Hypertension for Dummies - or - Blood Pressure Explained

You want hypertension and blood pressure explained? No problem. Here's the 'regular guy' explanation (long form, 'cuz we like to run off at the keyboard).

Your whole body is a weak hydraulic system. It's a sack of mostly water, with miles of water-filled tubes (ok, blood vessels and other plumbing). The notion of hydraulics is that pressure applied to a non-compressible liquid gets transmitted through that liquid to every part of whatever contains it.

If it's your circulatory system that we're talking about, then we say it's a "weak" or inefficient hydraulic system because the miles of tubing are not rigid pipes or armored hoses - they're flexible. Think of a plastic garden hose, compared to copper pipe or armored hydraulic hoses.

High blood pressure is the working pressure of your arteries and veins, with the settings cranked a bit higher than is good for you. We say "a bit higher" because, if it's a lot higher, then you are not long for this world, sorry.

Blood Pressure Has Basically Three Components

Stay with us here - we'll have hypertension and blood pressure explained in no time (if you're a fast reader).

• The heart pushes the blood out one end, it circulates through all the pipes (arteries, arterioles, capillaries, venules, veins), and it comes back in the other end. OK, there are two outs and two ins (out to the lungs and back in, then out to the rest of the body, and back in), but the basic principle applies - the heart goes boom (push), and the blood rushes out into the biggest artery.The faster, and more forcefully the heart beats, the greater the pressure in the system.
• The second aspect of blood pressure is the pipes, all the blood vessels in your body.That big artery (mentioned in our first point) that exits the heart splits into smaller arteries that head out to this-and-that parts of the body, those arteries in turn split into smaller arteries, until eventually becoming the tiniest arterioles, and those lead into capillaries, the smallest blood vessels in the body, and also the most permeable and pervasive.Capillaries suffuse pretty-much every living part of your body. The blood in the capillaries offloads oxygen to the surrounding tissues and picks up carbon dioxide (and other substances).Coming out the other end the capillaries join to venules, which join to larger and successively larger veins, all the way back to the heart.Th heart would not be able to make the blood go all that distance, if the arteries and veins were just soft, limp noodles. The pressure of the blood being pushed out of the heart would dissipate shortly after it left, and never get anywhere.Instead, the arteries are strongly walled tubes, lined with contractile tissue (involuntary muscle) that prevents expansion of the tubes, and actually helps the blood along the way. The tighter and more clenched the arteries are, the stiffer the pipes, and the farther the pressure wave from the heart can push each pulse of blood.The veins aren't reinforced as much - they are slightly controllable for dilation, and they've got check-valves to prevent back-flow, but that's about it - since they are the return collectors in a closed system.As long as there's enough pressure on the artery side of the system to force the oxygenated blood all the way through to (and past) the tiniest vessels - those capillaries - that's enough.
• The third element of the blood pressure system is the actual amount of blood in the system. The kidneys manage the salinity and overall volume of liquid, allowing water (the biggest component, by volume, of your blood) to seep out of the system, or causing it to be reclaimed back into the circulatory system, depending on how much is needed, to maintain sufficient pressure.

So far, so good. We're keeping up our end by ensuring that we get this hypertension and blood pressure explained - you keep up your end by reading and paying attention; there's a test.

It's a balancing act. The heart keeps pounding, pumping blood. The arteries tighten up or relax, according to demand and according to the amount of blood that's in 'em. The kidneys regulate the concentrations, thereby causing the blood to be thicker or thinner (more or less dilute) and and have more or less volume.

So What's The Problem?

As long as the heart keeps pumping, the rest of the system just maintains, right? Adjusting to how much liquid and salt you've been consuming and losing (as urine, as sweat, as water-vapour in your exhaled breath), right? Well, yes. But there are limits to the adaptability.

Keeping Your Concentration

You can alter the concentration of a liquid (say water) that has something dissolved or suspended in it, in two ways. You can add-or-subtract water (pour some in or evaporate some off), or you can add more of the substance that was dissolved. You can also subtract some of the dissolved material, though that's usually the hardest one to accomplish.

Now how does that work in the body for, say, the blood?

It's hard to consume too much water, but it can be done. You can dilute the blood so much that the filtration mechanisms don't work properly. That can shoot your blood pressure so far out of range that you wouldn't survive it... except that, when you are that diluted, several other things are killing you even faster.

Consuming that much liquid in a short time takes a lot more determination than most people have. So it's rare.

