Urinary System PDF

Good day. This presentation is about the urinary system, which is the major excretory system of the body. So, what are the functions of the urinary system? Number one is excretion. So, the kidneys will remove based products from the blood. So, what are these based products? It could be metabolic byp...

Good day. This presentation is about the urinary system, which is the major excretory system of the body. So, what are the functions of the urinary system? Number one is excretion. So, the kidneys will remove based products from the blood. So, what are these based products? It could be metabolic byproducts of cell metabolism, such as carbon dioxide, other ions, and water. Toxic substances that are absorbed from the intestines, they can be removed as well from the blood through the kidneys. The urinary system is also involved in the regulation of blood volume and blood pressure, how that is through urine production. So, through urine production, the volume of the extra cellular space is controlled or is regulated. That's why it also affects the changes in the blood volume and as well as the blood pressure. The third function of your urinary system is the regulation of the concentration of solutes in the blood, such as glucose, sodium chloride, potassium, calcium. So, these are just examples of the solutes that can be regulated through the function of your urinary system. So, here are the other functions of the urinary system. The specific kidneys can regulate extra cellular fluid pH through excreting variable amounts of hydrogen to help regulate the blood pH. If you remember, the hydrogen will dictate or the amount of hydrogen will dictate the acidity of the blood. So, if there's too much hydrogen, meaning that the blood is very acidic, so the kidneys will be able to regulate the blood pH by excreting the excess hydrogen, making the blood less acidic. The kidneys also regulate the synthesis of red blood cells. If you remember, the kidneys will secrete the hormone erythropoietin to stimulate the bone marrow to produce red blood cells, which is especially in decreased oxygen conditions or hypoxic conditions. Then, the kidneys, to be specific again, it helps in the regulating or regulation of vitamin D synthesis, because once of the steps in the production of the active form of vitamin D involves the presence of the kidneys. So, it's not just in this skin, the kidneys is also involved in the activation of vitamin D. So, if there's a problem in the kidneys, there's also a problem in the activation of vitamin D. So, vitamin D in third controls the blood levels of calcium. The excretory system or the urinary system is a system which mainly functions to cleanse the body of waste products. It is composed of the kidneys, the ureters, urinary bladder, and the urethra. Let's discuss the growth anatomy of the kidneys. So, we have one pair of kidneys. They are found retroperitoneally. So, the kidneys are retroperitoneal organs at the superior lumbar region. So, they are found on each side of the vertebral column. So, they run at the T12 or they run from T12 or the 12 thoracic vertebrae down to the first lumbar vertebrae. So, that's their borders in landmark. The kidney is a bean shaped organ which is the size the same as that of a tightly clenched fist. The right kidney is lower than the left, as you can see in the picture. That's because that is attributed to the presence of the right lube of the liver. So, its size is basically 12.5 by 6 by 2.5 cm. So, its weight is at about 150 grams each. So, here is a picture that is found in your book, again on the kidneys. We have one pair. So, this is the left side and this is the right side. It runs from T12 or the 12 thoracic vertebrae down to the left to the L1 or the first lumbar vertebrae. On top of the kidneys, you can find the adrenal glands. If you remember, the adrenal glands are the ones that would produce your hormones like your epinephrine or epinephrine, especially in the adrenomethala. Then, in the adrenal cortex, you have the mineralocorticoids, sex hormones and the cocorticoids. So, below your adrenal glands or the adrenal glands actually sit on top of the kidney. So, here, then the right is lower than the left because of the presence of the right lobe of the liver. Again, kidneys are retroveritoneal organs. So, if you look at the picture here below, this is a cross-sectional view of the abdomen. So, this is the right side of the abdomen. This is the left side. So, this is your right kidney and then this is the left kidney. As you can see, the kidneys is actually encapsulated or is wrapped around by a connective tissue called the renal capsule, this dark one. This is your renal capsule. Then, immediately beside the renal capsule, there is a layer of adipose tissue or fat. And then another protein, another connective tissue that coats around that fat is called the renal fascia. As you can see, the kidneys are very well protected. It has renal capsule that actually surrounds it. Then, after that, a layer of adipose tissue, then after the adipose tissue, there is another layer of renal fascia. The other term for your renal fascia is called gyrotas fascia, G-E-R-O-T-A. That is another term for your renal fascia, gyrotas fascia. So, again, we have the renal capsule here that immediately covers or wraps around the kidney. This is a layer of connective tissue that surrounds each kidney. Then adjacent to it is a layer of adipose tissue, then another fascia. So, these structures would actually help protect the kidney from any direct term or direct injury. Then, another prominent part that is found in the kidney is the renal high lung, this one. This is found on the medial side of each kidney. This is where the renal artery and nerves enter. This is where also the renal vein, urethra, and the lymphatic vessels would exit the kidney. If you try to cut the kidneys, longitudinally, these are the structures that you will see. So, the kidneys is divided into two major regions. You have the renal cortex, which is the outer layer, and then the medulla, or renal medulla, which is the inner layer. Okay, this one. So, the cortex contains nephrons. So, the nephrons are the structural and functional unit of the kidneys, meaning this is the specific structure where urine formation is happening. So, this is where the urine is formed. It's in the nephron. Okay, so, we will discuss or we will get to know about nephrons in the next few slides. Okay, just know that the nephrons are found in the renal cortex. So, they form urine. Then, below it, or yeah, below it, we have the renal medulla. Okay, so, it contains at about 5 to 12 renal pyramids. So, all the urine that is formed in the renal cortex, they will be drained into the inner region, which is the renal medulla. So, I have made mention about the renal pyramids. Now, these are cone-shaped structures. It's base is located at the boundary between the cortex and medulla. So, this is the base of one renal pyramid. This is another base, another base, okay. And its apex is projected toward the center of the kidney. So, this is the apex, the apex. I know how the apex is here. This is a different structure. This is actually renal papillae. Okay, this is the apex. It's projected towards the center. The urine that is collected here in the renal pyramids will be or will empty into the calyx. Okay, this is your calyx. This is another calyx. This is a calyx. Okay. The renal