Semipermeable Membranes - Significant?

Semipermeable Membranes and Fluid Compartments

The water moves back and forth between a cell, the space surrounding a cell and a small member of the blood circulatory system called a capillary.

The cell's interior water is intracellular water and occupies the Intracellular Fluid Compartment of the body. When the water leaves the cell through its semipermeable cell membrane it enters the Interstitial Fluid Compartment of the Extracellular Fluid Compartment that occupies the space between the cell and the circulatory system. When it enters the capillary of the circulatory system through its single cell layer semipermeable membrane it is now in the Extracellular Fluid Compartment. Remember,, the Extracellular Fluid Compartment is made up of the interstitial fluid compartment and the circulatory system.

Your Digestive System breaks down fluids and food into items that easily (sometimes) pass through the selectively permeable membrane with or without help.

Water is like a stream with all these breakdown products floating in it. This is pretty simplistic but you get the idea. 

The reason water flows is the ability of the body to move particles (solute particles)  to the side of a selectively  permeable membrane where the body needs the water to flow. The cells of the body need the breakdown products of digestion. This is the way the breakdown products make it to the circulatory system for distribution to all the cells in the body.

This is the ultimate purpose of glucose. Food for the manufacture of insulin in the pancreas. These strips test for glucose in the blood.

Now were getting to Act Two. The whole process above is reversed to supply those products of digestion to the destination cells.

Since were talking to interested diabetics the destination products, for us, is going to the Pancreas.