1. Lesson Overview
30.4 The Excretory System

2. The Excretory System
Excretion = process by which metabolic wastes are eliminated to maintain homeostasis
Excretory system includes = skin, lungs, liver, and kidneys (ureters, urinary bladder, and urethra are also involved)

3. The Skin
The skin excretes excess water, salts, and a small amount of urea in sweat.
By releasing sweat in very small amounts, this process eliminates wastes even when you may not think you’re sweating.

4. The Lungs
When you exhale, your lungs excrete carbon dioxide (a waste product of cellular respiration) and small amounts of water vapor.

5. The Liver
The liver converts nitrogen wastes (toxic byproduct of protein breakdown) into less toxic urea
Urea is then transported to the kidneys for elimination from the body

6. The Kidneys
Kidneys = remove excess water, urea, and metabolic wastes from the blood and excrete a waste product known as urine.
Ureters = transport urine from the kidneys to the urinary bladder
Urinary bladder = stores urine until it is released through the urethra
Urethra = empties bladder to outside the body

7. The Kidneys
Each kidney contains nearly a million individual processing units called nephrons.
Nephrons = where impurities are filtered out, wastes are collected, and purified blood is returned to the circulation

8. Label the organs of excretion: