Excretory system : Kidney - Part 2

Summary

Highlights

• 20% of plasma is filtered through the kidneys as part of the GFR. 🌊
• Filtration occurs at an effective pressure of 10 mmHg despite the blood entering at 60 mmHg due to opposing pressures like oncotic pressure. 💧
• Maintaining blood pressure is crucial for adequate kidney filtration; low blood pressure can stop urine formation. 🩺
• Kidney stones can block urine pathways, increasing pressures and halting filtration processes. 🚧
• The kidneys reabsorb necessary nutrients but filter out waste, maintaining a balance. 🔄

Key Takeaways

• Kidneys filter around 20% of plasma as part of the glomerular filtration rate (GFR). 🌊
• The effective filtration pressure is about 10 mmHg, despite the blood pressure being higher due to opposing pressures. 💧
• Creatinine levels in blood reports can indicate kidney efficiency—important for diagnosing issues. 🩺
• Kidney stones can obstruct urine flow, increasing capsular pressure, and stopping filtration. 🚧
• The kidney selectively reabsorbs essential molecules like glucose, amino acids but filters out wastes like creatinine. 🔄

Overview

Chapters

• 00:00 - 01:00: Introduction and Objectives The chapter opens with background music, setting an introductory tone for the series. The primary focus of this chapter is to present an overview of the topics that will be covered. It outlines the main objectives, providing a roadmap for the lessons to follow. This introduction aims to give the audience an understanding of what to expect, highlight key themes, and create a foundation for deeper exploration in subsequent chapters.
• 01:00 - 04:00: Blood Flow and Filtration The chapter begins with an interactive session where the instructor asks about Proto sites (also known as podocytes). The students are encouraged to speak freely and multiple responses are recorded simultaneously. The instructor acknowledges correct answers and praises contributions. The term 'Proto sites' is clarified as cells, specifically in the context of their role in blood flow and filtration within the body. The chapter seems to focus on understanding how these cells function and their importance in the broader physiological processes related to blood regulation. The instructor then transitions to address a complex question related to these topics over a specified period.
• 04:00 - 07:00: Filtration Process Explanation The chapter explains the filtration process of blood in the kidneys. It discusses the amount of blood flowing through the kidneys per minute and specifically how much of this blood is filtered. The transcript mentions that the combined blood flow through both kidneys is approximately 1100 ml per minute. The speaker uses a jar as a metaphor to aid in the explanation.
• 07:00 - 11:00: Nephron Functionality and Pressure Dynamics The chapter discusses the process of measuring nephron functionality and understanding pressure dynamics in the kidneys. It begins by visualizing a scenario where 1100 mL of blood is placed into a jar, representing the amount that flows through both kidneys in one minute. The conversation continues with an explanation of centrifugation, a method used to separate the components of blood, including hematocrit which consists of red blood cells (RBCs), white blood cells (WBCs), and other particulate matter. This setup provides a framework for exploring kidney function and blood filtration dynamics.
• 11:00 - 14:00: Molecular Processing in Kidneys In this chapter, the focus is on the molecular processing that occurs in the kidneys. The discussion begins with a basic introduction to blood components, specifically the separation of plasma and hematocrite when blood settles. The example provided uses 1100 mL of blood, showing that approximately 500 mL will consist of cells (hematocrite), while 600 mL will be plasma. This demonstrates a typical blood composition ratio of 55% plasma and 45% hematocrite, with a slight margin of variation by 1 or 2%. Understanding this basic separation is crucial for comprehending how the kidneys process and filter blood at the molecular level. The chapter will further explore the roles of these components, particularly plasma, in kidney functions.
• 14:00 - 18:00: Creatinine Role and Kidney Health Notes The chapter discusses the blood flow through the kidneys, focusing specifically on plasma flow rather than blood. It questions how much plasma flows through the kidneys together in a minute, which is established as 600 mL. The teaching seems to involve a step-by-step explanation emphasizing the distinction between blood and plasma flow.
