why is isotonic saline solution usedto dilute the drop of blood obtain for cross matching?

Answer 1

Saline solutions can be isotonic (of the same osmotic activity as the cells, 0.9% NaCl), hypertonic (of greater osmotic activity) or hypotonic (of less osmotic activity).

Isotonic saline is used because both hyper- and hypo-tonic solutions cause problems with the red blood cells.

In a hypertonic solution, the greater osmotic activity of the surrounding fluid would draw water OUT from inside the RBC by the process of osmosis. The RBC's would crenate (shrink) and it would be difficult to do the blood typing and cross matching.

In a hypotonic solution, the lesser osmotic activity of the surrounding fluid would mean that the RBC would draw water IN to itself. They then haemolyse making it impossible to do the blood typing and cross matching.

Answer 2

Isotonic means that there is equalized pressure. Basically put, if it is not isotonic and it is a regular saline solution, then this would cause the red blood cells to get engorged with saline in the inside and burst, basically destoying the cross match.

Answer 3

because saline does no longer enter the pink blood cellular to reason it to lyse(destroy down) or burst. If a fluid which includes water were used to attempt to dilute blood it ought to reason pink blood cells to burst, because water enters the cellular by osmosis by the cellular wall. So saline is used to dilute the blood and does no longer have an result on causing the cells to burst open.

Answer 4

You have a couple excellent answers. I can only add that it is said that human blood mimics the sea (and is therefore saline) and perhaps all life originated in the sea. That is why the (correct) saline solution is used instead of buttermilk, etc.