calyx is a funnel shaped structure that surrounds the tip of each renal pyramid. So, they channel urine from the renal pyramids down to the renal pelvis. So, the renal pelvis is here underneath. Okay. So, the renal pyramids is from the formation or from the union of the renal calyxes or from the renal calyx. So, when the renal calyxes converge, it will become your renal pyramids. So, what we have here, a very important structure. This is the ureter. This is a small tube from the narrowing of the renal pelvis to the urinary, that transports the urine from the kidneys down to the urinary bladder. So, these are just the important structures that I need you to know. Of course, we have here the renal artery that supplies the oxygenated blood to the kidney. Okay, and then we have also have here the renal vein, which transports the deoxygenated blood from the kidneys to the inferior vena cava or to the, goes back to the heart. So, basically, this is how the urine flows after its formation. So, it's formed in the renal cortex because of the presence of your nephrons here. So, let me use another color in the blue. Okay. Nephrons here. So, urine is formed. It drains into the renal pyramids. Okay. What it goes into the renal pyramids, it drains into the calluses or the colleagues. Then it drains to the renal pelvis. Then it goes to the ureter. So, the nephron is the functional unit of the kidney. So, each kidney has approximately 1.3 million nephrons. So, if you look at this picture, this is one nephron, one set of nephrons, and then this is another nephron. Okay. So, each of the nephron consists of the following structures. You have the renal carpussel. Okay. So, please look at the picture. This is your renal carpussel. The other one, this one. Okay. So, the renal carpussel contains the bone and capsule and the glomerulus. So, this is, if you look at the picture on the right, this is like an open structure. Okay. So, you can see here the glomerulus, the red capillaries that is your glomerulus. And then the bone and capsule is the one that surrounds it. Okay. That is, if you open up the carpussel, that's how it looks like inside. So, another structure that is found inside the nephron is your proximal convoluted tube view. This is the proximal convoluted tube view. Then you have the loop of Henry. This entire thing, this is your loop of Henry. Okay. So, you have your thick descending limb of loop of Henry. This is your thin descending limb loop of Henry. This is the thin segment, the thin ascending limb of the loop of Henry. And then this is the thick ascending limb of the loop of Henry. Okay. So, its name is based on the structure of how thick or thin it is or its direction. So, it could be ascending or descending. Then you have here the distal convoluted tube view after. Okay. This is your distal convoluted tube view. And then of course you have the collecting duct. Okay. This is the collecting duct. So, we have two types of nephrons based on the extensions of their loop of Henry. So, we have the cortical nephron and then we also have the joksta medullary nephron. So, the cortical nephrons, it is about 85% of the nephrons in the kidneys are corticale, in classification. We have loops of Henry that do not extend deep into the medallas. As you can see, the loop of Henry is quite superficial here in the renal medalla. Okay. It's just up to here. Okay. And then for the joksta medullary at about 15% of the nephrons. Okay. 15% of the nephrons in the kidneys are joksta medullary in classification. We have loops of Henry that extend deep into the medalla of the kidneys. As you can see, it's a very long loop of Henry. Okay. So, although there are two types of nephrons, their function will still be the same. So, let's go back to the parts of the nephron. So, first is the renal corpuscle. This houses the filtration portion of the nephron. So, meaning this is the part where the actual filtration happens. So, it consists of bone and capsule and the glomerulus. So, if you look at the picture, the bone and capsule is the enlarged end of the nephron, which serves as a double wall chamber. So, this yellow part, this is your bone and capsule. Okay. So, the inner layer of the bone and capsule is lined with podocytes. Okay. It is a specialized cells which wrap around the glomerular capillaries. So, the other term for your glomerular capillaries is glomerulus. Please do not be confused with the terms. Okay. They are just the same. So, this is your podocyte. Okay. They wrap around your glomerular capillaries or glomerulus. The outer layer of the bone and capsule is lined with sepposchemous epithelial cells. So, you can see that in a picture here. These are sepposchemous cells. Yeah. Then we have the glomerulus, which is a top of capillaries that lies within the bone and capsule. So, this is your glomerulus. Okay. These are capillaries. So, this is capable of the filtration, the exchange of ions and other cells. And other molecules. If you look at the closer picture of the arrangement of the podocytes and the glomerular capillaries. So, this entire thing, this entire circle, this is your glomerular capillary or this is your glomerulus and it is surrounded by food processes. The other term for food processes is podocytes. Okay. So, these are your podocytes. Okay. Podocytes actually has the ability to increase the diameter of the pores in between. Okay. So, if this contracts, it will open some of the pores here so the ions can go in and out of the glomerulus. So, it has the ability to decrease the diameter of the glomerulus and as well as it has the ability to dilate the glomerulus. Okay. So, here are the other structures that you need to know when you try to study the renal corpuscles. So, we have the afferent arteriol. This supplies blood to the glomerulus for filtration. So, this is your afferent arteriol. Okay. So, the blood goes here and then the blood enters the afferent arteriol has to go through these capillaries in order to be filtered. Okay. Then we also have your efferent arteriol which transports the filtered blood away from the glomerulus. So, after filtration here in the glomerulus, the blood will go to the efferent arteriol and it will return to the circulation. So, another important structure that you need to know here is your filtration membrane. Okay. So, this is the area where the filtration happens. So, you have the endothelial of the glomerular capillaries. You have the presence of the podocytes and you also have the basement membrane or the glomerular basement membrane. So, if you look at this structure, again, this is a focused version of what's inside or what is happening here inside the glomerular capillaries. So, this is your glomerular capillaries. Okay. So, this is the endothelium of the glomerular capillaries. This is your glomerular basement membrane, the whitish thing here which supports your capillaries and then you also have the podocytes, okay, which controls the diameter of your glomerular capillaries. So, again, it has the ability to constrict the capillaries or to decrease its size. It also has the ability to help dilate the diameter of your glomerular capillaries. Let's try to see how the process of filtration happens. So, as a review, the renal corpuscle consists of a bone man capsule and the glomerular. So, this is where the actual filtration happens. So, the bone man capsule is the enlarged end of an affron, this one, okay, this one, okay, and