Thursday, July 19, 2012

Fluids - Extracellular - Interstitial - Intracellular

Fluid and Electrolytic Balance

Water is a solvent, not a solute molecule or particle. Water does not have a "concentration" if it is a body solvent. Things dissolved in water, in living things form a solution.

Fluid is compartmentalized. The basic structure consists of Extracellular Fluid (Outside the Cell) and Intracellular Fluid (Inside the Cell).

The Extracellular Fluid Compartment consists of all the fluid outside the cells. One compartment is the Blood (contained in blood vessels) and the other compartment of the Extracellular Fluid Compartment is the Interstitial Fluid. It is the fluid that exists between the blood vessels and the cells.

The body controls the changes that occurs in the  fluids (what's dissolved in the water that makes up the fluid) to shift fluid from one compartment to another compartment when needed.

This is Fluid Balance.

When fluid flows from one compartment to another it does this in response to the differing concentrations of solutes dissolved, in the water, of each compartment. 

Before we proceed, we need to understand a workable definition of Osmosis. Remember this definition.

Osmosis is the diffusion of water through a selectively permeable cell membrane from an area of low solute concentration to an area of high solute concentration.

Since a cell membrane is constantly changing, and is selectively permeable, the body breaks down large molecules in the fluid into small, electronically charged particles called ions. Some of these are simple like the positively (+) charged Hydrogen Ion and some are complex like the negatively charged ( - ) Bicarbonate Ion discussed in a post earlier about Buffer Systems.

A good way to look at electrolytes is replacement drinks for athletes after a workout. Heres one product below.

These particles are collectively referred to as Electrolytes

The body need to shift these essential electrolytes from compartment to compartment to help balance the concentration of electrolytes throughout the body.