More likely is that you take in too little water, or that what you do take in has too much salt in it. The result can be excessive concentrations in the blood, putting a lot of stress on the kidneys, which gamely try to keep up with whatever you throw at them.

Various bad things can happen if you habitually drink too little (water), or habitually consume too much salt.

Pipe Liners

But there's more. There are other things that affect blood pressure, and the amount of effort that the heart must exert to keep the blood moving.

One problem is physical blockage, the accumulation of crud on the walls of the arteries. Eventually, that accumulation causes the arteries to lose their flexibility - their ability to react and adjust to changing conditions and demands. It also makes the arteries narrower, by filling up the interior space, so it takes more effort to push the blood through.

Consider also that there's a quantity of blood vessels that is sufficient to get blood to all the tissues in the body. It's nominally the amount of piping needed for an average-sized person.

The heart is made to pump blood through that many miles of vessels. The mechanisms of controlling blood pressure are optimized to work with your body's optimum size and shape.

In other words, nature kinda expects you to be that optimum size and shape. So does your heart.

How Much of You Is There?

Now consider what happens when you get fat. You increase your mass, the sheer amount of you that needs to have blood circulated through it. Each additional pound of fat needs a lot of extra little arterioles, capillaries, and venules in order to carry in oxygen and carry away metabolic wastes.

All that extra tubing represents extra work for the heart, and lots of small tubes represent extra resistance to the flow of liquid, so the whole system increases blood pressure to keep the blood flowing.

Put It All Together And...

So, we have blood pressure explained as pipes, pump, and fluid volume-and-thickness control, and we have crud from the years of junk-food clogging and stiffening the arteries, and making the holes (the pipes) smaller.

We have extra fat tissue causing the existence of many more tiny pipes. The blood pressure in the system begins to average higher and higher, just to maintain operation.

Death By Passivity

Any more contributors? Well, at least one more. We noted that the arteries actively help to propel the blood along and constrict or relax to help adjust pressure. But the veins are nearly-passive hoses. They contain/carry the blood, but they don't help much to move it.

So, aside from a bit of suction at the inlet of the heart, how does the blood in the veins get back to the heart? Well, part of the solution is the small left-over pressure after the blood emerges on the veinous side of the capillary network. But the rest is the tissues surrounding the veins.

Physically active tissue, muscles, basically massage the blood along the veins, back toward the heart. Every squeeze sends some blood along, and the internal valves prevent backflow. The actions of your leg muscles are particularly helpful in getting blood from your feet and lower legs all the way back up to the heart.

So, sitting around has the effect of removing that assistance. The blood still needs to get back to the heart, but without the outside assistance from working muscles, it means the heart must push-and-suck that much harder when it should be relaxing, and the whole system must maintain a higher overall pressure, just to keep working.

So the Pressure Is Higher - BIG DEAL

It all works, right? You can have hypertension/high blood pressure and your blood still flows, your kidneys and lungs and brain and everything still all work, right?

Well, yes and no. The system initially has a lot of over-capacity built-in. You test that overcapacity every time you lift something heavy, sneeze, cough, strain to make a bowel movement.

The problem is that the overcapacity is in relation to a normal baseline. Now, constantly pushing the system near the upper limits of that capability - by being fat, by having too much salt inside, by having gunk clogging the pipes - stresses everything, and it leaves no reserve, no headroom, for exertions like coughing and sneezing and straining.

Filtration and Volume Control - Under Pressure

The kidneys take a real beating. They are a compact network of very, very delicate tubes and structures, whose job is to be so thin and porous that water and all sorts of chemicals can pass through, in both directions, in controlled fashion. When something that fine and delicate is kept at high-pressure, it eventually begins to shred and leak.

Shredding and leakage in the kidneys means that they are in the process of failing. It can take years, but if you don't remove the stressor - the high blood pressure and the things that cause it - they eventually do fail.

Healing Leaves Damage

Before failing completely under excessive blood pressure, your kidneys, like any other damaged organ, try to heal. But "healing", just like for wounds and tears to skin and muscles, is not a perfect thing. In fact, healing generally results in the formation of scar tissue, whose only real capability is to hold stuff together.

So, if you gouge or scrape your skin and it scabs and scars, the scar is different from the rest of your skin. Not only does it look different, it has no sweat glands, no hair follicles, and no nerves. It's not dead, but it doesn't contribute except to plug the hole. Now think of the same thing happening inside your kidneys and inside your arteries and veins. Tears and other damage keep happening, due to the relentless excess pressure, and scar tissue keeps replacing working tissue. The affected organ becomes inflexible and less productive. Less resilient.

