Capillary Exchange

hi everyone Dr Mark here in this video we're taking a look at capillary exchange a really important concept when it comes to the cardiovascular system but also when it comes to fluid balance of the body and understanding this system helps you make a lot of sense of things like edema and also inflammation as well let's take a look [Music] so to begin we need to have a look at the basic circulation of the body so there's two major circulations those of the pulmonary circulation of the lungs and that of the systemic circulation and we know that the right hand side of the heart deals with deoxygenated blood and the left-hand side deals with oxygenated blood as the deoxygenated blood leaves the left hand side sorry the right hand side of the heart it goes to the lungs gets oxygenated and then goes back to the left hand side of the heart left atrium left ventricle the left ventricle will contract and pump this oxygenated blood filled with nutrients out via the aorta which will Branch multiple times and turn from an artery into smaller muscular arterioles to capillary beds and it's at these capillary beds that we have exchange occurring so what I've drawn up here is a capillary bed and you can see the blood's coming in on this particular side and this is the arterial and and then we've got blood leaving on this side and this is going to be the venous end and in between what do we have we've got the capillary bed and we've got some cells here so firstly let's talk about what do we want to exchange with these cells so there's a couple of things first thing is we want to give the cells oxygen and we want to give the cells nutrients what do we want to receive from the cells well we want to take from the cells carbon dioxide which is a waste gas an exhaust of using oxygen and nutrients but we also want other various wastes so this might be urea creatinine whatever it may be so these are the major things that we want to exchange so as you can see we don't just want to push things out at the capillary bed we want to bring things back in and this is the basic point that we need to understand when it comes to capillary exchange is things are going in two directions so now let's take a look at this run as the left hand side of the heart contracts and pushes that blood out via the aorta it's pushing it out at a maximum pushing force which we call the blood pressure of 120 millimeters of mercury now as we move through these various pipes that pressure of 120 millimeters of mercury obviously drops right the pressure drops the longer you or the basically the longer the pipe the longer the track think about if I had a hose and a tap and I had a 50 meter long hose and I turned it on it's going to be at its highest pressure right at the tap and think about it as it moves through the hose it's experiencing resistance so the blood or the water slows down so same thing happens here it goes from 120 millimeters of mercury at the aorta but by the time it reaches the capillary bed the blood pressure is around about 30 millimeters of mercury now blood pressure is simply the pushing force that the blood is putting on the walls of the vessels so up here you've got 120 millimeters of mercury pushing on the walls of the arteries and then it drops to maybe 90 at the arterials and then when it gets to the capillary bed the outward pushing force is 30 millimeters of mercury so let's write this down you've got this outward pushing force of 30 millimeters of mercury that's the first thing now we don't call it here blood pressure right there's another term and it's called hydrostatic pressure but basically it's blood pressure so here we've got the and let's just write as HP the hydrostatic pressure in the blood here in the capillary bed is 30 millimeters of mercury so what we're doing we're pushing things out now the things we're pushing out are nutrients and oxygen and electrolytes and other small things that can fit through the holes of the capillary beds but the thing is as we push this stuff out there are things that remain things that are too big to move through the walls of the capillary beds what are these things well they're things like white blood cells they're things like red blood cells they're things like proteins they're things like platelets so there's a whole bunch of cells and structures and things that are too big to move out now I want to think about this some of these like proteins have a really strong negative charge remember a lot of phosphate associated with proteins and there's a lot of negative charge associated with them particularly that of albumin which is a very common protein within the bloodstream it's got a negative charge and what do you know about things with negative charges they love to pull water towards them so at the same time as having an outward pushing force from the blood pressure or the hydrostatic pressure we have an inward pulling Force and the inward pulling force is simply the attractant force that these negative proteins are placing on the water we call this osmosis right so this is called the osmotic pressure so we've also got an inward pulling Force and this inward pulling force is not 30 millimeters of mercury it's about 20 millimeters of mercury and remember it's the osmotic pressure sometimes it's called the oncotic pressure the oncotic part is referring to proteins osmotic is just referring to the pulling of water let's just write those two terms down right you can have osmotic or you can say oncotic but regardless what the textbook says that's this pulling Force that's happening primarily because proteins are pulling it in now have a look we're still on the arterial end here what wins an outward push or an inward pull if it's if you've got 30 people pushing something out and only 20 people pushing something in who's going to win the 30 and it wins by what's the difference 10 millimeters of mercury so what you're going to find is on the arterial end there is a net outward push of 10 millimeters or Mercury and this is important because it's this outward pushing force so it wins things go out on the arterial end nutrients and oxygen these are the things that go out now think about it the blood's going to continue to move through right and as the blood continues to move through what else is continuing