what is going on it's medicosa's perfect status where medicine makes perfect sense let's resume our biology playlist in the last two videos we talked about the embryology of the kidneys the anatomy of the kidneys and we talked about some basic physiology Concepts today we shall continue and we'll learn about the proximal convolut tibial the loop of henle the distal convoluted tubules Etc so in order for this video to make sense please watch the previous videos first let's review functions of the kidney regulation excretion secretion gluconeogenesis we talked about secretion before today we'll focus on regulation water and electrolytes what are electrolytes oh we have electrical charge lysis by electricity let's go back to square one the left ventricle of your heart is going to pump oxygenated blood to the aorta and then we have ascending aorta aortic Arch descending thoracic aorta then abdominal aorta and then we will go and become the renal artery which will supply the kidney with blood right as you know the blood is made of what plasma and cells the plasma is water and plasma proteins out of this which one should be filtered well the only one that should be filtered is the plasma the water without the proteins without the cells only the plasma should be filtered all right this plasma contains some good stuff which will be returned back to the heart in a process known as reabsorption however the bad stuff will dump those in the urine and this is called secretion and excretion example of the good stuff sodium glucose amino acids and most of the water notice the kidney reabsorbs but the gut absorbs because the gut happens first called absorption and then later when you reabsorb that's a kidneys function how about the bad stuff that will be excreted we have urea we have ammonia we have protons and we have potassium when you combine the ammonia with hydrogen ion or a proton you get ammonium add some chloride you get ammonium Chlor alright don't forget that your metabolism secretes acids such as pyruvic acid lactic acid phosphoric acid Etc and these acids will secrete protons how does the kidney get rid of protons many mechanisms here is just one of them in the form of ammonium compounds such as ammonium chloride Back to Basics renal artery is giving blood to the kidney as you know the real artery is going to Branch as we discussed before let's do it abdominal yield and then renal art after this you have segmental artery interlobar artery or quit artery interlobular artery and then afferent arterial afferent arterial after arterials what do you get capillaries oh this is the capillary tuft known as the glomerulus or the glomerular capillaries and then after this you have what efferent arterial between the afferent arterial and the efferent arterial there is the capillaries the glomerulus all right now this can contains what it contains plasma it contains plasma proteins and blood cells the only thing that should get filtered is the plasma and the plasma will get filtered through this filtration membrane which is made of three layers layer number one the endothelium which lines the glomerular capillaries two glomerular basement membrane three the podocytes with their famous foot processes this is what filtration of the plasma only how about the plasma proteins and cells they shall go back to the efferent arterial and bacterial circulation they cannot be filtered for many reasons one the fenestrations are very narrow and these are Big molecules they cannot pass two the glomerular basement membrane is negatively charged and if you remember your biochemistry plasma proteins are negatively charged too so they will repel each other hey proteins excess denied the moral of the story is the process of getting the fluid from here to here is called filtration let's filter that fluid get it from the afferent arterial to the capillaries and then filtered chew into the tubule into the nephron let's talk about the nephron first part is the Bowman's capsule and then you have the proximal convoluted tibial Loop of henle this siliconvoluted tibial collecting tubules collecting that minor chalesis major choleces renal pelvis ureter urinary bladder urethra and boom to the street as we have discussed before getting the fluid from the capillary blood into the tubular luminous cold filtration all right the good stuff should be returned back to the circulation in the vicinity of the efferent arterial and the peritubular capillaries but the bad stuff should be dumped into the urine in a process known as secretion so from the tubule to the blood reabsorption from the blood to the tubule is called secretion as you know your blood is made of plasma and cells the plasma water and proteins the plasma proteins are albumin or globulin the only thing that should be filtered is the fluid of the plasma not the proteins and not the cells the heart is pumping blood to the aorta and then the blood pump is known as cardiac output 5 liters every minute pumped by your left ventricle this is what leaves the heart as you know the kidney is not the only organ in your body we have other organs to fade about 20 or 25 percent of the cardiac output is going to reach the kidney and this is known as renal blood flow how about the other 75 or 80 percent to the rest of the body doofus not to the kidneys and as you know not all of the blood that reaches the