What is the primary purpose of the renin-angiotensin-aldosterone system (RAAS)?

The primary purpose of the renin-angiotensin-aldosterone system (RAAS) is to regulate blood pressure and fluid balance. This complex hormonal system is critical for maintaining hemodynamic stability in the body.

When blood pressure drops or there is a decrease in blood flow to the kidneys, specialized cells in the kidneys release renin. Renin then catalyzes the conversion of angiotensinogen, a protein produced by the liver, into angiotensin I. Angiotensin I is subsequently converted into angiotensin II by angiotensin-converting enzyme (ACE), primarily in the lungs. Angiotensin II is a powerful vasoconstrictor that raises blood pressure by narrowing blood vessels. Additionally, it stimulates the release of aldosterone from the adrenal glands, which promotes sodium and water reabsorption in the kidneys. This reabsorption increases blood volume, further contributing to higher blood pressure.

Moreover, angiotensin II also has effects on the hypothalamus, stimulating thirst and further promoting fluid intake. Through these coordinated actions, the RAAS plays a crucial role in maintaining blood pressure and ensuring an adequate blood supply to vital organs.