my little-big friend

Pandi, June 19 1989
he is my old friends until now, it sound so funny i think
i never imagine that i will with him for 15 years .ckck
yeah we were always together in same school since we were elementary school.

water balance and disposal depend on transport epithelia

ability to move spesific solutes in particular direction.
transport epithelia are arranged into complex tubular network (salt glands in marine birds).
molecular structure of membranes determine kinds and directions of solutes that are transported (active versus passive transport).

general mechanisms

reduce the permeability of membranes to salt and water.
volume regulation : alter the permeabilitty of cell membranes to keep the volume inside cells constant despite changes in ECF composition.
conservation of salt and/or water by excretory organs.
active transport of salts (againts a gradient) across boundary membranes

osmoregulation

osmoregulation is balancing uptake and loss of water and solutes
controlled movement of solutes between internal fluids and enviroment (water follows solutes by osmosis)
animals have complex organs (kidneys in vertebrates) to mantain fluid composition