kidney is made of plasma because you know the plasma is just 55 percent the other is just red blood cells white blood cells platelets oh out of this renal blood flow how much is renal plasma flow 55 percent of the Arena blood flow is renal plasma flow amazing now will all of this get filtered heck no we will filter about 20 percent this is known as GFR what's going to happen to the rest the remaining 80 medicosis they will go to the efferent arterial so suppose that the afferent arterial had 100 MLS of plasma 20 MLS will be filtered into the nephron and the remaining 80 percent will hang around in the efferent arterial let's do it again here is a hundred renal plasma flow in the afferent arterial going to the glomerulus only 20 will be filtered the rest will not be filtered this time can it be filtered in the next cycle and the next cycle and the next cycle sure you have a million Nephron in each kidney you will have fun okay my friend using these numbers can you tell me the GFR or the glomerular filtration rate I want the rate of filtration sure medicosis this number the 20 20 MLS but I said rate rate implies what time so it is 20 MLS per minute of course this is not the real GFR it's just a hypothetical example if your GFR is like this you are in big trouble that is very low this is kidney failure we're just playing with numbers here okay that was the GFR can you tell me the filtration fraction oh fraction division time okay medicosis it is what got filtered which is 20 over what we began with which is the 100 IE it is the GFR the 20 over the renal plasma flow the 100 GFR over a real plasma flow 20 over 100 equals 20 percent is my filtration fraction so in a nutshell GFR equals the filtered volume over time filtration fraction equals the GFR over the renal plasma flow both concepts are explaining the same exact thing GFR is doing it in absolute terms filtration fraction is doing it in relative terms that was deep we played with hypothetical numbers if you want the real numbers they are here that's your normal GFR that is normal not 20 20 is not much 20 is bad 125 is the norm of course it depends on many factors like the age Etc what's the fate of this 125 oh all of them are going to end up in the orange shut up most of them will be reabsorbed because most of them contain good stuff glucose sodium amino acids most of this will be reabsorbed all right but then I can also add to this 125 in a process of secretion dump the waste from the blood onto the tubular fluid and therefore if I have a camera and I'm waiting in the urine my special camera is waiting in the urine to measure rates what do you think I'll be measuring you'll be measuring the filtration minus the reabsorbed what I took out plus the secreted what I added on get the equation this is the urinary excretion rate well terminal causes what are the factors that determine how much to reabsorb how much is a crate should I reabsorb more secrete more or what this is the story of the stalling forces for this part of the video to make sense to you please watch the previous video titled Starling forces hydrostatic and oncotic pressure in this biology playlist as you recall we have a pushing force and a pulling Force what's the name of the force that pushes fluid to the outside of the capillaries hydrostatic pressure all right what's the name of the force that pulls fluid towards the capillaries uncartic pressure or osmotic pressure or colloidal pressure why do they call it colloidal because it's caused by colloid by a protein plasma protein known as albumin y because albumin is more abundant than globin and as you know osmosis cares about the number of particles and not the size so hydrostatic pushes uncuttic or osmotic or colloidal poles hydrostatic pressure is going to push fluid from the inside of the vessel towards the outside and this depends on how much fluid how much blood how much plasma is inside the vessel conversely osmotic pressure the one that pulls towards the capillary depends on the number not the size but the number of osmotically active particles in the fluid I.E how much albumin have you got hydrostatic pushes flow to the outside of the vessel which depends on the volume of the plasma in the vessel uncortic pressure is the pressure that pulls fluid towards the capillary vessel and this depends on how much albumin you've got the story of the stalling forces applies to the kidney filtration and to capillary filtration today we're talking about the kidney filtration the net result is always 10 millimeters of mercury three so let's go in order for the flow to leave the afferent arterial and go towards the nephron the forces that push have to exceed the forces that pull so that the end result is to move in this direction hashtag filtration I get it medicosis you mean to say that the forces that favor filtration will exceed the forces that oppose filtration by a value of 10 millimeters of mercury right that's exactly right you want to do some math let's go capillary hydrostatic pressure is about 60 millimeters of mercury this is a favoring Force because it pushes fluid towards the nephron how about this another favoring Force but it happens to be zero this is the Bowman's oncotic pressure you know why because there is no albumin in the nephron because it was never filtered it is too big and it's negatively charged duh these were the favoring forces let's talk about the opposing forces that oppose filtration let's go first one is the Bowman's hydrostatic pressure 18mm limiters of mercury and there's the capillary oncotic pressure thanks to the albumin in the capillary which is about 32 millimeters of mercury let's do some math okay favoring minus opposing what are the favoring I have 60 pushing and I had zero points so forget the zero 60 pushing from here that's the favoring all right minus the opposing we have two opposing forces the 18 and the 32 the 18 is the Bowman's hydrostatic pressure and the 32 is the glomerular capillary oncotic pressure 18 plus 32 is 50. 