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-   -   Renal Venous versus Medullary Oxygen Content! (https://www.usmle-forums.com/usmle-step-1-forum/3290-renal-venous-versus-medullary-oxygen-content.html)

Androide89 07-14-2010 10:35 PM

Renal Venous versus Medullary Oxygen Content!
 
In physio kaplan it says renal venous o2 is the highest because it receives the highest blood flow/gram of tissue, but then goljan says the renal medulla has the lowest pO2, so low that it can induce sickling of RBC's in sickle cell trait even. Can someone explain. Thanks

Seetal 07-15-2010 02:08 AM

Quote:

Originally Posted by Androide89 (Post 11972)
In physio kaplan it says renal venous o2 is the highest because it receives the highest blood flow/gram of tissue, but then goljan says the renal medulla has the lowest pO2, so low that it can induce sickling of RBC's in sickle cell trait even. Can someone explain. Thanks

ok i cant find exact explanation from books but im gonna try n give u an explanation of how i see it n if im wrong PLS correct me:

renal venous PO2 has to be high because the renal gets 25% blood flow. n medulla PO2 has to be lower if not blood from the renal medulla will flow into the renal veins so fast (blood flows from high to low pressures) causing blood to rush from the renal arteries into the veins so fast not allowing adequate GFR.:o

sigh... did that make sense? i guess what im tryin to say is that there must a low medulla pressure to ensure no renal blood "dumping" (there's no such renal blood dumping but if u can see what i mean here).

Androide89 07-15-2010 02:27 AM

hmn i dont get exactly what you're saying =D but yeah i still dont get this one =/ I know during shock the kidneys are hit hardest (ATN) so extraction of arterial o2 would be high and venous o2 would be low but i thought during normal state renal venous o2 is the highest of all venous blood and cardiac coronary sinus the lowest of all.

Seetal 07-15-2010 04:35 PM

Quote:

Originally Posted by Androide89 (Post 11983)
hmn i dont get exactly what you're saying =D but yeah i still dont get this one =/ I know during shock the kidneys are hit hardest (ATN) so extraction of arterial o2 would be high and venous o2 would be low but i thought during normal state renal venous o2 is the highest of all venous blood and cardiac coronary sinus the lowest of all.

yes also cardiac coronary veins has to have low PO2 because a lot of O2 is extracted in the coronary capillaries to supply O2 to the cardiac muscle. which can be understood when we are exercising, our venous PO2 becomes lower than usual because extraction of O2 at the capillaries increase.

ya?:o


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