know final thing here is secretion now secretion is mainly and even to a certain degree of reabsorption it's going to be based upon your current conditions so secretion we're going to be removing actually i should make it a different color make it black secretion is removing waste from the peri tubular capillaries into the and putting them in the nephrons to the nephrons okay so this guy up here is removing from blood this guy down here is removing from blood and reabsorption is putting it back into the blood so here we would be taking stuff from the capillaries and putting it back in or putting it into the tubules okay so we'd be taking stuff from the blood and putting it into the tubules all right so filtration and secretion remove things from the blood reabsorption puts back into the blood so what happens when uh you make a drug is that you're going to one of the tests you're going to want to do once you've determined that the drug is a good drug and it's not going to hurt people and you know kind of how much is a good therapeutic dose you have to figure out the excretion rate okay how quickly is that drug excreted because the quicker it's excreted the more times the person will have to take it during a day okay for instance penicillin you usually have to take four times a day at least you used to haven't taken penicillin in years and years and years but i remember when i did um you had to take it four times a day and that's because it's excreted quickly now they may put something on a drug to prevent it from being excreted easily like tag it with a protein or something but some things are excreted easily other things aren't so the excretion rate for a substance i'll just put r for rate equals okay you figure out how much is filtered and secreted and subtract from that anything that's reabsorbed okay so the excretion rate we're looking at what's in the urine and anything that's filtered and secreted it's going to be in the urine but if it's put back in it won't so you you do a lot of tests with your drugs to see how much of it ends up in the urine how quickly and then you may want to do things to try to increase the length of time or it may be fine you know it depends okay now notice i said filtration happens at the glomerulus only reabsorption and secretion they happen all along the tubule system okay most reabsorption let me get rid of the little capillary here the peritubular capillary and by the way there's one other kind of capillary let me just talk about that for a second um and that is called the vasa recta and let me erase this here okay the vasa recta is the third one here and the vasa recta it kind of looks like you ever see necklaces that have all of these um like strands on them like pearls we have a real long strand then one that's shorter another that's shorter and another shorter vasarecta goes down around the loop of henle mesarecta is involved in maintaining the osmolarity of the medullary region and this is important for making it either really dilute or really concentrated urine and we'll talk more about that later but just for completeness that's the laser that recta i didn't do drawing it but it sort of looks like strings of pearls you know you wear a necklace and you have or gold chains or something that you know each successive one is a little bit longer and there's a whole bunch of them all right that's what the vasorecta looks like so we have three different types of capillary beds the glomerulus peritubular capillaries and the vasa recta and they each play a role in the kidney and these are specific to the kidney these three types of capillary beds all right so the next thing i want to talk about oh wait the so almost all reabsorption ah no okay almost all reabsorption is going to happen right here the proximal convoluted tubule and a lot of secretion is going to happen there as well all right but nearly all reabsorption happens at the pct so you filtered a bunch of stuff based upon size and now there's a bunch of good stuff in that filtrate you want to get it back in the blood as quickly as you can so you don't lose it and so that's where these guys are going to be working really hard trying to the transporters are going to be working really hard to try to get things back into the blood before they get lost or they get washed away in the urine and so a hundred percent of glucose 100 of amino acids and then like 65 of the water 65 of sodium you know variable amounts of things like chloride calcium and other things a lot of the secretion happens there as well and then the rest of the tubule system is mainly just to tweak things to get them perfect fine tuning to get it perfect for your exact situation right now what kind of condition are you in right now do you have enough calcium do you need more calcium what's your solute balance what's your blood pressure like all of that then is to get the conditions in your body correct for what your condition is now okay so you filter a whole bunch of stuff based on size you got a lot of good stuff you don't want to like get away you put that in back in the blood right away and then you're going to kind of figure out where your body's at and what you have to put back in and take out okay all right so are there if you have any questions please stop me along the way so let me erase a little bit of this um and we'll talk about the or actually let me move to another another page and i'll save this one and what i want to talk about are the is the filtration system at the glomerulus okay plug in my ipad so it doesn't go dead okay so at the glomerulus we have the glomerular capillaries and capillaries we have different types of capillaries remember we have the continuous capillaries that we have most places and then we have the fenestrated ones that sort of look like little holes in them and then the type that we look at looked at in um the digestive system where the the sinusoids they look like i mean they look like uh they have big chunks taken out of them if you're looking like at the side view of it so this one the side view may let me just make that so the finest trade is going to have holes like this the one with sinusoids is going to have big holes and these each type of capillary is a different function right sinusoids are you want proteins and formed elements to be able to enter and exit the capillary so you're going to find these in the liver the spleen in the bone marrow the fenestrated are going to be used for filtration so we're going to have these in the kidney in the brain and the choroid plexuses in the eye in the um i can't think of the name of it place where the filtration occurs in the eye the ciliary body all right so any place where we're going to filter and then continuous are everywhere else so each of them has a specific kind of purpose so right now we're going to be looking at the fenestrated ones they have holes in it they're not huge holes that would allow formed elements and proteins to go through it but they're big enough that pretty much everything else can go through except for proteins and formed elements okay now remember that capillaries have a little bit of basement membrane around them they have a little bit of connective tissue around the outside all blood vessels do and so when we're looking at the different layers that we're going to have right we're going to have three separate little filters that the blood has to to go through