URINE FORMATION

2. Reabsorption 1. Filtration 3. Secretion

GLOMERULAR FILTRATION 180 liters per day filtered (4X total body water) Filters water & dissolved substances (plasma) Hydrostatic pressure forces substances out of capillaries As osmotic pressure increases in the capillaries, filtration decreases

Con’t Filtration is also regulated by changes in blood pressure or blood volume or by vasodilation Renin (enzyme) regulates filtration by reacting to a. Drop in blood pressure b. Sympathetic stimulation c. Decrease in ions (Na+, K+, Cl-)

TUBULAR REABSORPTION Substances are transported out of the tubular fluid & into intersticial fluid PURPOSE: reclaim materials body needs & remove waste MOVEMENTS: A. Lipid soluble B. Channel proteins C. Active transport

CON’T Most absorption takes place in the proximal convoluted portion Examples of substances that get reabsorbed: proteins, water, vitamins, amino acids, glucose, creatin, uric acid, urea, Na+, K+ Water is reabsorbed by osmosis As Na+ reabsorption increases, so does water reabsorption

Primary substances UREA: Byproduct of amino acid metabolism URIC ACID: byproduct of organic base (in nucleic acids) metabolism

TUBULAR SECRETION Substances move from capillaries into tubule to be secreted out of body Active transport Examples of substances secreted: K+, H+, creatine, histamines, antibiotics, narcotics, ammonia Secretion of H+ ions regulate body fluid pH

URINE COMPOSITION 95% Water Urea Uric acid Trace amts of amino acids, electrolytes

URINE PRODUCTION Produce 0.6-2.5 liters urine per day AFFECTED BY: a. Fluid intake b. Environment: temp/humidity c. Emotional condition d. Body temperature/respiration

Urine tells a lot about your body! Cloudy urine indicates high # of RBC, WBC, bacteria, food pigments, or poisons Urine pH ranges 4.5-8; a urine pH out of this range could be result of diet or infection (urinary tract infection)

CON’T Calcium crystals can result in kidney stones Bilirubin can indicate liver disease Too much sugar (glucose) indicates diabetes Too much protein in urine can indicate pregnancy or high protein diet; high protein can also be an indication of bone cancer