which is indented to form a double wall chamber. So, the bone man capsule surrounds the glomerulose, which is a network or a path of capillaries. This entire thing, this is your glomerulose. Okay. So, the blood flows from the afferent arterial. So, from the afferent arterial, the blood that needs to be filtered goes to the afferent arterial, then it goes to the glomerulose and then leaves the glomerulose through the afferent arterial. So, fluid from the blood from the glomerular capillaries will pass through this membrane and it will go through the bone man capsule. Okay. So, the passing through of the blood from the glomerular capillaries, then through the inner layer of the bone man capsule, then through the bone man capsule, that is already the process of filtration. Okay. So, the blood here in the glomerulose is being filtered out with this membrane and after filtration, it goes through the bone man capsule. Okay. So, from here from also the fluid or to the filtered fluid is collected in the bone man capsule, then after that it drains or the fluid passes into the proximal convoluted tubule, okay, on the afferent, then it goes to the, this is the proximal convoluted tubule that it goes through the lupofenli, then the rest of the tubules in the afferent. Okay. So, one important structure that you also need to recognize is the jokstav lomerular apparatus. If you look at the picture on the right, so the jokstav lomerular apparatus consists of the jokstav lomerular cells in the maculadenza. So, here the jokstav lomerular cells, these are cells that surround the wall of the afferent arterial and the distal convoluted tubule. So, jokstav lomerular cells are very essential because they release the hormone renin. And renin is a part of the cascade of events that would actually control the blood pressure in the body. So, renin is part of the renin angiotensin-adosterone system, which helps in the controlling of the amount of blood volume and blood pressure in the body. So, with the presence of jokstav lomerular cells, which near the afferent arterial, so any changes in the diameter or in the pressure here in the afferent arterial can cause changes also in the secretion of your jokstav lomerular cells. So, it will also cause a change or cause some secretion of your renin depending on the situation. They just know how, in this case, just know the presence of where the jokstav lomerular cells are located and what is the function of the jokstav lomerular cells, and that is to release renin. For the activity of the renin, we will discuss that in the next few slides. Then you also have your maculadenza, these are cells which are sensitive to the levels of sodium that are entering or that is present in the blood. It also helps in the regulation in the reduction of renin, renin is spelled as R-E-N-I-N. But for the action of renin, we will discuss that in the next few slides. Let's focus on how a glomerulus looks like. If you try to look at it closely, so the glomerulus is composed of fenestrated capillaries. When you say fenestrated, it means that it has small gaps or pores, as you can see here. You have your fenestrated. Meaning that this capillary is very leaky, as long as the blood pressure inside here, or the blood pressure inside the glomerular capillaries will facilitate the filtration process. It's high enough to cause filtration. The visceral layer of the woman capsule consists of specialized cells called podocytes. This is a podocyte and these are the legs of the podocyte. The spaces between the podocytes' processes are called filtration slits. This is where the filtered blood will exit or the filtrate will exit. After being filtered here in the glomerular capillaries, it will go out here and directly into the bone and capsule. This is also another look of the contents of your filtration membrane. It consists of your fenestrated glomerular capillaries. This one. You can see the fenestrate or the holes or the pores. Then you have your basement membrane, the white thing. This holds the capillary together and of course your podocyte cell processes. These are your podocytes. Fluid passes from this capillary through the filtration membrane, directly into the bone and capsule. These are the important parts that I have made mentioned a while ago. The jockstaglimarular apparatus, which is a unique set of a ferret arterial cells and specialized cells. It consists of your jockstaglimarular cells here. The jockstaglimarular cells are a cuff of specialized smooth muscle cells where the afferent arterial enters the renal corpus. It secretes the enzyme renin, which has a role in the regulation of filtrate formation and blood pressure. Macular denta is also an important structure. It lies between the afferent and the efferent arterials next to the renal corpus cell. It's sensitive to changes in the levels of sodium ions. It's not here, but it's here, this one. It's sensitive to changes in sodium ions. If it is able to detect some changes in sodium ions, it will be able to adjust the secretion of renin. After the discussion of the renal corpus cell, let's proceed with the flow of the filtrate within the renal tubules. So again, we have the proximal convoluted tubules, the lipofenlight thin and thick descending limb, thin and thick ascending limb. Then we also have the distalk convoluted tubules and the collecting ducts. So the ones that are highlighted in red or pink, these are simple cuboidal epithelial, and they actively transport molecules and ions across the wall of the left front. Please take note of the key word. No, so if the ones that are in red or pink, Canadian proximal, distalk, collecting ducts, both thick descending and ascending limb, they actively transport molecules. The key word is active transport. For the purple ones or the, yeah, purple ones, like your thin descending limb and your thin ascending limb, they're made up of simple screams epithelial. And with that, because their epithelial is so thin, so the water and solutes can pass through the walls by simply the process of diffusion. There's no need for the usage of your ATP. So let's discuss the blood flow to the kidneys. So let's start with the renal arteries, which is a direct branch of the abdominal aorta. So this is a renal artery, it enters the kidneys. So once it enters the kidneys, it branches out into different branches. So first is your interlobar, sorry, interlobar artery. Okay, this is the artery that is found between the renal pyramids. So this is your interlobar artery, then it branches off into archuate artery here, because it forms an arch between the cortex of the kidney and the medulla. So here, this is your archuate artery, then it branches into interlobular artery here, which projects into the cortex. So it is the interlobar artery that branches off into a ferret arteriole. So if you look at this picture, this is your interlobar artery. This is a closer look of your interlobar artery, then it branches into an a ferret arteriole. So the a ferret arteriole are the ones that will lead into the glomerular capillaries. So it goes here into the renal corpuscle, then it undergoes a process of filtration here, and then it exits or the blood exits via the efferent arteriole, so this one. Okay, so from the efferent arteriole, the blood will go to the peritoneular capillaries, meaning these are the capillaries that surround the tubules. So it surrounds the proximal convoluted tubule, the distal