today we're going to talk about a system that is crucial when it comes to pH balance and fluid balance today we're going to talk about the ait's version 7 portion of the exam more specifically human anatomy and physiology and we're going to be discussing the urinary system let's get started let's begin by tackling two crucial survival challenges first we need to maintain osmotic pressure this is essential because it involves the regulation of water and solute levels found throughout our body secondly the body must elimin metabolic waste metabolic waste can include things like carbon dioxide and nitrogenous waste which are byproducts of protein breakdown a frequent occurrence in metabolic processes the urinary system is designed to address these two critical issues with various organs and structures contributing to its function the skin for instance plays a role in excreting water and other substances the liver is heavily involved in detoxification and produces Ura and the lung are responsible for expelling carbon dioxide gas it's important to remember that these organs also participate in other body systems the skin is part of the integumentary system the liver assists with digestion and the lungs are crucial when it comes to the respiratory system our primary focus today is going to be on the kidneys which are a key player when it comes to the urinary system but just know that all these systems work concurrently in order to help Tain these survival balances the urinary system is made up of a couple different kinds of organs we start off with the kidneys up here at the top which are just like kidney shaped beans that hold all of our urine and helps process all of those metabolic waste they go down to the uers that ultimately lead down to our bladder where the urine is stored and then ultimately to the urethra where the urine is going to be expelled so when we talk about urine production this is primarily occurring in the kidneys each kidney contains approximately 1 million nephrons which are the fundamental working units of the kidney the primary function of our nefron is to filter waste products from the blood and convert it into urine we're going to start our exploration of the nefron when it comes to the glus which is a specialized cluster of capillaries this cluster is going to be encased in our Bowman's capsule here blood pressure is going to push that fluid from the blood into the Glarus into the Bowman capsule initiating what we call the filtration process once the fluid enters the Bowman capsule it is referred to as filtrate but what exactly does filtrate mean filtrate is a fluid that's going to contain several key components you're going to see things like water glucose amino acids and various different kinds of salts additionally you're going to see things like hydrogen ions bicarbonate ions and other miscellaneous ions if present medications as well as some vitamins may also be found in our filtrate and it's also going to contain things like Ura which is is a nitrogenous waste product generated by our liver that the body needs to eliminate the nefron subjects that filtrate to an intensive processing Journey as the filtrate moves through that nefron some of that is going to be reabsorbed which means that specific filtrate components are going to cross back from the nefron into the surrounding interstitial fluid and then are going to be recirculated throughout the body however specific components are going to be retained in the nephron tubules to be eliminated as waste materials and eventually they're going to be excreted as urine renal secretion refers to the process of either passive or active transport of substances from the blood into the renal tual where they will eventually be excreted as urine this is basically the opposite of reabsorption substances might move in and out of the nefron passively or they may undergo facilitated diffusion processes that do not require at P also known as passive transport these types of transports operate along a concentration gradient where solutes or fluids are going to move from higher concentrations to lower concentrations occasionally some substances will need to go through the process of active transport where they are going to require ATP typically you're going to see substances moving from a lower concentration to a higher concentration while we aren't delving deeply into the specific types of transports when it comes to this video you can rewatch them through the chemistry portion of our ait's videos now that we understand these Concepts let's dive deeper into our nefron from our Bowman's capsule we're going to move into our proximal convoluted tubio proximal means near indicating that this tubal is closest to our Glarus which is significant because there's another tubal further along in the proximal tubal salt is going to be transported into our interstitial fluid as you may know water follows salt by osmosis which is to be expected since that interstitial fluid becomes hypertonic due to that salt moving out into our interstitial fluid thus we typically say that salt and water are going to be reabsorbed because they're leaving the nefron and moving into that fluid other substances like glucose amino acids potassium as well as bicarbon also going to be reabsorbed here meaning that they are going to leave that proximal convoluted tubal and be transported