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Renin-angiotensin-aldosterone system
Make it clearer
The renin-angiotensin-aldosterone system, or RAAS, is what regulates how much blood is circulating, how the electrolytes, the body's salts, are balanced, and how much resistance the vessels put up against blood flow. It has three classic pieces: renin, angiotensin II, and aldosterone.
It works as a chain, and the order matters. The juxtaglomerular cells, which sit in the arteriole entering the kidney's filter, release renin. Renin cleaves angiotensinogen, and that cut yields angiotensin I. Then angiotensin-converting enzyme, which lives mostly in the endothelium of the pulmonary circulation, turns it into angiotensin II, which is the one that acts. It is a chain in which each link appears only because the one before it made it.
Angiotensin II does two things worth remembering together. It contracts the smooth muscle of the arterioles, meaning it narrows the small vessels. And it stimulates aldosterone in the zona glomerulosa of the adrenal cortex, the outer layer of the gland that caps the kidney.
In brief
The renin-angiotensin-aldosterone system, with its three classic components, regulates blood volume, electrolyte balance, and vascular resistance.
Renin stored in the juxtaglomerular cells cleaves angiotensinogen into angiotensin I, and angiotensin-converting enzyme, mostly in the lungs, turns it into angiotensin II.
It is a chain in which each link appears only because the one before it made it.
Angiotensin II contracts arteriolar smooth muscle and stimulates aldosterone in the zona glomerulosa of the adrenal cortex.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Renin Angiotensin System, StatPearlsPublished
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