Oxygen and CO2 Lecture

Question 1

How do gases move and what causes it?

Answer 1

Diffusion and because of partial pressure diffusion
EX: Oxygen diffuses from alveoli into pulmonary capillary because PO2 in alveoli is greater than PO2 in pulmonary capillary

Question 2

Diffusion of oxygen molecules between the alveolar air and pulmonary blood?

Answer 2

Alveolus PO2 = 104 mmHg
Venous blood at arterial end PO2 = 40 mmHg –> initial pressure difference = 64 mmHG
—Rapid rise of blood PO2 as blood passes through capillary

Question 3

Why would diffusing capacity for O2 increase 3-fold during exercise?

Answer 3

Increased surface area of capillaries
Ideal ventilation-perfusion ratio in upper part of lungs
- In non-exercising conditions, blood becomes almost saturated with O2 by the time it has passed 1/2 of pulmonary capillary

Question 4

How much of the blood that enters the left atrium has alveolus PO2 of 104 mmHg?

Answer 4

98%

– 2% of blood passed from aorta to bronchial circulation (shunt flow)

Question 5

PO2 of shunt blood= ?

Answer 5

= normal system venous blood = 40 mmHg

Question 6

PO2 of mixed blood = ?

Answer 6

95 mmHg

Question 7

Diffusion of O2 from peripheral capillaries into tissue fluid?

Answer 7

PO2 in tissues is still 95 mmHg

• • Tremendous initial pressure difference
• • Cause oxygen to diffuse rapidly from capillary blood to tissues

Question 8

Increase blood flow = ?

Answer 8

Increase quantities of oxygen and increased PO2 (and vice versa)
- MAX PO2 = 95mmHg

Question 9

Increased O2 consumption = ?

Answer 9

Decreased interstitial fluid PO2 (and vice versa)

Question 10

PO2 is determined by a balance between?

Answer 10

Rate of O2 transport to tissues in blood

Rate at which O2 is used by tissues

Question 11

O2 –> CO2?

Answer 11

All of the O2 used by the cell becomes CO2
Increasing intracellular PCO2 which diffuses from cells into capillaries and travels to the lungs
– Once in the lungs, it diffuses from pulmonary capillaries into alveoli and is expired

Question 12

Only a ___ difference causes all the required CO2 diffusion out of the pulmonary capillaries into the alveoli?

Answer 12

5mmHg pressure

Question 13

RBCs

Answer 13

Most specialized cells in the body

• Transport both O2 and CO2
• Cytoplasm made up of water 66% and 33% proteins and Hb makes up 95% of the proteins

Question 14

Structure of Hb

Answer 14

Responsible for cell’s ability to transport oxygen and carbon dioxide
- 97% O2 binds to the iron in the heme
CO2 binds to the globin

Question 15

% Saturation of Hb

Answer 15

Progressive increase in % of Hb bound with oxygen as blood PO2 increases

• PO2 = 95 mmHg in blood entering systemic circuit
• PO2 = 40 mmHg in venous blood

Question 16

Transport of CO2 in blood?

Answer 16

Small amount of CO2 react loosely with plasma proteins
Dissolved CO2 in erthrocyte reacts with water to form carbonic acid via carbonic anhydrase
Dissociation of carbonic acid into bicarbonate and H+
CO2 is also transported in combo with hemoglobin to form the compound carbaminohemoglobin

Question 17

CO2 + hemoglobin?

Answer 17

Form very loose bond that is reversible and the CO2 can be released into the alveoli where the PCO2 is lower than in the tissue capillaries

Question 18

PCO2?

Answer 18

Arterial blood = 40 mmHg
Venous blood = 45 mmHg
– Normal concentration of CO2 in the blood is 50 volumes %