60 minus 50 favoring minus opposing is 10 millimeters of mercury so the net result is that the fluid is going to move this way which means filtration from the capillary towards the nephron from the glomerulus towards the tubule let's take it to the clinic nephrotic syndrome when your kidney is losing protein in the urine but how many courses you said that protein should not be filtered in normal people protein should never be filtered but if I am sick if I have nephrotic syndrome the kidney is losing protein in the urine when I'm losing protein in the urine what's going to happen to protein in the blood low hypoproteinemia and when I'm losing protein who's gonna pull no one is gonna pull the fluid towards the capillary you lost your pulling force and therefore blood is going to leave the capillary and leak to the outside to the interstitial fluid and you will swell this is the story of Edema which is accumulation of fluid in the interstitial space away from the capillaries here is what happened your kidney was screwed you lost lots of protein in the urine that's not normal protein inside the blood vessel decreased oncotic pressure decreased your ability to pull fluid towards the capillary decreased therefore the fluid is gonna go outside accumulates causing edema now let's talk about this nephron proximal tubule let's go if you remember my videos about the digestive system we had trans cellular route and paracellular Route if molecules are passing through the cell this is Trend cellular between cells is paracellular paracellular is always passive transcellular could be active or passive if you've watched my previous video you know that cell membrane transport is either passive no energy needed or active energy is needed passive happens along the gradient active happens against the gradient let's talk about this passive diffusion all right it's passive no energy is needed do we need a carrier well most of the time no it's called Simple diffuse sometimes they do it's called facilitated diffusion how about the active well I always need a carrier and I have two types primary active transport and secondary active transport in primary active transport the energy is liberated here secondary active transport does not burn energy but depends on the energy produced by the primary active just like this just like this do you remember the active transport yeah we had primary active and secondary active do we have primary active transport in the proximal tubule yes how about secondary yes do we have some vesicular transport yes we have some pinocytosis Pino in the proximal for proteins and peptides for the next segment to make sense to you please watch my video on absorption in the digestive system which will be found here in the biology playlist before watching the next part here is the primary active transport here is the secondary active transport remember when I told you to focus on the sglt sodium glucose co-transporter does anyone remember my videos on the digestive system yeah especially in the one titled absorption so let's get started we have two main functions for the proximal tube the first function has nothing to do with acid base the second function has to to do with the acid-base balance let's start with the first function all right as always there is a primary sodium potassium atypase here why because the kidney follows Grandma's rule of handling money do not overspend save save save do not spend money unless it's necessary the kidney follows the same rule the kidney only spends energy once here at the primary sodium potassium 80 base at one border only which is the basal lateral border everything else is dependent on this one time spending sodium potassium atpase let's go we will reabsorb sodium to the blood we will secrete potassium towards the tubular cell sodium is leaving the tubular cell leaving the tubular cell leaving the tubular cell which decreases the level of sodium inside the tubular cell now all of a sudden there is more sodium in the tubular fluid than in the tubular cell oops creating a concentration gradient so sodium is gonna flow downhill passive diffusion along its electrochemical gradient do we need ATP for this no this is passive simple diffusion no energy needed no ATP needed no carrier needed at the apical border now contrast that with what happened at the base lateral border we actually did spend energy which was necessary why because it created a gradient on the apical border sodium is going downhill taking glucose with it uphill secondary active transport y active because glucose is against gradient why active because this is dependent on this this is secondary active secondary to the primary sodium potassium atypase hay sodium you are already going