The Excretory System Getting rid of metabolic wastes!

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

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

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

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

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!

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.

Excretory System: The Nephron The NephronThe Nephron

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

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