The Kidney

Abstract

The kidney performs four vital functions in its role as an exocrine and endocrine organ:

• 1. Excretion of metabolic end products: The waste products resulting from protein metabolism are excreted mainly by the kidneys.

• 2. Regulation of the acid-base balance: The excretion of H⁺ ions (acidification of the urine) and bicarbonate.

• 3. Regulation of the salt-water balance: The kidneys vary the excretion of salt and water so as to maintain extra- and intracellular isotonicity and isovolemia. This function is regulated by hormones secreted both extra-and intrarenally.

• 4. Formation of renin and erythropoietin: The renin-angiotensin system plays a role in the regulation of blood pressure and renal blood flow. The kidneys influence erythropoiesis by the formation or activation of erythropoietin.