The kidney is surrounded by tough fibrous tissue, the renal capsule, which is itself surrounded by perirenal fat (adipose capsule), renal fascia, and pararenal fat (paranephric body).
- Renal tissue is used to study the toxicity of anti-cancer therapies, for example, and to study the safe concentrations of other drugs in development. Kidneys are also used to identify new biomarkers to determine their transplantability and to produce safer cold preservation methods.
- The kidneys secrete a variety of hormones, including erythropoietin, and the enzyme renin. Erythropoietin is released in response to hypoxia (low levels of oxygen at tissue level) in the renal circulation. It stimulates erythropoiesis (production of red blood cells) in the bone marrow. Calcitriol, the activated form of vitamin D, promotes intestinal absorption of calcium and the renal reabsorption of phosphate. Part of the renin–angiotensin–aldosterone system, renin is an enzyme involved in the regulation of aldosterone levels
Source: Wikipedia, https://en.wikipedia.org/wiki/Kidney