Answer
Fluid is exchanged by way of capillary walls and plasma membranes.
Chemical composition differs more from one compartment than another because water can freely travel between compartments, which stabilize osmolarity across the compartments.
Work Step by Step
Water can easily pass through the plasma membrane of cells. It is continually exchanged between compartments. Because of this, osmotic gradients between compartments never last long as osmosis helps to stabilize osmolarity across the different compartments.
Since larger particles cannot travel as freely as water, the chemical composition of one compartment differs more than the osmolarity of another compartment.
