Tonicity

Passive transport are means by which molecules move because of their own Inherent energy. The movement is random. This random movement eventually produces an equal distribution of the molecules throughout an environment.

Tonicity Diffusion is one type of passive transport. If an area has a higher concentration of a substance, this substance tends to move toward areas of lesser concentration of that substance until an even distribution of the substance is achieved.

Tonicity A drop of food coloring diffuses from an area of high concentration (the drop) to the area of low concentration ( the rest of the container). Examples in our bodies would include the movement of glucose, oxygen, and ions. Original photograph

Tonicity The tendency to move to an area of lesser concentration is a pressure or concentration gradient. This is true in all fluids; gases and liquids. No energy is required to be added in order for this movement to occur.

Tonicity Osmosis is a special type of diffusion. Osmosis is the diffusion of water through a semi-permeable or selectively permeable membrane. Water molecules are small enough to pass through the pores of the membrane but other larger molecules can not pass through the membrane.

Tonicity Our cell membranes are selectively permeable membrane. Osmosis follows the same pressure gradient as do molecules during diffusion; they move from an area of high water molecule concentration to an area of lower water molecule concentration. This is referred to as osmotic pressure.

Tonicity Solution Types: Isotonic – A solution that has the same Amount of solute as the solution it is compared to. Hypotonic – A solution that has a lesser concentration of solute than the solution it is compared to. Hypertonic – A solution that has a greater concentration of solute than the solution it is compared to.

Tonicity - Isotonic Public Domain image From WikiMedia Commons Red Blood Cells in an isotonic solution. The amount of solute in the cells is equal to the solution. Osmosis is taking place. Water enters and exits the cells at an equal rate. There is no net gain in cell volume or mass.

Tonicity - Hypotonic Red blood cells in a hypotonic solution. The amount of solute in the cells is more than the solution (less solvent). The solution has more water than the cells, a pressure gradient exists. Water moves by osmosis into the cells. The cells swell and may burst. Public Domain image From WikiMedia Commons

Tonicity - Hypertonic Red blood cells in a hypertonic solution. The amount of solute in the cells is less than the solution (more solvent). The solution has less water than the cells, a pressure gradient exists. Water moves by osmosis from the cells. The cells shrink and may get a scalloped looking border. Public Domain image From WikiMedia Commons

Tonicity Remember these are comparative strengths based upon the amount of solute. ISO means the same HYPO means below HYPER means greater Solutes “suck”. A greater amount of solute “sucks” the water to it.

Tonicity Diffusion and osmosis are important processes to cells and to our bodies. These processes are part of a group of processes that help our bodies maintain homeostasis a stable internal environment. The body has many homeostatic processes. Diffusion and osmosis form the foundation for many of them.

Tonicity Diffusion can be used by our bodies to deliver and remove molecule to and from our cells. Osmosis helps us maintain fluid and electrolyte balances in our cells.

Tonicity In a medical situation you might require a transfusion of saline solution because of sudden blood volume loss. A saline transfusion (0.9% NaCl) is isotonic. If you are in medical care for an extended time and require many transfused medicines an isotonic saline can be used to periodically flush and rinse the catheter that has been inserted into a blood vessel