Respiratory System (GE) II

Question 1

Describe the respiratory membrane

Answer 1

3 layers - Very thin (0.2um)
High SA - GE by diffusion (solubility)
Affect by partial pressures and solubility of O2 and CO2

Question 2

Define total pressure (Dalton’s law)

Answer 2

Sum of pressures of individual gases

Question 3

Describe the correlation of partial pressures between gases and the atmosphere (O2/CO2)

Answer 3

Partial pressures of O2 is lower than that of the atmosphere

Partial pressures of CO2 is higher than that of the atmosphere

Question 4

Which areas of the body has oxygenated blood?

Name them

Answer 4

Areas with greater O2 partial pressures

Alveolar air, Pulmonary veins, Systemic arteries

Question 5

Which areas of the body has deoxygenated blood?

Name them

Answer 5

Areas with greater CO2 partial pressures

Systemic veins, Pulmonary arteries

Question 6

Describe gas pressures in the air

Answer 6

Atmosphere: Po2 (160mmHg), Pco2 (0.23mmHg)

Alveolar air: Po2 (100mmHg), Pco2 (40mmHg)

Question 7

What Factors are linked to alveolar air?

Answer 7

Gas exchange, dead space, water vapour

Question 8

Describe gas pressures in the blood

Answer 8

Pulmonary and systemic veins: Po2 (100mmHg), Pco2 (40mmHg)
Cells: Po2 (<40mmHg), Pco2 (>46mmHg)
Pulmonary veins: Po2 (40mmHg), Pco2 (46mmHg)
Systemic veins: Depends on tissue activity

Question 9

Describe how rapid gas exchange occurs

Answer 9

At a start point of 40, end point of 100 - Blood flows through 1/3 of capillary length completing gas exchange

Question 10

What is the other 2/3 of the capillary for?

Answer 10

Used as a reserve in case part of the lung doesn’t work, oxygenated blood can be contributed to other areas where needed

Question 11

Describe the efficiency of rapid gas exchange

Answer 11

Within 1/3 of capillary PPco2 decreases from 46>40 so efficiency is applied to both O2/CO2, completing both their gas exchange within 1/3 of the capillary

Question 12

Describe the properties of gas exchange

Answer 12

Via diffusion, driven by pressure differenc, very thin respiratory membrane (0.2um), High SA, Rapid ~0.25sec, ⅓ of pulmonary caps, occurs in lungs and respiratory tissue

Question 13

Describe the solubility of gases in terms of Henry’s Law

Answer 13

c = kP
At equilibrium (btw gas/liquid) concentration of dissolved gas (c) is prop to PP (P) and solubility (k) of gas

Question 14

Describe the link between solubility and partial pressure in terms of O2 and CO2

Answer 14

Different types of gas have different solubility

CO2 is more soluble than O2

Question 15

Describe the effect having the same partial pressure has on the concentration of gases

Answer 15

With same partial pressure of CO2 and O2, theres a higher concentration of CO2 in the solution than O2

Question 16

Describe the transport of O2 in the blood

Answer 16

Solubility of O2 very low (3ml/L of blood), Not meet demand (250ml/min)

Question 17

What percentage of O2 is transported by haemoglobin?

Answer 17

98.5% (the rest is done by blood itself)

Question 18

Briefly describe haemoglobin

Answer 18

4 subunits each with globin and Has a haem group, binds to O2 reversibly, Oxyhaemoglobin/deoxyhaemoglobin

Question 19

Describe the structure of haemoglobin

Answer 19

2 alpha, 2 beta globins, 4 haem groups (Fe2+) for each O2

Question 20

Describe the difference in haemoglobin in sickle cell anaemia patients

Answer 20

b-subunit shape altered not a-subunit

Question 21

Describe the saturation of haemoglobin with O2

Answer 21

Arterial blood 98.5% saturated vs Venus blood 75% saturation reserve gained as 3 o2 bind to haem

Question 22

Describe venus blood

Answer 22

Reserve gained as 3 O2 bind to haemoglobin

Question 23

Describe the oxyhaemoglobin dissociation curve

Answer 23

% saturation inc as PO2 inc
S-shaped curve (sigmoidal), positive cooperativity (binding of one O2 inc affinity of next)
Systemic arteries - 100mmHg, 98.5% saturation
Systemic veins - 40mmHg, 75% saturation

Question 24

Describe the temperature effect on O2 saturation

Answer 24

Higher temperature - Active tissues, shifts right, more O2 unloading in tissues, more O2 delivered to tissues

Question 25

Describe the pH effect on O2 saturation

Answer 25

Bohr effect - Lower pH inc O2 unloading, Active tissues > Produce more [H+], pH dec in tissues, Dec pH causes shift right in saturation curve, More O2 unloaded to tissues

Question 26

Describe the factors affecting haemoglobin O2 affinity

Answer 26

Temperature inc, affinity dec
CO inc, affinity dec
pH dec, affinity dec (bohr effect)
Pco2 inc, affinity dec (carbamino effect)
2,3-BPG (biphosphoglycerate) or 2,3-DPG (diphosphoglycerate) inc, affinity dec

Question 27

Describe the transport of CO2 in the blood

Answer 27

5-6% CO2 dissolved, 5-8% bound to haem, 86-90% dissolved in blood as HCO-3 (CA - Cardonic anhydrase)