What are blood vessels
Synonyms: vein, bloodstream, vas sanguineum
English: blood vessel
A Blood vessel is a hollow organ that is responsible for transporting blood. It is a tubular tissue that is made up of at least one, but usually several wall layers and encloses a cavity, the so-called lumen.
The blood vessels in their entirety form the anatomical basis for the blood circulation and thus for the oxygen and nutrient supply to the body. In them the blood is transported to the periphery of the body and from there back to the heart.
Blood vessels are divided into:
Due to their anatomical characteristics, the aorta and the vena cava are sometimes listed separately.
The wall of larger blood vessels basically consists of three different layers:
Capillary vessels have a simpler structure. They only consist of a thin endothelium on which richly branched pericytes rest on the outside. In contrast to other blood vessels, they are permeable, i.e. permeable for certain molecules and blood cells.
The intima consists of a single layer of endothelial cells aligned in the longitudinal axis of the vessel. It is used for gas, liquid and substance exchange between the blood and the surrounding tissue.
The media consists, depending on the type of vessel, of a more or less pronounced muscle layer made of smooth muscles and / or elastic connective tissue. One differentiates, for example, the arteries close to the heart of the elastic type (see Windkessel function) and the more distal arteries of the muscular type.
Adventitia is the name given to the tissue that surrounds the vessel on the outside. In larger vessels with a thick vessel wall, it may lead to small feeding vessels, the so-called vasa vasorum.
The blood vessels are able to change the vessel diameter by contraction of their muscle layer and thereby modify the blood flow. This applies above all to the arteries, with some restrictions also to the veins.
The regulation of the vessel diameter is controlled by fibers of the autonomic nervous system and can trigger two antagonistic processes:
With the help of this simple mechanism, the body is able to control the distribution of the available blood volume, e.g. for improved oxygen supply or thermoregulation of individual body sections.
Within the blood vessels there is a physiological blood pressure that is between 80 and 120 mm Hg in the arterial vascular system and up to a maximum of 10 mm Hg in the venous system (central venous pressure).
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