Blood vessel

Human blood vessels

A blood vessel ( Latin - anatomically the vas sanguineum ) or a vein is a tubular structure in the human or animal body, a vessel in which the blood is transported. All blood vessels together with the heart as a pumping organ form the blood circulation . Intact blood vessels are a condition for the transport of blood to the periphery of the body and the undisturbed blood flow back to the heart.

Vascular is the technical term for "concerning the blood vessels", endovascular stands for "within the blood vessels" ( ancient Greek ἔνδον éndon , German for 'inside, inside' ).

The medical field of angiology deals with blood vessels and their diseases .

Classification

Light microscopic cross section of small blood vessels, 1 arteriole, 2 venules with confluent capillary 3

Blood vessels are divided into:

Aorta (main artery)
Arteries (arteries)
Arterioles (small arteries)
Capillaries (hair vessels )

Venules (small veins)

Veins (blood vessels)

Cavernous veins : upper / lower ( Vena cava superior / inferior )

Functionally, a distinction is made between Vasa publica and Vasa privata .

A distinction is also made between central and peripheral blood vessels.

Anatomical structure

Structure of the vessel wall using the example of the aorta
1 adventitia - 2 media - 3 intima

Representation of the blood vessels in the head area according to Albrecht von Haller

The wall of a larger blood vessel basically consists of three different layers:

the tunica interna or tunica intima , short: intima
the tunica media , in short: media
the tunica externa or tunica adventitia , in short: adventitia

Capillaries consist only of an endothelium into which pericytes are inserted.

Intima

The intima is the innermost layer of the vessel wall of the arteries, veins and lymph vessels. It consists of a single layer of endothelial cells aligned in the longitudinal axis of the vessel , which are used for gas, liquid and substance exchange between the blood and the surrounding tissue. It consists of a basement membrane , a subendothelial layer of connective tissue cells and often an internal elastic membrane that separates the intima from the media.

Media

The media consists of a more or less pronounced muscle layer , depending on the type of vessel, which is bounded on both sides by a fiber lamella made of elastic connective tissue . A distinction is made between the arteries close to the heart of the elastic type (see Windkessel function ) and the more distal arteries of the muscular type. The membrana elastica externa , which separates it from the adventitia, lies above it .

Adventitia

The adventitia is the surrounding loose connective tissue for anchoring and embedding the blood vessel in its environment. In the case of larger vessels, it contains vasa vasorum , i.e. fine blood vessels that supply the vessel wall. In the case of smaller blood vessels, the supply comes from the lumen of the vessel itself.