Valve in the thin‐walled vessel (GB#103G01) | 基礎医学教育研究会(KIKKEN)Lab
● Tubes with many valves make good use of other power
There are a large number of valves in the body. The valve prevents backward flow so that things flow in a certain direction. The most noticeable and known, of course, are the atrioventricular valves and arterial valves in the heart. These are constantly working hard and supporting our lives, but there are a number of other valuable valves.
● In a vein, not in an artery
For example, blood vessels in limbs also have valves. However, it is not in an artery or a capillary but only in a vein.It is said to be a venous valve. There are also more valves in the lymph duct. Both the venous valve and the valve of the lymph duct, the common function is that it is in the direction to return blood and lymph fluid towards the heart. But the valves in these tubes not only prevent backflow but also have more clever mechanisms. It uses other power to drive the contents.
The pressure of the blood flow sent out by the heart with energy is suddenly weakened each time the blood vessel branches, and it is totally quiet at the peripheral capillary. It is inevitable that blood pressure is low so as not to break the thin wall of the capillary. Since the capillary tube is extremely fine, its flow is fast. However, the branch ahead gradually gathers in a thick venous blood vessel. As a result, the blood flow slows down at once. In the flow of the river, it is similar to the way that flow streams flowing fast are gathered together and flowing through a stream into a larger, more spacious river flow. The lymphatic duct draws the tissue fluid leaked from the capillary blood vessel little by little from the end capillary lymph duct. The flow slows gradually as this tube gathers from a thin capillary lymph vessel gradually into a thick lymph vessel. It is disadvantageous for a lymph vessel because there is no tube actively pushing interstitial fluid like an artery of a blood vessel.
● The wall of the circulation path returning to the heart is poor
The walls of venous blood vessels and lymph vessels are much thinner and lighter than arteries of the same level. However, it has a proper smooth muscle. So it’s not just a tube like a rubber balloon. By contracting or loosening the smooth muscle, it will work as a pump like a very poor heart. But this alone is not enough to return blood and lymph fluid to the heart against gravity.
Well, in fact, veins and lymph vessels and the flow of big river seem to resemble each other, so there really is a big difference.
Even though the flow of the river is relaxed, it always flows in the direction in which the force of gravity is pulling. So the flow of the river does not know where to stay. That way, the earth is on my side. On the other hand, veins and lymph vessels are generally flowing from the tip of the limb towards the heart, so if it is standing, it is mostly against gravity. This flow is interfering with the earth. There is no way he can win. What do you do, what will you do?
● The circulation path to the heart is the whole body system
Venous blood vessels and lymph vessels make good use of the power of others. Even so, it borrows secretly without the other party knowing.What is being used silently is the movement of skeletal muscles that are solidifying around. It seems that if the arteries are next to each other, they are also using the pulsation of the artery.When skeletal muscle enters force and expands, the vein itself collapses. At that time the valve exerts its power and sends blood and lymph fluids to the front. When the circumference loosens, the pipe bulges with slightly remaining internal pressure. When the surroundings exerts force, the valve also works and sends the liquid to the front.
Actually, it may be because the vein walls are thin, so veins use the movement around them straightforwardly. These tubes are poorly made, but the strategy was skillful. However, if there is no cooperation around without knowing it, the valve’s power will be halved. That’s why your feet tend to swell when you are standing still. Originally it means that a circulation system is made on the premise that the entire body acts like walking, standing or sitting. (Nonetheless, it is physiologically disadvantageous for animals that evolved from the quadruple, with their heads upright. So even if we move somewhat, if we keep standing all day, it will swollen after all. )
If you lie down, the obstruction of gravity will be small, but since the place where it fell down is squeezed and crushed, you also need to turn over and turn it properly.
● Other valve
Speaking of tubes in the body, there are digestive tracts besides blood vessels. Because it is a long long pipe, it may feel that there are several valves. What comes out in the anatomical textbook is about a ileocecal valve (Bauhin valve) at the ileum to ileum boundary. This is not a matter of saying using other powers, it is a dignified valve which simply prevents backflow from the large intestine to the small intestine.
But that reminds me, there was another big valve in the digestive tract at the very beginning. By saying “to stand a valve” in Japanese it means good talking. It is obvious that this valve points to the tongue, which is a tool for talking.
○ Referenced sites
· People who want to know more about the functions of the circulatory valves ⇒ “Myocardium “Toho Media Network Center
・⇒ If you want to see the real thing of a venous valve ⇒ Venous valve(Web Histology/Umin)
・BodyParts 3D/Anatomography← Various body parts are prepared by 3D CG.
○ Related articles
○ Referenced books
・ぐるぐる回す循環器 文光堂 (2013/11)
・臓単―ギリシャ語・ラテン語 (語源から覚える解剖学英単語集 (内臓編))
・カラー図解 人体の正常構造と機能 全10巻縮刷版，坂井 建雄，日本医事新報社