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Blood vessels are classic “lifelines” that run through the entire body and supply it with nutrient-rich blood. The so-called “life arteries” are divided into veins and arteries.
Definition
Unlike the arteries, which carry blood to the so-called periphery, the veins carry blood to the heart . Furthermore, the pressure in the veins is lower than in the arteries.
However, the definition that the veins carry oxygen-poor blood throughout the body while the arteries carry oxygen-rich blood applies only to systemic circulation. This is not the case with the pulmonary circulation.
The vena cava, which runs near the heart, has a diameter of around 2 cm. The peripheral veins are significantly smaller; the vent holes have a cross-section of just 15 μm.
Anatomy
The vein wall is relatively thin because there is very little pressure inside the vein. The vein itself consists of three layers: The inner vein layer is called tunica intima. The tunica intima consists of a single layer of squamous epithelium. This means that there is an association of flat mucosal cells that sits on the so-called basement membranes. This layer forms, among other things, the veins distant from the heart or the valves of the veins.
Below that layer is the middle layer. The technical name for this is tunica media. The tunica media consists primarily of spirally arranged or ring-shaped bundles that are built up on smooth muscle. This muscle layer, which is particularly strong in the arteries, is relatively weak. The outer layer, the tunica adventitia, consists of pure connective tissue. That fixes and protects the veins. The nerves and blood vessels, which subsequently feed the large vessels, also run in this layer.
Function
The heartbeat propels the blood through his arteries. That heartbeat or the entire process has only a very small influence if the blood is already in the body periphery or has entered the veins through the vascular resistance. The blood transport, which takes place via the veins, depends on various mechanisms and processes. Those processes are also often referred to as vein pumps.
The veins that run in the immediate vicinity of the muscle are squeezed, or squeezed, during a contraction. It is thus possible that the blood is not prevented from being transported. Many veins are considered to be the so-called “companion veins” of the arteries. The arteries also compress the veins with their pulse waves , so that the blood continues to be propelled forward. In the veins close to the heart, on the other hand, the blood flow depends on the change in pressure caused by breathing. This change in pressure is primarily influenced in the area of the chest cavity.
In the abdomen, this task is performed by intestinal peristalsis. Many factors are based on the fact that the blood is transferred. However, it is also (theoretically) possible that the blood is directed in the wrong direction. That factor is prevented by the venous valves. The venous valves (or pocket valves) are directional valves. They only open when blood is transferred in the right direction. This means the valves are only open when blood is flowing toward the heart.
Thus, the valves act against gravity. The veins also serve as capacity vessels. This means that due to the widening, very large amounts of blood can be absorbed. In the further course, the blood is stored and returned to the body if necessary so that the circulation is regulated or not interrupted.
Diseases
- vein enlargement
Common diseases in which the veins are the focus are varicose veins or the formation of varicose veins . Due to a congenital weakness of the connective tissue or an insufficiency of the venous valves, venous dilatation – in the context of blood congestion – can subsequently occur. Depending on the location of the varicose veins, a distinction is made between spider veins (skin veins), truncal varicose veins (deep veins) or reticular varicose veins (subcutaneous veins).
Most of the time, the problems are purely cosmetic, with ruptures, cramps and swelling also occurring in the advanced stage. The varicose veins can be sclerosed or treated with laser beams.
Surgical removal of the varicose veins is also possible. If the person concerned suffers from congested veins, there is a risk that venous edema will develop. This means that water collects in the surrounding tissue. Another complication or long-term consequence is the leg ulcer or ulcus cruris.
The most dangerous disease in the veins is thrombosis. In this case, the vein is blocked by a detached blood clot . If the thrombus gets into the lungs , the dreaded and life-threatening pulmonary embolism develops. In the further course, inflammations are also possible, which are referred to as phlebitis. If the phlebitis is accompanied by thrombus formation, the doctor speaks of thrombophelbitis, the benign disease. Phlebothrombosis describes the more dangerous disease.
Hello and welcome to my Health Guide & Encyclopedia! My name is Dorothy Farrar, and I'm the founder and main author of this platform.
My passion for health and wellness started at a young age when I became interested in the connection between the food we eat and the way we feel. This fascination led me to study nutrition and dietetics in college, where I learned about the importance of a balanced diet and the impact of various nutrients on the body.