3 - Pulmonary Gas Exchange

Question 1

At rest, blood becomes saturated with O2 by the time it’s passed through _______ of the capillary.

This means:

Answer 1

the first 1/3

At baseline blood stays in the capillary three times longer than it needs to

This is why during exercise, even though flow may not increase the partial pressure and amount of time in the capillary are sufficient to supply enough O2

Question 2

What is the PO2 at the arterial end of the capillary?

Interstitial fluid?

Venous end of the capillary?

Intracellular?

Answer 2

95

40

40

23 (average)

Question 3

When blood flow increases, what happens to interstitial PO2?

When blood flow decreases?

Answer 3

It increases

Decreases

Question 4

What partial pressure gradient of O2 (PO2) is required to drive cellular respiration?

Answer 4

Cellular PO2 only needs to be 1-2 mmHg lower than interstitial, but the average in cell is 23 and interstital is 40, so there’s plenty of safety net

Question 5

What is the PCO2 at the arterial end of the capillary?

intracellular PCO2?

Interstitial PCO2?

Venous end of the capillary?

Answer 5

40mmHg

46mmHg

45mmHg

45mmHg

Because CO2 can diffuse so much easier, it doesn’t need as much of a partial pressure gradient

Question 6

When blood flow increases, what happens to interstitial PCO2?

When blood flow decreases?

Answer 6

decreases

increases

Question 7

Under normal conditions, how much O2 is transported from the lungs to the tissues for each 100 ml of blood flow?

Answer 7

5ml O2/100ml Blood

(total 19.4 ml delivered, 14.4 ml leave capillaries still attached)

Question 8

If during exercise the muscle interstital PO2 falls to 15mmHg from 40mmHg, how much O2 will be transported to the tissues?

Answer 8

About 3-4 times as many ml O2/100ml blood

Normal is 5, may be increased to 15

(19.4ml delivered, 4.4ml leave the capillary)

Question 9

What is the utilization coefficient?

Answer 9

percentage of blood that gives up its O2 as it passes through the capillaries

Question 10

What is the utilization coefficient normally at rest?

Answer 10

25%

Question 11

What does a shift to the right on the oxyhemoglobin dissociation curve cause?

Answer 11

Decreased Hgb affinity for O2:

Enhanced release of O2 from blood to tissues

Enhanced oxygenation of blood in the lungs

Question 12

What is the Bohr Effect?

Answer 12

An increase in CO2 or H ions causes O2 to be displaced from hemoglobin, causing a shift to the right

Question 13

A decrease in 2,3-BPG causes a shift to the _______

Answer 13

right

important in adapting to low tissue perfusion

Question 14

A shift to the right in the blood results in a shift to the _______ in the lungs

Answer 14

left

Question 15

As long as cellular PO2 is greater than 1mmHg, O2 avialability is not a limiting factor in cellular respiration.

What is?

Answer 15

The concentration of ADP in the cell

The more ADP there is in the cell, the more oxygen will be consumed in order to convert it to ATP

Question 16

The rate of O2 consumption in the cells is determined by:

Answer 16

the rate of ADP conversion to ATP

Question 17

During CO poisoning, the PO2 is ______

Answer 17

normal

Question 18

In addition to 100% oxygen, what else can be given to speed up displacement of CO?

Answer 18

CO2

stimulates respiratory drive and increases alveolar ventilation

Question 19

Under normal resting conditions, how much CO2 is transported from the tissues to the lungs?

Answer 19

4ml CO2/100ml blood

Question 20

When CO2 diffuses into the blood from the tissues, it reacts with water to form _______ with the help of ________

Answer 20

carbonic acid

carbonic anhydrase

Question 21

Immediately after CO2 reacts with water to from carbonic acid, it dissociates into ________

Answer 21

HCO₃ and H⁺

Question 22

What is the chloride shift?

Answer 22

When carbonic acid dissolves into HCO3 and H, the H bind to the hemoglobin and the bicarb is shuttled back and forth across the red blood cell membrane in exchange for chloride (to maintain isoelectric status)

Because of this, venous RBCs have a much higher intracellular [Cl] the arterial RBCs

Question 23

Carbonic anhydrase CO2 conversion is responsible for what percentage of CO2 transport?

Answer 23

70%

Question 24

What percentage of CO2 is transported to the lungs via carbamino bonding with Hgb and plasma proteins?

Answer 24

30%

Question 25

What is the haldane effect?

Answer 25

Binding of O2 with Hgb displaces CO2 from the blood

Question 26

Why does the haldane effect occur?

Answer 26

Combining O2 with hemoglobin in the lungs converts the blood from a weak acid system to a strong acid system

The H ions that were bound to hemoglobin are released and combine with bicarb, dissociating into water and CO2

The CO2 is then released into the alveoli and is expired

Question 27

What is the respiratory exchange ratio?

Answer 27

(Rate of CO2 output) / (rate of oxygen uptake)

THIS IS THE SAME R USED IN THE ALVEOLAR GAS EQUATION

Question 28

What is a normal R?

What effects R?

Answer 28

Usually around 0.825

Different diets (just carbs would be 1, just fats would be 0.7)

Question 29

The epithelium consists of:

Bronchi

Bronchioles

Alveoli

Answer 29

Goblet cells and ciliated cells

columnar cuboidal

squamous

Question 30

Clusters of alveoli are sometimes called _______

Answer 30

acinus

Question 31

What are pores of Kohn?

Answer 31

tiny septa from alveolus to alveolus that allow collateral ventilation

Question 32

How many alveoli does a normal adult have?

Answer 32

480 million!

Question 33

What are Type I and Type II alveolar cells?

Answer 33

Type I provide structure and stability

Type II secrete surfactant

Question 34

Besides decreasing surface tension, what does surfactant do?

Answer 34

decrease release of proinflammatory mediators

Prevents oxidative injury

regulates the role of fibroblasts in airway remodeling

Question 35

Describe perfusion pressure in:

Zone I

Zone II

Zone III

Answer 35

I: P_A > P_a > P_V

II: P_{a >} PA > PV

III: P_a > P_V > P_A