Reniiniangiotensiinialdosteronijärjestelmän

Reniiniangiotensiinialdosteronijärjestelmän (RAAS) is a physiological system that regulates blood pressure and fluid balance in the body. It is composed of several hormones and enzymes that work together to maintain homeostasis. The RAAS system is initiated by the renin enzyme, which is released by the kidneys in response to low blood pressure or low blood volume. Renin acts on angiotensinogen, a protein produced by the liver, to produce angiotensin I. This is then converted to angiotensin II by the enzyme angiotensin-converting enzyme (ACE) in the lungs. Angiotensin II is a potent vasoconstrictor, which increases blood pressure by narrowing blood vessels. It also stimulates the release of aldosterone from the adrenal glands, which in turn promotes sodium reabsorption and potassium excretion in the kidneys, further increasing blood volume and pressure. The RAAS system also plays a role in fluid balance and electrolyte regulation. It is regulated by several negative feedback mechanisms, including the renin-angiotensin-aldosterone system (RAAS) and the natriuretic peptide system. Dysregulation of the RAAS system can lead to various cardiovascular and renal disorders, including hypertension, heart failure, and kidney disease. The RAAS system is a complex and tightly regulated system that is essential for maintaining normal physiological function.