 Hey everybody, Dr. O here. In this video, we already talked about the fluid part of these fluid compartments. We're going to talk about the other ingredients, the other players in your intracellular fluid, which is fluid inside your cells, interstitial fluid, the fluid between your cells and your plasma as you can see here. So the first thing I notice when I look at this image is that plasma and interstitial fluid are very similar. So it's good on the line here. Plasma is going to be high in sodium, chloride, we have our bicarbonate and then we jump down to protein. So those are going to be key ingredients in your blood plasma. And if you look at the interstitial fluid, the light blue there, you're going to see the sodium and the chloride and the bicarbonate, but what you don't see is the protein. So hopefully you understand why that is when fluid is filtered out of your capillary. So filters are size dependent. The filters in your capillary beds do not capture sodium chloride and bicarbonate, but they do capture proteins because they're large. So proteins stay in the plasma. So I always say that the key difference between blood plasma and interstitial fluid is that the large proteins and the cells of course stay in your blood. So that's going to be the key difference there between plasma and interstitial fluid. Then you have the same thing with lymph. Lymphatic fluid is interstitial fluid. Once it enters a lymphatic capillary, it is now called lymph, but it's not on here, but lymph would look exactly like interstitial fluid. All right, then we have intracellular fluid. Let's go. So now we have the tan, whatever, brown, whatever it is. So you see that the potassium is going to be really high. And then you have your phosphates there. And then we have magnesium and proteins. So those are going to be the key things that are going to be inside your cells. So the main thing I look at when I look at this image is, number one, sodium is outside your cells, potassium is inside your cells. And number two, protein is inside your cells and inside your plasma, but not in your interstitial fluid. Key functions. Let's just walk down the list here. In nutrition, we cover these things in a lot more detail, but sodium, it depolarizes nerves. That's going to be its primary function. It also plays a huge role in fluid balance chloride. Its primary function is fluid balance, but also plays a role in the production of hydrochloric acid in the stomach by carbonate, think the bicarbonate, carbonic acid buffer system. So super, super important buffer, potassium, its primary job is to repolarize your nerves. So we said sodium turns your nerves on by depolarizing them. Potassium turns them off by repolarizing them, both very, very important. Then we have your phosphorus source here. Your phosphates are the phosphorus source you need to make DNA and RNA. And obviously you need lots of phosphates to make ATP as well. Calcium, like wildly important. We think about bone health with calcium, but every muscle contraction, neurotransmitter release, blood coagulation, enzyme activity, and it's a second messenger for your hormones. So it's super, super important. Magnesium, its primary roles helps in ATP production and DNA repair. And then protein does everything, right? We've got literally thousands and thousands of enzymes built out of proteins, proteins or transporters, structural proteins, you name it. So without protein, of course we couldn't survive. So those are going to be just the key functions of each of those that are on this list here. So these are going to be the other ingredients that make up your intracellular fluid and your examples of extracellular fluid. One just last thing to note, I've already talked about sodium and potassium a couple of times here. The most, when looking at this list here and what's going to change, the most common problems are going to be an imbalance of sodium gains and losses, either a real high sodium diet where you're bringing in more than you're losing or you're sweating a lot and you're losing more than you're bringing in. So the most common disturbance on this screen would be as imbalance in sodium gains and losses. But potassium gains and losses are a lot less common, but imbalances are a lot less common, but a lot more dangerous. Too much potassium, too little potassium, much more dangerous and much more potentially fatal than sodium issues. As far as like how would you measure these things clinically, so you see the top three, sodium, potassium and chloride, they all can be measured in a routine urine sample. Jumping down, you have calcium and phosphate, notice how it's measured per day. So the amount of calcium in your urine is in phosphate way too variable in a standard urine sample. So these would be 24-hour urine samples where they would collect urine for 24 hours to determine how much calcium or phosphate you're losing. And then notice that bicarbonate isn't in urine. So usually bicarbonate is all going to be conserved by the kidneys so we can use it as that very important buffer because it buffers carbon dioxide or carbonic acid. But so you shouldn't see it in urine sample to begin with, such a little bit of a clinical pearl there. Okay, that's going to be the key players, the key electrolytes and obviously protein involved in all the fluids of your different fluid compartments. I hope this helps. Have a wonderful day. Be blessed.