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## Functions of the Kidney Kidneys are very important homeostatic organs. They filter our blood and excrete waste and extra fluid from our body by urine. Kidneys work as an endocrine organ secreting vital hormones like: * **Renin** maintains the blood pressure * **Erythropoietin** is involved in...

## Functions of the Kidney Kidneys are very important homeostatic organs. They filter our blood and excrete waste and extra fluid from our body by urine. Kidneys work as an endocrine organ secreting vital hormones like: * **Renin** maintains the blood pressure * **Erythropoietin** is involved in red blood cell production. Kidneys produce an active form of vitamin D3 which helps absorb calcium and phosphorus in the bones. These minerals keep bones strong. Kidneys balance the pH of our body by making changes to the amount of bicarbonate ($HCO_3^-$) from the urine back to the blood and _vice versa_. Kidneys regulate the water producing dilute and concentrated urine according to environmental changes. The process of producing urine occurs in three stages: * **Glomerular filtration** * **Selective reabsorption** * **Secretion** | Substance | Concentration | | -------------- | --------------- | | Water | | | Protein | | | Glucose | | | Urea | | | Uric acid | 0 | | Ammonia | 0 | | Creatinine | 0. | | $Na^+$ | 0. | | $K^+$ | 0 | | $Cl^-$ | 0 | | $PO_4^{-3}$ | 0.0 | | $SO_4^{-3}$ | 0.0 |