hey everyone it's nurse Sarah with registered nurse rn.com and in this video I'm going to talk about how fluid and solutes move within our body so let's get started the human body likes to maintain a homeostatic environment to make sure that our fluids and solutes are equally balanced and to do this it has different types of transport processes that allow this to be achieved so in this review I'm going to be talking about the two types of diffusion known as simple diffusion and facilitated Fusion along with osmosis and active transport and hydrostatic pressure and oncotic pressure also known as colloidal osmotic pressure first let's talk about the processes that move substances within the cell specifically that cell membrane here you're going to see a phospholipid bilayer that is found within the cell membrane and this phospholipid bilayer acts as this medium to really allow substances to flow in and out of the cell so here you see the circular yellow little balls those are known as the hydrophilic heads and then coming off those heads are the hydrophobic tails and they really just come together to help form this barrier that separates the extracellular part the outside of the cell from the intracellular part the inside of the cell and then scattered within this membrane are these channels carrier proteins now one thing I want you to remember about this bilayer is that it is very particular it only allows certain substances to go in through certain processes so really based on the size and if this solute is charged will depend on how it's going to enter or exit the cell so first let's talk about simple diffusion simple diffusion is just as its name says it's a very simple process because it requires no energy from the cell and it's a passive form of Transport so what happens with this process is that molecules hence solutes are going to move from a high concentration to a low concentration so here we see outside of our cell a lot of solute there's a high concentration of them and according to simple diffusion they are just going to easily diffuse hence move through that phospholipid bilayer to the inside of the cell where there's not a lot of solutes until homeostasis has been achieved so this mass movement will continue until we have equilibrium where we have a balance of these solutes now an important thing to remember about simple diffusion is that only tiny non-charged molecules are going to be able to go straight through this phospholipid bilayer so we're talking about things like oxygen carbon dioxide and so forth now a bigger charged polar molecules want to move in and out of the cell they need to do it through a different process known as facilitated diffusion and facilitated diffusion is very similar to simple diffusion but with facilitated diffusion it's going to use these special help proteins that are found within that phospholipid membrane to move these solutes molecules to and from the cell so again these molecules hence solutes are going to go from a high concentration to a low concentration it's going to go down that concentration gradient it's a passive form of Transport requires no energy but it's going to allow big molecules that are charged and polar to move to and from the cell they just can't go straight through the phospholipid bilayer so we can move glucose and ions to and from the cell now we have a different type of transport that's sort of going to do the opposite of what diffusion did because with diffusion we went from high to low concentration we were going down the concentration gradient it was a very simple process we didn't have to go against it but sometimes our body wants to move against this concentration gradient and wants to go from a low concentration to a high concentration and this is where where active transport comes into play so with active transport there's going to be the movement of molecules and solutes from a low concentration to a high concentration through these special proteins found within that phospholipid bilayer but it's going to use energy in the form of ATP so here we have our phospholipid bilayer notice on the inside of the cell we don't have a lot of solutes but on the outside of the cell we have a lot of them so with this transport process we want to go from low to high so we're going against that concentration gradient rather than just down the concentration gradient so when we go against it it requires effort a lot of energy so this is where we utilize ATP so in order to move this molecule from the inside the cell to the outside of the cell it's going to flow through this special protein Channel but ATP is going to help energize this process and we're going to be able to flow to that higher concentration now let's take a look at all osmosis so with osmosis we're talking about the movement of water water is going to move through a semi-permeable membrane that is only permeable to water and nothing else and it's going to do this through a passive process it's a passive form of Transport requires no energy and the whole goal of Osmosis is to achieve homeostasis in the terms of water it water wants to shift around until we've equaled out the concentration of water inside and outside the cell and we've equaled out that solute concentration so whenever you're trying to understand osmosis you can look at it one of two ways one way is that you can remember that water will move from a high water concentration to a low water concentration or water is going to move from a low solute concentration so the solutes hints the dissolved substances that are in that water are low and that water wants to move to a fluid hence water situation where the solutes are high it has a high osmolarity of is a lot of solutes in it so water is attracted to solutes hence water is attracted to sodium got a lot of sodium on board it's going to draw a lot of water in so those are two ways you can look at osmosis and when we're talking about a cell we're talking about water moving in and out of the cell and it all really depends on that solute concentration whether it's High inside of the cell or outside of the cell so let's look at this illustration here on the outside of this our extracellular part of our cell there is a lot of water but there's not a lot of solute so it has a low osmolarity on that extracellular fluid but on our inside of the cell notice there's a lot of solute but not a lot of water so it has a high osmolarity in there so according to osmosis effortlessly no energy needed that water wants to achieve some homeostasis it's really salty or high osmolarity inside of that cell so that water is going to be drawn through a semi-permeable membrane and it's going to go and enter in to that cell until it's tried to equal out