Yay… Fluid Regulation…

I’m going to take a page from my paramedic instructor’s book and talk to you about the most exciting subject in all of Anatomy & Pathophysiology…

That’s right, were going to talk about the RAAS System!!!

The Renin-Angiotensin-Aldosterone System, or “RAAS” for short, is the hormone system that controls blood pressure regulation and fluid balance.  AKA, it’s the system that makes you pee…

So why did I choose to pick such a dry (pun intended) subject to talk about today?  Well, because it’s probably one of the most important hormone systems in the body.  Without it, your body wouldn’t have a way to regulate your blood when needed, and that’s a pretty important task.

But how does it work???

In short, the system starts in your kidneys, with the production of Renin.  This renin converts into Angiotensinogen and travels to the lungs.  It is then converted to Angiotensin I and meets up with Angiotensin-Converting Enzyme or “ACE” for short.  This then becomes Angiotensin II and travels to the Adrenal Cortex of the kidneys, which releases Aldosterone.  So what does all that mean???

Well, Angiotensin II causes vasoconstriction and Aldosterone causes the body to retain salt and restrict urine production.  So long story short, it makes you stop going to the bathroom and raises your blood pressure.  A lot of steps for such a simple function right???

So what happens when you take blood pressure medications?

Everyone has probably heard of the medication Lisinopril.  Lisinopril is the most common hypertension medication on the market and is typically the golden standard for HTN treatment.  Most doctors will prescribe Lisinopril first before trying any other medications to treat hypertension.  But what is Lisinopril?

Lisinopril is an Angiotensin-Converting Enzyme (ACE) Inhibitor.  So remember when Angiotensinogen travels to the lungs and is converted to Angiotensin I?  After that it is supposed to mix with Angiotensin-converting enzyme (ACE) to produce Angiotensin II, however Lisinopril BLOCKS ACE from doing its job. By doing so it blocks the blood vessels from vasoconstricting (lowering blood pressure) and continues urine production (essentially making you pee out the excess fluids).

So this VERY simple system with VERY hard words to pronounce plays a key function in the body’s fluid regulation.  Just about every endocrine function can somehow be related back to this system.

But what happens when the body’s fluid levels are low?

The RAAS system is just a small part of the body’s regulation to maintain adequate fluid levels.  One of the ways your body can increase fluid pressure is for your Pituitary Gland to secrete Anti-Diuretic Hormone (ADH) which especially turns your kidneys off to retain water.  Another way is the release of Epinephrine and Norepinephrine.  Your Hypothalamus sends a message to your Pituitary Gland to inform your Adrenal Medulla to secrete Cortisol, Epinephrine, and Norepinephrine.  Your body does ALL of this without you even knowing it, how cool is that???  Now if I could just get my body to fold the laundry, do the dishes, walk the dog, clean the bathroom, etc….