 Hi everyone, I'm Leah, your lead course instructor here at Advanced E-Clinical Training. I'm sure you know me by now as we've been going through these anatomy and physiology lessons and we're getting near the end. So today we are going to talk about the urinary system. Alright, so functions of the urinary system include filtration. So every day the kidneys filter gallons of fluid from the bloodstream. There's water processing. So the kidneys process, filtrate from the urine, allowing waste to leave the body in urine while returning required substances to the blood. There's also elimination, so the kidneys are responsible also for eliminating nitro, gasses, waste, toxins, and drugs from the body. Regulation, the kidneys also help to regulate the blood's volume and chemistry so that the proper balance between water and salts and between acids and bases is maintained. And then other regulatory functions include the kidneys help to produce the enzyme renin and to help regulate blood pressure and their hormone urethra protein that helps to stimulate red blood cell production in the blood marrow. Organs of the urinary system include, of course, the kidneys. So the kidneys alone perform the functions just described and manufactured urine in the process. So while the other organs of the urinary system provide temporary storage reservoirs for urine or serve as transportation channels to carry it from the body to another region of the body. So the urinary system includes, of course, you have two kidneys, you have two ureter tubes on both the right and left side. You have a urinary bladder and then the urethra. So here we have the kidneys. So the kidneys are located against the back of the body while in a retroperitoneal position in the superior lumbar region. So they extend from T12 or thoracic 12 to lumbar 3 of your vertebrae and the lower part of the rib cage serves as protection to the kidneys. So the adult kidney is about 12 centimeters or five inches long and six centimeters or two and a half inches wide. And it is about three centimeters thick and it's about the size of a large bar of soap. So you have two adrenal glands and we talked about the adrenal glands in the endocrine system. But sitting on top of each kidney on the right and left side is the adrenal gland. And so, as I said before, this is part of the endocrine system, which we talked about and the endocrine lesson. And it's actually a totally separate and distinct separate organ functionally. It just happens to live on top of the kidneys. There is the fibrous capsule. So the fibrous capsule of the kidney is a transparent capsule that encloses each kidney. You have the renal fascia. So the renal fascia is the outermost capsule of the kidney and helps to anchor the kidney by holding it in place against the muscles of the trunk wall. Then we have the renal cortex. And you can see all of these structures here in this diagram. So the renal cortex is the outer region, which is light in color. And then you have the renal medulla. And so superior to the cortex is a darker, reddish-brown area known as the renal medulla. So then we have renal columns, renal columns, or they're pyramids that are separated by... So pyramids of the kidney, excuse me, are separated by extensions of cortex-like tissue called renal columns. Then you have the renal pelvis. And the medial to the hylum is the renal pelvis. And that runs with the ureter leaving the hylum. We have the calluses and these extensions of the pelvis form a cup-shaped area that enclose the tips of the pyramids and collect urine. And these calluses continually drain from the tips of the pyramids into the renal pelvis. And then we have the renal artery. And the renal artery is the arterial supply to each kidney, one on the right and the left, which divides into segmental arteries as it approaches the hylum. So moving on to nephrons. So nephrons are very, very important to the urinary system and to the kidneys. So each kidney contains over one million nephrons responsible solely for forming urine. So you have the glomerulus. One of the main structures of the nephron is the glomerulus and it is a knot of capillaries. You also have the renal tubule. One of the main structures in a nephron is this renal tubule. So you can see all of these structures that I'm speaking about right here in this diagram. So there it's the Bowman's capsule. And this is also known as the glomerular and it surrounds the glomerulus. You have foot processes or pedocytes. They have long branching processes called foot processes that intertwine with one another and cling to the glomerulus. There's the collecting duct of each nephron. And so a collecting tubule called the collecting duct receives urine from many nephrons. The loop of Henle. The loop of Henle is the hairpin loop following the proximal convoluted tubules. So you can see that right here. And then you also have the distal convoluted tubule. And so after the loop of Henle, the tubule continues to coil and twist as you can see here before the collecting duct. And