Ventillation And Diffusion Flashcards
Describe the structure of the conducting airways?
Made of cartilage, few smooth muscles
- will rarely collapse
what is alveolar ventilation?
what is pulmonary ventilation?
- Alveolar ventilation is the exchange of gas between the alveoli and the external environment
- Pulmonary ventilation is the process of air flowing into the lungs during inspiration (inhalation) and out of the lungs during expiration (exhalation) – about 500ml of air inhaled and expired on each breath
- Pulmonary ventilation includes the gas used in gas exchange, and the anatomic dead space air that fills up the respiratory system, but isn’t used in gas exchange
Describe the structure of the respiratory and alveolar ducts?
Are the susceptible to collapse??
- no cartilage, lots of smooth muscle
- susceptible to collapse during expiration
How much air is there in anatomical dead space?
At what generation does the dead space turn into respiratory area?
250mls
Generation 17
How much alveoli do humans have?
&
Across what surface area?
Humans have around 300 million alveoli in a cross sectional area that increases from 2.5cm2 at trachea to around 100m2
Why does airflow velocity decrease?
At what number of airway generations/divisions does aggregate cross-sectional area start to rapidly increase?
Where will this area be around?
- Airflow velocity decreases to allow adequate time for diffusion once the air reaches the capillaries
- At about 12-14 airway generations/divisions, the aggregate cross-sectional area starts to rapidly increase
- The area will be around the respiratory bronchioles, as this area is where alveoli start to appear
What are the primary functions of the respiratory and cardiovascular systems?
- transport O2 from the lungs to all tissues in the body.
- remove CO2 from the tissues to the lungs
- lungs will expire this CO2 to the atmosphere
How are Oxygen and CO2 able to move by diffusion?
Where is Oxygen and CO2 partial pressure high and low?
How does partial pressure change affect diffusion of gas?
What is this principle the basis of?
- Oxygen and CO2 can diffuse (passive) as both gases move by diffusion down their partial pressure gradients (also down their concentration gradients)
- Oxygen partial pressure is high in the air, and low in the tissues
CO2 partial pressure is high in the tissues and low in the air - These both allow the gases to move down their partial pressure gradient
- If the partial pressure in the liquid becomes greater than in the air, the gas will diffuse out of the liquid, and vice versa, due to gases flowing down partial pressure gradients
- This is the basis for O2 moving into the blood from the lungs, whereas C02 moves out of the blood into the lungs
Describe the movement in concentration gradient for both CO2 and O2
Both gases move down their concentration gradient.
O2 goes down concentration gradient as it moves from air to the tissues
CO2 moves down the concentration gradient as it moves from tissues to air.
What is Daltons Law?
“Total pressure (Ptotal) of a mixture of gases is the sum of their individual partial pressures (Px)”
what is the value for atmospheric pressure?
atmospheric pressure at sea level is 760mmHg or 101.325 kPa
if atmospheric pressure changes …
is proportion of gas changes …
if atmospheric pressure changes then partial pressure changes
is proportion of gas changes its partial pressure changes
what is Henry’s law?
- states that the concentration of O2 dissolved in water (O2(dis)) is proportional to the partial pressure (PO2) in the gas phase
(O2) dis= s x PO2
where s = solubility of O2 in water
How soluble is CO2, O2, and N2 in blood at atmospheric pressure?
Why do we need haemoglobin?
- CO2 is the most soluble in blood plasma
- O2 is about 1/20th as soluble as CO2
- This means the blood can carry far more dissolved CO2 than O2
- This is why we need haemoglobin as a special oxygen carrier, otherwise we wouldn’t have enough oxygen in the blood
N2 is barely soluble in blood at atmospheric pressure
What happens to alveolar air?
Why is this important?
How is this affected on a cold day?
- Alveolar air is warmed and humidified by adding water vapour to it
- This is important alveolar cells are sensitive to pressure/temperature
- When the air is cold, the humidity in the air is decreased, so the air becomes dry
- There is not enough time to warm this air, so it dries out the respiratory system
what is the partial pressure for water vapour?
Water vapour also has a partial pressure, so when we breath gases in and add water vapour, we have to subtract the partial pressure of water vapour from the partial pressure of these gases that make up atmospheric pressure
The partial pressure of water vapour is 47mmHg