The kidney is made up of kidney units, which are composed of glomeruli and tubules. One kidney has about one million kidney units, and when blood flows through the kidney, the kidney units filter the body’s metabolic waste, water, and electrolytes to form urine. So, what are the functions of the kidneys? 1.Excrete the metabolic wastes of the body and produce urine The kidney can excrete nitrogenous products such as urea, creatinine and creatine. Otherwise, these urea, creatinine, creatine, etc. accumulate in the body and cause poisoning and even uremia. The average daily urine volume of normal people is 1500-2000ml. 2, the kidneys regulate water, electrolytes, acid-base balance The human body in the process of digestion of food and body sugar, fat, protein metabolites produced by a large amount of acid and a small amount of alkaline substances released into the blood, and then through the kidneys out of the body. 3.The kidney has endocrine function and can secrete hormone active substances such as renin, bradykinin, prostaglandin and erythropoietin.