The Urinary System

1. The Urinary System • The organs, tubes, muscles, and nerves that work together to create, store, and carry urine are the urinary system. The urinary system includes two kidneys, two ureters, the bladder, two sphincter muscles, and the urethra.

2. Excretion • Excretion is the process of removing wastes and excess products from the body • Three of your body systems are involved in excretion: • Your skin releases waste products and water when you sweat • Your lungs expel carbon dioxide and water when you exhale • Your urinary system removes waste products from your blood

3. Cleaning the blood Your blood is like a supply train that comes into a town to drop off supplies and take away garbage The train has to find a way to get rid of the garbage before it can load up with more supplies. If the garbage is not removed, the townspeople will be in a very unhealthy environment

4. Kidneys The kidneys are a pair of bean-shaped organs that constantly clean the blood. Your kidneys filter about 2,000 liters of blood each day Your body only holds 5.6 liters of blood, so your blood cycles through the kidneys about 350 times a day

5. Inside the Kidney Inside each kidney are more than 1 million microscopic filters called nephrons Nephrons remove a variety of harmful substances from the body.

6. How the Kidneys Filter Blood A large artery brings blood into each kidney Tiny blood vessels branch off the main artery and pass through part of each nephron Water and other substances are forced out of the blood vessels and into the nephrons

7. Nephrons As these substances flow through the nephrons, most of the water and some nutrients are moved back into blood vessels A concentrated mixture of waste materials is left behind in the nephrons The cleased blood leaves each kidney in a large vein to recirculate in the body

8. Urination The yellow fluid that remains in the nephrons is called urine Urine leaves each kidney through a slender tube called the ureter and flows into the urinary bladder Urine leaves the body through another tube called the urethra Urination is the process of expelling urine from the body.

9. Water In, Water Out • Our bodies would swell up with excess water if we did not excrete as much water as we take in. • The balance of fluids is controlled by chemical messengers in the body called hormones

10. Sweat and Thirst When you get hot, you lose more water in the form of sweat The evaporation of water from your skin cools you down As the water content of the blood drops, the salivary glands produce less saliva This is one of the reasons you feel thirsty.

11. Antidiuretic Hormone When you get thirsty, other parts of your body react to the water shortage A hormone called antidiuretic hormone, or ADH, is released ADH signals the kidneys to take back water from the nephrons and return it to the bloodstream, thereby making less urine When your blood is too watery, smaller amounts of ADH are released The kidneys react by allowing more water to stay in the nephron and leave the body as urine

12. Diuretics When you are thirsty, your tissues are asking for more water Some beverages contain caffeine, which is a diuretic Diuretics cause the kidneys to make more urine, which decreases the amount of water in the blood So instead of giving your body more water, caffeinated beverages cause additional water to be lost in urine

13. Urinary System Ailments • Since the urinary system regulates body fluids and removes wastes from the blood, any malfunction can become life-threatening • Some common urinary system disorders are: • Bacterial infections • Kidney stones • Kidney disease

14. Bacterial Infections • Bacteria can get into the bladder and ureters through the urethra and cause painful infections • It is important to treat such an infection early because it could spread to the kidneys and lead to permanent damage • Drinking six-eight 8 oz glasses of water can help prevent these infections

15. Kidney Stones Sometimes salts and wastes collect inside the kidneys and form kidney stones. Kidney stones interfere with urine flow and cause pain Most kidney stones pass naturally from the body, but sometimes a medical procedure is necessary

16. Kidney Disease Damage to nephrons can prevent normal kidney functioning, leading to kidney disease If the kidneys do not function properly, a kidney machine can be used to filter waste from the blood. The machine pumps blood from an artery in the forearm or wrist to a kidney machine, where it is filtered. • The cleaned blood is then pumped back into a vein in the arm.