Diseases of the liver or obstructions of bile drainage from the liver impart a dark “tea” or “cola” hue to the urine. A kidney stone or a cancer of the urinary system may produce sufficient bleeding to manifest as pink or even bright red urine. Urine color may also be affected by certain foods like beets, berries, and fava beans. The “heme” of hemoglobin is converted by the liver into water-soluble forms that can be excreted into the bile and indirectly into the urine. The color of urine is determined mostly by the breakdown products of red blood cell destruction (Figure 1).
Unusually large quantities of urine may point to diseases like diabetes mellitus or hypothalamic tumors that cause diabetes insipidus. Normally, only traces of protein are found in urine, and when higher amounts are found, damage to the glomeruli is the likely basis. Urinalysis (urine analysis) often provides clues to renal disease. Normal Urine CharacteristicsĠ–2 HPF (per high-power field of microscope) Producing clear urine may take only a few minutes if you are drinking a lot of water or several hours if you are working outside and not drinking much. Another way of looking at this is that the quality of the urine produced is an average over the time it takes to make that urine. This is good advice however, it takes time for the kidneys to process body fluids and store it in the bladder. Athletes are often advised to consume water until their urine is clear. For example, if you exercise or work outside, and sweat a great deal, your urine will turn darker and produce a slight odor, even if you drink plenty of water. Some of the characteristics such as color and odor are rough descriptors of your state of hydration. The glomeruli create about 200 liters (189 quarts) of this filtrate every day, yet you excrete less than two liters of waste you call urine.Ĭharacteristics of the urine change, depending on influences such as water intake, exercise, environmental temperature, nutrient intake, and other factors (See Table 1). All other solutes, such as ions, amino acids, vitamins, and wastes, are filtered to create a filtrate composition very similar to plasma. The glomerulus is the first part of the nephron, which then continues as a highly specialized tubular structure responsible for creating the final urine composition. Because the glomeruli filter the blood based mostly on particle size, large elements like blood cells, platelets, antibodies, and albumen are excluded. The urinary system’s ability to filter the blood resides in about 2 to 3 million tufts of specialized capillaries-the glomeruli-distributed more or less equally between the two kidneys. Describe the characteristics of a normal urine sample, including normal range of pH, osmolarity, and volume.Compare and contrast blood plasma, glomerular filtrate, and urine characteristics.By the end of this section, you will be able to:
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