convoluted tubule, and even the loops of any. Okay, here. These are your peritoneular capillaries. So all of these vessels here, okay, that surround your tubules. So one important thing structured that you also need to know is the presence of your vasarecta. The vasarecta is a specialized portion of the peritoneular capillaries that extends deep into the mandala and surrounds the loop of Henley and collecting ducts. Okay, so here. Your vasarecta surrounds the collecting ducts. So the deeper portions or the deeper structures of your peritoneular capillaries, that's your vasarecta. So it goes back, or so blood from the different peritoneular capillaries in the vasarecta will return to, it will return to the interlobar vein that goes back to the archivate vein, then it goes to the interlobar vein, and then it goes back to the renal vein. So basically the vein just corresponds, the name of the vein just corresponds to the name of it. It's counterpartum artery. So what I want you to remember is that it's the flow of blood. Okay, so memory is the flow of blood from the renal artery down to the vasarecta. Okay, or even with the returning of the blood back to the renal vein. Okay, just as long as you know, the order from the renal artery down to the vasarecta, I think you'll be able to know the sequence of its return back to the renal vein, because again, the name just corresponds, the name of the vein just corresponds to the name of its counterpartum artery. So here, let's talk about the faciella genical. So how is urine formed? The primary function of the kidney is to regulate body fluid composition, and that is through the process of urine formation. So basically the urine formation is the sort thing of substances from the blood for either removal or return to the blood. So the most common substances that are removed from the blood through the kidneys and via the urine, that those are your waste products, toxins, excess materials that the body doesn't need anymore in order to maintain or to conserve homeostasis. So urine formation takes place in the left-fronts and it involves three major processes. These processes are in order. So first is filtration, tubular reabsorption and tubular secretion. So let's briefly describe each. Now, first is filtration. filtration is the movement of materials across the filtration membrane into the bone man capsule. So if you look at this image right here, I think I've already made mention about filtration in the previous slides. So let me just give you another graphic representation. So this is your filtration membrane, and then the filtered fluid or the filtered blood has to go through this filtration membrane. Okay, and it will now become your filtration. The filtration is found in the bone man capsule. Okay, so from the bone man capsule, the filtration will go to the... to abuse. Okay, so by definition filtration is just the movement of materials across the filtration membrane. In this first phase or in the first process, there's already removal of the subsets that the body doesn't need anymore. Some of the subsets is only. So I will give further discussion of this process in the next few slides. Then we also have here your tubular reabsorption. In here, the solutes are reabsorbed across the wall of the nephron into the interstitial fluid by transport processes. Okay, so the water is reabsorbed in certain areas of the tubules. Okay, and that is through the process of osmosis. So basically in the process of tubular reabsorption, if you look at the purple arrow, the filtration, some of the contents of the filtration, such as water and other ions, they are being absorbed back into the circulation. Okay, it depends on the conditions. Okay, wherever is the concentrated part, which one has a lesser concentration of sodium, where the sodium goes. Okay, so I will discuss more of this in the next few slides. Then we have the tubular secretion, which is the last step in the urine formation. Here, the solutes are secreted across the wall of the nephron into the filtration. So these are some of the solutes that will bypass the first and second steps. So here, tubular secretion, the solutes are secreted back here to the wall of the nephron. From the capinearies, it goes to the tubules. So we will briefly describe each in the next few slides. So by definition, filtration is a passive process that the kidneys use to remove excess fluid and waste products out of the blood into the collecting tubules of the kidney. So you have to remember that the filtration is a non-selective process. So meaning it's not really as juicy as to what it can allow us to pass through as long as the material is small, or as long as the molecule is small, and as long as the molecule is positive in charge. Okay, please remember that. So the driving force of filtration is the blood pressure. Okay, to be specific, the glomerular capineary pressure. But of course, the glomerular capineary pressure or the pressure inside the glomerulus reflects the pressure that is found in the systemic blood pressure. So as long as your Bp is maintained at the normal level, then the process of filtration is continuous. So you have to maintain your blood pressure at the normal rate, which is at about 120 average over 80. I mean, Hg, okay, as long as it doesn't drop to as low as 60, 50, then filtration process is okay, it's normal. 21% of the cardiac output is set to the kidneys for filtration. Okay, about 180 litters of filtration is formed per day. Only about 1% becomes urine. Okay, so you can imagine the amount of filtrate that is being absorbed. So only 1% of it actually becomes urine. So let's try to talk about the concept of filtration pressure. So this is the pressure that influences the formation of filtrate. So this forces the fluid from the glomerulus or from the glomerular capillaries across the filtration membrane and into the Boman capsule. So this is the proper term. Okay, it's the filtration pressure that forces the fluid from the capillaries to the Boman capsule. This results from forces that move fluid out of the glomerular capillaries into the Boman capsule minus the forces that move fluid out of the Boman capsule into the glomerular capillary. So based on this description, the force that moves fluid out of the glomerular capillary is the glomerular capillary capsule, meaning this is the pressure, sorry, the glomerular capillary pressure. So meaning this is the pressure that is present inside the glomerulus. The force says that move fluid out of the Boman capsule into the glomerular capillary is or are the capsular pressure or the pressure inside the Boman capsule and the colloidal smotic pressure. So let's try to break down each of these pressures in the next slide. Here we have the pressures that were mentioned in the previous slide. The activity of these pressures will dictate the effectiveness of the process of filtration. So you have the glomerular capillary pressure. This is the blood pressure within the glomerulus. So it moves fluid from the blood into the Boman capsule. So if you look at the arrow here, so this is the blood capillary or this is the glomerulus. So the blood here is being moved out of the, out towards the Boman capsule through the force exerted by the glomerular capillary pressure or the pressure inside the glomerulus. So this pressure, if this is increased, this will promote filtration. So this will support filtration. So we have another