1. The Excretory System How Our Body Eliminates Cellular Wastes

2. Excretory System – removes excess water, H 2 O, urea, carbon dioxide, CO 2, and other wastes from our blood.  Kidneys – filter out excess water and urea  Lungs – filter out carbon dioxide, CO 2, from the blood.  Skin – excretes water, as sweat, which contains some trace chemical wastes, including urea.

3. I. The Kidneys  Every drop of blood in your body is filtered by your kidneys more than 300 times per day!  Kidneys eliminate urea, minerals and excess water.  Kidneys regulate the amount of water we need to maintain in our bodies.

4. Kidneys – filter wastes and excess water from the blood. Ureters – tubes that take urine from the kidney to the urinary bladder. Urinary Bladder – a sack that stores urine. Urethra – small tube that leads urine out of the body.

6. II. Nephrons  Unit in the kidney that filters the blood.  Two steps: 1 st a large portion of the water from the plasma leaves the blood capillaries and enters the nephrons. 2 nd return of water, salts, calcium, vitamins, hormones, pigments and amino acids to the blood through the blood capillaries that surround the nephron tube.  The fluid that remains in the nephron is called urine.

8. III. Urine  Contains mostly water and waste products.  Protein digestion produces ammonia which is converted to urea by the liver.  Much of the urea is left in the nephron when the blood is filtered.

9. IV. Signs of Disease Doctors analyze urine for disease; Normal urine contains water, urea and trace minerals. Sugar in urine indicates Diabetes Protein in urine indicates the kidneys are not working and the person, or animal, is very sick.

10. Sometimes the kidneys fail and a dialysis machine is necessary.