The Urinary System Melissa Shultz CMA Review April 7, 2011

The Urinary System Consists Of:  The Kidneys  The Ureters  The Urinary Bladder  The Urethra

Urinary System Basics Waste products in the blood filter through the kidneys. The urine then travels down the ureters to the bladder where it is held until the bladder is full. Once the bladder is full, the urine is voided through the urethra. Figure 1

How The Parts Of The Urinary System Function  The kidneys are located below the ribs toward the middle of the back. Their job is to remove waste from the blood in the form of urine; keep a stable balance of salts and other substances in the blood; and produce erythropoietin which aids in the production of red blood cells.  The ureters are narrow tubes which carry urine from the kidneys to the bladder. Muscles in the ureter walls contract and relax continuously to force urine downward.

How The Parts Of The Urinary System Function  The bladder is a triangular-shaped, hollow organ located in the lower abdomen. It’s sole purpose is to act as a holding tank for urine to be stored until voided. The walls of the bladder relax and expand to fill and contract and flatten to empty. Urine is kept from leaking by two sphincter muscles that close tightly around the opening of the bladder.  The urethra allows urine held in the bladder to be eliminated outside the body. The female urethra is shorter than that of a males, making it easier to contract urinary tract infections and possibly bladder infections.

The Kidney: Your body’s filtration system Each kidney consists of: The renal hilum The renal cortex The renal medulla The renal pelvis The renal hilum is the concave portion of the kidney where the renal artery and vein enter. Figure 2

The Kidney: Your Body’s Filtration System The Renal Cortex  The renal cortex is where the blood is actually filtered, is grainy in appearance, and has very little obvious structure to the naked eye.  The arteries, veins, convoluted tubules, and glomerular capsules are found in the renal cortex. The Renal Medulla  The renal medulla contains the renal pyramids.  The renal pyramids are made up of collecting tubules.  Neighboring renal pyramids are separated by narrow renal columns which are extensions of the cortical tissues.

The Kidney: Your Body’s Filtration System The renal pelvis is funnel shaped and is divided into two or three large tubules called major calyces which are then divided into minor calyces. The calyces collect the urine that continually drains through the renal pyramids. The renal pelvis empties directly into the ureters.

A Detailed Look Into The Renal Cortex: The Nephron The renal cortex contains thousands of nephrons. Each nephron contains different parts which need to work together to filter metabolic waste from the blood. The nephron consists of two parts; the renal corpuscle and the renal tubule. The renal corpuscle consists of the glomerulus and the Bowman’s capsule. The renal tubule consists of the proximal tubule, the loop of Henle, the distal tubule, and several collecting ducts.

A Detailed Look Into The Renal Cortex: The Nephron  Blood enters the renal corpuscle through the glomerulus which is a ball of capillaries.  The Bowman’s capsule surrounds the glomerulus. Everything except blood cells and larger molecules are pushed from the capillaries into the bowman’s capsule.  As filtrate travels through the renal tubule, nutrients are either absorbed or excreted, depending on the body’s needs at that moment.  Filtrate begins it’s journey through the tubule in the proximal tubule and moves on to the loop of Henle.  The loop of Henle is made up of the descending loop and the ascending loop.  The filtrate then moves on to the distal tubule, then to the collecting ducts which lead to the minor and major calyces and finally to the renal pelvis and down the ureter.

A Common Urological Disease: Kidney Stones  Kidney stones result when substances in the urine crystallize in the renal tubule, often because the concentration of that substance is higher than normal.  Kidney stones occur in as many as 10% of people in North America before the age of 70 and occur more commonly in men than women.  Patients with kidney disease, who have had bariatric surgery, or who have bone disease are at higher risk for developing kidney stones.  Stones can be made of many substances but the most common is calcium or uric acid.

Treatment Options For Kidney Stones  Treatment for kidney stones depends on the number, size, location, and composition of the stones.  Sometimes simply drinking water and waiting for the stone(s) to pass is enough.  Some patients are prescribed medication, usually corticosteroids, to increase the chance of passing the stone(s).

Treatment Options For Kidney Stones  Extracorporeal shock wave lithotripsy uses shock waves applied to the outside of the body to break up the stone so that it’s small enough to pass.  During ureteroscopy, a fiberoptic endoscope is threaded up the urethra, through the bladder and into the ureter. An instrument attached to the end of the endoscope shatters the stone and captures the pieces.  Percutaneous nephrolithotomy uses an endoscope and a small incision to remove large stones.

Figure 3 Figure 4 Figure 5

Fun Facts  Normal urine is sterile. It contains fluids, salts and waste products, but is free of bacteria, fungi, and viruses.  Kidney beans were named after your kidneys because of their similar color and shape.  Adults void about a quart and a half of urine each day.  About 440 gallons of blood flow through the kidneys every day!  The tissues of the bladder are isolated from urine and toxic substances by a coating that discourages bacteria from attaching and growing on the bladder wall.

References  FIGURE 2 - Anatomy of the Urinary System. (n.d.). The Ohio State University Medical Center. Retrieved April 8, 2011, from atomy_urinary_system/pages/index.aspx  Your Gross and Cool Body: Urinary System. (n.d.). The Yuckiest Site on the Internet. Retrieved April 8, 2011, from  Anthony, C. P., & Thibodeau, G. A. (1987). Textbook of Anatomy and Physiology. St Louis: Times Mirror/Mosby College Publishing.  FIGURE 3 - Extracorporeal Shockwave Lithotripsy. (n.d.). First-hand information for kidney stone pain relief, treatment and prevention. Retrieved April 10, 2011, from  FIGURE 4 - Glossary: ureteroscopy, Masonic Cancer Center, University of Minnesota. (n.d.). Masonic Cancer Center, University of Minnesota Home Page. Retrieved April 11, 2011, from  FIGURE 5 - Percutaneous nephrolithotomy - Revolution Health. (n.d.). Revolution Health - Start your Revolution - Revolution Health. Retrieved April 11, 2011, from  FIGURE 1 - Urinary System. (n.d.). Find Me A Cure. Retrieved April 8, 2011, from findmeacure.com/wp-content/uploads/2008/03/define-kidneys-and-urinary-system-1.jpg