pressure that we need to study. This is the capsular pressure. The capsular pressure is the pressure inside the Boman capsule. It's very easy to remember. Capsular pressure, the pressure inside the Boman capsule. So it moves the fluid from the capsule into the blood. So this one, so this, if you look at the arrow, the capsular pressure moves the fluid from the capsule or the filtrate inside the capsule into the blood. So it goes to the opposite direction. So this type of pressure will oppose the filtration, will oppose the process of filtration. Okay, so this opposes filtration. So if there's an increase in your capillary pressure, it's very difficult for the filtration process to occur. So another pressure that you need to know is the colloid osmotic pressure, this number 3. The colloid osmotic pressure is produced by the concentration of blood proteins. Okay, so this moves fluid from the Boman capsule into the blood by the process of osmosis. So again, the colloid osmotic pressure is brought about by the presence of proteins in the blood. So the most common protein that is found in the blood that causes or that facilitates colloid osmotic pressure is albumin. Albumin is commonly found here in your the mirror capillaries or any capillaries or in any blood vessels in the body. So if there is an increase in the number of albumin in the blood, it also increased the colloid osmotic pressure. So the colloid osmotic pressure will facilitate the osmosis of water or the osmosis of the fluid from the Boman capsule to the inside of the blood capillaries or inside the glomerulus. So this pressure per se will oppose filtration. Okay, so these two nodes, the capsular pressure, colloid osmotic pressure, if there's an increase in both of these, they will oppose filtration. So the relationship of these pressures is basically summarized by the equation that was showed in your book. So the glomerular pressure or the glomerular capillary pressure should be greater, should always be greater than your capsular pressure and colloid osmotic pressure in order to facilitate filtration. Okay, so if there's an increase in filtration pressure, there's also an increase in the filtrate volume. Okay, there's an increase in the amount of fluid that was filtered and there's also an increase in the urine volume. Because the filtrate eventually, after the process of reabsorption and secretion, eventually this filtrate will become your urine. So how is the process of filtration regulated? You have to remember that the process of filtration is greatly influenced by the pressure inside the glomerular capillaries or the glomerular capillaries pressure. And then the pressure inside the glomerular capillaries also corresponds to the pressure in the systemic circulation. Like say for example, if your BP is 120 over 80, so automatic also that your pressure inside the glomerular capillaries is also 120 mmHg. So as long as the two are constant, then there would be no problem in the process of filtration. However, in the case of circulatory shock or vigorous exercise, so in these two conditions, there is massive fluid loss. Okay, there could be massive bleeding or you could be losing fluid because of exercising too much or sweating too much. So this will stimulate the sympathetic nervous system. Okay, so the sympathetic nervous system would constrict the renal arteries because the body is trying to conserve fluid. Okay, so it will constrict the renal arteries and if there's a decrease or if there is a constriction of the renal arteries here. Okay, here if this is constricted, then there will be a decrease in the blood flow to the kidneys. So if there's a decrease in the blood flow to the kidneys, so there will be a decrease in the formation of filtrate. Because again, no, the blood that goes to the kidneys is decreased. So there is lesser amount of blood that can be filtered out. So there's a decrease in the filtrate formation and this will also subsequently decrease the formation of urine. Okay, because urine came from filtrate. So the autonomic nervous system actually has an influence also in the regulation of your filtration. Okay. The second step in the process of urine formation is tubular reabsorption. So this is a selective, active process of reabsorbing substances from the filtrate in the renal tubule. So this process happens in the renal tubule cell. You already have the clue in the term itself, it's tubular reabsorption. So there is reabsorption of the filtrate in the tubules. So only 99% of the original filtrate volume is reabsorbed and then the 1% enters the peritubular capillaries to form urine. Okay. So in the proximal convoluted tubule, this is the primary site for the reabsorption of solutes and waters. So solutes and water rather. Okay. So these are some of the substances that are reabsorbed in the proximal convoluted tubule. So some of the proteins that leak, you have your amino acids, glucose and some of the fructose that have leaked, as well as your sodium ions, potassium, calcium, bicarbonate and chloride ions. Water is reabsorbed, so at about 65% of water is reabsorbed in the proximal convoluted tubule. Okay. The reabsorption of water is through the process of osmosis. So through osmosis, the water inside the tubules will then do, I'm sorry here, the water inside the tubules will then do go out. Okay. They will go out because they're trying to concentrate the urine. So you have to remove the fluids here, so at about 65% of water is removed in the proximal convoluted tubule. So this is just another graphic representation in this picture. This is just another graphic representation on how the solutes and water is reabsorbed. So again, this is your proximal convoluted tubule here, and then the filtrate flows here, the water, which is in orange arrow. It's reabsorbed through the process of osmosis, then for the green one here. Okay. So some of the solutes are reabsorbed through the process of co-transport, and some are reabsorbed through the process of active transport. For the descending limb of the loop of Henley, so this part, okay, descending limb, right? You focus your attention here. So there is further concentration of the filtrate because 15% of water is reabsorbed in this part. Okay. There's further concentration of urine. Okay. So some solutes are also reabsorbed through the process of diffusion. Okay. But what I want you to remember in this area in the descending limb of the loop of Henley, 15% of water is reabsorbed. So if in the descending limb of the loop of Henley, there is the concentration of urine. In the ascending limb of the loop of Henley, it's the opposite. Okay. So this part here, the square, a rectangular one. The ascending limb of the loop of Henley will try to dilute the filtrate again, but not as much, okay? So it will just try to dilute the filtrate by removing the remaining solutes. Okay. So it reabsorbs the remaining solutes. So in the thin segment of the loop of Henley, this part right here, okay, let me change the color. Okay. Thin segment of the ascending limb of the loop of Henley. This area is not permeable to water. So I've indicated that here, that is not permeable to water, but that area is very permeable to solutes, such as your sodium chloride. So it reabsorbs your sodium chloride, but there is no change in the volume because the water is still there. Okay. It's not permeable to water. For the thick segments of the ascending limb of the