The kidneys are a pair of bean-shaped organs that lie on the posterior wall of the abdominal cavity. They receive >20% of the cardiac output, filtering the plasma to maintain a suitable extracellular environment.
Primary functions of the kidneys include:
- Regulating water/electrolyte content
- Contributing to acid-base balance through retention or excretion of acids
- Removal and excretion of metabolic waste products and xenobiotics
- Regulating arterial pressure through the production and release of renin
- Regulating red blood cell production through production of erythropoietin
- Participating in calcium/phosphorus metabolism through production of 1,25-dihydroxy vitamin D
Macroscopically, the kidneys consist of an outer cortex and inner medulla, with cavities present called the major and minor calyces. Within the renal medulla are millions of microscopic functional units called nephrons that intercalate throughout the cortex and medulla.
