[Music] all right you guys welcome back to another video lesson from icu advantage for those of you who don't know me my name is eddie watson and if this is your first time to the channel welcome if not welcome back so i created this channel with the hope of bringing you some of the best in-depth free online critical care educational content out there i cover many different topics so if you don't want to miss out on a future lesson then make sure and subscribe to the channel down below when you do make sure you hit that bell icon and select all notifications that way you'll never miss out when a new video is released alright so in this lesson here today this is going to be the first lesson in a series of lessons talking about continuous renal replacement therapy or crrt now before we get into talking about this therapy though it helps to have a good understanding of the normal anatomy and physiology of the renal system to really better understand what it is that we're trying to accomplish with this and that's the point of this lesson here is to go over this renal system review now this lesson is not going to go too in depth as i know most people have already had the anatomy and physiology class but i am going to review through some of the helpful information and so to start let's begin talking about some of our renal anatomy now as we know the organ of the renal system is the kidney which we have two of they sit in our retroperitoneal cavity on each side of the spine between the 12th thoracic and third lumbar vertebrae and just interesting note the right kidney is actually lower than the left due to the placement of the liver now we can divide the kidney up into three layers we have the cortex which is this outer layer here next we have the medulla which is going to be this inner sort of open section here and then finally we have the renal pelvis which is going to be this area here and this is where the urine is collected and sent to the urethra now the cortex and the medulla they contain various parts of the nephron which is actually what we're going to talk about here next and so the the nephron this is our functional unit of our kidney and so what's really interesting is that each kidney contains more than one million of these nephron units in it and collectively together that they work to maintain the water electrolyte waste and acid-base balance in our body and the way that they do that is through this pretty complex structure that you see that i have the picture of here and so let's go through and talk about some of the different parts of this pretty complex nephron structure so the first is going to be this big capsule-like structure here and this is going to be something that we call the glomerulus and as you can see it's surrounded by this membrane something that we call the bowman's capsule now the first section coming out of the glomerulus is going to be our proximal tubule and then continuing on from here this is actually still technically part of the proximal tubule but this is something that we call the loop of henle and the loop of henle is composed of three sections we have the thin descending loop the thin ascending loop and then the thick ascending loop and then from here we go on to the distal convoluted tubule before finally going into the collecting tubule and the collecting duct now important to go along with the tubules of the nephron is also going to be the renal blood supply that we have going through here and interestingly 20 to 25 percent of cardiac output is going specifically to the kidneys and so everything really begins with the renal artery branching off the aorta and so we can see that coming in on the image here on the right and then from there it's going to branch down until we have something that we call the afferent arterioles and this afferent arterial is going to be what enters the bowman capsule and really helps to form that glomerulus now from there the blood is going to exit the glomerulus via what we call the efferent arteriole and then the efferent arterial is going to become this pretty big complex something that we call the peritubular capillaries and really these peritubular capillaries are going to interface with all the different parts of the tubules to continue to perform functions that need to happen within the nephron all right so now that we have the basic structures out of the way let's talk about the actual renal physiology that's taking place here and so the main goal of the kidney here is to filter the blood and form urine again like i said in this process the nephron is going to be regulating water electrolytes waste and the acid base imbalance so like i just talked about the afferent arteriole is what goes in and forms the glomerulus which is actually a high pressure capillary bed to which then the blood exits via that efferent arterial now here the afferent arterial is actually a larger diameter than the efferent arterial and this is what allows a greater volume of blood to enter the glomerulus than what's actually exiting and this is going to create a high pressure and it's specifically this high pressure that creates the hydrostatic pressure allowing water to be filtered across the basement membrane and so then the basement membrane of the glomerulus is actually a semi-permeable membrane and it's going to allow all but the larger molecules to pass through it so think here we're excluding things like protein albumin red blood cells and so here we're going to have particles that are small enough to pass across the basement membrane which are going to be moving from areas of higher concentration to lower concentration and this is also something that we