downhill why don't you take some glucose with you sure I'm going downhill I'm going to take glucose uphill for the glucose what should I call this carrier sodium glucose co-transporter sglt sodium glucose transporter number 2. the mnemonic is sglt2 is number two secondary active why because you have two kidneys the one found in your intestine was also sglt but not two one is in the gut two is in the kidney two is in the tubules of the kidney okay medicosis will I only reabsorb glucose together with sodium now sodium is the hero sodium can take any one with them I can take glucose against gradient amino acids calcium bicarbonate any good stuff can be absorbed here baby this is awesome now tell me what's going to happen for the glucose later on the basil lateral border well we only need a carrier but there is no need for energy oh so this is facilitated diffusion and not secondary active transport yeah because diffusion is passive but transport is active and these are some very difficult questions on your exam hey what's the mechanism of glue too what kind of Transport facilitated diffusion do we need energy no do we need a carrier yes and this was the of glucose absorption and the basol lateral border of the proximal tubule contrast that with sglt2 what are we doing reabsorbing glucose at which border apical border what kind of Transport is that secondary active transport do we need energy yes we do do we need a carrier yes we do all of this was reabsorbing the good stuff the glucose the amino acids the sodium Etc how about dumping the bad stuff sure the proximal tubule will do this for you dump the uric acid oxalic acid bile salts and paramine hyperic acid all of them will end up here in the tubule and they will end up in the urine next story is the story of the acid base in the proximal tibial let's go carbon dioxide is everywhere yeah go back to the glycolysis and the TCA cycle and biochemistry they release carbon dioxide like mad carbon dioxide is a product of metabolism you find it everywhere and you find water all over your body sixty percent of your your total body weight is water carbon dioxide plus water before you know it this is carbonic acid you can thank the enzyme Carbonic anhydrase because Carbonic I act on a carbon anhydrase N means no Hydro means water I'm going to remove the water from here and give you a molecule that's not wet that does not have water and hydrase Brilliant this carbonic acid will then dissociate into bicarbonate which is a base reabsorb the base please and hydrogen ions which are acids secrete the acid please why do you want to reabsorb the base and secrete the acid for a very simple reason your metabolism naturally secretes acid if I leave your metabolism alone you will die from acidosis too much acid how come my metabolism secretes acids remember pyruvic acid lactic acid oxalic acid all of these are acids oh that's why the kidney is trying to balance the issue I'll reabsorb the base so that you get some Alkali there so that you do not die from acidosis so that your normal blood pH becomes slightly alkaline 7.4 which is protective against the metabolic acids and I will dump the acid into the trash primary active transport is still here the primary sodium potassium antibase secondary to the energy liberated here there is a secondary active transporter also known as sodium hydrogen exchanger or sodium hydrogen antiport we're done with the proximal tubule let's talk about the loop of henle descending segment ascending segment the descending is thin all the way the ascending has thin ascending and then it becomes thicker descending lamp permeable to water what is going to leave the tube leave leave and it will go to the middle area interstitial space water is leaving all right awesome what do you think is going to happen to the fluid inside it is getting more concentrated because because water is leaving sodium is staying in the tube is getting more concentrated I started with an osmolality or a concentration of 300 as you go down it's getting higher 400 500 600 700 800 until each the Zenith the apotheosis which is 1200 milliosmos this is the most concentrated urine that your kidney can ever produce but as you go up the ascending limb the opposite is happening water is staying sodium is leaving oh I'm getting more diluted than 1200 1100 1900 800 until you reach 100 and this is about the most diluted urine that the kidney can ever produce that's why they call it the counter current mechanism I'm getting more concentrated going down I'm getting more diluted coming back up the descending limb is permeable to water impermeable to Salt conversely the ascending limb is permeable to Salt impermeable to water permeable to Salt how we have a beautiful beautiful carrier here called sodium potassium two chloride co-transporter it reabsorbs all of them together one positive one positive two negatives to maintain the law of Electro neutrality so that you have two cations and two anions the equation is balanced you want something neat the reabsorption of sodium here is what attracted the water over there why do you think this water is leaving because it's getting attracted to the sodium because water loves to follow salt it's called osmosis Cody now pause and review the descending limb is the concentrating segment the ascending limb is the diluting segment counter current multiplier