When referring to the composition of urine in junior middle school physical health text, it is pointed out that urine contains metabolic wastes such as inorganic salts, urea and uric acid in addition to water. In addition to these ingredients, what other ingredients are contained in urine? What substances are they produced by metabolism? Let's talk about this problem below.
Generally speaking, under the general diet, the solute discharged in 24 hours is 47 ~ 65g, half of which is urea. One quarter is sodium chloride, and the other quarter is various organic and inorganic components.
1. Nitrogen-containing substances: mainly urea, uric acid, creatine and creatinine, amino acids and ammonia.
1. Urea: It is the main product of protein metabolism, which is produced when the liver is detoxified, and its content in urine changes with the metabolism of protein. Changes in urea content can also be seen in some diseases. Severe liver dysfunction will affect urea synthesis and reduce urea output. In diabetic patients, the decomposition of tissue protein increases, and the urea content in urine increases. Chronic nephritis patients, due to renal dysfunction, decreased excretion, decreased urea excretion and increased blood urea content.
2. Uric acid: It is the metabolic end product of purine compounds. Eating a lot of food rich in nucleoprotein or decomposing a lot of cells in the body will increase the amount of acid discharged from urine. Uric acid is easy to crystallize and form stones in acidic urine.
3. Creatine and creatinine: Creatine is a metabolite of creatine. The output of creatinine is relatively constant, and the way of excretion is mainly through glomerular filtration.
4. Amino acids: Amino acids are normal products of protein metabolism. The body has a strong ability to retain amino acids. There are only trace amino acids in urine. However, when suffering from severe diabetes, liver disease and some hereditary renal tubular reabsorption defects, more amino acids are excreted in urine.
5. Ammonia: The ammonia contained in urine exists in the form of ammonium salt, which is generated in the distal convoluted tubule. The generated ammonia is secreted into the lumen by the distal convoluted tubule and combined with hydrogen ions to form NH+4. It exchanges with Na+, which can make the body expel acid and keep alkali. The output of ammonia plays an important role in maintaining acid-base balance in the body. When acidosis occurs, the urine ammonia output increases.
2. Other organic compounds: hippuric acid, bound glucuronic acid, lactic acid, β-hydroxybutyric acid, oxalic acid and sulfur-containing compounds.
Hippuric acid is a combination of benzoic acid and glycine in the liver, which is a metabolic mode of benzoic acid in the body. Combining glucuronic acid is also a way of detoxification in liver. When strenuous exercise and hypoxia of muscle tissue are caused by various reasons, anaerobic oxidation is enhanced and blood lactic acid is increased, so is urine lactic acid output. Oxalic acid comes from vegetables, and calcium oxalate is easily excreted in acidic urine and becomes a component of urinary calculi. ? -Hydroxybutyric acid is one of the main members of ketone bodies. When metabolic acidosis occurs, ketone bodies can appear in urine.
Electrolyte: Inorganic salts in urine are mainly Cl-, Na+, K+ and phosphate. The excretion of Cl- and Na+ in urine often goes hand in hand. If you eat more, you excrete more, eat less and excrete less, and you don't have to excrete when your body is deficient. K+ is different, even if the body lacks K+, as long as there is urine, it will still be excreted with urine. Therefore, the ability of kidney to preserve Na+ is stronger than that of K+.
In addition, although there is a small amount of protein and sugar in urine, it is regarded as physiological because it cannot be detected by general methods. If protein and sugar are detected in urine, it is considered pathological.