~~THE KIDNEY~~
| Basic Function | To filter out substances and maintain a balance of fluids and molecules by expelling and reabsorbing |
| Location | at the sides of the abdomen |
| # in body | usually 2, but 1 is sufficient |
| System | Part of the Urinary system |
~~NEPHRONS~~
| Basic Function | -The microscopic filters of the kidney -these small tubes are where the substances are expelled and reabsorbed to and from the blood stream |
| # | -too many to count |
"Kidney Tubule". http://www.colorado.edu/epob/academics/web_resources/cartoons/nephr.html
Kidney regulations on HOMEOSTASIS
· The kidney maintains homeostasis by regulating the following mechanisms:
1. Water balance
· Hypothalamus of the brain directs the pituitary gland of the endocrine system to control levels of the hormone vasopressin or andtidiuretic hormone (ADH) in the blood
· This hormone travels through the blood to the kidneys where it directs the rate of water reabsorption
· Increased vasopressin Ü increased water reabsorption
· Decreased vasopressin Ü decreased water reabsorption
2. Blood pressure
· Blood volume is regulated by the hormone aldosterone
· Aldosterone affects the rate of sodium ion reabsorption which in turn affects the rate of water reabsorption
· Increased aldosterone Ü increased water reabsorption Ü higher blood pressure
· Decreased aldosterone Ü decreased water reabsorption Ü lower blood pressure
3. Blood composition
· Useful materials contained in the filtrate (glucose, amino acids, etc) are reabsorbed until the threshold level of the given material is reached
· Defined as the maximum amount of material that can be moved across the nephron back into the blood
· When the threshold is reached, the remaining material is removed as waste e.g. glucose in diabetes
4. Blood pH
· Should be close to 7
· The kidney removes excessively acidic or basic substances from the blood
5. Waste removal
· Urea is the major waste product removed from the kidneys
· Placed in the blood by the liver through the detoxification process
· Excess amino acids are broken down in the liver
· Converted to ammonia and then to urea
"Unit IV HOMEOSTASIS." http://www.gonzaga.k12.nf.ca/academics/science/sci_page/biology/homeostasis_notes.htm
