this is the inside of a real human kidney and these little organs do so much more than just produce urine they can get involved in regulating blood pressure if you were to start exercising and sweating they could make adjustments for fluid and electrolyte balance the kidneys even secrete hormones and of course filter the blood of waste products drugs and even potential toxins so in today's video we need to go on a little bit of a tour of these amazing organs the kidneys to figure out how they perform all of these amazing functions of course it's
going to be of all sorts of anatomical awesomeness so let's jump right into this as I mentioned in the intro one of the main functions of your kidneys is to filter blood so do you have any idea how much blood your kidneys could actually filter in a 24-hour period could it be 5 to 6 lers or a gallon and a half as that's close to the blood volume of an average adult male well let's make this a little bit more V visual this is a 5G jug of fluid do you think this little guy could
handle filtering that much blood in a day try multiplying this by 10 and you get closer to what your kidneys can filter in a 24-hour period your kidneys can filter up to 50 gallons or about 190 L per day that is incredible so let's figure out how they do this so here we have two different kidneys on the tray this one is intact we haven't cut inside but this one we've done a frontal section through so you can obviously see some of that awesome internal anatomy you'll also notice that there are various tubes going in
and out of the kidneys and we'll talk about the significance of those tubes in just a second because I first want to give a quick FYI on the location of your kidneys your kidneys are located on both sides of your vertebral column or spine from the levels of about the 12 thoracic vertebrae down to the third lumbar vertebrae so from T12 to L3 now the right kidney is a little bit lower than the left because that liver takes up some extra space on that right side but also the 11th and 12th rib will cover up
the upper portion of the kidneys on the back side and that does provide some protection but is also a little bit of a double-edged sword because if someone were to sustain significant enough trauma and break or fracture those ribs that could potentially slice into the kidneys and in certain situations could be life-threatening but moving on from the gloom and doom of potential kidney injuries we did say that the kidneys can filter up to 50 gallons of blood per day now obviously we don't have 50 gallons of blood inside of us so that means that the
blood that we do have will be cycling through the kidneys multiple times throughout that 24-hour period and the blood will first enter into your kidneys through this artery called the renal artery and as this renal artery enters into the kidneys it starts to Branch into smaller arteries and some of those arterial branches will get so small that we can't see them with the naked eye and they'll move into the outer portion of the kidney called the renal cortex and the renal cortex plus these awesome masses of tissue that you could see if you look closely
called the renal pyramids these areas the cortex and the pyramids is where blood filtration takes place and therefore where will start to produce some magnificent urine now if we were to zoom into the renal cortex and the renal pyramid we would be transported into this microscopic world within the kidneys and you would see that each kidney contained about a million of what you could think of as these biological filtration units and each one of these units is called a nephron now this nephron contains blood vessels and urinary tubes and from here on not all refer
to these urinary tubes as renal tubules renal just means kidney tubules just tiny tubes and you can see those here and another part of the nefron is this little capillary ball called the glomerulus and this is where the blood is first filtered this is where things such as water ions like sodium and even glucose vitamins and amino acids waste product products like ammonia and Ura will pass from the blood and into these renal tubules you can kind of think of this filtration process that occurs between the glomerulus and its surrounding glomular capsule as similar to
how you might use a strainer or a colander when you're cooking the Glarus is a much more leaky capillary when you compare it to the other capillaries throughout the body it has more pores and so you can kind of think of anything that's small enough and has the right charge that can fit through the pores or the strainer or filter will pass from the blood and into these renal tubules larger items like blood cells and larger plasma proteins should not pass through this filter if they do it could signify a problem with the filter or
damage to this Glarus and that can occur in certain kidney conditions but there are two things we need to consider here one within each kidney there are up to a million of these nephrons and throughout a 24-hour period up to 50 gallons or 190 L are going to be filtered at the glomeruli now we don't urinate 50 gallons a day or 190 L more like 1 to 2 lers per day and so we need to address this but secondly you may have noticed that there were some substances or items that got filtered out that we
may actually want to hold on to for example the water sodium and even the glucose to name a few the ammonia Ura and other waste products they can stay in the renal tubules but to address these two situations we're going to see this process of reabsorption take place if we move further down these renal tubules and some of you might know the specific names like the proximal and distal convoluted tubules and the nefron Anza but these renal tubules will be wrapped with another set of capillaries called the parat tubular capillaries and this is where we