• 18:00 - 22:00: Proteins and Osmotic Pressure This chapter discusses the relationship between proteins and osmotic pressure, focusing on the filtration of plasma. Out of 600 mL of plasma, approximately 20 mL gets filtered. The filtered plasma lacks large proteins, which are normally present in the unfiltered plasma. This suggests that osmotic pressure is influenced by the presence or absence of large proteins in the plasma.
• 22:00 - 25:00: Low Blood Pressure Effects on Filtration The chapter titled "Low Blood Pressure Effects on Filtration" discusses the relationship between the glomerular filtration rate (GFR) and plasma flow through the kidneys. It explains that about 120 ml of plasma is filtered per minute, which constitutes 20% of the total plasma flow through the kidneys, emphasizing the significant role of GFR in the filtration process.
• 25:00 - 27:00: Kidney Stones and Health Implications The chapter discusses the importance of filtration in the context of kidney stones and health implications. The process of filtration is highlighted, emphasizing the need for the blood to maintain a specific pressure upon reaching the Bowman's capsule. The required pressure is 60 mm Hg to ensure effective filtration, which is supported by maintaining a blood pressure level of 120/80 in the aorta.

Excretory system : Kidney - Part 2 Transcription

• 00:00 - 00:30 [Music]
• 00:30 - 01:00 do you remember what are pyes what are pyes what are pyes everybody can talk at the same time I'll follow what are Proto sites they are they are cells very good excellent protes very good very good now what I'll do is we are trying to address a very inter the question is over a period of 1
• 01:00 - 01:30 minute how much of blood and out of that how much is filter okay so how much is filtered how much is not filtered okay so uh the literature tells us that combined blood flow through both the kidneys is about how much 1100 what ml per minute okay so what I'll do is I'll take a jar are you with me
• 01:30 - 02:00 take a jar and in that jar I'll put 1100 mL of blood okay all right we are okay so far and I'll look at that blood and I tells myself that this is the volume of the blood that is going to flow through both the kidneys over a period of 1 minute okay now what I'll do is I'll centrifuge all that quantity whatever it is and as a result of centrifugation for 10 minutes then the hematocrite you get that word hematocrite which consists of rbcs and wbcs and all the the particulate matter
• 02:00 - 02:30 which will settle to the bottom okay and the plasma will remain to the top so when I do it for the 1100 mL of blood I get the hematic crate of about 500 ml is cells and about 600 mL of plasma that's about approximately ratio are you with me so far generally 55% is the plasma and 45% is the hematocrite okay so far give and take one or 2% so how much of plasma I have now 600 mL how much
• 02:30 - 03:00 how much 6 so over a period of 1 minute how much of plasma is flowing through the two kidneys put together plasma plasma how much of how much of blood is Flowing blood again go back how much of blood is the of 1 minute okay now I don't want to talk in terms of blood I want to look at the same thing we're talking terms of plasma so how much of plasma flowing through it 600 good how much of how 600 mL
• 03:00 - 03:30 plasma out of that 600 mL of plasma I find that the filtered amount filtered amount is about 20 ml is about how much so 600 minus 120 is the amount of the plasma that will just come and go okay and about 120 ml of plasma okay the liquid part I cannot call it absolute plasma because now that that filtered part doesn't contain large proteins are you with me
• 03:30 - 04:00 so it contains but it contains lot of but how much quantity it is it is about 120 ml per minute which is about 20% of the plasma filter so out of 600 120 that is 20% are you with me so what is the message we have okay out of the total amount of blood that is total amount of plasma that is flowing over both the kidneys about 20% of plasma and I'll call that as the glomer filteration rate are you with me so far what will I call it as GFR or glomular filtration
• 04:00 - 04:30 rate okay now this is extremely important because this is actually filtration is happening okay this is the filtration happening and for that filtration to happen Okay I have to make sure that the blood as it arrives in the bman capsule should have the pressure of how much 60 very good how much 60 MH for to keep that 60 at the level of aorta I should have 80120 80120 when at the level of aite is 120 by the
• 04:30 - 05:00 time the blood flows through arteries smaller arteries arterials da da da finally it goes to it goes to the bman capsule it has come to 60 where the blood is entering the blood pressure is about 60 and uh at that blood pressure how much of filtration I'm getting I'm getting about I'm getting about 120 ml of plasma per minute are you okay so far good now remember this and we'll move ahead now let's see what happens to the filate this a cartoon that shows you the I'm sure you can appreciate the the uh
