the atmosphere
What does Boyle’s Law state?
In a closed system, with fixed temp and pressure
The pressure is solely based on volume
Explain the muscles needed for inspiration and expiration
Contract diaphragm and external intercostal muscles increase volume and decrease pressure below atmospheric pressure = inspiration
Relax diaphragm and external intercostal muscles decreases volume, increases pressure above atmospheric pressure = expiration
Explain the muscles needed for DEEP inspiration and expiration
Deep inspiration and expiration is an ACTIVE process
Deep EXHALATION requires contraction of internal intercostal muscle and more forceful contraction of diaphragm and external intercostal muscles = to bring about GREATER VOLUME CHANGE
What is intrapleural pressure?
Pressure within the pleural cavity = filled with pleural fluid
The thin space between the visceral pleura (lining the lungs) and the parietal pleura (lining the chest wall)
What is the value of intrapleural pressure?
Usually negative to intrapulmonary and atmospheric pressure
What is the function of pleural fluid?
Acts as suction to keep lungs inflated
What factors affect intrapleural pressure?
Surface tension of alveolar fluid = inward
Elasticity of lung = inward
Elasticity of thoracic wall = outward
What happens to intrapleural pressure during inspiration and expiration?
Thoracic wall moves outward, increasing volume and decreasing intrapleural pressure
More negative pressure allows lungs to expand during inspiration
Thoracic wall recoils inward, decreasing volume and returning intrapleural pressure to -4mmHg relative to atmospheric pressure = allowing lungs to recoil
When does intrapleural pressure become positive?
During forceful expiration
What can cause excess pleural fluid to expand the pleural space?
Pleural effusion = serous fluid leaking from capillaries with increased hydrostatic pressure
Hemothorax = blood leaking from injured vessels
What can cause excess air to expand the pleural space?
Pneumothorax = from puncture of lung, causing lung to collapse
