1. The Excretory Systems

2. As your body performs chemical activities to keep you alive, waste products, such as carbon dioxide and ammonia, are made
These waste products are toxic to cells
Excretion is the process of removing waste products from the body
Three of your body systems play a role in excretion: integumentary system releases waste and water when you sweat
respiratory system releases carbon dioxide
when you exhale
urinary system removes waste from the blood

3. The Urinary System

4. The urinary system organs produce, store and eliminate urine
The kidney removes waste from the blood
The ureters are tubes that connect the kidneys to the bladder
The bladder is a saclike organ that stores urine
The urethra is the tube urine exits the body from

5. The Kidneys

6. The kidneys are a pair of organs that constantly clean the blood
They filter about 2000 liters of blood each day – our bodies hold only 5.6 liters of blood
Inside each kidney are more than a million nephrons – microscopic filters in the kidney that remove harmful substances from the blood – ex. Urea

7. How the Kidneys Filter Blood

8. A large artery brings blood into the kidney
Tiny blood vessels branch off and pass through part of each nephron
Water and other substances are forced out of the blood vessels and into the nephrons
As these substances flow through the nephrons, most of the water and some nutrients move back into blood vessels – the remaining waste is left behind in the nephron
The cleaned blood leaves the kidney
The yellow fluid that stays in the nephrons is urine
Urine leaves the kidneys through the ureter and goes into the urinary bladder
Urine leaves the body through the urethra

9. Water In, Water Out

10. You drink water every day and you lose water every day in sweat and urine
You must get rid of as much as you drink – if you don’t you will swell up
The balance of fluids is controlled by chemical messengers in the body called hormones
When you are warm, you lose a lot of water in the form of sweat and water content in the blood drops
A hormone is released that signals the kidney to conserve more water and make less urine
If there is too much water, less of the hormone is released and more urine is produced

11. Urinary System Problems

12. Bacterial infections – bacteria can get into the bladder and ureters through the urethra and cause painful infections
Kidney stones – salts and other wastes collect inside the kidney and form kidney stones – may interfere with urine flow
Kidney disease – damage to nephrons can prevent normal kidney function – may lead to dialysis – a machine that performs the job of the kidneys