Hydrostatic and osmotic pressure

 Hydrostatic and osmotic  pressure, drive fluid out of and back into your blood vessels. 

These pressures might seem a bit unimportant at first, 

but the help us explain some interesting cases of edema or tissue swelling

Here we have a tissue like muscle or nervous tissue, which is being supplied with blood by this network of capillaries 

capillaries with their Thin wall  pores and gaps are specially designed to allow for the exchange of nutrients, gases waste and fluid between the blood and the tissues. They’re the place in the cardiovascular system where we can get stuff into the blood and get stuff out of the blood. for example, as blood into capillary on the arterioles noticed that some fluid is filtered out of the blood vessel. However we normally don’t want that fluid to stay in the interstitial space as this could lead to fluid collecting in the tissues causing swelling. Many of you have probably experienced this before if you’ve ever stayed standing for too long, you might’ve noticed that your ankles which looked normal before started to swell up or experience was called Adema. This is caused by fluid, staying outside the blood vessel within the interstitial space, causing the tissue to swell to prevent the swelling from happening much of the fluid that was filtered out is normally reabsorbed back into the capillary at the venule Outside the blood vessel within the interstitial space, causing the tissue to swell prevent the swelling much of the fluid that was filtered out, is normally reabsorbed back into the capillary at the venous end, so fluid out fluid out and fluid back in, but why was fluid forced out in the first place and how does it get reabsorbed? Well let’s zoom in first on the fluid being filtered out to see what’s going on the pressure that drives fluid movement out of the blood is called hydrostatic pressure instead of some fancy definition of hydrostatic pressure is I’m just gonna show you what it is using an example that some of you might be able to try out at home. I have a straw like what you might use to drink, but I’m gonna do is put my finger on this end of the straw preventing fluid from leaving. Then I’m gonna fill up the straw with Water if I were to take this straw and poke a hole in it over here what do you think would happen you might’ve guessed it Water is gonna begin to leak out static pressure and generates an outward pressure that will dry fluid out of the straw. You might be thinking I’m all right dude we don’t care about the straw what is with this straw what I just showed you is basically the same thing that happens in your capillary. Your cardiovascular system is basically just a long straw with holes in the capillary and in our capillaries due to the amount of fluid in our cardiovascular system and the hydrostatic pressure in the arterial capillaries fluid is forced out through microscopic, pars and channels in the capillary walls, but if hydrostatic pressure were all we had fluid would collect in the tissues and we Adema or swelling just about all the time OK, so time for second key term osmotic pressure pressure is based on one key fact, bi, osmosis water always flows towards regions in the body. They have a higher osmolarity or a higher concentration of solute particles. For example, we have some water surrounding vessel shown here in yellow. This vessel has some pores or small holes which allows certain particles to cross and prevent others from crossing inside this vessel upper high concentration of some particle shown here in orange notice that this particles concentration is much higher on the inside of the vessel compared to the outside, but if this particle is relatively large, maybe like a protein molecule and cannot leave this vessel through the small pars, that means that the concentration of these large protein molecules is going to remain high inside the vessel and remain low on the outside of the vessel, but since water always flows towards regions with the higher concentration of particles, what do you think Water is gonna do in this case in this case, Water is going to be reabsorbed back into the vessel towards the higher concentration of particles. This situation again is exactly what is happening in your capers in your blood. You’ll find a higher concentration of proteins like the serum protein albumin compared to outside the blood vessels in the interstitial space because of this higher concentration of proteins in your blood fluid tends to be reabsorbed back into the blood driven by osmosis and by osmotic pressure so hydrostatic pressure tends to dry fluid out of your blood osmotic pressure tends to drive it back in quick sidenote. This osmotic pressure caused by large molecules like proteins is called colloid osmotic pressure or oncotic pressure so as I mentioned osmotic pressure in this video I’m really talking specifically about what’s called colloid osmotic pressure. Just FYI. Also we do have other solids in our blood besides proteins like ions like sodium and chloride. however, these do not contribute to the osmotic pressure or the reabsorption of fluid. If you’re curious as to white you can check out the comments below zooming back out let’s put it all together to see how high Rostatic pressure and osmotic pressure, filter and reabsorbed fluid at the cap at the arterial end of the capillary hydrostatic pressure is higher than the osmotic pressure. This causes fluid to be forced out into the interstitial space, but is hydrostatic pressure decreases as we move through the capillary. Osmotic pressure eventually becomes equal to, and even greater than the hydrostatic pressure, causing nearly all of the filtered fluid to be reabsorbed back into the capillary at the Venyl end of the capillary, you might notice that there’s still a small fraction fluid sitting in the tissues, though not all of it is reabsorbed back by osmotic pressure. That’s why our final player comes in the lymphatic system vessels of the lymphatic system will help re absorb the remaining small fraction of filtered fluid that wasn’t reabsorbed by osmotic pressure, helping us to prevent swelling or enema, and they have it in the next review a few cases were fluid. Does Collect with the tissue caused by abnormal changes in hydrostatic pressure or osmotic pressure, for example, ox explain in detail why our ankle swell up when we sit or stand for too long.