The kidneys are two , and are located on the sides of the spine , between the eleventh thoracic vertebra and the second-third lumbar vertebra. The right kidney is located below the liver , the left kidney behind the spleen . The kidneys are primarily responsible for making urine . They reach a length of about 12 centimeters , are characterized by a shape similar to that of a bean . Each kidney weighs around 110-130 g.
What are kidneys?
The kidneys are two small organs responsible for the production of urine. Each of the kidneys is composed of a renal functional tissue (the renal parenchyma), the branches of the renal blood vessels and the intrarenal excretory pathways (calices and a part of the renal pelvis). All these parts of the kidneys are enclosed by a capsule of resistant and non-elastic fibrous tissue. They end in the ureter, bladder and urethra, i.e. in extrarenal excretions, the remaining part of the renal pelvis.
The renal parenchyma is made up of a medullary part and a cortical part . The medullary part is more central, the cortical part is peripheral. The main function of the renal parenchyma is to produce urine. Its medullary portion is formed by 10-12 renal pyramids which blossom into the renal sinus. Their function is to direct their product into the ureter through the renal calices. The cortical portion of the kidney is largely formed by Malpighi’s corpuscles and twisted tubules .
What are kidneys for?
Although the main function of the kidneys is to originate urine from the blood, allowing the removal of waste existing in the body, these two organs are also fundamental for other functions. For example, the kidneys secrete erythropoietin , the hormone that promotes the maturation of red blood cells or secrete renin , an enzyme that plays an important role in controlling blood pressure .
The kidneys also process vitamin D in its active form, so that it can be used efficiently by the body. The presence of only one healthy kidney is sufficient to guarantee the performance of all these functions.