what's up guys today we're going to talk about fluid compartments and how they react to changes in osmolarity so starting off let's start with the basics which is a case where we have isotonic Bluett loss when I say isotonic I mean I mean that we're gonna lose about an equal amount of water and let's say in this case salt an example of this would be in case of diarrhea vomiting or hemorrhage in which you're losing both amounts of solutes and water so the way I tackle these is that a look at osmolarity first if there's no change or not similarity then I'm just gonna move on to the second step which is to look at ECM and see what changes here hey boss molarity however does change either increase or decrease I will expect to see that change in not only easier but also ICF so if there's no changing osmolarity believe ICF alone so in the case of isotonic fluid loss we don't have a change in osmolarity because we have lost water and solutes at about an equal amount so this remains the same meaning I will completely ignore ICF in this case it'll only focus on ECM the extra stuff is our compartment in this case since we're losing fluid will decrease and that is it no ass expected if we gain isotonic fluid it will be the same case osmolarity will stay the same that's my step one my step choose to look at ECF UCF here will increase because we have added fluid that is isotonic there's no change in osmolarity so in the case of loosing hypotonic fluid meaning I'm losing mostly water examples of this would be losing it in the urine in diabetes mellitus or in diabetes insipidus it could be due to dehydration in this case since we are losing more water in the urine the osmolarity in our blood will actually go up because it's we've lost more water we've got more salt or solutes in our blood now since we have lost water that means that my ECF compartment is going to come down and in this case in particular since there was a change in osmolarity the ECF is going to have lost water but it needs more water to balance out all of this extra salt so it's got an attempt to pull water from the next compartment which is the ICF so ICF will now go down so to review my step one was to look at house molarity I'm losing more water than salt I was molarity and the blood will go up I have more salt in the blood the easy of compartment will go down because I've lost water and because there's so much salt in so little water I'm gonna try and pull out of the ICF some water to balance the extracellular fluid out and try it to attempt to make it isotonic meaning I will lose full it from the eyes yeah okay no let's practice a similar one but with gain of hypotonic fluid so I'm gaining water so it could be something as simple as just drinking too much water or giving it a hypotonic saline okay so step one we're gonna be looking at osmolarity now my osmolarity here will have to be low because I'm giving so much water that it's diluting all that salts right so I'm gonna go ahead and draw this lower and the next step would be to look at ezf so the ECF here since i'm gaining water is actually come right out here have a lot of water and sins I have so much water so little salt the ECF is gonna attempt to try and give some of that extra water to the next compartment that ICF so the other F will actually increase as well okay it's looking a lot easier now huh let's move on till the last year so in the case when we're losing hypertonic fluid meaning that we're losing more salt than the water what we would have is a change in osmolarity in which since we're losing salt our blood levels of salt are going to be low so since I'm losing so much salt there will be little salt in my blood and more water now the ECF wants to become to make this as isotonic as possible so it's going to actually come down by giving some of this water to the ICF so the ICF will actually increase so we're shifting the volume and the ECF to ICF why we lost salt there's so little salt so much water the easier wants to make this that's isotonic as possible so it's going to give away some of that excess water to the ICF compartment now this would be the case in adrenal insufficiency so last but not least we've got gain of mostly salt and this would be for example due to SIADH so what's going to happen is our awesome molarity since we're gaming salt is automatically going to increase because we have so much salt now in her blood art UCF is gonna need more water right so what it's gonna do is it's going to achieve getting all of that water but at the cost of pulling it from the ICF so the ICF will decrease because it gave water to the ECF so that the easier can kind of balance out all of that excess salt so I hope all of this made sense to you if you have any questions feel free to let me know in the comments if you have anything else you would like me to go over I'll do my best to make it simplified and short thank you for watching and I hope you have a wonderful day good luck steady