call diffusion now on top of that if we have enough water that's being forced across that membrane via that hydrostatic pressure that we just talked about additional particles or solutes are also going to be dragged along with it something that we call convection and so typically with our kidneys large volumes of water are going to be filtered allowing for this additional waste clearance that we see so now we have blood that's left with these large molecules and proteins and it's going to be leaving via that efferent arterial now having these large molecules and proteins in there is actually going to provide oncotic pressure for water and solutes to be reabsorbed in those peritubular capillaries and so as you can see the blood that's exiting via the efferent arterial is still oxygenated blood and so in addition to also going into those peritubular capillaries another responsibility that it has is to actually perfuse the kidney itself and that's why finally at the end here we do see the blood becoming deoxygenated as it goes out into a vein all right so like we talked about we have that high volume of water filtrate that has left out of the glomerulus and first we're going to enter into the proximal tubule and this is going to be responsible for the reabsorption of water and important solutes and electrolytes and here we're talking about things like potassium sodium chloride glucose and bicarbonate now on top of this reabsorption we also have hydrogen ions that are going to be passively secreted here now continuing on we actually have different nephrons that have different responsibilities for what actually takes place in the loop of henle so we have shorter cortical nephrons which are going to focus on the excretion and regulatory functions while we have longer juxtamedullary nephrons which either dilute or concentrate the urine depending on what needs to happen now if you remember looking at the loop of henle there's a big distinction between parts one and two and part three in terms of the thickness and it's this thickness of the loop henle that actually impacts the permeability of the membrane allowing it to do different things so then moving on we have the distal convoluted tubule which plays an important role in the regulation of blood pressure while also regulating solutes by absorbing or excreting them in this section and in this section we also have the antidiuretic hormone or adh which aids in water reabsorption towards the end of this distal convoluted tubule now we do see some bicarb being reabsorbed here as well as hydrogen ions being actively secreted and then the main waste products that we're looking to excrete through this active filtration by the nephron are going to be our bun uric acid and creatine and so as you can see the the kidney and their functional units the nephrons really play that vital role in the homeostasis of our bodies they're regulating the fluid balance by controlling how much water is reabsorbed waste electrolytes and solutes are going to be filtered out but then the regulation of the electrolyte solute reabsorption is going to take place to ensure that our body has proper levels and then also through the reabsorption of bicarb and the secretion of those hydrogen ions they're going to be working to regulate the body's acid base imbalance and so when our patients go into acute kidney injury and ultimately renal failure this important regulation really becomes ineffective or non-existent and in order for us to be able to support these patients we really need to recreate the work of what's happening inside this nephron and so much of what we attempt to do with the therapies that we offer is based on what the natural nephron is doing and therefore having an understanding of what normally happens in here is going to be important to understand the how and why the therapy that we provide does what it does and so that's why i wanted to do this renal system review for you guys so that you had this understanding of what was going on here because as we move forward and begin to talk about crt and how that works much of what's going on there is really driven with the purpose of trying to recreate what happens here so that we can effectively filter the body's waste as well as controlling the fluid balance as well as the electrolyte and solute balance of the body as well as having an impact on our patient's acid-base balance so i hope this was a good quick review of what's going on here in the renal system like i said we're going to apply this information moving forward continuing on the crt lessons i really hope that you guys did enjoy this lesson if you did please leave me a like down below really goes a long way to help out in the youtube algorithm as well as leave me a comment and let me know what you thought of it i love reading and responding to to all the comments that that come up on this channel now a quick shout out to the awesome youtube channel members as well as our patreon members out there you guys are willing to show additional support for this channel and receive some additional content and in regards to that and so i really just want to say a big thank you to you guys uh if you'd be interested in showing additional content click on the join button down below or feel free to head over to the patreon page to see some of the additional perks that you get for the channel memberships now after this we'll continue the series going into looking at crt a little bit more in depth so make sure and stay tuned for that in the meantime make sure and check out a couple really awesome videos that we have for you right here as always thank you guys so much for watching have a great day