Passive Transport: Osmosis (Nursing)

00:00 So when we talk about the passive transport of water, this is actually separated and given a different name.

00:07 This process is referred to as osmosis or the net movement of solvent through a selectively permeable membrane.

00:15 Just like with the other passive processes, we're moving from an area of high water concentration to low water concentration.

00:24 But be mindful that when we use the word concentration, by definition, is the percent of solute inside of the solvent.

00:34 So, a 95% concentration would be 95 particles of solute per 5 units of water.

00:45 So, a lot of times it appears that osmosis is happening backwards because it looks like it's going from low concentration to high, but it's not because a high concentration is a low water concentration and a low concentration is actually a high water concentration, so let that sink in for a second before we move on.

01:09 So in our blood vessels, we often refer to the term tonicity.

01:14 Tonicity relates to how a solution influences the shape of a body's cells.

01:20 Specifically, the movement of water in and out of cells based on the solution that those cells are in.

01:28 In an ideal situation, you want your solution in which the cells are sitting in to be isotonic.

01:36 This means that the concentration of the solution that the cells are in is equal to the concentration of the intracellular environment.

01:46 This means there is no net movement in or out of the cell and the cell maintains its shape.

01:53 If however, we were to put a cell inside of a solution that has a much higher concentration than the intracellular environment of the cell, that solution would be referred to as a hypertonic solution and what would happen is, all of the water would move down the water concentration gradient or up the concentration gradient and cause the cells to shrink.

02:21 This is referred to as crenation.

02:25 Opposite to that, if we were to take cells and put them into a solution where the concentration of that solution is much lower than the concentration of the intracellular environment of that cell, this would cause water to rush into the cell and this would lead to hemolysis and specifically in our red blood cells, the blood cells will actually pop.

02:49 They don't have a cell wall, so just like a balloon, there's nothing stoping it from popping and you can kill a whole bunch of red blood cells just that fast.

02:58 This is especially important when we're thinking about IVs and putting any type of fluid into the blood.

03:05 And so, again, if I put the cells in a hypertonic solution, that means that the outside of the cell is higher concentration than the inside of the cell and water goes out of the cell.

03:20 The best way to remember this is, water follows salt.

03:25 So, wherever there's a higher concentration, that is where the water is going to go in order to try to reach equilibrium.