this part is called the distal convoluted tubule. Moving on to the ureter. So as I said before, you have a kidney on the right side, a kidney on the left side, and then you have ureter tubes. One from each kidney that extends from the kidney to the bladder. So really the ureter's active role is for urine transport. The ureters are two slender tubes each 25 to 30 centimeters long and six millimeters in diameter. Each ureter tube runs behind the peritoneum from the renal hyalum to the bladder, entering it at a slight angle. And so the function of the ureters again acts as a passageway transporting urine from the kidneys to the bladder, propelling the urine into the bladder by peristallosis. And we've talked a lot about peristallosis in our last lesson in our gastro lesson. So we shall know what that is by now. But the urine is also prevented from flowing back by a small valve like folds of the bladder mucosal that flop over the ureter openings right about here. Moving on to the bladder. So the bladder is a smooth, collapsible, muscular sac that temporarily stores urine. It is located retroperitoneally in the pelvis just behind the simpus pubis. The smooth triangular region of the bladder base outlined by these three openings is called the trigo, where infections definitely tend to persist, which would be like right around here. And then you have the detrusive muscle, and this bladder wall contains three layers of smooth muscle known as the detrusive muscle, and its mucosa is made of transitional epithelium cells. So the urethra. So the urethra is a thin wall tube that carries urine by peristallosis from the bladder to the outside of the body. So there's the internal urethra sphincter. And this is an involuntary sphincter that keeps the urethra closed when the urine is not being passed. Then there is the external urethra sphincter, which passes through the pelvic floor, and this is the sphincter that is voluntarily controlled. So this is the sphincter that allows you to hold your urine when you have to go into the bathroom. The female urethra is about three to four centimeters long, and its opening lies interiorly to the vaginal opening. The male urethra is obviously longer, and it's approximately 20 centimeters long, and has three named regions, the prostatic, the membranous, and the spongy. And it opens to the tip of the penis where the urine is released. So obviously in the urinary system it's important to discuss urine formation. So urine formation is the result of three processes known as glomerular filtration. So water and solutes are pushed through the capillary walls and pores of the glomerular capsule into the renal tubule. The tubular reabsorption happens. So water, glucose, amino acids, and ions are transported out of the filtrate into the tubule cells and into the capillary blood. And then you have tubular secretion. So hydrogen, potassium, creatinine, and drugs are removed from the aperitubular blood and secreted by these tubular cells into filtrate. So you can see it's filtrate, reabsorption, secretion, and then excretion. So characteristics of urine in 24 hours, the kidneys filter approximately 150 to 180 liters of blood plasma through their glomeruli into the tubules. In 24 hours only about 1.0 to 1.8 liters of urine is produced. So urine contains nitrogen, waste, and unneeded substances. Of course, the color of urine, freshly voided urine, should be clear and pale to deep yellow and a healthy individual. Now of course, in healthcare we don't always see healthy individuals. You know, if somebody has a urinary tract infection, a lot of times the urine is cloudy or it's malodorous, or you know, if somebody is dehydrated, usually the urine is a lot darker and more concentrated. Of course, when urine is formed, it's mild smelling, but if it is allowed to sit, it produces an ammonia odor. And that's caused by bacteria on those urine solutes. So the pH of urine is usually acidic around 6 on this scale, but changes with body metabolism. So also certain foods may cause urine to be much more acidic or more basic as well. The specific gravity of urine usually ranges from 1.001 to 1.035. And solutes found in urine include sodium, potassium, ions, urea, uric acid, creatinine, ammonia, bicarbonate ions, and various other ions as well. So moving on to mixturition, and so this is actually voiding. It's the active emptying the bladder. You have the accumulation and the bladder will continue to collect urine until it's about 200 ml. Then there is activation at this point stretching of the bladder while it activates the stretch receptors. Then you have transmission. So impulses transmitted to the sacral region of the spinal cord and then back to the bladder via this pelvic splenic nerves cause the bladder to go into reflex contractions. And then you have the passage of urine. So as the contractions become stronger and the bladder is forced past the internal urethra sphincter into the upper part of the urethra. And then the external sphincter, which we just talked about because it's controlled.