It's Not Just Kidneys, Man

Breathe Easy?

Of course, as important as your kidneys are, they are not the only delicate organ connected to the over-pressured circulatory system. The lungs are quite delicate, being mostly thin membranes designed to allow gas and vapor exchange. If they suffer years of micro-shredding and cumulative scarring, they become less able to do their job, and less able to be trained to greater capacity, if (say) you took it into your head to start exercising. Well, at least you weren't dumb enough to smoke... or if you were, at least it was pot or something that gave a bit of return for the damage, right?

Give Some Thought To The Brain

There's more. Somewhere above your neck, that mound of jelly behind your eyes - your brain - is another delicate tissue. If tears happen in the tiny blood vessels, the contents (blood) leak into the surrounding tissue (the brain). The rest of the body is, as we observed above, a meat sack. It's got an outside container of muscle, fat and skin, but all of that material is flexible. Stretchy, more or less. A bit of leakage here and there in the body is not good, but it can be accommodated by expansion of the container - pressure from internal leakage can be accommodated to a certain extent.

The brain, however, is inside the skull. The skull is a notoriouslyinflexible box. If fluid leaks from the pipes in the brain, it has nowhere to go, so it just pools in the brain and presses, crushing the tissue around it against the unyielding inside of the skull. Brain tissue dies, and you lose some functional capability, either in gradual fashion, or as a sudden event - a stroke. When a piece of brain dies, it's gone for good. So is the function that it performed.

Stroke Recovery Is Partial... And Slow - Really Slow

Elsewhere, we recounted a story about accidentally poking a sharp object into the end of a finger, just above the final knuckle and, in the process, severing the nerve that served that quadrant of the finger. That quadrant of the finger-end, from the knuckle to the tip was unable to feel pressure and other sensation.

It's taken 12 years, so far, for nerves from the adjacent quadrants of that finger-end to slowly grow into the "dead" zone and give it a semblance of ability to feel again. It's not quite like the original. It's coarse and it feels odd.

That was a single nerve serving a relatively minor functional area, way out in the periphery. The brain, on the other hand, is mostly nerve tissue. And it's the center of everything that you are and do.

Our point is that, if you damage some of the nerve tissue in your brain when you are forty, fifty, sixty, even if the rest of the brain tries to adapt and grow into the gap, it will never be as good, and even a pale imitation of the old function will take decades to develop, if ever.

In other words, you'll reach the end of your life before you get major brain function back, assuming it even tries to come back.

Not Me - I'll Be Like Those People Who Make Miracle Recoveries

No you won't. Why do you think you read about them in the newspapers, and why do you think the stories are so breathless and playing up the event? Same as everything else you read in the news (or see on TV or get from your RSS news services on the Web) - it makes the news because it's rare and unlikely. It's the exception. If you could count on being so rare and exceptional that you would make a miraculous recovery from a stroke, don't you think you would have been miraculously spared the damage in the first place? Teenagers think that way. It's well past time you stopped thinking you are immortal and somehow exempt.

The Reason Why

Why do you think we've created this website? It's because we've seen enough of what's happening to our own aging carcasses that we are scared into [finally] doing something about it.

We've also seen relatives lingering for years and years, with their brains and bodies only partially working due to stroke.

Wake up.

Read this page every time you feel you motivation slipping.

Quick Links to all our BP pages

Here's the handy selection of our Blood Pressure / Hypertension related pages on this Men's Health Tips (MHT) site:

The MHT page	What the page is about
About Blood Pressure (this page)	How blood pressure works in your body
Measure Your Blood Pressure	How a blood-pressure measuring kit works and how to use it to measure your own BP and that of family members
Prevalence of High Blood Pressure	How likely is it that you or a member of your family has damaging high blood pressure?
Find Your Blood Pressure Numbers	Some general ways to learn what your numbers are
Relieve Hypertension / Reduce High Blood Pressure	A non-pharmaceutical way to help lower the BP while you work on eliminating the cause
Control Weight/Control Hypertension	Straightforward, relatively easy ways to get your weight down and thereby control your BP

And if this page wasn't where you wanted to be, then return to the Home page from this blood pressure explained page.

Or return to the introductory Blood Pressure page from this blood pressure explained page.

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