• 05:00 - 05:30 nephron there there the diagrammatic view of the Nephron and then you can see the blood is coming and the blood is getting filtered plasma is getting filtered and whatever is unfiltered is going and then it is going into uh into the so there aant arterial eant arterial the peritubular capillary Network and then it is somewhere here that de oxygen will be given deoxygenated and deoxygenated blood will flow into the into the renal finally into the renal AR renal veins and renal venes good good good so again going back just tell me what will you what pressure do you
• 05:30 - 06:00 expect in this vessel there loudly everybody 60 MH and how much of pressure do you expect in the vessel that takes the blood away from there 59 how much is it 59 by the time the blood has flown through an enriched capillary Network it is in the what you call as a peritubular we the diagram we have seen yesterday by the time it has come here the blood pressure has fallen to about about less than that about 15 15 16 20 that range the the the blood pressure is and by the every time it goes here it has further fallen down to
• 06:00 - 06:30 5 6 7 8 okay remember these pressures good now this tells us something very interesting look at the number one there which is very simple and straightforward that is what that is 20% of the GFR are you with me number one that is just the filate that is that's a filtration that's of filtration that's happening the fluid that is passing by the side of the phocytes okay and which contains all the small ions small molecules no large proteins and and then by the time the and then this is the uh this is the rest
• 06:30 - 07:00 of the nefron ascending descending whatever let's not bother and then we find that lot of things are being look at the arrow number two very important that lot of things are being reabsorbed means lot of things are filtered okay and lot of and lot amongst them are being what reabsorbed secondly look at the point three lot of the substances that that are already in the blood which did not Escape which escaped being filtered there okay they're being actively secreted from the blood into
• 07:00 - 07:30 the tubule so there are two Avenues by which the substances in the blood can get into the tubule one they can be filtered and number two they can be actively secreted at the level of what peritubular network it can be secret into the into the tubules and then fourth of course is the is the is the urine urine that is now very simple what you are getting at one whatever you are getting at one is it urine no it's not urine
• 07:30 - 08:00 it's actually filter plasma minus large proteins largely okay that's it's plasma it's still plasma okay it is it that plasma when it is being acted upon by the urinary tubule as it goes as you can see in step two and three there's lot of processing happening okay and then finally by the time it reaches the pelvis and the Urus that you get is a urine okay so a lot of processes happening into the and that that's what we are going to talk about today and in the next there's a lot of processing is going to happen we'll call this
• 08:00 - 08:30 filtrate many people like to call it as pre urine are you get the language okay it's it's something that will give rise to urine eventually but that's not urine proper now this is an interesting diagram that tells us as to how the kidney has got to capability of identifying different molecules and treating them separately every molecule has its has its character has its personality I can use that word every molecule has it and the kidney cells are able to dis distinguish them on the basis of so
• 08:30 - 09:00 let's see look at the one in a the kidney is looking at the molecules which fall in the category a and they are the waste product waste product like creatinine now creatinine I'm using the word again creatinine remember this word it will come down two slides creatinine what word did I say remember this word creatinine like substance which is a waste will just filtered will just go through is it being reabsorbed look at the diagram and tell me look at no it is not being reabsorb good now let's go to B in the B what do you have electrolytes
• 09:00 - 09:30 the moment I say sodium potassium are with me whatever the electrolytes electrolytes are being filtered okay and then look at that diagram are some of the electrolytes being being reabsorbed are some of the electrolytes being discharged through the urine yes look at the figure C in the C1 amino acids and glucose look at the figure C are they being filtered yes are they being absorbed all of them all of them why all of them is needed nutrition because you
• 09:30 - 10:00 don't want glucose to lose you don't want you don't want the glucose to be lost through urine okay if you do that you are a DI diabetic okay so you make sure that that that that whatever is filtered Amino is filtered back and substance D is drug metabolites okay we don't want them okay and there metabolites which are which are of course filtered they are small molecules they can be filtered and those which are not filtered are actively secet actively secreted from the blood into the UR so they are thrown out the
