11. FINAL STARTS HERE: Respiratory System 1

Question 1

What two factors can cause a given quantity of gas to alter its volume? (2 + formula)

Answer 1

1. Pressure: inverse (v = c/p) - BOYLES LAW
2. Temperature: proportional (v=c x t) - CHARLES LAW

Question 2

What factors determine how much of a certain gas will be dissolved in water? (2 + formula)

Answer 2

1. Pressure
2. Solubility coefficient

V = P x SC

HENRYS LAW

Question 3

How do the solubility coefficients of carbon dioxide and oxygen compare?

Answer 3

O2 = 0.024
CO2 = 0.51

Carbon dioxide is 22 times more
soluble than oxygen

Question 4

Explain the partial pressure of a gas (2)

Answer 4

1. Pressure exerted by a given gas in a mixture
2. Sum of the partial pressures of each gas in a mixture is always equal to the total pressure

Question 5

What is the partial pressure of water vapor at 37°C?

Answer 5

47 mm Hg

Question 6

Show how the partial pressure of a gas is determined.

Answer 6

concentration of a gas x total pressure

Question 7

Find the partial pressure of O2 given dry air: 20.93%, total pressure at sea level is 760mm Hg

Answer 7

PO2 = (0.2093 x 760) = 159 mm Hg

Question 8

How do gases move between areas of different pressure, and what factors influence their diffusion in mixtures or solutions? (4)

Answer 8

1. Gases exhibit net movement by simple diffusion.
2. Diffuse from areas of high pressure to areas of low pressure
3. Applies to gases in a gas mixture, gases in solution and gases from the gas phase into the dissolved state
4. Regardless of the total pressure for the gas mixture the individual gases diffuse in response to their particular partial pressures

Question 9

Demonstrate the factors affecting the diffusion of gases and relate them to the anatomy of the lungs. (4)

Answer 9

1. Rate of diffusion proportional to:
   A (surface area) -
   D (diffusion coefficient) -
   P1 – P2 (difference in partial pressure between the two sides) -
2. Rate of diffusion inversely proportional to:
   T (tissue thickness) -

Question 10

How does surface area and diffusion relate to the anatomy of the lungs. (7)

Answer 10

1. 70 m2
2. Emphysema
   - Reduces SA
3. Small animals
   - Need more O2
   - Relative lung volume same
   - Efficient due to greater number of small alveoli that increase SA

Question 11

How does diffusion coefficient and diffusion relate to the anatomy of the lungs. (2)

Answer 11

1. Diffusion coefficient = Sol √MW
2. For a given pressure difference, carbon dioxide diffuses through the membrane about 20 times more rapidly than oxygen.

Question 12

How does difference in partial pressure between the two sides and diffusion relate to the anatomy of the lungs. (3)

Answer 12

1. P1-P2
2. Difference between the partial pressure of alveolar air and gas in the blood
3. When P1 exceeds P2 there will be a net movement of the gas into the area of less P (in this case P2)

Question 13

How does thickness and diffusion relate to the anatomy of the lungs. (4+ 3 mini points)

Answer 13

1. 6 layers
2. 0.5 microns (avg)
3. Edema
4. Pulmonary capillaries
   - 8 microns
   - Therefore RBC touch walls
   - Little plasma to pass through

Question 14

The partial pressure of oxygen in dry atmospheric air is 159 mm Hg, while that of alveolar air is 104 mm Hg. What causes these differences? (3)

Answer 14

1. Oxygen being removed from the alveoli and entering the blood
2. Carbon dioxide being added to the alveoli from the blood.
3. Air is humidified which dilutes the concentration of oxygen.

Question 15

***Why does arterial blood have a lower partial pressure of oxygen than alveolar air (100 vs 104 mm Hg)?

Answer 15

Some blood bypasses the alveoli and enters the arterial circulation without being oxygenated (shunted blood)

Question 16

*****Why is the same effect (as in card 8) not seen with carbon dioxide?

Answer 16

1. Much higher diffusion coefficient than oxygen.

This allows carbon dioxide to rapidly diffuse into the alveoli despite the small difference in partial pressure between arterial blood and alveolar air.

Question 17

*****Why does expired air have higher oxygen and lower carbon dioxide partial pressures than alveolar air?

Answer 17

1. Expired air is combination of alveolar air and dead space air
2. Dead space air is air that has not participated in gas exchange.
3. This means that expired air will have a higher partial pressure of oxygen and a lower partial pressure of carbon dioxide than alveolar air.

Question 18

Describe the exchange of gases in the lungs and at the tissue level (tissue respiration). (5)

Answer 18

LUNGS:
1. OXYGEN: alveoli to pulmonary capillaries
2. CARBON DIOXIDE: pulmonary capillaries to alveoli

TISSUE LEVEL:
3. OXYGEN: systemic capillaries to tissues
4. CARBON DIOXIDE: tissues to systemic capillaries.

THEY ALL MOVE FROM AN AREA OF HIGH CONCENTRATION TO LOW CONCENTRATION

Question 19

Given the solubility coefficient of oxygen, what would be the amount of oxygen delivered to the tissues per 100 ml of blood?

Answer 19

PO2 is equal to 100 mm Hg there can be 0.3 ml of dissolved oxygen in 100 ml of blood.