loop of Henley, the upper part, that one, it is also not permeable to water, but it can actively transport sodium, okay? The difference down both actually, your thin and thick segments are not permeable to water. Both are permeable to solutes, such as your sodium chloride, but the difference is the transport mechanism. In the thin segment, the solutes are transported through simple diffusion, but for the thick segment, the transport is through the process of active transport, okay? Those are just the things that you need to know how I already simplified this one. So if you look at this photo here, let me clear this up. This is a graphic representation of what happens in the thin segment of the descending limb of the loop of Henley. So in here, there is a smoothest of water because this area will be absorbed 15% of the water, okay? In that is sending limb of the loop of Henley. So here, this is what happens in the thin segment of the ascending limb. You have to remember that this area is insoluble to water, sorry, it is not permeable to water. However, it is permeable to solutes through the transport or through the process of diffusion. Here, this is what happens in the thick segment of the ascending limb of the loop of Henley. So again, this area is impermeable to water, so the water cannot pass through here, as seen here. However, there is active transport of the sodium. So if there is active transport of the sodium, then the potassium and chloride can also diffuse or can also be reabsorbed through the process of co-transport. Okay. So in the distal convoluted tube build and collecting duct, these portions here, okay, focus your attention here. Okay, they remove water and additional solutes from the filtrate. So all the excess water and excess sodium chloride and others on YouTube will be reabsorbed in this area. The reabsorption is controlled by the hormones and the diuretic hormone in a Dosteron. So I believe these hormones are quite familiar to you. These were already discussed in the endocrine module. ABH will reabsorb water. Okay, water. While your Dosteron will be absorbed your sodium, however, it will expel or excrete your potassium. Okay, you remember the action of these hormones. So these are hormones will act on the distal convoluted tube builds and the collecting ducts. The last step in the process of urine formation is tubular secretion. So in this process, there is removal of some toxic substances from the blood directly. So it doesn't have to undergo the process of filtration, doesn't have to undergo the process of reabsorption. So as long as it's very toxic, no, some of the substances are toxic and it undergoes directly through, or it bypasses the first two processes or the first two steps and it goes directly to tubular secretion. So some of these could be excess ions or unwanted substances or metabolic waste products. In some toxins. So an example is your ammonia. Ammonia is a byproduct of protein metabolism. So this is very toxic if it is accumulated inside the body. So automatically it diffuses into the lumen of the nephron. No, and then it will be excreted together with your urine. Okay, so other substances that can be secreted in the tubules for elimination would be hydrogen, okay, which can cause the acidity of the urine. It could be excess potassium, creatinine is also toxic. If in excess, then your excess is tamein and pinnicillin, which is a drug that is excess, so they can be removed as well. So let's talk about the regulation of urine concentration and urine volume. So the kidneys can change the concentration or can regulate the concentration of the body fluids. So if we talk about fluid concentration, it means that it pertains to the ratio of solute and solvent in a solution. So if there's an increase in body fluid concentration, meaning there's an increase or there's a greater amount of solute compared to the amount of solvent in a solution. So meaning there's a lot of salt, there's a lot of sodium, there's a lot of fluoride, potassium, other ions, waste products, et cetera. Other components that are immersed in the fluid, okay, that is for your increased fluid concentration. The opposite thing happens with your decreased fluid concentration. So in the decreased body fluid concentration, the amount of solvent or meaning the amount of water or the amount of blood is greater compared to the amount of solute that is immersed in it. Okay, so that's the opposite thing. So it's like mixing your coffee and your water. So if there's too much coffee, meaning it's very concentrated. So it's very bitter and stuff like that. So the opposite thing happens if there's very less coffee in your drink and there's a lot of water. So there is decreased concentration of coffee in that solution. So just like that. Okay, so in the body, if there's increased body fluid concentration, I say for example, in the case of vigorous sweating, you're sweating too much, you're losing too much fluid. So your body will try to compensate by conserving water. So how does it conserve water? It will increase water reabsorption in the tubules. Okay, so it will increase reabsorption of water in the tubules. So this will result in small volume of concentrated urine. So meaning there's a decreased amount of water in the urine because you're trying to reabsorb it. So what's in the urine would be your solutes and small amount of water. Here the solutes are lost and the water is conserved. So it will decrease the body fluid concentration. Okay, as a result, it will decrease the body fluid concentration because again, you are reabsorbing the fluid. In cases where there is a decreased body fluid concentration, you have too much water in your body. So the kidneys will try to decrease the reabsorption of water because your goal is to try to excrete that excess water. So what your kidneys do is that it will decrease the reabsorption of water. So there is large volume of the urine. So water is lost in this process and the solutes are conserved. So with that, it will eventually increase the body fluid concentration because you are excreting the water and then you're trying to retain the solute. So it will increase the body fluid concentration. So now that's how the body regulates the concentration of body fluids through the function of the kidneys. So these changes or these processes are influenced by three major hormonal mechanisms. You have your renin angiotensin, aldosterone mechanism. You also have your antidiuretic hormone mechanism and you have your E&P or atrial notriuretic peptide hormone mechanism. So let's discuss each. First is the renin angiotensin aldosterone system. So this is one way to regulate the concentration of the body fluids through the function of the kidneys. So this mechanism or this system is sensitive to changes in the BP or changes in the blood pressure. Please remember that sensitive to changes in blood pressure and this is usually initiated in the low blood pressure conditions. So if your blood pressure falls to as low as 80 or 70 or even below that. So it will initiate the activity of your renin angiotensin on the australone system or your ras. So say for example the cystic case there is a decrease in blood pressure in a person. So the cells of the jockstag lomerular apparatus if you remember this is the structure that is found in your afferent arterial. If you remember the structure of your glomerulus like that. If you're afferent arterial there