Urinary System Part 2

Summary

In "Urinary System Part 2," Larry Young continues exploring the urinary system by delving into the renal tubules. The video starts by outlining the three main regions of the renal tubule: the proximal convoluted tubule (responsible for significant reabsorption processes), the loop of Henle (known for its descending and ascending branches that aid in salt and water reabsorption), and the distal convoluted tubule (where secretion and regulation of salts occurs). The importance of microvilli in reabsorption and the structure and function of these tubules are highlighted throughout the discussion. This educational session concludes with a preview of the next video, which focuses on filtration processes.

Highlights

• Larry Young breaks down the renal tubules with clear simplicity. Understanding these components is key to grasping the broader urinary system! 🏥
• Each segment of the renal tubules—from the proximal convoluted tubule to the loop of Henle and distal convoluted tubule—holds unique functions crucial for maintaining the body's internal balance. ⚙️
• The proximal convoluted tubule focuses on reabsorbing essential nutrients and water, using a brush border of microvilli for maximum efficiency. 🏄‍♂️
• The loop of Henle navigates through water and salt reabsorption—a nifty physiological marvel that saves resources! 🌊
• The distal convoluted tubule, through hormone action, fine-tunes the reabsorption and secretion process, keeping the body's internal environment in check. 🔄

Key Takeaways

• The renal tubules have three main parts: proximal convoluted tubule, loop of Henle, and distal convoluted tubule. Each plays a unique role in filtration and reabsorption. 🧠
• The proximal convoluted tubule reabsorbs 75% of the lost water and all glucose. It's all about saving resources! 💧🍭
• The loop of Henle features a descending and ascending branch crucial for regulating water and salt balance. It's a loop of wonders! 🔄
• The distal convoluted tubule is where secretion happens, heavily influenced by hormone regulation—quite the balancing act! ⚖️
• The collecting duct's final task is reabsorbing water when necessary. It's like the last safety checkpoint before urine formation. 🚰

Overview

In this fascinating session, Larry Young takes us deeper into the world of the urinary system with a focus on the renal tubules. From the proximal convoluted tubule's diligent reabsorption duties to the loop of Henle's impressive balancing act of water and salt, each segment plays their specific role in making sure our body functions at its best.

The proximal convoluted tubule is particularly notable for its reabsorption of water and glucose, holding a vital position in the nephron's overall structure. Meanwhile, the loop of Henle—famous for its distinctive loop shape—continues the reabsorption job, ensuring our body maintains a delicate balance of essential elements.

Finally, Larry brings us to the distal convoluted tubule and the connecting collecting ducts—highlighting how hormonal regulation impacts secretion and reabsorption processes. As the journey through the renal tubules concludes, viewers get a clear preview of the upcoming topics on filtration and secretion in subsequent videos.

Chapters

• 00:00 - 00:30: Introduction and Overview of Renal Tubules In this chapter, the focus is on the renal tubules, an integral part of the urinary system. It begins with the context of the previous video, which covered the basic anatomy and structure of the renal corpuscle. The forthcoming sections promise to delve into the specific details of the renal tubules.
• 00:30 - 05:30: Proximal Convoluted Tubule The chapter discusses the proximal convoluted tubule, which is a part of the renal tubules in the kidney. It is named 'proximal' because it is the closest region to the renal corpuscle. It is one of the three regions of the renal tubule and plays a crucial role in renal function.
• 05:30 - 14:00: Loop of Henle The chapter introduces the Loop of Henle, a segment of the renal tubules in the kidney, characterized by its twisted and winding structure. The name 'Loop of Henle' aptly describes its tube-like shape and convoluted path, fitting into the broader context of renal physiology.
• 14:00 - 18:00: Distal Convoluted Tubule The chapter titled 'Distal Convoluted Tubule' provides an overview of the structure and function of the distal convoluted tubule within the kidney. It describes the formation of a loop structure, composed of a descending and an ascending branch.
• 18:00 - 21:00: Collecting Duct The chapter titled 'Collecting Duct' discusses the anatomy of the nephron, focusing on the loop of Henle. It highlights the structure and function of the descending and ascending segments of the loop, which are collectively known as the loop of Henle, named after the person who discovered it. The chapter also briefly mentions the renal segments, indicating a focus on the physiological and anatomical aspects of the kidney's filtering units.
• 21:00 - 25:00: Conclusion and Overview of Nephron Functions The chapter provides an overview of the distal convoluted tubules in the nephron. These tubules are defined as distal because they are furthest from the renal corpuscle, convoluted due to their winding and bending nature, and they retain the characteristics of a tube.
• 25:00 - 30:30: Next Topics: Filtration, Reabsorption and Secretion The chapter discusses the three segments of the renal tubules, emphasizing the role of the collecting duct. It introduces the terms 'filtration,' 'reabsorption,' and 'secretion' as upcoming topics and specifies that the collecting duct is not considered part of the other segments of the renal tubules.