into that interstitial fluid either through active or passive transport when we discuss reabsorption it's really important to note that not all substances are going to be fully reabsorbed some of these substances even though they're being reabsorbed in this particular area are still going to remain in that filtrate inside that proximal convoluted tubio secretion refers to substances moving from the fluid outside of the tube tubal to inside our proximal convoluted tubal so in this case you're going to see certain things being secreted like hydrogen ions and ammonium with certain substances being reabsorbed and others being secreted such as like we see with our bicarbonate and our hydrogen it's clear that the proximal convoluted tubo plays a crucial role when it comes to regulating our body's pH next up let's explore our Loop of Henley which consists of a descending limb that moves downward and an ascending limb which moves upward we're going to begin by discussing our descending limb and this contains numerous aquap porns that are going to be found here these are special channels that facilitate the easy passage of water here water is going to be reabsorbed into our interstitial fluid which at this point we know is hypertonic because we have a higher concentration of solutes found inside of this area versus what's found in the filtrate inside of the loop of Henley as we discussed water is going to move osmotically towards that hypertonic area following that gradient solute concentration what's also interesting is that the descending Loop of Henley does not have channels for most solutes such as salt like we talked about before so all that salt that's still remaining within our Loop is going to remain here inside this portion of the nefron as the water's continuously exiting outside the descending Loop of Henley and as we continue to move further down this Loop you're going to find that the concentration of solutes found within our filtrate is going to increase so what exactly does that mean that means that we're going to see a lot more salts in this area without a whole lot of water so as we transition to that ascending Loop of Henley you're going to find that there's no aquaporin here so that remaining water is going to remain in our filtrates however in this segment you're going to find that there are specific specific proteins that are going to allow this salt to exit this particular section in the thin segment of our ascending Loop salt is going to move from that higher concentration within the filtrate to the lower concentration in our interstitial fluid so as we move upward into this thicker segment of our ascending Loop of Henley we're going to see a mass Exodus of salt as it continues to move from the filtrate into our interstitial fluid this is done through active Transportation further reducing that solute concentration within our filtrate and making this section more dilute as the filtrate loses more salt you can see that it becomes less concentrated by the time that it reaches the top of our ascending limb now we've moved on to our distal convoluted tubio substances like hydrogen pottassium and ammonium are going to be secreted into the filtrate with this particular section meanwhile our salts water and more bicarbonate are going to be reabsorbed from the filtrate back into that interstitial fluid the disto tual plays a crucial role again in PH regulation by readjusting the secretion and reabsorption of these substances and then lastly we reach our collecting dect where the transformation of filtrate becomes urine in this phase salt continues to be reabsorbed water is also reabsorbed here as well but is really tightly controlled by hormones which are going to regulate the volume of water that is needed to be reabsorbed based on what the body needs so like we discussed hormones are going to regulate the water permeability within those collecting Ducks which is crucial for maintaining body hydration for instance if you have a dehydrated person the collecting duck is going to kick in and reabsorb as much water as possible back into the interstitial fluid this is going to result in a more concentrated urine because you have less water conversely someone who has consumed a lot of water means that they are overhydrated so the body is going to be less reactive to reabsorbing water back into the interstitial fluid leading to a less concentrated urine because there's a lot more water we've also discussed previously how Ura is reabsorbed and secreted at various points in the nefron in the collecting duct a significant amount of Ura is going to remain in the filtrat however due to its high concentration samura is going to diffuse back into the interstitial fluid and as we finish our journey when it comes to urine production and expulsion through the body we know that urine that's produced by the kidneys are going to move down here into our uers where it's ultimately going to be stored on our bladder and then it's eventually excreted through our urethra I hope that this information was helpful in understanding the urinary system as always if you have any questions make sure that you leave them down below I love answering your questions head over to nurse Chun store.com there's a ton of additional resources in order to help you Ace those a TI's exams and as always I'm going to catch you in the next video bye