1. The Excretory System

2. Its Purpose Collects wastes produced by cells
Removes wastes from body (excretion)

3. Organs/Structures Involved
Kidneys
Ureters
Urinary bladder
Urethra

4. The Kidneys Two kidneys are the major organs of the excretory system
They act like filters by removing waste from blood
They eliminate
Urea – a chemical that comes from the breakdown of proteins
Excess water
Other waste materials
All come out in the form of urine (a watery fluid)

5. Urinary Tract From the kidneys, urine travels through…
Two narrow tubes called ureters
To the urinary bladder
Finally through the urethra – a small tube

6. The Bladder A sack-like muscular organ that stores urine
When full enough, and the walls are stretched, you feel the need to urinate

7. Urine Formation Two stages
First, wastes and needed materials like glucose are removed from the blood
Second, much of needed material is returned to blood

8. Filtering Process
Kidneys filter every drop of blood in your body more than 300 times a day
Each kidney contains approximately 1 million nephrons or filtering factories
These are tiny filters that remove waste
Blood enters kidney and travels through smaller and smaller arteries until it reaches capillaries in a nephron

9. Capillary Clusters/Capsules
In the capillary clusters (capsules), urea, glucose, water, and other chemicals move from blood into the capsules
Blood cells and proteins do not move in

10. Urine Forms from filtered material in the capsule
Needed materials for the body are reabsorbed into the blood (glucose, much of water, small amounts of other materials)
Urea and other wastes remain

11. What Urine Tells a Doctor
When urine is analyzed
Check for glucose and protein (not normally present)
Glucose could be a sign of diabetes (body can’t absorb glucose)
Protein can be a sign that kidneys are not functioning properly

12. Water Balance Kidneys help maintain homeostasis
Regulate amount of water in body
Amount of water reabsorbed depends on outside conditions
Sweat a lot more absorbed, small amount of urine