to move through these substances that don't leave right including the proteins right so you've got these negative proteins here but you've also got the cells moving through and so forth what do you think has happened to this hydrostatic pressure do you think it's the same on the venous end do you think it's higher or do you think it's lower well what if you had a hose connected to a tap again 50 meter long hose but this time you put holes every meter down the hose holes down the hose and then turn it on what do you think is going to happen water's gonna squirt out those holes but the water closest to the tap will squared out highest and then as it gets to the end it's going to go lower lower lower because the pressure reduces As you move through so this hydrostatic pressure drops as we move through from the arterial to the venous end the still an outward push but it's no longer 30 millimeters of mercury this outward push this outward pushes now 15. millimeters of mercury it's dropped what do you think about the inward pulling Force this oncotic or osmotic Force do you think it's changed gone up gone down all the same well none of these things have left they've all remained the same so the inward pulling force is about the same 20 millimeters of mercury so now we've got this inward pulling Force of 20 millimeters of mercury again the osmotic or oncotic pressure and again this was the hydrostatic now who wins well the inward pulling force is now winning right by five so now what do we have instead of a net outward push we've got a net inward pull of five millimeters of Mercury which means on the Venus end things get pulled back in what get pulled what's what get put what gets pulled if I can speak properly what gets pulled back in carbon dioxide and wastes that's exactly what we want right now the thing is there's fluid going out it's these things are dissolved in the fluid so fluid gets pushed down here moves through fluid gets pulled back in and the fluid continues right this plasma not all the fluid gets pulled back in some fluid will remain out in what we call the interstitium inter station this is the space outside of the blood outside of the cells but between the blood and the cells right this is the interstitium so fluid remains in the interstitium where does it go well it gets thrown into the lymphatic system it gets thrown into the lymph the lymphatic system but luckily for us the lymphatic system connects back with the venous system and any of that fluid that wasn't reclaimed gets put back into the venous system brilliant this is the basics of capillary exchange now why would you possibly need to know this a couple of reasons first reason is there's inflammation inflammation is any time you have damage to vascularized tissue damage to vascularized tissue here's vascular tissue this is the tissue that needs to be fed here's the blood vessel so if I damage anything here I'm going to get inflammation now inflammation results in the release of chemicals and these chemicals include things like prostaglandins histamine bradykinin just to name some of the most common what these three chemicals do is they vasodilate the incoming blood so more blood gets in right so the hydrostatic pressure what do you think happens goes up but what they also do is they tell these gaps to get bigger these gaps now get bigger now what do you think that means it means that you've got more of a stronger outward pushing force now firstly why why do these chemicals get released in inflammation for this to happen because if you've got damage to these cells and maybe it's some sort of bacteria that's present right you need the white blood cells to come out to start attacking it so what it does increases the pressure more white blood cells come in makes these gaps really big why so that the white blood cells can now leave some of these white blood cells turn into these macrophages right so these are good eaters and they're going to come along and they're going to ingest the bacteria or the damaged cells or whatever it may be so this is great inflammation but it also means that the proteins leak out too all right so if the proteins leak out what do you think that means as we move through to the venous end are these proteins there no so is there an inward pulling Force no so what do you think happens fluid stays outside of the blood vessel fluid accumulates in the interstitium and you get swelling at the tissue this is edema swelling at the tissue because of inflammation does that make sense hopefully the other important thing is this what if someone had right side heart failure right side Harper so here's the heart right here's the right hand side let's separate down here's the right hand side of the heart what if this side of the heart failed to act as a pump that's what right side heart failure means so it's supposed to contract and push the blood out of the right ventricle to go to the lungs to get oxygenated but if that didn't work it means that it's not Contracting very hard so can the blood leave to go up not really it's really difficult so it backs up instead that doesn't happen and it backs up into the atrium backs up into the venous return backs up into the venous system which means the blood backs up from here into the venous system into the capillary bed which means the hydrostatic pressure on the venous end goes up let's say back to 30. and what does that mean it means again similar to inflammation you have a net outward push and fluid accumulates in the tissues of the periphery so right side heart failure can result in peripheral edema so hopefully this makes sense this is capillary exchange and why you need to know it I'm Dr Mike hi everyone Dr Mike here if you enjoyed this video please hit like And subscribe we've got hundreds of others just like this if you want to contact us please do so on social media we are on Instagram Twitter and Tick Tock at Dr Mike tadarovich at [Music] d-r-m-i-k-e-t-o-d-o-r-o-v-i-c speak to you soon foreign

Channel: Dr Matt & Dr Mike

Views: 37,520

Keywords: capillary, exchange, dynamics, hydrostatic, oncotic, osmostic, pressure, oedema, edema, heart failure, venous, arterial, proteins, cells, inflammation, prostaglandins, bradykinin

Id: GnriknE4YRY

Length: 14min 44sec (884 seconds)

Published: Mon Sep 25 2023