Kidney in cross-section
Kidney in cross-section showing the renal calices and pelvis with the ureter coming out of it. The kidney is a retroperitoneal bean-shaped organ pair. With its excretory function, it influences the blood pressure and the acid-base balance. The kidneys are located next to the spine on the psoas muscle in an adipose capsule. They are divided into a medullar and a cortical area. Its vitally important functions are the excretion of metabolic waste products and regulation of blood pressure. Furthermore, it produces eryhtropoitin (EPO, for hematopoiesis).