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The 9 types of blood vessels (and their functions and characteristics)

Blood is a vitally important liquid connective tissue that circulates through different types of blood vessels with the in order to carry out multiple essential functions for life: transport of waste substances, help in dementia against infections, thermoregulation of the body, transport hormones, enzymes and also other regulatory substances, transport of nutrients etc

In this article we will talk about the different types of blood vessels that the human body has, so that we can better understand its functions.

  • Related article: "Circulatory system: what it is, parts and characteristics"

What is the circulatory system?

Before explaining the different types of blood vessels, it is convenient to give a few small brushstrokes about the circulatory system, this being one of the most important devices that the body has human. Its most important functions are the following:

  • Transport hormones and also immune cells.
  • Transport waste products.
  • Regulate and maintain water and electrolyte homeostasis.
  • Regulation and maintenance of homeostasis of body temperature.
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  • Plays an important role in human reproduction.

What are the types of blood vessels?

There are basically 3 types of blood vessels in the human body: arteries, capillaries, and veins.. And each of them has a different structure that characterizes it, and there are also differences regarding the way blood flow circulates through each of these types.

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1. The arteries and their functions

The first types of blood vessels that we are going to talk about are the arteries that are found around the body, they are made up of 3 layers, called have also been called "tunics" and these, from the center outwards, are known as: the tunica intima, the tunica media and, finally, the tunica adventitia or external.

The blood that flows through the arteries does so at a high pressure, with fundamentally gradients of pressure (from a higher pressure to a lower one) and, secondarily, is aided by the force of gravity.

Before talking about the first types of blood vessels, which are the arteries, it is convenient to explain its main functions, these being the ones that we are going to list below:

  • Transport blood from the heart to the thinner capillaries.
  • Maintain pressure and blood flow; Essential for blood to reach arterioles and capillaries.
  • Dampen possible fluctuations in pressure and blood flow.
  • Correctly regulate the distribution of blood that reaches each tissue according to its needs.

Now that we know roughly what the main functions of the arteries are, let's see what the different types are. They can be classified according to their size and the characteristics of the tunica media., thus differentiating between elastic, muscular, small arteries and arterioles.

arteries

1.1 The elastic arteries

The elastic arteries they are the thickest that can be found in the body and are the ones that come out directly from the ventricles of the heart, the organ that is responsible for pumping blood at high pressure through these arteries, as well as through the pulmonary artery and the aorta.

In addition, the elastic arteries are responsible for conducting blood to the pulmonary and systemic circuits of the body, which is why they have also been called "conducting arteries". On the other hand, the branches that leave from the larger arteries are also classified within the category of elastic arteries.

It should be noted that these types of blood vessels are arteries that are called elastic because its tunica media has an elastic component of great importance for proper blood circulation.

  • Related article: "The 12 Human Body Systems (And How They Work)"

1.2 The muscular arteries

Muscular arteries are intermediate in size between small and larger arteries, and are known as "muscular" because they the tunica media they possess has a lower percentage of elasticity than the previous ones and also has a greater muscular component.

It is important to mention that in muscular arteries blood flows at a lower pressure than in larger arteries (eg. g., elastic arteries).

  • You may be interested: "Muscular system: what it is, parts and functions"

1.3 Small arteries and arterioles

The arteries branch more and more into narrower vessels, until they finally end in tiny ones that are known as arterioles, these being the last small branches of the arterial system.

On the other hand, the small arteries of the body have a wide variability in diameter and are usually distinguished from one another by the number of smooth muscle layers. What's more, these small arteries could have up to 8 layers; while arterioles usually have 1 or 2 layers.

The small arteries are the ones in charge of regulating the blood flow that goes to the capillary networks and this is possible thanks to the contraction of its smooth muscles, and that is why they are also known as "vessels of resistance".

It should be noted that at the ends or final parts of the arterioles there are very small vessels that form the metarterioles and that is where They find some precapillary sphincters, these being the ones in charge of lowering blood pressure so that it can reach the capillaries.

  • Related article: "The 25 main organs of the human body"

2. capillaries

Another of the types of blood vessels that we are going to talk about in this article are the capillaries, which are the blood vessels that have a smaller size and because of them the blood pressure is lower, so it circulates at a lower speed in order to enable an exchange of substances between the tissues and the blood. In addition, the wall of the capillaries is formed by a basal lamina and an endothelium.

Next, we are going to see the 3 types of existing capillaries: continuous, fenestrated and discontinuous capillaries.

capillaries

2.1 Continuous capillaries

First, continuous capillaries are those that are surrounded by a continuous endothelium, being also the least permeable capillaries and the most abundant. These capillaries can be found in the lungs, central nervous system (CNS), heart, skeletal muscle, connective tissue, etc.

2.2 Fenestrated capillaries

The capillaries generated have endothelial cells that are perforated and are found within the endocrine glands and also in all those tissues of the body where there is a very intense exchange between different substances, such as the gallbladder, the kidneys or the mucosa intestinal.

2.3 Discontinuous capillaries

Discontinuous capillaries, which are also known by the name of "sinusoids", are those capillaries that have a higher permeability due to the fact that the endothelial cells leave larger spaces in them and, therefore, these are capillaries that usually found in body sites where there is a great exchange between substances, such as the liver, spleen or bone marrow I mean.

  • You may be interested: "The 8 differences between veins, arteries and capillaries"

3. The veins

The last of the groups of blood vessels that we are going to talk about would be the veins, which They are the ones that are in charge of receiving the blood that comes from the capillaries and it is the veins that return the blood flow to the heart. with the aim of restarting the entire circuit through which the blood passes in order to that the whole body and its organs can fulfill in the most efficient way possible all their functions.

The blood that circulates through the veins does so at a lower speed and pressure than when it circulates. they do for the arteries and, in addition, the veins have the same structure as the arteries, formed by 3 robes.

Notably veins have the ability to store a large amount of blood, which is why they have also been called "capacitance vessels". On the other hand, these are also usually classified according to their size (from smallest to largest).

Veins

3.1 Venules and small veins

The smallest veins in the entire body, also called venules, are some veins that have a very small size and, within this category, there are some postcapillary venules that are they are in charge of receiving the blood that comes from the capillaries in order to direct that blood flow towards the venules muscular. Following the venules are the small veins.

3.2 The medium veins

Medium veins are the ones that are found in greater quantity in the body, being a type of veins that can reach a diameter of 10 millimeters. A large part of the medium veins, especially those found in the lower extremities, They have a kind of valves in their inner tunic that serves to prevent a retrograde flow of blood. due to the force of gravity, since otherwise the blood would not circulate correctly through this part of the body and would remain accumulated in the same place.

3.3 The large veins

Finally, within these types of blood vessels, such as veins, we are going to talk about the large veins, which are responsible for receiving blood flow coming from the other veins of the body in order to take care of returning it to the heart, at the level of the right needle that connects with this organ.

It should be noted that these veins are the ones with the largest diameter in the entire body., far exceeding the 10 millimeters that could reach a maximum of medium veins.

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