{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

BICD 102 Lec 4

# BICD 102 Lec 4 - BICD 102 Lec 4 Gas exchange occurs be...

This preview shows pages 1–3. Sign up to view the full content.

BICD 102 Lec 4 Gas exchange occurs be diffusion. Ficks law of diffusion. FLUX = ( Pgas) x Area X D/Thickness, D=Diffusion coefficient X Solubility / (mol weight) The flux of a molecule diffusing is given by the driving force . Driving foce is concentration gradient (measured by partial pressure)and permeability (given by the area). Solubility- more soluble the gas in water and lipd bilayer, faster the diffusion, inversely proportional to the square root of molecular weight. If one can measure the flux and knows the concentration gradient, one could measure the diffusion capacity of the lungs. what can change is driving force or the area or the thickness. constant diffusion coefficient, solubility, and mol weight are the same for the gas driving force can change – for example if there is low o2 in the alveoi or if theres some problem with ventilation the area can change and decrease in people with emphysema, they lose alveoli because of proteases thickness can increase in people with fibrosis and congestant heart failure or pulmonary edema what is partial pressure of gas in liquid? We must use henry’s law. If one equilibrates a liquid with a gas phase, the gas will dissolve in the liquid and come into equilibrium. Partial pressure of gas in liquid is equal to equilibrium of gas in the gas phase. [C gas]= Pgas x solubility Co2 solubility is 20x higher than the solubility of oxygen

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Alveoli at sea level – po2=100mmHg Blood in lung capillaries (mixed venous blood) same blood that came from right ventricle, mixed venous because it mixes the venous blood from all the diff parts of the body, on avg Po2 V bar is 40mmHg Po2a (Po2 arterial) which eventually equilibrate with Alveolar PO2 which is around 100mmHg. Venous blood has less oxygen but its not 0, actually gradient is now 60mmHg is now driving force for oxygen diffusion, and its larger in the alveoli so o2 diffuses into blood into plasma, for plasma into RBC, the RBC concave shapes maximizes area/volume ratio so hemoglobin is closest to the surface. Once blood goes into pulmonary veins, the left atrium and left ventricle is pumped to aorta and pumped to various tissues of systemic capillaries and now diffusion of o2 is in opposite direcion following concentration gradient in cells, so oxygen diffuses into cell. Those cells that have higher metabolic rate
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 6

BICD 102 Lec 4 - BICD 102 Lec 4 Gas exchange occurs be...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online