1. Excretory System
Chapter 12

2. Excretion
Substances that are not used by the body are removed through the digestive system and by the excretory system
The excretory system removes liquid and gas wastes from the body. This system includes—
lungs
skin
liver
kidneys
ureter
bladder
urethra

3. Excretion (cont.)
When the liver breaks down proteins, urea forms. Urea is toxic if it stays in the body.
The kidneys remove urea from the body by making urine.

4. Excretion (cont.)
Urine leaves each kidney through the ureter and is stored in a flexible sac, called the bladder.
Urine is removed from the body through the urethra.