the thick ascending limb contains the carrier protein known as 1 sodium one potassium two chloride this is the thick ascending limb at which border at the luminal border one sodium one potassium two chloride what do you call it I am sodium potassium two chloride co-transporter because all of them are going the same direction it's not an anti-port it is a co-transport is this secondary or primary secondary active secondary to what to the primary Act of sodium potassium antibase which is found in every single stinking cell in your body and the kidney it's always found on the basal lateral Border in the thick ascending limb of loop of henle sodium is getting reabsorbed chloride is also getting reabsorbed if you are reabsorbing sodium and chloride water is going to follow it's called osmosis and potassium is mostly reabsorbed as well plus reabsorption of calcium magnesium and bicarbonate we're done with the proximal we're done with the loop of handling let's talk about the distal convolutibule and the acting Ducks you can divide the digital converter tibial into an early part and the late part the late part is exactly similar to the collecting dots the distal convoluted tubules and the collecting ducts contain two main cells the principal cell and the intercalated cell who do you think is more abundant the principle cells that's why we call them principle where do you find the principal cells in the collecting ducts how about the alpha intercalled collecting ducts and part of the distal as well why do you call this principle cells two reasons they are the more abundant and hormones principally act on this part of your nephron what do you mean I mean aldosterone and antidiuretic hormone to understand the difference between aldosterone and antidiuretic hormone referred to my previous video titled ADH versus Aldo in a nutshell alduri absorbs salt and water this is obligated water ADH reabsorbs only water this is free water here because it's free it does not have to follow any electrolytes all right Miracles how about the alpha integrated cells they have one job in life acid base balance let me reabsorb bicarbonate to counteract the acidity caused by your metabolism and let me dump the protons in the trash distal convoluted tibial here's the early part and as you know the late part of the distal is very similar to the collecting so we will lump them together in the early part what do you have here well well well sodium and chloride are getting reabsorbed that's fine pth can help us here as well all right why not parathyroid hormone reabsorbs calcium if you remember because parathyroid hormone has one job in life to raise calcium in the blood and to dump the phosphate too late distal and collecting all right principle cell and Alpha intercalated cell principal cell your hormones will principally act here what do you mean I mean aldosterone and ADH aldosterone reabsorbs salt and water it will also secrete potassium and hydrogen if you remember oh if you're secreting hydrogen you are anti-acidity and therefore you are pro alkalosis you will reabsorb the bicarbonate since you are reabsorbing the bicarbonate and this is negative you have to dump something negative oh that's the exchange right hashtag Electro neutrality a negative for a negative a base for an acid reabsorb the base dump the acid genius dump the acid oh this is hydron plus NH3 together they are nh4 add some chloride to them where did it come from from here and you get ammonium chloride which we talked about early in this video they call this titratable acidity for Regions that are beyond the scope of this video just remember that this is one of the methods your kidney gets rid of the acid of the protons by throwing them in the trash in the form of ammonium compounds all of this was Mr aldosterone reabsorbed salt and water secrete potassium and hydrogen how about 88 83 absorbs free pure water water alone water without electrolytes free water here is ADH also known as vasopressin vasopressin is going to act on the V receptor V1 or V2 V2 because you have two kidneys and we're talking about kidney tubules all right V2 is in the kidney and this water is free to live free to choose this is free facultative water not the obligated water to understand the difference between free water and obligated water check my video on ADH versus aldosterone and here is aldosterone just to remind you remember the renin Angiotensin aldosterone system yeah what were the functions of aldosterone it acts upon the principal cells in my distal cell tubules and collecting ducts and will tell them to reabsorb salt and water but secrete potassium and hydrogen this is how the kidney is a major regulator pause and review we were just scratching the surface if you want to take it to the pro level download my renal physiology course on my website medicosisperfectness.com to get into more details if you want the pharmacology of the kidney download my cardiac pharmacology course on my website no subscription required you can download it once and retain it for you forever no pun intended thank you for watching please subscribe hit the bell and click on the join button you can support me here or here or click the thanks button under this video go to my website to download my premium courses be safe stay happy study hard this is medicosa's Perfect Nails where medicine makes perfect sense