The kidneys are substantial organs, located on either side of the retroperitoneal spine, one on each side, immediately adjacent to the posterior abdominal wall. The upper pole of the left kidney is level with the 11th thoracic vertebra and the lower end is level with the 2nd lumbar vertebra. The right kidney is adjacent to the liver above and is positioned half to one vertebra lower than the left kidney, with its upper pole leveling the 12th thoracic vertebra and its lower pole leveling the 3rd lumbar vertebra. The kidney is shaped like a fava bean, with a reddish-brown color and a firm and soft texture. The upper pole is wider, the lower pole is slightly narrower, and the front is slightly more elevated than the back. The outer edge is bowed and convex, and the inner edge is concave in the middle. The depression is the renal hilum, which provides access to renal vessels, ureters, nerves and lymphatic vessels, with renal veins in front, renal arteries in the middle and ureters in the back. The left kidney is slightly larger than the right kidney, and the length of both kidneys is 11-12 cm, width is 5-6 cm, thickness is 3-4 cm, and weight is 100-150 g. Women are slightly smaller than men. The renal unit is the basic unit that makes up the function and structure of the kidney. It includes the renal tubules and the renal tubules connected to them. There are about 1.3 million kidney units in the renal parenchyma of each kidney, and the renal tubules are composed of the glomerulus and the renal capsule. When you look at the glomerulus with a microscope, it is a spherical tissue composed of many very fine capillaries, and the many holes above these capillaries are like a sieve. Although the kidney is small in size and weight, it has a high blood flow and can filter blood throughout the body once per minute. Glomerulus The glomerulus is composed of a network of arterial capillaries coiled into a spherical shape, with an encapsulated wall forming a cavity. The glomerulus has a small artery at one end, called the vascular pole, and the urinary pole, which is connected to the renal tubules, at the opposite side. The glomerulus is composed of intrinsic cells including thylakoid cells, endothelial cells and pedicle cells. The filtration membrane of the glomerulus is composed of endothelial cells, glomerular basement membrane (abbreviated as GBM) and pedicle cells (named because of their cytoplasmic protrusions resembling pedicles) from inside to outside. The function of the glomerulus is mainly filtration, and the filtrate enters the urinary bladder cavity to form primary urine, which is produced by the body about 150 liters per day to remove metabolites and toxins from the body. The renal tubules are divided into three parts according to different morphological structures, distribution locations and functions: 1, the proximal tubule, the fine segment and the distal tubule. The renal tubules can also locally secrete certain regulatory factors, secrete certain metabolites and drugs for clearance, and regulate the acid-base and water balance of the body; 3, the collecting ducts and renal pelvis: urine discharge pipeline, and participate in the regulation of the body’s water balance. The physiological functions of the kidney are mainly in the following three areas: 1. Excretory function: – secrete urine, excrete metabolic waste and toxic substances such as urea, creatinine, uric acid, creatine, etc. If the kidney is damaged, metabolic waste and toxic substances can not be excreted and retained in the body, uremia will occur. Crisis life. 2, regulatory function: – regulate the balance of the body, regulate water, electrolytes and acid-base balance; if the kidney function is diseased, affecting the permeability of glomerular filtration, can not well discharge excess water and metabolic substances from the body, there will be a series of clinical symptoms, swelling, low urine, hypertension, nausea and vomiting, appetite Decrease in appetite, anemia, etc. 3, endocrine function of the kidney: – the kidney can produce certain hormones physiologically active substances, such as: through the secretion of renin, prostaglandins to regulate blood pressure and water and salt metabolism, through the secretion of erythropoietin to participate in human hematopoietic function, through the promotion of biologically active vitamin D3 secretion and regulation of calcium and phosphorus metabolism, to maintain the normal structure and function of the bones. normal structure and function of bones by promoting the secretion of biologically active vitamin D3 and regulating calcium and phosphorus metabolism. When the kidneys are diseased, they cannot synthesize it, resulting in hypertension, anemia, and osteoporosis.