Normally, a person has two kidneys that look like oversized beans. The kidneys are located to the right and left of the spine at the lower end of the chest.
Each kidney is about the size of a piece of soap or a clenched fist and weighs 135 to 150 grams. The bulged edge of the kidney is directed inwards towards the spine. In the middle of the indentation lies the so-called Hilus. This is where blood vessels, nerves, and lymph vessels run. In addition, the ureter emerges from the kidney at this point.
How are the kidneys structured?
Each kidney is surrounded by three sheaths of fat or connective tissue, the so-called kidney capsule. These sheaths keep the kidney stable, protect it from external injuries and anchor it in the surrounding tissue.
The kidney tissue can be divided into two areas: The outer layer is the renal cortex. It contains about 2.4 million renal corpuscles in which urine is produced. The renal medulla is located inside the kidney. It contains blood vessels and twisted renal tubules through which the urine passes via the renal pelvis into the ureter and the bladder.
What are the functions of the kidneys?
The kidneys are the purification plants of the body: they produce urine and excrete waste products such as urea, which are produced in the body or ingested through food. Urea is produced when proteins are broken down. In addition, the body can dispose of medicines, drugs or toxins through the urine.
In addition to urine production, the kidneys also have other important functions: They regulate the fluid balance by either retaining water or excreting more water in the urine. If they retain water, more fluid gets into the blood vessels. This increases the amount of blood and blood pressure. If the kidneys excrete more water, the blood volume decreases and blood pressure drops. In addition, certain cells in the kidneys produce the protein renin. It has a hormone-like effect that causes blood pressure to rise.
In addition, the kidneys produce the two important hormones erythropoietin and calcitriol. Erythropoietin promotes the formation of red blood cells. Calcitriol is the active form of vitamin D and regulates the amount of calcium in the body.
The kidneys also keep the so-called acid-base balance in balance. They, therefore, ensure that the blood does not become too acidic and not too alkaline. Energy metabolism is also influenced by the kidneys: if there is too little sugar (glucose) in the blood, the kidneys can produce sugar themselves and release it into the blood.
Like a small-cap, each kidney has a pyramid-shaped gland: the adrenal gland. The adrenal glands form various vital hormones, including cortisol.