Urinary System Part 2 Transcription

• 00:00 - 00:30 hello welcome back to part two of our look at the urinary system and in part two our focus is on the renal tubules all right and so we concluded the last video with a look at the basic anatomy and structure of the renal corpuscle and so this time we're going to focus on
• 00:30 - 01:00 the basic structure and anatomy of the renal tubules for which we know that there are three regions of the renal tubule first region is what we Define as being the proximal convoluted tubule we call it the proximal convoluted tubule because it is the closest to the renal corpuscle hence the name proximal
• 01:00 - 01:30 convoluted because of how twisty and winding it is tubule because well it is a tube um and so that name kind of makes sense right that name makes sense the second segment of our renal tubules is the loop of Henley
• 01:30 - 02:00 we call it a loop because it is just that it is a loop and that Loop is made up of the descending branch because it's going down and it's made up of a ascending
• 02:00 - 02:30 branch because it is heading up and then we've got this thinner section right here which is the loop all right and so the descending the loop and the ascending segments all equal the loop of Headley Headley because it's named after the guy that discovered it and then the third segment of the renal
• 02:30 - 03:00 tubules is this area right over here this is what we Define as being the distal convoluted tubules distal because it is furthest from the renal corpuscle convoluted because it also winds and bends tubule because it is still a tube
• 03:00 - 03:30 and so they are the three segments of the renal tubules the collecting duct the collecting duct which is the sky right here the collecting duct is not part of
• 03:30 - 04:00 the renal tubules it is not a part of the renal tubules in fact the collecting duct is where um the distal convoluted tubule of multiple nephrons will merge to go ahead and deposit uh the filtrate that has now passed through them once that filtrate moves through the
• 04:00 - 04:30 collecting duct and there are last minute Minor Adjustments to the concentration of that filtrate only then does it become urine and so once it goes down through that papillary duct at the bottom of the collecting duct then and only then do we finally uh refer to this um filtrate as being urine all right and I
• 04:30 - 05:00 again want to go back and I want to stress the idea that it is the renal corpuscle in conjunction with the renal tubule and it's three segments the proximal convoluted tubule the lupophenally and the distal convoluted tubule that we Define as being the Nephron all right so that is what we Define as being the Nephron
• 05:00 - 05:30 so I want to go ahead and kind of look at each of these segments um of the renal tubule right they each have their own little differences that can go ahead and differentiate them you've seen some of those differences already when we've looked at the histology and so we know that
• 05:30 - 06:00 um the proximal convoluted tubule and the cuboidal cells that line those tubules look very different than the cuboidal cells that make up um the distal convoluted tubule all right and the the loop of Henley looks completely different as well and there's reasons for that and we'll talk about that so we're going to kind of go start now and move our way through these tubules
• 06:00 - 06:30 kind of looking at their overall characteristics and uh we'll see where we go from there and we'll see how far we can get in this uh in this session so again this is the proximal convoluted tubule and the job of the proximal convoluted tubule is uh basically to reabsorb much of the excess water that was lost
• 06:30 - 07:00 during filtrate all right and so again the job of the job of the proximal convoluted tubule is to reabsorb 75 percent or more
• 07:00 - 07:30 of the Lost water during filtration it is also within the proximal convoluted tubule where 100 percent of the glucose is reabsorbed 100 of the glucose is reabsorbed uh within the proximal convoluted tubule
• 07:30 - 08:00 now we're going to find out that it's not just water and glucose that are absorbed within the proximal convoluted tubule but the majority of the reabsorption takes place right here in the convoluted tubule we're also going to have vitamins and minerals that are going to be reabsorbed here as well and you might have some other byproducts that are are reabsorbed you might even reabsorb some more urea or nitrogen within the proximal convoluted tubule
• 08:00 - 08:30 but the vast majority of what will be reabsorbed is water and glucose and essential vitamins and minerals and so um that is the job of that is the job of your proximal convoluted tubule that is reabsorption all right and it's designed for that it's designed for reabsorption because within the lumen
• 08:30 - 09:00 all right you have these very fine brush borders all right that brush border is made up of microvilli all right that is then sitting on top of the brush border itself and so if you were to look at this even closer you would see that there would be tiny little micro Villi sitting on top of the brush border lining these cuboidal cells and again we have microvilli on this back side as well
• 09:00 - 09:30 because this is where um the capillaries that make up the peritubule capillary bed is going to be located so remember that you've got this network of capillaries that surround the proximal convoluted tubule and the distal convoluted tubule and again that network of capillaries is what we refer to as
• 09:30 - 10:00 being the Perry tubule capillaries all right Parry meaning around tubule means the tubes and so these are a network of capillaries that are surrounding both the proximal and the distal convoluted tubules and so the microvilli on uh the apical surface I'm sorry on the basal surface of these cuboidal cells this here would be the
• 10:00 - 10:30 apical surface lining the Lumen this here would be the basal surface and so that microvilli lining the basal surface is to allow for more interaction within those peritubal capillaries within the loop of Henley we see a transition from
