veins … my understanding


Veins are not Capillaries, nor are they Arterioles, nor are they Arteries. Now that sounds rather obvious and silly to say, but please bear with me. I’m working on a better personal understanding of Klippel-Trenaunay Syndrome so challenging old memories from high school biology seems like a decent starting point.

I think of veins as our primary blood reservoir. This reservoir regularly contains about 60% of our total blood volume when at rest. That word “at rest” is an important concept, so much so that I likely will mention it repeatedly in this and other queries. I think of the circulatory system in a resting state first and then build on it to establish capacities and operational changes from that conceptual point. As pertains to Arteries, Veins are comparatively larger. Veins are also comparatively more pliable or stretchable than the typical artery. Looking at the physical design and engineering of these two components of our vascular system helps make these distinctions a lot clearer for me. Another distinction is the remarkable difference in the mass of the smooth muscle layer in each.

Wait a moment! Arteries and veins are muscles? Wow, now that is a point I did not recall from high school biology. As I revisited the books, I learned it is an amazing aspect in the fundamental understanding of how blood gets around in our body. I bet most folks think the heart does all or the majority of the labor. A vascular surgeon reported to me years ago that if we relied on the heart alone to pump blood out and back, it would fail from exhaustion. I let his explanation drift right on by not thinking to ask him to explain all the systems that worked cooperatively with the heart. Ok, getting back on point. What else works with the heart to pump blood through our bodies? In line after our heart are artery muscles and then arterioles muscles. At any point in time about 30% of our blood supply is in the latter two vessels.

Yahoo! Something I did remember. The Arterioles which are the smaller extensions of our Arteries connect to our Capillaries. I recall these target points are actually more like beds of porous vessels which surround muscles and internal organs and feed these critical body parts. What I did not realize is that our Capillaries operate different than arteries in a very key way. These vessels do not have a smooth muscle layer. In a way they are more like sponges packed around the objects they feed receiving pumped blood. Feeding is an interesting process in and of itself – some material passes through tiny feeding holes in the Capillaries while others go through a breakdown process in the Capillaries and then move through vessel walls at a molecular level.

What I found noteworthy was this. The pumping process stops here. This begs the question – how is it that the Capillaries don’t burst from being over filled. And, if the pumping action stops here how does blood get out of the Capillary beds. I think the best answer to this is to think of the balance of our vascular system as a network of venous tubes that become the delivery system for a couple of mechanical systems that pull the blood back to the heart. So, here we go! If the heart had to do all the work it would fail from exhaustion. Yup, that wonderful tidbit of information from that very special vascular surgeon that treated me so many years ago. I had always thought the heart did all the work using a closed loop system and that one chamber of the heart pumped blood to my toes and the other pumped it back to my lung and heart complex.


Turns out our bodies are built with several support tools which help the heart pull the blood back to the lung/heart complex, at least close enough that the heart can then pull it back into its chambers for redistribution. Nope, I haven’t forgotten the lungs which are a critical part of our biological and physiological processes. However, they really don’t have a critical role in the actual pumping and pulling of the blood. However, our Diaphragm does, as do our leg muscles. These are two huge support systems.

So, how does this all work from here?

As our physical activity increases, the veins are used like plumbing to move blood back to the heart. The net result is to support increased circulation. Worth noting, the veins do have smooth muscles which assist to pull blood back to the heart; however, these muscles are not near as capable as the artery muscles. How so? These venous smooth muscles are very thin and incapable of reciprocating the arterial pump. That is a point of anatomy and distinction that cannot be overlooked.

Ok then, how does our body balance things out? How does it get our blood back to the heart?

The primary assist for pushing blood back to the heart/lung complex is called the “skeletal muscle pump. Our Veins pass through our skeletal muscles. When we move, when physical activity occurs, the skeletal muscles squeeze our veins. This action increases our blood pressure in that section of the vein and that pressure causes our blood to move up the vein. This is a good place to recall another feature that makes veins unique — as the venous blood returns to the heart it benefits from one-way valves that insure unidirectional flow of blood. When our leg muscles constrict, this physiological change causes the upstream valve to close and the downstream valve to open. [Note: upstream means furthest from the heart] Repeated movement, called cycles of contraction and relaxation, effectively pushes blood back to the heart.

“And that ain’t all!” While the skeletal muscle pump pushes venous blood out of the lower limbs, our breathing adds in another assist. It helps to push venous blood out of the abdomen. That mechanical action or system is called a respiratory pump. The diaphragm descends when we breathe increasing abdominal pressure. With increasing pressure in the abdomen, the resident veins are push blood back toward the heart in the same way as the veins in the skeletal muscles. From there the heart has sufficient strength and mechanical ability to manage the balance of the movement of blood through the heart and ling complex.