• 10:00 - 10:30 body doesn't want them are you with me now let us see as to how does the how does the system deals with it in a quantity yeah why is creatinine not actively secret into the UR why is creatinine not actively secreted it it is shown as a which is just filed but not secret okay it is it is not it is not the property of the the the the the peritubular that's a good question the cells of the peritubular capillary are not equipped with a system to to selectively secret that Mo to secrete
• 10:30 - 11:00 that actively transfer the molecule from the cells into the space and then and and extracellular space and then into the urinary tibule it is not possible for the system to handle that molecule that way so what it does is filter the blood again again again again so let it be thrown out but only by way of the ultra filtration at the level of bomas capsule got so let's see uh what is this table about we are talking about different molecules they are being filtered okay and uh let's see uh glucose okay glucose what is it G per day okay what about glucose how how much
• 11:00 - 11:30 is the amount filtered 20 G there a lot of lot we 2 25 I'm sorry 24 hours how much how much both the kidneys are filtering 180 180 g of glucose and how much reabsorbed all of it all of it okay if if you are a diabetic then it would be something less than 180 or whatever or or or because you have more blood sugar that 180 may be 280 depending on what graduation of diabetic you get my word
• 11:30 - 12:00 graduation nobody smiled okay then you have so zero bicarbonate 4 4,300 a little is excreted sodium 25,000 something reabsorb 25 something about 150s so some is there some sodium now okay okay okay now look at sodium sodium 25565 150 is excreted now go back to the experiment which we did yesterday what was the experiment you suddenly your sodium intake was what was what was it was increased by 10 hold so what would happen there in this particular case
• 12:00 - 12:30 that 25,000 will go 25,000 will go to I don't know 50,000 60,000 whatever okay the amount reabsorbed will be very low hello whereas the amount excreted from 150 it may go to$ 25,000 I don't know the figure it will be very high okay because now your your your kidney is making sure potassium UA and then let's go to again creatinine okay I'll come to that in next slide it's 1 Point amount filtered is 1.8 G per day uh nothing is reabsorbed okay whatever is filtered is
• 12:30 - 13:00 completely thrown out and therefore amount excreted is 1.8 okay now let's talk about creatinine listen to this this is interesting particularly two organs of our body namely the skeletal muscle and the Brain okay these are again two of the very expensive organs expensive in terms of what ATP ATP is very high okay now let us focus on muscles okay now muscle the moment okay okay uh you you are taking rest and then you start exercising see
• 13:00 - 13:30 the amount of you see every cycle when I mean by cycle I mean I mean AC m in cycle are you with me ac m in cycle with every cycle you are going to use 1 ATP 1 ATP every cycle and there thousands of them thousands of them so you your your your utilization of ATP is very high and it's not possible for mitochondria to supply all that DP at the speed at which you using it get the problem okay
• 13:30 - 14:00 therefore the Nature has come up with an amazing solution and the solution is that these two organs are equipped with yet another molecule called as creatin what was the earlier word I told you now now I'm telling you new word what is the word creatin now the creatin word creatin molecule has an interesting property that it can easily get phosphorilated it can easily so it becomes what creatin phosphate what does it become it becomes creatin phosphate good good good good so whenever you are testing and whenever you are not there's
• 14:00 - 14:30 not much burden on your ATB Supply the creatin becomes creatin phosphate so you have sort of reservoir are you with me you have a sort of what Reservoir and the moment you start exercising and the moment your need for ATP suddenly goes up that phosphate okay that phosphate okay okay let me go back so you are suddenly doing exercise so you are using ATP and you are giving ADP ADP is there now suddenly too much ADP is there you are exercising are you with me so far now suddenly that
• 14:30 - 15:00 ADP will take that phosphate from creatin and itself become ATP so what has become now that creatin phosphate has now become creatin so that creatin molecule is a very loose Bond it can take phosphate give phosphate take phosphate give phosphate depending on the available when available make yourself creatin phosphate when it is in poor Supply give it away to ATP and ADP make it ATP so that ADP ATP can again is available for a muscular for muscle contraction to take place are you with me now when so that that's what is happening creatin okay ATP ATP it's a
