3 characteristics of blood VESSELS

To reach every area of ​​the body, blood circulates through the interior of compliant ducts called blood vessels. The blood vessels of the body are the arteries, veins and capillaries and each one has its own particular characteristics that serve to develop its function. Another system that is closely related to blood vessels are the lymphatic vessels. In this lesson from a TEACHER we will see what the characteristics of blood vessels. If you want to find out, keep reading!

Index

1. What are the characteristics of blood vessels
2. Arteries, one of the types of blood vessels
3. Vein characteristics and types
4. Capillaries and their characteristics

Blood vessels begin in the central organ of the circulatory system, the heart. From here, the largest arteries of the human body come out, which are becoming smaller and smaller and lead the blood under high pressure to all the cells of the body. This exchange takes place in the capillary networks,

As a general rule, the wall of the arteries and veins (capillaries differ slightly) are made up of three tunics or capes, that from the light of the glass to the outside are: intimate tunic, middle tunic and adventitious tunic. Among the characteristics of blood vessels are the following.

Intimate tunic

The inner tunic is the innermost layer of the wall. It is composed of an endothelium (simple flat epithelium), a basal lamina, and a subendothelial layer of loose connective tissue.

Half tunic

The tunica media is mainly made up of smooth muscle fibers in a concentric arrangement. Between smooth muscle cells there are variable amounts of elastin fibers, reticular fibers, and proteoglycans.

Adventitious tunic

The tunica adventitia is the outermost layer and is made up of connective tissue with collagen fibers and elastic fibers. The tunica adventitia of the arteries and great veins contains a system of blood vessels called the vasa vasorum (vessels of the vessels) that supply the vascular wall.

The different types of vessels differ in the thickness of the vascular wall and the composition of the tunics.

We are going to know now the different types of blood vessels in order to better understand the characteristics of each typology. According to their size and the characteristics of their tunica media, the arteries are divided in large or elastic artery, such as aorta or pulmonary artery, medium or muscular artery, and small arteries or arterioles. Lipids accumulate in the muscle cells of the arteries of hypertensive people.

Large arteries

In large or elastic arteries, the tunica intima is relatively thick and consists of an endothelium and a subendothelial connective tissue containing collagen fibers, elastic fibers, and muscle cells smooth. Endothelial cells are flat and elongated, whose longitudinal axis is oriented to the direction of blood flow. They have inclusions called Weibel-Palade bodies, which contain Von Willebrand factor and P-selectin (important for coagulation).

The middle robe It is the thickest of the three and is made up of concentric layers of smooth muscle cells separated by elastic fenestrated sheets (with small holes or fenestrations). The adventitious tunic is a layer of connective tissue with fibroblasts, macrophages and vasa vasorum.

Medium arteries

Also called muscular arteries, they have a intimate tunica thinner than the elastic arteries with an elastic lamina separating it from the tunica media. The middle robe it is made up almost exclusively of smooth muscle cells and few elastic fibers. The adventitious tunic It is separated from the stocking by an external elastic membrane, it has collagen fibers, elastic and vasa vasorum and it is relatively thick.

Small arteries and arterioles

Their diameter is highly variable and they are usually distinguished from one another by the number of smooth muscle cells. The arterioles usually have one or two layers, while the small arteries can have up to eight.

The intimate robe of the small arteries have an internal elastic membrane, while in the arterioles it may not be present. The endothelium is similar to that of other arteries. The adventitious tunic it is a thin layer of connective tissue.

The veins they house the largest blood volume. They consist of the same tunics as the arteries, although not as well defined and according to their size they are divided into venules and small veins, medium veins and large veins.

Venules and small veins

Venules are very small in diameter and are divided into postcapillary venules and muscle venules. Postcapillary venules receive blood from the capillaries and are characterized by the presence of pericytes (mesenchymal stem cells found around the capillary endothelium). Next, the muscular veins are located, which are differentiated by the presence of one or two muscular layers in their half robe. They do not have pericytes and have a thin adventitial tunic.

Medium veins

Most of the veins in the body are medium veins, measuring about 10 mm in diameter. Many of them, especially those of the lower extremities, have valves that are projected towards the light and prevent the retrograde flow of blood by action of gravity.

In the medium veins, the robes are clearly distinguishable and they follow the general structure. His half robe it is somewhat thinner than in the medium arteries and has a muscle cell. The tunic adventitia is the thickest.

Large veins

These veins are more than 10 mm in diameter. They have the general structure, although the middle tunic and the internal one are not well distinguished. The tunic adventitia is the thickest. Examples of large veins are the superior and inferior vena cavae, which supply blood to the right atrium.

Image: Typesde.com

We finish this review of the characteristics of blood vessels knowing another type: capillaries. They are the blood vessels with the smallest diameter and in them the exchange of substances between the blood and the cells takes place. They form blood vascular networks and are composed of an endothelium and a basal lamina. They differ:

Continuous capillaries

In continuous capillaries, the endothelium forms a uniform layer that only allows the passage of very small molecules. In addition, they contain pericytes or Rouget cells, which are muscle cells that surround capillaries with their cytoplasmic processes. They are the most abundant in the body and are found in the central nervous system, lung, skeletal muscle, heart, etc.

Fenestrated capillaries

These capillaries have fenestrations in their cytoplasm and are located where blood exchange is very intense, such as the endocrine glands, kidneys, intestinal mucosa or the gallbladder.

Discontinuous capillaries

Discontinuous or sinusoid capillaries are the most permeable, since there are spaces between the endothelial cells that allow the free passage of substances. They are found where the exchange is very intense, such as the spleen, liver or bone marrow.

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Ross MH et al, Histology. Text and color atlas with Cellular and Molecular Biology. 7th edition, Editorial Wolters Kluver