2. The Excretory System Getting rid of metabolic wastes!

3. Excretory System: A. Purpose:   Excretion is the elimination (removal) of metabolic wastes from the cells. B. Why? 1.To maintain homeostasis by:   regulating the water content of the blood (blood volume)   maintaining blood pH   removing waste products from the blood 2. How is the human excretory system similar to a one celled organisms?   Analogous to the cell membrane   Wastes and CO 2 diffuse out of cells

4. C. How? Using the excretory organs  SKIN: SKIN  Rids body of excess water and salt (SWEAT): largest gland   regulates body temperature through perspiration  LUNGS: LUNGS  Rids body of CO 2  LIVER   Recycling of red blood cells, production of urea   Urea is made from the breakdown of proteins (amino acids)  KIDNEYS:  Filter (clean) the blood  Maintain blood pH  Maintain water content of blood volume

5. Regent’s question   Which is NOT a role of the kidney?   Removal of waste products from the blood   Maintenance of blood pH   Regulation of water content of the blood   Maintenance of homeostasis   Excretion of carbon dioxide

6. The Kidneys  RENAL:  Refers to anything doing with the kidneys  Kidneys involved w/ these structures:  Ureter :  Tubes that carry urine to bladder from kidneys  Urinary bladder:  Collects urine for excretion  Urethra :  Transports urine out of body from bladder

7. Kidney Structure  Renal Artery:  Carries unfiltered (dirty) blood from heart TO kidneys  Renal Vein:  Carries filtered (clean) blood from kidneys TO heart  Renal Cortex:  Outer portion  Renal Medulla:  “Corn” shaped inner portion  Nephrons:  Functional unit of the kidneys!  Lie between cortex and medulla  Millions of them!

8. Excretory Homeostasis Disorders 1. Gout: Caused by deposits of uric acid in joints. This disease is common with high protein diets. Suffer from stiffness and pain in joints. 2. Kidney Stones: caused by a calcium buildup due to improper diet. Painful in the ureter. 3. Cirrhosis: cause by the consumption of too much alcohol. The liver works extra hard and produces an excess of fats which scar the liver causing liver to shut down.

9. Excretory System: The Nephron The NephronThe Nephron

10. Excretory System: The Nephron  Nephrons are the functional units of the kidney  This is where filtration, pH balance, and blood volume are maintained!  Glomerulus:  Bundle of capillaries  Bowman’s Capsule:  Surround glomerulus  Loop of Henle:  Maintains water balance  Collecting Duct:  Collects wastes from filtered blood  Connected to ureter

11. Excretory System: Nephron Process  Nephrons clean and maintain blood in 3 steps: 1.Filtration (filtering of blood): Glomerulus  PRESSURE  Bowman’s Capsule  Blood is filtered of water, urea, salts, and other materials  These filtered materials called FILTRATE 2.Reabsorption (maintaining blood volume and nutrients)  The “good” part of filtrate is reabsorbed by blood  Most filtered water re-enters blood to maintain volume 3.Secretion: (maintaining blood pH)  The “bad” part of filtrate is secreted back into filtrate  H+ ions, some water, salts, and urea  These together are called URINE!  Urination: Urine in Loop of Henle  Collecting Duct  Ureter  Bladder  Urethra