• 15:00 - 15:30 reversible reaction and it's convert to phos so your phosphor creatin creatin phosphor creatin never mess up is a buffer is a reservoir for however creating phosphate over a period of time that molecule you see in biology everything breaks down and finally when it breaks down that molecule is called as creatinine what is it called as so creatin molecule eventually it comes it serves and it breaks down when it breaks down that new form of molecule is called
• 15:30 - 16:00 as what say that again creatinine say that loudly creatinine okay we are not going to mess up creatinine creatin I'm sorry creatin is very useful creatin now creatinine is a relatively waste molecule okay and therefore when it is filtered it is not reabsorbed we want to get rid of okay and and but but there is continuous um our body is continuously
• 16:00 - 16:30 generating and we are continuously losing it through your continuously throwing it out of our body okay as a result of that I'm going to ask you a question beware of that as a result of that I take your blood sample moment and I find that and from the blood I separate serum and I I I subject that serum to analysis of creatin me and I find that your concentration of creatin can you please read for me [Music]
• 16:30 - 17:00 7 to how much that's a remage okay now now I'm telling you something anytime you see blood pathological report of anybody including yourself okay and if you have just do random sample I'm absolutely sure the paolog is going to report on the level in your blood okay make sure that it falls in this range now if you find that this is creatinine in a particular report is exceeding going to one 1.4 uh 1.4 1.8 2 2.8 it means
• 17:00 - 17:30 what it means what kidney is not working properly kidney is not working very good it is it's it's efficiency in getting clearance of creatinine is going down but but you absolutely absolutely correct the kidney is a problem are with okay why am I hammering this on you I
• 17:30 - 18:00 want the moment you see anybody's blood report anybody's blood report okay I want you to go to what what what parameter and look for what level and make sure that it is in what range that's it that's it that's it anything anything more than that okay the Bell should start ringing that there could be something wrong with uh the kidney okay okay we are we are back to our problem of uh uh filtration of blood and I'm sure you can
• 18:00 - 18:30 appreciate we have the Bas capsule there the glomerulus is there and offer the author has taken a tiny rectangle okay from there which is the which is one of tiny part of the capillary okay and then the author has blown it up for us and then we are actually focusing on what's happening during ultra filtration and we find that the blood that is arriving over the capillary is at about we have already done it we have already done it we have already done it what is the pressure 60 60 what M 60 MH
• 18:30 - 19:00 okay about 60 MH is the blood it is under pressure but the question is is the blood actually being filtered at that pressure the answer to that question is no the answer to that question is no why no because in the blood there are proteins and those proteins have osmotic pressure and as a result of that those proteins are drawing water from outside are you with me is it disal water there in the capillary no there are there are a l large number of protein molecules
• 19:00 - 19:30 and they will themselves expert what osmotic pressure and what in what way it they'll attract water okay as a result and how much is that is how much is that it is called as plasma CID osmotic pressure it is also called as oncotic pressure oncotic pressure what is oncotic pressure it is a pressure created by the proteins in the blood because of which it will draw water from outside from outside into the capillary to draw the blood because of osmotic large number of protein molecules there and how much it is it's it's quite large it's quite large how much it is 32 it is
• 19:30 - 20:00 taking the it is it is it is acting in opposite direction therefore author has author has used what what sign negative minus secondly is this you see on the other this the capillary this is the capillary outside the capillary there are pyes and outside that there is space and there's fluid there well that fluid is also exerting some pressure okay that pressure is called as capsular hydrostatic pressure what is it called as capsular Hydro so the filtration has to take place okay
• 20:00 - 20:30 against two forces number one is the anotic pressure and number two number two is what capsular hydr hydrostatic pressure which comes to about how much people have calculated it about minus 18 so effectively 18 + 32 is 50 that is subtracted from 60 so the effective pressure at which the blood is being filtered in the kidneys how much only 10 only 10 that that that 60 can be deceptive it's not at it is not at the pressure of 60 mmhg that the blood is
