Functions of the kidney
Kidneys excrete waste products, such as urea and creatinine produced in the body. If kidneys malfunction the waste products will accumulate in the blood resulting in harmful effects on the body. Kidneys have the ability to concentrate the urine according to the body requirements, i.e. if there is a deficiency of water, the kidneys will concentrate the urine to conserve body water while in water excess states diluted urine is excreted to get rid of the extra water. Hence, essentially it is the kidneys that are responsible for regulating the amount of body water. Like water, kidneys also regulate the amount of electrolytes such as sodium and potassium in the body. When there is deficiency of these electrolytes in the body, kidney tries to conserve these salts while in excessive electrolyte states body get rid of these electrolytes through urine. The maintenance of these electrolytes at an optimum level is essential for the normal functions of the body. Acid- Base balance; Normally acid is produced in the body and kidneys excrete these acidic ions to keep the blood at normal PH at 7.4 i.e. a neutral acidic/alkaline level
Hormonal functions
A number of hormones are synthesized by the kidney, the important ones are:
- Erythropoietin: It helps in the formation of red blood cells (RBCs) in the bone marrow. When there is a decreased oxygen supply to the kidney because of low hemoglobin in the blood or due to any other reason, erythropoietin production is stimulated by the normal kidney which acts upon the bone marrow to enhance RBC formation.
- Activation of Vit-D3: Vit-D3 is activated to 1-25 dihydroxycholecalciferol by an enzyme (1 alpha-hydroxylase) present in the kidneys. The 1-25 dihydroxycholecalciferol (Activated Vit-D3) with the help of another hormone known as Parathyroid Hormone (PTH) keeps a normal calcium level in the blood and mineralizes the bones.
A number on vasoconstrictive (constriction of blood vessels) hormones are secreted by the kidneys to keep the blood pressure (BP) in physiological range. The most important one is Renin. When there is fall in systemic BP, renin is secreted into the circulation by the kidney. It acts upon another chemical called Angiotensin-I in the blood capillaries of the lung parenchyma to convert it into Angiotensin-II which is one of the most powerful vasoconstrictive hormones.
Vasoconstriction results in an increase to BP.