tissue fluid

Question

http://img245.imageshack.us/img245/1391/67608126ne1.jpg

P 係artery,R係vein,Q係capillary

點解water potential around Y係大過in blood?
乜唔係blood (in vein)大d咩,d glucose,amino acid等等被tissue absorb左,咁跟住water potential應該大左ga,點解反而低左?

also,please explain the fluid movement indicated by arrow Y...

Answer 1

點解water potential around Y係大過in blood?
Due to the pressure different between vein and artery, the high hydrostatic pressure caused by the pumping action of the heart causes all constitutes of blood to go into the interstitium ,Y, except RBC, blood protein. Since water also is forced into the interstitium ,Y, due to the high hydrostatic pressure, the water potential is thus increased.
More water in Y and water potential around Y係大過in blood.

乜唔係blood (in vein)大d咩{forms blood capillary not vein but venule and arteriole}
Not in vein but in venule that join the arteriole forming the bed of capillary. At the venule, the drop of blood pressure (venule blood pressure lower than arteriole) and the colloidal plasma protein(too large can pass through the blood capillary) inside the venule makes the water in the interstitium ,Y, to be drawn back to the blood vessel again. This explains why when glucose,amino acid等等被tissue absorb左,咁跟住water potential不是大左ga,反而低左.

To cause the absorption of water back to the venule is due to colloidal plasma protein with lower osmotic potential. This colloidal plasma protein makes water be absorbed back to venule.

I hope you understand what I am talking about.

2007-02-09 20:48:13 補充：
Due to the pressure different between vein and artery,改為Due to the pressure different between venule and arteriole.blood protein 改為 colloidal plasma protein