18

Question 1

What is virtual capacity

Answer 1

Maximum volume of air you can shift in and out of your lungs

Question 2

Answer 2

Question 3

How much air do we breathe in and out

Answer 3

Question 4

How much litres of air per minute in an adult

Answer 4

6

Question 5

What is the dead space?

Answer 5

• some of the inhaled air never gets to the alveoli so channot gas exchange (VD) - about 150ml
• about 150mls of each breath just fills upper airways and is no use for gas exchange

Whats important is the amount of air that gets into the alveoli… Alveolar ventilation VA

Question 6

What is alveolar ventilation

Answer 6

VA
The amount of air that gets into the alveoli

Question 7

How to calculate Alveolar vetilation

Answer 7

• must suntract dead space

Question 8

Why are tiny rapid breaths not helpful

Answer 8

• most of the air would just enter the dead space not the alveoli

Question 9

Dalton’s law:

Answer 9

The pressure of any gas in a gas mixture is determined by its proportion

Question 10

Gas diffusion depends on

Answer 10

Partial pressure

Question 11

What is partial pressure

Answer 11

In a gas mixture, Each gas exerts its own individual pressure, called the partial pressure

Question 12

The pressure of a minute of gasses =

Answer 12

The sum total of the pressure of each individual gas

Question 13

Partial pressure on various conditions table

Answer 13

• higher water vapour pressure - water at body temp when inhaled
• lower oxygen as it’s given to the blood

Question 14

Moving gas across the membranes (blood air barrier)

Answer 14

• the goal is to move gas back asn forth between the alveoli and the capillaries - until equilibrium
• transport inhaled oxygen into the capillaries
• transport carbon dioxide into the alveoli to be exhaled

Question 15

How do gasses move across the membranes between alveoli and the apiliaareis ?

Answer 15

Difffusion

Question 16

What determines the rate of diffusion?

Answer 16

• surface area of the membranes
• thickness of the membranes
• pressure difference between the two sides

Question 17

Equation for rate of diffusion

Answer 17

Question 18

What does the diffusion constant depend on?

Answer 18

Gas solubility (S) and its molecular weight

• on a per molecule basis, CO2 diffuses about 20x faster then O2 due to CO2 higher solubility

Question 19

Why doesn’t nitrogen diffuse into circulation

Answer 19

Very low solubility

Question 20

What does the bulbous structure of alveoli and the high density of capillarys create?

Answer 20

Lots of surface area for gas exchange

Question 21

what creates the large surface area for gas exchange?

Answer 21

• bulbous structure of alveoli and the high density of capillaries

Question 22

What is emphysema

Answer 22

A disease characterised by dilation of the alveolar spaces and destruction of the alveolar walls

• reduction in surface area means less contact between the air and capillaries, so oxygen exchange is greatly reduced

Question 23

What is the result of reduction in surface area

Answer 23

Less contact between air and capillaries, so oxygen exchange is greatly reduced

Question 24

What is emphysema an example of

Answer 24

Chronic obstructive lung disease

Question 25

What is an example of chromic obstructive lung disease

Answer 25

Emphysema

Question 26

What is the blood air barrier consisting of?

Answer 26

- alveolar - capillary walls

Question 27

Distance between the alveolar air and blood is very…

Answer 27

Small

Question 28

Pulmonary fibrosis and consequences

Answer 28

- thickening and scaring of the alveolar membranes - can arise from chronic inflammation or exposure to industrial chemicals - thickness increases therefor rate of diffusion decreases (People appear pale and blue as they are not getting enough oxygen)

Question 29

3 factors that affect diffusion

Answer 29

- alveolar area for diffusion (emphysema) - thickness of alveolar membrane (fibrosis) - MAIN FACTOR IS: pressure difference - must have pressure gradient across e membrane or gas will not move

Question 30

Pressure difference drives

Answer 30

Diffusion Alveolar - arterial - high O2 in alveolar for flow to low - high CO2 in arterial for flow to low

Question 31

What does PAO2 depend on? Atmosphere?

Answer 31

1. Partial pressure of oxygen in inspired air 2. Alveolar consumption 3. Oxygen consumption - blood oxygen The atmospheric PO2 is usually constant, so it is the balance between oxygen consumption and alveolar ventilation that is most important

Question 32

What pressure does equilibrium occur

Answer 32

100 mm mercury

Question 33

Low activity - oxygen

Answer 33

- reduced oxygen consumption - higher levels of oxygen in the venous blood

Question 34

High activity - oxygen

Answer 34

- increased oxygen consumption - lower levels of oxygen in the venous blood (This means there is a greater pressure difference between alveoli and capillaries) (High metabolism = more oxygen leaving the alveoli0

Question 35

Gasses diffusing down their pressure gradient

Answer 35

- PO2 in venous system at beginning of diffusion = 40 - PCO2 in venous system at beginning of diffusion = 46 - PO2 in alveoli at beginning of diffusion = 100 - PCO2 in alveoli system at beginning of diffusion = 40 Breathing and metabolism control the difference in pressure thus the rate of diffusion?