Urine Formation and Characteristics

• What are the three processes that result to the urine formation?

  Glomerular Filtration, Tubular Reabsorption, Tubular Secretion
• Glomerular Filtration - a nonselective, passive process in which fluid passes from the blood into the glomerular capsule part of the renal tubule
• Filtrate - the fluid in the renal capsule; it is essentially blood plasma without blood proteins
• Tubular Reabsorption - begins as soon as the filtrate enters the proximal convoluted tubule
• Tubular Reabsorption - the process of taking up needed substances from the filtrate and then passing them out into the posterior aspect to the extracellular space
• Where do most reabsorption occurs in the kidney?

  Proximal Convoluted Tubule
• Tubular Secretion - is essentially tubular reabsorption in reverse
• Tubular Secretion - this process seems to be important for getting rid of substances not already in the filtrate or as an additional means for controlling blood pH
• Nitrogenous Waste Products - they tend to remain in the filtrate and are found in urine excreted from the body because we do not need them
• What are common nitrogenous wastes?

  Urea, Uric Acid, Creatinine
• Urea - formed by the liver as an end product of protein breakdown when amino acids are used to produce energy
• Uric Acid - released when nucleic acids are metabolized
• Creatinine - associated with creatine metabolism in muscle tissue
• Urine - the final product after the filtration and reabsorption process, which contains nitrogenous wastes and unneeded or excess substances
• Urochrome - the normal yellow color of the urine is due to this; a pigment that results from body's destruction of hemoglobin
• Glycosuria - glucose in urine, which could indicates an excessive intake of sugary foods
• Proteinuria - presence of proteins in urine, which may indicate kidney disease, hypertension, or pregnancy
• Pyuria - pus found in the urine, which indicates a urinary tract infection
• Hematuria - red blood cells in the urine, means bleeding in the urinary tract
• Hemoglobinuria - hemoglobin in the urine
• Bilirubinuria - bile pigment in the urine, which indicates a liver disease