• 20:30 - 21:00 being filtered the effective pressure is how much 10 10 mmhg now now starting there is 60 starting there is 60 now imagine you have a patient with a blood with with a with a low BP and the pressure instead of being instead of being uh instead of being 8120 okay uh it is 700 are you with me by the time the blood arrives okay at an afferent arterial is is about to enter
• 21:00 - 21:30 into the bomman capsule it has already fallen to 4550 if it already fallen to 50 the effective pressure maybe 2 mm HG 3 mm HG is it good enough it's not good enough it's not good enough okay because the Nature has pro has provided a very little margin just 10 mmh is the effective pressure available in a he kidney therefore therefore the point that I want to hammer is low pressure can be dangerous because if it falls here the
• 21:30 - 22:00 urine formation will stop are you with me and now you know now you know why the union formation will stop if the blood pressure Falls be below a particular limit now kidney is such a yeah can you explain sure sure it is a okay uh it's a cup it's a cup okay now uh the the cup has two walls okay are you with me the uh in the in the inner wall in the inner
• 22:00 - 22:30 wall we have a tough of capillaries okay and they are continuously um the filate is coming filate is going where the filate is going the filate is going in the in this yellow space here the filate is going in that yellow space it's continuously receiving the fluid and it's flowing but the fluid is still there whatever is the fluid there at any given moment it exerts certain pressure done right so where was I okay so so the point that
• 22:30 - 23:00 I want to make is that 10 MH G defective pressure okay okay okay I got I I certainly remember what I wanted to Sir question sir earlier you mentioned about during stying hypothesis the blood entering the cap was at 30 but still fluid moved out because the external pressure was lower but here why is the combination of osmotic and hydrostatic
• 23:00 - 23:30 pressure more than 30 so that like why is it more P there it's lesser ah why is it more here it is more here because this this is a bound volume okay this is a bound volume it is bound by the by the parital membrane of the bomas capsule relatively in the capillary it is relatively an open space okay so it is it is much more easier for the pressure to dissipate there here it is not
• 23:30 - 24:00 possible yeah sure sure I'll talk to you later again if necessary system we learn that re re angiotension mechanism ensures that the blood pressure entering into the kidneys is maintained so when you spoke about low BP patient uh how does the kidney account for that does Pati the answer to that question why is the person sick in the first place lot
• 24:00 - 24:30 of homeostatic mechanisms are not working okay what so so there could be 10 reasons again AL so one of the reasons is I don't know which there are 100 reasons out of which some reasons are there which are applicable as a result of that the person is not able to compensate for the fall in the blood pressure and then and then so so are the J cells not releasing enough amount of raining I don't know if there's not you know enough angot tensing gen there I don't know anyone any one of good reasons are
• 24:30 - 25:00 are the Angiotensin 2 is there but the receptor is not there there are 100 reasons possible because of which the uh because you get because so you don't know what has gone wrong but you have the patient and you see the blood pressure and you see that the uh urine formation is not good enough or whatever so not every blood pressure patient will suffer from oh no no that how is it possible human body is so complicated 100 things can go wrong it's it's just not possible it's just not possible you ask a doctor he will tell you every patient is unique now here is an interesting pathological case we have
• 25:00 - 25:30 all heard of uh kidney stones kidney stones okay as a result of something going wrong with the calcium metabolism then calcium precipitates or urates precipitate and you have a stone formation and here is a diagrammatic picture in which you can see one stone there in the medula one stone here in the pelvis and one stone look at look at this nasty Stone which is sticking right at the mouth of the urer what will happen obstruction obstruction very good
• 25:30 - 26:00 step number one obstruction step number two yeah the the the ultra filtration is happening okay so that hydrostatic pressure will go up hello are you with me that hydrostatic pressure which was about about how muchus 80- 18 or so am I right there that pressure will go up because because the fluid is fluid is coming and there's no way to go okay as a result of that 18 will become 28 it may become 38 and as as a result of that ultra filtration will
• 26:00 - 26:30 stop are you getting the argument and this could suddenly be a very emergency case Okay the stone the stone if the stone just sits there and and just obstructs the passage of urine okay it could be a very serious condition because uh and there's a picture of you can actually literally show the see the stones there okay
• 26:30 - 27:00 [Music] [Applause]