• 10:30 - 11:00 we see the transition from simple cuboidal in the descending Loop to simple squamous in the thinnest part simple cuboidal up here and again in the ascending branch of the loop of henle we go back
• 11:00 - 11:30 to seeing simple cuboidal so in the thickest regions of our Loop of henle we have SIMPLE cuboidal in the thinnest regions of the loop of henle we have simple squamous and there is a practical reason for that once we get into a little bit more of the function all right once we get into a little bit more of the function um what I will give you a hint at is we
• 11:30 - 12:00 have two processes that are happening here at the same time you have saltery absorption that is happening on the ascending side and you have water reabsorption that is happening on the descending side
• 12:00 - 12:30 as well as down here in the loop all right and so you've got water the secretion that is happening all along this area where water reabsorption that's happening all along this area and then the ascending you have salt reabsorption we're going to talk more about that when we get into this in the next PowerPoint and again here you can see those simple squamous epithelia right it is the loop it is the
• 12:30 - 13:00 loop again that is going to be dipping down into the medulla in the cortical Nephron it's a small dip into the medulla and in the juxta
• 13:00 - 13:30 medullary Nephron It's a larger dip down into the medulla in other words more of the loop extends down and again that's gonna that's gonna make more sense once we get into a little bit more of the function uh
• 13:30 - 14:00 of the loop of penalty coming up in the next video the distal convoluted tubule is next on our list and we can see here the distal convoluted tubal once again is located over here at this end all right um cuboidal epithelia simple cuboidal
• 14:00 - 14:30 epithelia once again is the primary cell that we're going to see lining the distal convoluted tubule very few microvilli uh and that the cells tend to be more uh Compact and so the the um the nuclei tend to be more pronounced um as opposed to the proximal convoluted tubules and one of the things that we see again here is the
• 14:30 - 15:00 um the simple cuboidal cells of the distal convoluted tubule uh we can see that there are fewer microvilli uh that are present and the other thing I'll draw your attention to is that we also have as a function
• 15:00 - 15:30 here secretion now secretion is very subjective so uh what we have is uh surrounding the proximal convoluted tubule all right we have our this is a horrible trolling I really apologize uh we have our peritubule
• 15:30 - 16:00 capillaries all right and that peritubal capillary that is or capillaries that are surrounding the distal convoluted tubule will depending on um the chemical makeup of what is now in the blood can actually go ahead and secrete back into
• 16:00 - 16:30 the distal convoluted tubule and so when we talk about secretion we're talking about a movement from the capillaries into the distal convoluted tubule whereas when we are dealing with
• 16:30 - 17:00 reabsorption we are talking about going from the distal convoluted tubule back into those peritubule capillaries and so reabsorption is going from the distal convoluted tubule into the capillaries and what I will say is that as of right
• 17:00 - 17:30 now again we'll get into this a little bit more later what is driving whether or not we are doing reabsorption or whether we are doing secretion comes down to hormone regulation and what is regulating that hormone regulation within the distal convoluted tubule
• 17:30 - 18:00 is the macula densa and so the macula densa is regulating the chemical composition whether or not we need to go ahead and do reabsorption or secretion this is where antidiuretic hormone is actin this is where aldosterone is acting and functioning and we're going to talk more about that and what's what's really happening here um a lot of what we've already talked about in the respiratory system and the
• 18:00 - 18:30 digestive system is going to come back into into play here so um I won't spoil all the fun yet we'll we'll leave that here for a few minutes and then of course here is the collecting duct um the collecting duct uh is uh once again made up of cuboidal cells uh the collecting duct is um really functioning in both strata
• 18:30 - 19:00 of the kidney what do I mean by that exactly I'm glad you asked hold on one second let's do blue so this segment up here is in the cortex
• 19:00 - 19:30 but this segment down here is in the medulla and so um whereas the proximal convoluted tubule is all in the medulla and whereas the distal convoluted tubal is all I'm sorry whereas the proximal convoluted tubule is in the cortex and whereas the distal convoluted tubule is in the cortex and whereas the majority of
• 19:30 - 20:00 uh the juxta medullary nephrons are in the medulla all right the collecting duct is split uh and so what we actually see here is in the medulla the region of the collecting duct down in the medulla is where we see a last-ditch effort
• 20:00 - 20:30 for water reabsorption and we'll talk more about that in upcoming videos as well but know that the primary function outside of urine delivery of the collecting duct is it's one last-ditch effort to go ahead and um remove water excess water conserve that water uh from within the urine depending on
• 20:30 - 21:00 again plasma concentration blood pressure and all those other factors that can go into regulating that and so let's go ahead and stop here this is a good place to stop we kind of get a good idea and a good sense of what the overall structure of the Nephron is and and where the functions are happening when we come back with the next video we're actually going to look at the process of filtration
• 21:00 - 21:30 all right we're going to look at the process of filtration um and then we'll also look at in the fourth video the process of reabsorption and secretion so they are our next two videos filtration gets its own video and reabsorption and secretion gets its own video and with that said I will see you guys on the flip side