F.5 Bio. Homeostatis -- 2 questions -- urea and rental vein

用戶21707

2007-10-13 7:17 am

1. Is there any urea in rental vein? The answer is yes, but is the urea entering the Bowman's capsule by filtration or diffusion?
2. After fasting for 12 hours, will we have urine? Why? ( Assume that we didn't take any water ) Is the urea toxic, so we have to excret it or by any other reasons?

Thank you

回答 (1)

Kei

2007-10-13 7:51 am

✔ 最佳答案

rental vein ?
is it a typing mistake? it should be renal vein

1. Yes,urea will enter the Bowman's capsule by facilitated diffusion.

2.No, it's less likely to have urination.Whether having urine depends on the osmotic /water potential in blood plasma.(If we drink water, more water is absorbed in blood, osmotic potential in blood increases and less water is readsorbed in collecting duct, more water will be excreted as urine to balance water level in our body) As now we didn't drink water,osmotic potential of blood plasma is low(blood is more concentrated),the body cells are in short of water.So, more water is reabsorbed in collecting duct and less of it will be excreted as urine.Urine output is nearly drop to zero.

Urea is toxic so we have to excret it.

參考: me

👍 0 👎 0