The urinary system works to clean waste from the blood through the kidneys and excrete it as urine. The kidneys contain over 1 million nephrons that act as filters to clean the blood. When the body becomes dehydrated from sweating or other fluid loss, the kidneys respond by reabsorbing more water from urine with antidiuretic hormone to maintain water balance in the blood. Common disorders of the urinary system include bacterial infections, kidney stones, and kidney disease.

1. Life Science 3.2The Urinary System

2. Objectives:Describethe parts and functions of the urinary system.Explain how the kidneys filter blood.Describe three disorders of the urinary system.

3. Cleaning the BloodThe urinary system contains the organs that remove waste products from your blood.

4. The Kidneys as FiltersKidneysPair of organs in the urinary system that clean the blood and excrete products as urine. Inside each kidney are more than 1 million microscopic filters called nephrons.

6. Water In, Water OutSweat and Thirst The evaporation of water sweat cools you down.As the water content of the blood drops, the salivary glands produce less saliva, resulting in thirst.Antidiuretic Hormone When you get thirsty, antidiuretic hormone is released. This hormone signals the kidneys to take water from the nephronsand return it to the body.Diuretics Cause the kidneys to make more urine, which decreases the amount of water in the blood.Example: beverages containing caffeine

7. Urinary System ProblemsBacterial Infections Bacteria can get into the bladder and uretersthrough the urethra and cause painful infections.Kidney StonesSalts and other wastes can collect inside the kidneys and form kidney stones.Kidney DiseaseDamage to nephrons can prevent normal kidney functioning and can lead to kidney disease.