Respiratory Physiology 5 - O2 and CO2 Exchange

Question 1

This is the amount of air you can breathe per minute.

Answer 1

Respiratory minute volume

Question 2

This describes the inhaled air that never gets to the alveoli and so cannot undergo gas exchange.

Answer 2

Dead space

Question 3

Dead space is approximately how many mL of air?

Answer 3

about 150 mL (it usually just fills the upper airways and of no use to gas exchange)

Question 4

This describes the amount of air that can get to the alveoli.

Answer 4

Alveolar ventilation

Question 5

What determines the alveolar ventilation?

Answer 5

Tidal volume - dead space * respiratory rate

Essentially breathing strength and breathing speed

Question 6

What is the equation for respiratory volume per minute?

Answer 6

Respiratory volume = tidal volume * respiratory rate

Question 7

Gas diffusion depends on what?

Answer 7

Partial pressures

Question 8

Dalton’s law states that the pressure of a mixtures of gases is?

Answer 8

Equal to the pressures of each individual gas.

Question 9

When a gas can exert its own individual pressure in a gas mixture, this pressure is known as?

Answer 9

Partial pressure

Question 10

True or false. Alveolar ventilation is affected by the amount of dead space in the respiratory system.

Answer 10

True. Because remember, alveolar ventilation takes into account the amount of dead space in the resp. system.

AV = TV - DS * Resp. Rate

Question 11

True or false. Alveolar ventilation is measured as a volume of air per unit time.

Answer 11

True

Question 12

The blood air barrier is made of what kinds of epithelia?

Answer 12

Type 1 pneumocytes => simple squamous epithelium (provides great SA for gases to diffuse across membrane

Capillary endothelium

Alveolar endothelium

Question 13

What law describes the movement of gases across membranes between the alveoli and the capillaries?

Answer 13

Fick’s Law of Diffusion

Question 14

According to Fick’s Law of diffusion, what are the 3 factors that determine the rate of diffusion?

Answer 14

1) surface area of the membranes
2) thickness of the membrane
3) pressure difference between 2 sides because remember, gases move down their pressure gradient

Question 15

Diffusion constant depends on what 2 things?

Answer 15

Solubility and molecular weight

• when something has a low solubility, it doesn’t have the ability to diffuse into the bloodstream or circulation (like Nitrogen)
• when remembering what determines diffusion constant, just think about what PROPERTY of gases are important in enabling this process.

Question 16

True or false. The low density of the capillaries creates lots of surface area for gas exchange.

Answer 16

False; capillaries are in higher density because it creates lots of available areas for gas exchange to occur.

More capillaries present = more gas exchange can occur

Question 17

This is a disease characterised by dilation of the alveolar spaces and destruction of the alveolar walls. It is an example of chronic obstructive lung disease.

Answer 17

Emphysema.

Question 18

Reduction in surface area means?

Answer 18

Less contact between air and capillaries so oxygen exchange would be greatly reduced

or less interaction between air and capillaries so less amount of oxygen can be exchanged.

Question 19

This structure is very important in separating two things together; it is mostly comprised of the alveolar and capillary walls.

Answer 19

Blood Air Barier

Question 20

Thickness of the membrane and rate of diffusion are inversely related to each other.

This means that as the thickness increases, the rate of diffusion?

Answer 20

Decreases. Because there’s more space in between the alveolar air and blood - so more distance for oxygen to travel through.

Question 21

Thickening and scarring of the alveolar walls can arise from?

Answer 21

Chronic inflammation or exposure to industrial chemicals.

Question 22

The main factor that affects the rate of diffusion is:

Answer 22

Pressure gradient

Question 23

How would O2 be moved from the alveoli into the pulmonary capillaries? (what would the pressure gradient look like?)

Answer 23

Remember: gases move down their concentration gradient. So in order for gas from the alveoli to move into the pulmonary capillaries,

The pressure inside the pulmonary capillaries must be lower than the pressure outside in the alveoli.

Question 24

How would CO2 move from the pulmonary capillaries and into the alveoli? (what would the pressure gradient between the two look like?)

Answer 24

The pressure must be higher in the pulmonary capillaries (so the pressure in the alveoli would be lower) so the air can move from the capillary out to the alveoli.

Question 25

Alveolar partial pressure of Oxygen depends on what 3 things?

Answer 25

Partial pressure of oxygen in the air

Alveolar ventilation (amount of air inhaled per minute)

Oxygen consumption - blood oxygen

*mainly oxygen consumption and alveolar ventilation

Question 26

Why doesn’t the atmospheric PO2 affect the alveolar partial pressure as much?

Answer 26

Because the atmospheric PO2 is usually constant.

Question 27

What happens to the oxygen consumption and levels of O2 in the venous blood when we’re exercising?

Answer 27

Oxygen consumption increases

Low oxygen levels in venous blood because exercise depletes level of oxygen

Question 28

What does the alveolar partial pressure of CO2 depend on?

Answer 28

Alveolar ventilation and CO2 production.

*atmospheric CO2 is negligible

Question 29

If the pressure between the alveolar walls and pulmonary capillaries are the same, what does this mean?

Answer 29

There will be no movement because gas can only move down once there is a pressure gradient/pressure difference between both sides.