you can see your jockstag lomerular apparatus. So this cells if you remember this is a crete renin which is a hormone. And it will also stimulate the liver to produce angiotensinogen. Both of these you renin angiotensinogen these are hormones. The renin, the activity of the renin is that it will convert angiotensinogen to angiotensin 1. Please remember that your angiotensin 1 is converted to angiotensin 2 through the activity of your angiotensin converting enzyme. Then after you have your angiotensin 2 this will stimulate the adrenal cortex to secrete aldosterone. So if you remember the activity of your aldosterone is that it will stimulate the reabsorption of sodium and chloride and it will promote the excretion of your potassium. So it will increase the reabsorption of the sodium and chloride in the distal collecting to bills and the collecting ducts. Please don't forget that the activity of the aldosterone is directed to the distal collecting to bills and the collecting ducts. So with the reabsorption of your sodium and sodium and chloride the water will follow. So there is water reabsorption. It will increase blood volume and it will subsequently increase the blood pressure. So if there's increase in the volume of course there will be an increase in the blood pressure. So this is just a graphic representation of what I explained a while ago. So this is the renin angiotensin aldosterone system. So this is triggered by or initiated by a decrease in the blood pressure. This is your main stimulus. So if there's a drop in your blood pressure it will activate the cells in your jocstaglomerular apparatus, which is found near your afferent arterioles. No, it will increase the it will stimulate the release of renin, which is a hormone. So it will stimulate the release of renin and at the same time your liver will also produce angiotensinogen. So the renin will act on your angiotensinogen so your angiotensinogen will be converted into angiotensin 1. Angiotensin 1 is converted into angiotensin 2 through the presence or through the activity of your angiotensin converting enzyme. So this enzyme is released from the lungs. So basically your lungs also has a role not in the regulation of your body fluids. It somewhat has a role. So it releases the enzyme called angiotensin converting enzymes. So please don't forget this. So it will convert angiotensin 1 to angiotensin 2. So your angiotensin 2 will act on your adrenal gland to be specific, your adrenal cortex. Your adrenal cortex will secrete the hormone aldosterone. So your aldosterone will act on the kidneys to be specific in the discharge convoluted to bills in the collecting ducts. It will increase the reabsorption of sodium chloride and the water will follow. Angiotensin 2 also has a role or has an effect on the blood vessels. So the presence of your angiotensin 2 can actually cause vasoconstriction. The vasoconstriction can further promote fluid conservation. So it helps in the conserving of fluid. Your vasoconstriction or your constriction of your blood vessels. So basically this is what happens in the renin angiotensin aldosterone system. So another mechanism that will regulate the body fluid concentration is the anti-diuretic hormone mechanism. So this mechanism is more sensitive to changes in the blood concentration. It's different from that with your ras because ras is more sensitive to changes in BP. So again over ADH is more sensitive to changes in blood concentration. So please do not forget about the difference. This is stimulated by a high blood solute concentration, meaning there's too much solute in a particular solvent in a solution. Or there could be very few solvents. So it's very dehydrated status. So your anti-diuretic hormones activity is that it increases the permeability of the distal convoluted tubules and the collecting ducts to water. So this promotes water absorption. So its effect would be water absorption and the kidneys would produce a small volume of concentrated urine. Because again, you're absorbing the water, so fuel in a lung will go to urine. So this is how the ADH is stimulated. So if there's increase in the solute concentration in the blood, action potentials are sent to the hypothalamus. The hypothalamus will stimulate the secretion of ADH in the posterior pituitary gland. And then the ADH will go or will go to its target organ, which is the distal convoluted tubules and the collecting ducts of your nephron. Another mechanism that will regulate the body fluid concentration is the atrial nitriuretic hormone mechanism or your atrial nitriuretic peptide mechanism. So they are just the same. This is sensitive to changes in the blood pressure, just like your ras. No, they are sensitive to changes in blood pressure. However, the difference lies in what triggers that. For your ANP or your atrial nitriuretic mechanism, it is triggered by an increase in the blood pressure. It's different compared to your ras. Ras is triggered by decrease PP. For ANP, it is triggered by increased blood pressure. So this is secreted from the cardiac muscle cells in the right atrium of the heart when blood pressure in the right atrium increases above normal. An increase in the blood pressure in the right atrium is usually caused by increased venous return. So there's a lot of blood that has come back or went back to the heart after being utilized by the tissues in the body. So there's a lot of the oxygenated blood in the right atrium. A lot of blood is returning, meaning there's increased blood volume in that area. So there is increase in blood pressure in that area. So this hormone, your ANP acts on the kidneys to decrease sodium reabsorption. So it acts on the kidneys to decrease the reabsorption of sodium. And then with sodium, the water will follow. So the water moves by osmosis into the nephron towards the sodium ions. So it will increase urine volume. And subsequently, it can decrease the blood volume and the blood pressure because you have already excreted water and salt. And yeah, you have excreted those two already. So it will decrease the blood volume and blood pressure. So that's how it lowers down an increased blood pressure. So based on the term itself, not atrial, notriuretic, any atrial is released. It is released or it is secreted by the right atrium. So that's the right atrium. Notriuretic, NAD stands for sodium, Na stands for sodium. Triuretic, or euretic, that means it is to die obese or to excrete urine. So you have to excrete sodium in the urine. That is how your atrial, notriuretic peptide or atrial, notriuretic hormone works. So basically, this is the order of the flow of urine. It starts with the collecting duct. So after it's being made in the nephron, goes to the tubular segments and goes to the collecting duct, then to the papillaria duct, here, to the minor calyx, to the major calyx. To the renal pelvis, here, urethra, urinary bladder, and to the urethra. So the urethra are small tubes that carry urine from the renal pelvis to the posterior inferior portion of the urinary bladder. So that's where it empties. So this is your urethra and then this is another urethra. Your urinary bladder, this is a hollow muscular container that lies in the pelvic cavity. If you remember, this is your urinary bladder. It can hold to a maximum of 1000 ml of urine. Its lining is transitional epithelium. So in a transitional epithelium, its lining is basically dome-shaped cells. And when it