hello and welcome to learn a level biology for free with miss s check this video it's going to go through tissue fluid so what it is how it's formed and how the water gets reabsorbed so first of all what is tissue fluid so this is the liquid which surrounds the cells and your body and a group of cells performing the same function is a tissue now this fluid contains water glucose amino acids fatty acids dissolved ions and minerals and oxygen and that liquid then surrounds your tissues and that means glucose can diffuse in oxygen can diffuse in and so on so this is how the cells of your body gain access to all of their essential molecules that are needed for survival for example for respiration so where does this tissue fluid come from say tissue fluid is formed because of the fact that capillaries are only one cell thick so it is one single layer of cells and in between each of those cells there are tiny tiny gaps but the gaps are big enough and that liquid say for example the water can be forced out and so can very small molecules so what happens is the capillaries are attached to arterioles which are attached to arteries now if you haven't seen the video yet on blood vessels I'll link up here so you can see that first but when the arterioles go to the capillaries the pressure increases and because you then have this high pressure of blood flowing into the capillaries that causes ultra filtration and what that means is water and small molecules are forced out of those tiny gaps between the capillaries and it acts like a sieve so small molecules are forced out large molecules and some of the water remains behind so that's how the water oxygen glucose and all of those small molecules that were being transported the blood end up being forced outs and bathing the tissues so they can then gain access to the essential molecules that they need so it's all to do with that high hydrostatic pressure which causes ultra filtration and that is at the arteriole end of a capillary so that's how does she fluid is formed but let's just have a summary of what is forced outs we said water dissolved minerals and salts glucose small proteins and individual amino acids fatty acids and oxygen so the molecules which are too large to be forced out of those tiny gaps are red blood cells platelets and large proteins so tissue fluid is not red in color because there are no red blood cells and this links to how that tissue fluid gets reabsorbed then so that liquid that tissue fluid that has been surrounding the tissues has to get reabsorbed because otherwise if you are constantly forcing liquid out and not reabsorbing it eventually you're going to run out of liquid in your blood and your cells will become covered in so much liquid that you'll see swellings in your body so the water has to be reabsorbed back into the capillary and this happens at the venule end and what that means is the end of the capillary bed or individual capillaries which is nearest to the veins and this time because the large molecules remained in the blood so the large proteins and red blood cells and lots of water was forced out the liquid that now remains inside the pillories has got a very negative water potential compared to the tissue fluid so as a result the water that is in the tissue fluid moves back into the capillaries by osmosis down that water potential gradient there's no more liquid being forced out at this end because the hydrostatic pressure has dropped very very low in the capillary now because so much liquid has been forced out so the venue end we have a low pressure in the capillary and a very negative water potential so no more liquid has been forced out but water is reabsorbed back into the capillaries by osmosis and within that water there will be dissolved waste molecules that the cells are releasing so as those cells are aspiring they'll be releasing carbon dioxide they'll be producing urea as well so molecules such as carbon dioxide and urea dissolve in that water they are then reabsorbed with the water bars maysa back into the blood and that's how the waste from the cells gets into the blood to then be removed from the body now not all of the tissue fluid is reabsorbed by osmosis back into the capillary and that's because eventually an equilibrium will be reached and osmosis is the movement of water from a higher to a more negative water potential so eventually with all of that water moving back into the capillaries you will reach equilibrium so that means the rest of the liquid that is still surrounding the cells and the tissues has to be reabsorbed by a different route and that's how the lymphatic system comes into it so you don't need to know much about the lymphatic system you just need to know that your lymphatic system has lymph vessels but to have very similar to veins because they have valves in and they surround the blood vessels so any liquid that doesn't get reabsorbed back into the capillaries by osmosis gets absorbed into the lymphatic system and we call it lymph and eventually the lymphatic system will bring that liquid back into the blood where the lymph vessels are entering near heart so that's how that liquid eventually gets back into the blood so that then goes through what tissue fluid is why it's important how it's formed and how it's reabsorbed so hopefully you have found this video helpful if you have please give a thumbs up and make sure you subscribe to keep up to date [Music] [Music]