Week 9 Lecture

Question 1

Diffusion

Answer 1

Where particles moves from area of high concentration to low concentration

Question 2

How is the rate of diffusion increased?

Answer 2

• higher concentration gradient (difference)
• shorter diffusion distance
• higher temperature
• greater surface area

Question 3

Gas exchange

Answer 3

There are 2 sites in the body:
- alveolar capillary membrane in lung
- tissue capillary membrane in tissues

Question 4

Alveolar-capillary membrane in lung:

Answer 4

• net diffusion of O2 from alveoli to the blood
• net diffusion of CO2 from blood to the alveoli

Question 5

Tissue capillary membrane in tissues

Answer 5

• net diffusion of O2 from blood to tissue
• net diffusion of CO2 from tissue to the blood

Question 6

Partial pressure of gases in a gas mixture

Answer 6

Partial pressure of a gas is the pressure of gases in a gas mixture which is dependent on:
1. The total (barometric) pressure
2. The fractional concentration of that gas

Question 7

Composition of dry ambient air at sea level

Answer 7

Made of O2, N2, and CO2 gases.

Recognize that there a discrepancy in which the N2 concentration is always ~60% higher than the O2 concentration.

Partial pressure of O2 will decrease as you go higher cause the pressure in the lungs and the pressure in the air starts to equalize

Question 8

Functional residual capacity

Answer 8

When you breathe out, you still have some left to expire. That is the functional residual capacity. It makes sure that the incoming breath of air only has a small effect on the composition of alveolar air. This way, partial pressure of gases in the alveoli remains relatively stable.

Question 9

How does partial pressure of gases get into the liquid (blood)

Answer 9

Henry’s law:
1. The pressure of the gas above the fluid, which is given by the gas concentration times the barometric pressure.
2. The solubility of the gas. CO2 is 20.3x more soluble than O2 in liquid.

Question 10

What is lung diffusing capacity?

Answer 10

Diffusing capacity for oxygen: the volume of O2 that crosses the alveolar-capillary membrane/min per mmhg between the alveolar air and pulmonary capillary blood.

Question 11

What factors can diffusing capacity be affected by?

Answer 11

1. The thickness of the respiratory membrane- how long the diffusion path is.
   
   • diffusing capacity decreases in restrictive lung diseases like pulmonary fibrosis or pneumonia
2. The number of red bloods cells or [hemoglobin]
3. The surface area of the respiratory membrane that is available for diffusion.

Question 12

How can we increase diffusing capacity?

Answer 12

1. Increased lung volumes during exercise means there is increased surface area for diffusion.
2. When more capillaries open up in the lung, there is a greater volume of blood flowing through the lung.

Question 13

Gas transport (in the red blood cell)

Answer 13

98% of oxygen carried in blood is carried in hemoglobin
2% is carried by plasma (liquid suspending the blood cell)

HbO2=oxyhemoglobin

Question 14

How much oxygen does one gram of hemoglobin take?

Answer 14

It carries 1.34ml of O2.

If we know that there is 15g of hemoglobin concentration/ 100ml of blood, we can determine the O2 carrying capacity of the blood:
1g=1.34ml
15g*1.34ml/g
20.qml of O2/ 100 ml of blood