osmolarity inside and outside of the cell and whenever that's achieved osmosis will cease now some problems that can arise whenever fluid does move in this Direction with osmosis because we have a cell that has such a high osmolarity is that too much water can go inside that cell and it can cause it to swell and rupture and the flip side can happen let's say that inside of the cell had a low osmolarity but the outside of the cell had a high osmolarity had a lot of solutes but and it didn't have a lot of water well too much water can leave that cell and go in the opposite direction to extracellular fluid and we could dehydrate that cell and shrink it now the neat thing about this osmosis process is that in healthcare we can actually use this to benefit our patient because sometimes patients come in with fluid volume deficit or fluid volume overload and they need certain fluids to help correct that imbalance and we can manipulate this osmosis process with those fluids based on the solute concentration of these fluids to help either rehydrate that cell or dehydrate that cell depending on what's going on with that patient so if you'd like to watch more in-depth review over IV fluids and this whole osmosis process you can check out these videos up here so we just reviewed how certain transport processes move fluid and substances to and from that cell through that cell membrane now let's look at some processes that move fluid from the capillaries to the inner stitchum also known as the tissue Space by talking about hydrostatic and oncotic pressure hydrostatic pressure and oncotic pressure are two pressures that literally work the opposite of each other but they work beautifully together to help maintain fluid going across our capillary wall into our inner stitching our tissue space with oncotic pressure it's going to pull water across that capillary a wall and hydrostatic pressure is going to push water across that capillary wall so first let's talk about oncotic pressure so oncotic pressure you may hear also referred to as colloidal osmotic pressure so if you also hear that term as well that's what it's talking about because sometimes I can get a little confusing and this is that pulling force on water created by proteins specifically the protein albumin which is known as a colloid and a cool thing about albumin is that a lot of it hangs out in our blood plasma and it is way way too big to pass through that capillary wall so it just hangs out there in that blood plasma and that intravascular space in high concentrations and whenever it does this by hanging out in high concentration it creates an osmotic pressure which pulls water through a process known as osmosis and we just talked about osmosis and we know that osmosis occurs because water loves to be where there's a high concentration of something hence solutes and in this case we're talking about albumin so there's a lot of albumin hanging out in this capillary wall which is going to result in water being pulled in so water is going to stay inside that capillary which is what we usually want so again just to drive home that point let's look at this illustration we have this example of a capillary and in white you see all these colloids since album and the proteins hanging out within this vessel and it's highly concentrated so what it's going to do is it's going to pull water from that surrounding area that interstitial area with the fluid in there and it's going to cause water to stay inside that vessel and the reason it's doing that is because there's a high concentration of the albumin inside that vessel it causes osmotic pressure to occur which is going to pull water in there and water is going to stay inside that vessel hence our capillary now sometimes problems arise in some patients where they don't have enough of this albumin in their blood plasma and they're experiencing a condition known as hypoalbum anemia and this can happen in cases of liver or kidney failure because your liver makes albumin so you just don't have enough in your blood or the patients let's say had severe burn so we've dropped those levels so what do you think is going to happen if you don't have enough albumin in your blood plasma well your oncotic pressure is really going to be affected you're not going to have a lot of it because there's not enough of it hanging out in the blood to create that pressure so instead water is going to leave that blood plasma go into that interstitial space and we're going to experience swelling now let's talk about hydrostatic pressure so this is the opposite of oncotic pressure because it creates a pushing effect on water across that capillary wall and in other words really what hydrostatic pressure is is it's the pressure or force of a fluid inside a restricted space so in our body when we're trying to think of that the restricted space is going to be our blood vessels hensor capillaries and that fluid is going to be our blood so what happens is that this pressure is created somewhere and it's created by our heart so our heart contractions create hydrostatic pressure and hydrostatic pressure varies throughout your circulatory system it's really high in the arteries and we need it to be high in the arteries because your arteries take that fresh oxygenated nutrient-rich blood it needs to push it out throughout your body so we need hydrocy pressure to be high but as we get closer to the venous system it gets lower because the venous system's job is to take that used blood back to the heart so we can make it better again give it more nutrients so whenever you're looking at the capillary and you're trying to figure out where these pressures are highest on the end of the arterial part of the capillary is where the hydrostatic pressure is the highest versus where it's the lowest which is the venous in of the capillary and the whole goal of hydrostatic pressure is that it needs to create a process known as filtration because we need to get this water and solute out of the capillary into their interstitial fluid so we can go and do its thing and then come back to us so what hydrostatic pressure does is it's that pressure that pushes that water and solutes out of the capillary into the interstitial fluid which is again known as filtration so as you can see with these two processes oncotic pressure and hydrostatic pressure how our body needs them to work we have one that's going to push out the water in the nutrients which is hydrostatic pressure and then we have the other oncotic pressure which is going to pull it and keep it inside the vessels okay so that wraps up this review and if you'd like to watch more videos in this fluid and electrolyte series don't forget to check out the link in the YouTube description below