stretches out because it is filled with urine, it will now become squamous cells. So an important part or an important structure that you need to remember in the urinary bladder is the trigon. This is your trigon, this one. This is a triangular shaped portion located between the opening of the urethra and urethra. So the urethra is a tube that carries urine from the urinary bladder to the outside environment. For the males, it's quite long now. It's at about 20cm so it extends up to the end of the penis. For the females, it's very short. It's at about 4cm. It opens into the vestibule and clear to the opening of the vagina. If you look at the anatomical position, it's very near to the vaginal opening. So what I want you to remember is that the males have longer urethra compared to that of the females. And also the male urethra carries both urine and semen. So for the females, the vagina has a different opening, the urinary tract, or the urethra has a different opening. So it's different. For the males, it's just one organ and one dog or one tract for the semen and the urine to flow. So there are two sphincters that control the flow of urine to the outside environment. So you have your internal urethra sphincter. It is found at the junction of the urinary bladder and the urethra. So this is your internal urethra sphincter. It prevents the leakage of the urine from the urinary bladder. So in the meas, it keeps the semen from entering the urinary bladder during sexual intercourse. During sexual intercourse, this area or the sphincter is contracted to prevent the entry of the semen with the sperm. So here we also have your external urethra sphincter. This is a skeletal muscle that surrounds the urethra. So this is your external urethra sphincter. It allows a person to voluntarily start or stop the flow of urine. So you can control your external urethra sphincter. Let's talk about the micturition reflex or the urinary or urination reflex. The micturition reflex is activated by a stretch of the urinary bladder wall caused by its filling with urine. So if it's filling with urine, the pressure inside the urinary bladder wall increases. So this will stimulate the stretch receptors in the bladder wall. As seen in the picture here, you have this green thing. So this is your stretch receptors. So it will send action potentials from the urinary bladder through the pelvic nerves. So these action potentials will go to the spinal cord for integration. Other reflex or for some processing, then the spinal cord will send action potentials along the parasympathetic nervous fibers to the urinary bladder to contract. So the signals will just go back here because it's a reflex. So it will cause the contraction of the urinary bladder, which will facilitate the excretion of urine. So what is the role of higher centers in the brain? When we talk about the higher centers in the brain, we are pertaining to the cerebral cortex to the other parts here above. One is your bell cortex, one is your bell loam, puns, and the rest. So what is the role? They send or they continually send action potentials through the spinal cord. So this will decrease the intensity of the autonomic reflex that stimulates the urinary bladder contractions. And it also stimulates the nerve fibers that keep the external urethra spinter contract. So basically the role of your higher centers in the brain is inhibition of mixture. So just imagine if there is a destruction of the higher centers in the brain, even as small as 50 ml or 100 ml of urine in the urinary bladder. There is no inhibition in its excretion. So it is important that both are intact, like your higher centers and also the spinal cord. Here are some of the random things that you need to know about the maturation reflex. At the age of two to three years old, this is the age when the ability to voluntarily inhibit maturation develops. So children younger than two years old or three years old, like your infants and toddlers, they are not able to control yet their maturation. So they just donate anytime, anywhere, because they are not able to control that yet. So it's important for children at about three years old, no, two to three years old, you have to start potty training them. So you train them in using the toilet. Voluntary initiation and maturation is possible when the city brew sends action potentials to the voluntarily relax the external urethra spinter. So if you want to pee or if you want to urinate, you can control that. That is through the action of your city brew. So you have to voluntarily relax your external urethra spinter. Voluntary contraction as well of the abdominal muscles. So if you contract your abs or your abdominal muscles, it will increase abdominal pressure and thereby enhances the maturation reflex. Here are some of the characteristics of urine. In 24 hours, about 1 to 1.8 liters of urine are produced. It's yellow in color because of the presence of the pigment urochrome. Urochrome is a byproduct of the destruction of hemoglobin. And urine is initially sterile. If it is exposed in the external air now, if it's exposed with the air and the outside environment, it becomes unsterial. So initially, if it's just fresh directly from the clean urethra, so your urine is sterile. It's slightly aromatic. However, if it is exposed to air again, so it will become slightly foul and older. Initially, it is slightly aromatic. Normal pH of urine is around 6, so it's acidic because of the presence of hydrogen. If you remember, hydrogen is one of those ions that were excreted during tubular secretion of urine. Okay, so may excretes on hydrogen. It will increase the acidity of the urine. Specific gravity for urine is 1.001 to 1.035. So a specific gravity actually measures the concentration of the urine. So if there's high specific gravity, meaning that the urine is very concentrated, so there's quite a slight decrease now on water content of your urine. If there is a decrease in your specific gravity, meaning it is very dilute. Okay, so there's too much water in your urine compared to the solutes. What are the solutes that are normally found in the urine? Sodium, potassium are normal, urea, uric acid, and creatinine, because these should be excreted actually. Okay, so they should be normally found in the urine. These are byproducts of your protein metabolism. Ammonia should also be found in the urine because it has to be excreted. And as well as bicarbonate and some hydrogen ions. Okay, they have to be found in the urine, normally found in the urine. Solutes that should not be found in the urine are the following glucose. Okay, glucose should not be found in the urine because these are large molecules. Okay, blood proteins as well. Okay, these are large molecules and they are negative in charge. So normally they should not pass through the filtration process in the urine formation. Red blood cells should not be found in the urine. Hemoglobin as well, white blood cells. Now if you found white blood cells in the urine, it signifies that there could be a possible infection. If you find red blood cells in the urine, there could be possible trauma to any part of the urinary tract. Or there could be renal injury or injury to the kidneys itself. Then bio should not be found in the urine as well. So basically that ends the discussion of the urinary system. So if you have questions, please do not hesitate to inform me. Thank you and have a great day.