reabsorb 99% of the water that was just filtered out plus we can reabsorb the electrolytes glucose and other substance that the body may need to hold on to now you may Wonder well why would we do this why would we just filter out so much stuff if we're going to reabsorb 99 % of the water and reabsorb a whole bunch of these other substances that we may need to keep well a high glomular filtration rate meaning a high flow rate through the Glarus and filtering out quickly provides an opportunity to get rid of waste products
very quickly and then we can selectively pull back in the things that we need to keep now there's another thing that we need to consider here there are some waste products that couldn't fit through the glomerulus and so this peritubular capillary relationship with these Ren tubules that are further Downstream provide another opportunity to move some additional waste products from the blood these parat tubular capillaries into these renal tubules so larger waste products and other drugs can be filtered out of the blood and into what eventually is going to make up the urine and what is
so incredible about this is that the kidneys are constantly making adjustments based upon the body's conditions like for example if you drank a whole bunch of water or increased your salt intake the kidneys could reabsorb less L water and less sodium if you were exercising and sweating losing water losing electrolytes the kidneys could reabsorb more water in electrolytes to conserve if your pH was changing in the blood the kidneys could secrete more hydrogen reabsorb more bicarbonate so you can see this incredible filtration and reabsorption process allows the kidneys to rid the body of waste products
and drugs help to regulate acid base balance as well as help regulate water and electrolyte balance and after this process of filtration and reabsorption takes place the blood from the par tubular capillaries will flow into venules which are just tiny veins and these venules will merge into larger veins and this merging process will continue to happen until all of the veins within the kidney merge into this large vein here called the renal vein and this is where the blood will leave the kidney as this filtered or purified blood and can circulate throughout the body now
everything that stays within the renal tub will become the urine and if we look at these renal pyramids again you can't actually see this with the naked eye but within the renal pyramids there are these tiny little collecting ducts that are collecting all of the urine and these pyramids you can see are flowing into this little tiny tube in this little tiny tube this is a minor kaix and a minor kaix and those minor kses will merge into a major kaix these names aren't totally important for you to remember the main idea in the concept
is that we have multiple tiny little tubes collecting the urine and we're of eventually converging all that into one larger tube here that we call the urer which will flow down into the bladder and that bladder will store your urine for your convenience and eventually flow out the urethra and into the toilet hopefully now one note on the bladder you may have heard me mention it's storing your urine for your convenience now the bladder I kind of want us to have this you know moment of Silent gratitude for it because as we've learned throughout this
video we're constantly filtering ing the blood and therefore producing urine 24 hours a day 7 days a week so if you did not have a bladder you'd be ping your pants 24 hours a day 7 days a week thank you bladder and since we just paid a little bit of homage to the bladder let's go back to paying even more homage to those kidneys because we still have a few more functions to discuss the kidneys can influence blood pressure and one of the ways they could do this is let's say we had too much blood
volume I mean literally too much fluid within the blood vessels this would increase the overall blood pressure and so as we've already learned the kidneys could excrete some excess fluid and that would lower the overall blood volume and their for the blood pressure now obviously there are limitations to this and there are multiple factors that influence blood pressure so if somebody's blood pressure is high and it's not due to excess blood volume the kidneys could only do so much the other way that the kidneys can influence blood pressure is through this renin Angiotensin system and
this can get complex but the quick version is that renin is an enzyme released by the kidneys when the blood pressure is too low and through a series of events this will eventually cause blood vessels to vasoconstrict or tighten down and that would bring the blood pressure back up the kidneys also secrete various hormones one of those is called arthop pootin or maybe you've heard of it by its abbreviated name EPO but EPO or orthop potin stimulates the bone marrow to produce red blood cells another hormone secreted by the kidneys is calat trial which is
the activated form of vitamin D now there are a lot of steps to vitamin D formation the skin and UV light get involved but we actually did a whole video on those details so if you're interested I can link that here but one of the important functions of vitamin D is to increase calcium absorption across the intestine so as you can see the kidneys are kind of showoffs they can do all these different things like rid the body of waste products help with fluid and electrolyte balance acid base buffering help with your blood pressure and
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