The least among the group of assisting mechanisms are the smooth muscles layer of the veins. Veins are actually considered to be a blood reserve. Recalling again that 60% of our blood is contained within these vessels. They are far more stretchable than arteries to accommodate volume and volume variance. The very thin smooth muscle layer in the veins do more to manage resting blood volume and pressure than movement of blood, although a very very small amount of work in the latter function is plausible. Recall, we don’t always always move about and when we don’t the heart needs the assist, although we do constantly flex and move our muscles even when sitting. In other words, our muscle skeletal pump is working virtually all the time because we never sit motionless and motion is our primary mechanism for pushing blood out of our lower extremities.

This is the point at which I take issue with posts in one of the KT support forums where the “constrict-dilate-dilate” theory was proffered. Recalling this theory was based on veins acting as a primary mechanical mechanism which pumps blood back to the heart (along with the heart doing its fair share of the pumping too). As I understand it, physiology/anatomy responds with a sound “no” and “no” to the aforementioned theory. Here is the fundamental physiological fact: Veins can vasoconstrict taking instructions from muscles and the like, but they do NOT do this in any sort of rhythmic way. I don’t know if this helps explain the dramatic difference in the role and function for veins versus arteries, but veins have no blood pressure to speak of!  Arteries do.  When we get blood pressure readings it is the arteries we read at the two stages. We find no such parameter with veins. KTS is triad of vascular malformations which are Venous, Lymphatic and Capillary.  When finding arterial malformations a different diagnosis is made. Reading into medical literature about the dynamics of vascular malformations in general requires culling to make sure the subject matter is about veins, lymphatic vessels and capillaries.

I think it prudent to mention that we have one more very important assist. It is not our bodies to do, but certainly our minds can convince our bodies to take advantage of it. That assist is gravity. Wherein Klippel-Trenaunay Syndrome (and many correlated syndromes) involve venous and lymphatic malformations or anomalies, our return plumping is weak and poorly configured. In many cases we have very bizarre constructions including malfunctioning valves, missing valves, missing veins, overstretched veins, veins that may even misconnect to body parts causing all kinds of calamities. Our skeletal pumps and respiratory pumps and heart can do all the proper work, but if our venous plumbing is not right, regardless of the mix of anomalies, elevation of our lower extremities above our waste/diaphragm, and in the more severe cases, above our heart gives us a huge assist from Mother Nature. Gravity is quite capable of assisting the resting body and the ever working heart. My doctors implored me to elevate – elevate – elevate.

Mechanical Medicine also has developed some assists. Two come to mind. First, there are prescription compression garments which help support weakened veins and lymph vessels. These garments also are engineered with what is called graduated compression which I more than imagine is designed to offer support for weakened or missing valves (the net result of both features is to move blood and lymph fluids up the leg and into areas with better natural circulation. Not to beat a dead horse, but please verify through a qualified, experienced KT Radiologist and Vascular Surgeon that you have sufficient deep vein blood flow before using these. Given you have competent flow while wearing these, by all means do it! Weakened venous vessels and valves only get worse over time and according to my doctors these do so at a remarkably accelerated pace with KTS affected folks. You can also read up on new compression machines which do lymphatic massage (and I’m more than guessing venous constriction). The idea is to help the body through external devices to push the blood back to the heart.

While I’m here. Look into lymphatic massage my licensed lymphatic massage therapists. Regular sessions with lymphatic massage is reported to clear out malformed and/or struggling lymphatic vessels. These techniques move fluids up the body and into areas that function more regularly. I separated this out because it is a human intervention, not a machine. Me, I would prefer the human touch to the machine. However, that is purely me being a spoiled kid and probably not liking the idea of a machine working me over. Many of my KT companions report remarkable success with both of these interventions.

I feel talked out. I bet your tired reading. I will finish with this upbeat note. Another source of external compression is swimming pools, rivers, lakes and oceans. It is physics that tells us that the deeper you go under water the more compression our body feels. Imagine that … our skeletal muscle pump gets another assist from Mother Nature. I wish I had the answer to a question that is still on my table, but I don’t as of yet. It is, “what is the compression level of water and how does it compare to mechanical compression, like from compression garments. I do know this from personal experience — swimming helps me tremendously. Ok, I don’t really swim all that well, but what I do do, when I do it, makes my legs feel great and my hourly and end of day swelling is much less. Is that a scientific study? Nope! It’s purely anecdotal. What is not anecdotal is the research that went into this article. I set out to refresh my very old memory of high school biology. I may not have read enough or properly understood what I read. To the latter please critique and correct as our KT community could use a common thread which results in accurate and helpful information about how human bodies work and why us KTS folks work so differently. I think from efforts like this we can garner reasoned and helpful regimes of care and treatment.

There is more to come as I work to advance KT Awareness in what is our mission to spread the word throughout our wonderful KT community and for that matter those who places where we could use a big hand up from governance and worldwide community. As now, in the future, please know I am not a doctor. I am KT diagnosed and a fierce advocate. I work to share my personal experiences, but also well researched and supportable information. Whenever I fail to deliver, I wish to know. Critique is the fire that turns naivety into metaphorical diamonds.

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