Expert: Florence M Rollwagen - 11/14/2008

Question
QUESTION: hi I'm in 8th grade and I want to know exactly how osmosis and diffusion work in the preservation of organs donated fopr organ transplant and WHY they are needed.
tnx

ANSWER: Hi again X.  From your question, I get the feeling that you want me to write your report for you.  So let me ask YOU some questions.

What do you know about osmosis and diffusion?
Do you understand anything about cellular metabolism?
How about blood flow?

Write back with these answers and we can start from there.  I can't give you a detailed answer without knowing what you know.

FM Rollwagen, PhD

---------- FOLLOW-UP ----------

QUESTION: well, i do know that diffusion is the movement of molecules from a greater to lesser point of concentration and osmosis is a kind of diffusion where molecules move from greater to lesser point of concentration through a semi-permeable membrane...

Answer
OK, good.  Organs taken from donors need to have their metabolism maintained.  Usually this is done with organ preservation solutions and chilling.  The preservation solutions have sugars and amino acids in them to provide nutrients for the cells.  Because there is no circulation, the preservation fluid has to be pumped through the organ, displacing the blood and filling the blood vessels (arteries and veins) with preservative.  The organ is chilled to slow down metabolism, to prevent the cells in the organ from starving and producing too many waste products.  

Diffusion (osmosis is the diffusion of water) occurs between the small blood vessels (capillaries) and the tissues of the organ.  As the cells use up the sugars, more diffuse into the cells from the preservation solution.  Even though they are chilled, they do use up these materials at a slow rate.  The carbohydrates also preserve the relative concentrations of water so the cells maintain their correct water content.

Is this what you wanted to know?

FM Rollwagen, PhD