Gas exchange Pulmonary gas exchange Tissue gas exchange Tissue cells 02人 CO CO.L 0 CO. Pulmonary capillary Tissue capillaries
Gas exchange Gas exchange Tissue capillaries Tissue cell s CO 2 O 2 CO 2 O 2 Pulmonary capillary CO 2 CO 2 O 2 O 2 Pulmonary gas exchange Tissue gas exchange
Physical principles of gas exchange Diffusion:continuous random motion of gas molecules. Partial pressure:the individual pressure of each gas,eg.Po2
Physical principles of gas Physical principles of gas exchange exchange Diffusion: Diffusion: continuous continuous random motion of gas random motion of gas molecules. molecules. Partial pressure: Partial pressure: the individual pressure of individual pressure of each gas, each gas, eg. Po 2
P,V1=P22 Compression Decompression ↓V→↑P ↑V→↓P Boyle's law states that the pressure of a fixed number of gas molecules is inversely proportional to the volume of the container
Boyle’s law states that the pressure of a fixed number of gas molecules is inversely proportional to the volume of the container
Laws governing gas diffusion ■Henry'slaw: The amount of dissolved gas is directly proportional to the partial pressure of the gas PaO2(mmHg）
Laws governing gas diffusion Laws governing gas diffusion Henry’s law: The amount of dissolved The amount of dissolved gas is directly gas is directly proportional to the partial proportional to the partial pressure of the gas pressure of the gas
Laws governing gas diffusion Graham's Law When gases are dissolved in liquids,the relative rate of diffusion of a given gas is proportional to its solubility in the liquid and inversely proportional to the square root of its molecular mass diffusion rate of CO2= 22 32 =19 diffusion rate of 02 44
Laws governing gas diffusion Laws governing gas diffusion Graham's Law Graham's Law When gases are dissolved in liquids, the relative rate of When gases are dissolved in liquids, the relative rate of diffusion of a given gas is proportional to its diffusion of a given gas is proportional to its solubility solubility in the liquid and inversely proportional to the the liquid and inversely proportional to the square root of square root of its molecular mass its molecular mass
Laws governing gas diffusion ■Fick'slaw The net diffusion rate of a gas across a fluid membrane is proportional to the difference in partial pressure,proportional to the area of the membrane and inversely proportional to the thickness of the membrane
Laws governing gas diffusion Laws governing gas diffusion Fick’s law The net diffusion rate of a gas across a fluid The net diffusion rate of a gas across a fluid membrane is proportional to the difference in membrane is proportional to the difference in partial pressure partial pressure, proportional to the , proportional to the area of the membrane and inversely proportional to the membrane and inversely proportional to the thickness thickness of the membrane of the membrane
Factors affecting gas exchange △P.S.T·A d.√MW ■ D Rate of gas diffusion △P Difference of partial pressure s Solubility of the gas T: Absolute temperature A Area of diffusion d; Distance of diffusion ■ MW: Molecular weight
Factors affecting gas exchange Factors affecting gas exchange d MW P S T A D ⋅ ∆ ⋅ ⋅ ⋅ ∝ D: Rate of gas diffusion Rate of gas diffusion ∆P: Difference of partial pressure Difference of partial pressure S: Solubility of the gas Solubility of the gas T: Absolute temperature Absolute temperature A: Area of diffusion Area of diffusion d: Distance o Distance o f diffusion ffusion MW: Molecular weight Molecular weight
Gas partial pressure(mmHg) Atmosphere Alveoli Arterial Venous Tissue P02159 104 100 40 30 Pc020.3 40 40 46 50
Gas partial pressure (mmHg) Gas partial pressure (mmHg) Atmosphere Atmosphere Alveoli Arterial Venous Alveoli Arterial Venous Tissue Po 2 159 104 104 100 40 30 Pco 2 0.3 40 40 46 40 46 50
c02 840 ml/mi 590 mlmin 200 ml/mir Alveolar ventilation=4 L/min 200 ml CO 250ml0 750ml02 →1000ml02 2800mlc02→2600mlc02 Lung capillaries Lung capillaries Tissue capillaries Tissue capillaries 750ml02+ -1000ml02 2800mlc02+ -2600mlCc02 250 02 00 el Begin In the lungs,the concentration gradients favor the diffusion of oxygen toward the blood and the diffusion of carbon dioxide toward the alveolar air;owing to the metabolic activities of cells, these gradients are reversed at the interface of the blood and the active cells
In the lungs, the concentration gradients favor the diffusion of oxygen toward the blood and the diffusion of carbon dioxide toward the alveolar air; owing to the metabolic activities of cells, these gradients are reversed at the interface of the blood and the active cells
Air P02= Alveoli 105 mmHg 40 mmHg p。=40mmHd 100 mmHo Pco.=46 mmHg =40 mmHg Pulmonary Lung capillaries Pulmonary arteries veins Left heart ear Systemic Systemic veins Tissue capillaries arteries 46 mmHg 8图 Cells 以 B96m9gmochonanarr5mo Changes in the concentration of dissolved gases are indicated as the blood circulates in the body.Oxygen is converted to water in cells;cells release carbon dioxide as a byproduct of fuel catabolism
Changes in the concentration of dissolved gases are indicated as the blood circulates in the body. Oxygen is converted to water in cells; cells release carbon dioxide as a byproduct of fuel catabolism