The circulatory system is a vital system for the human being, since it allows the circulation of the blood and with it of the oxygen and nutrients that all our cells need to stay alive. This system is configured not only by the heart but also by the blood vessels, there are several types of different sizes.

The two types of large vessels that are part of the circulatory system are arteries and veins. These are vessels with tasks and characteristics that make them different from each other. In this article we will look at some of the main differences between arteries and veins .

Blood vessels

The term blood vessels refers to those structures in the form of a hollow tube through which blood circulates and which, together with the heart, form the cardiovascular system. There are various types of blood vessels, which are responsible for either carrying the blood pumped by the heart to the organs or for returning the blood to the heart.

Among these blood vessels we can find large vessels and small vessels. The small vessels are the capillaries, arterioles and venules that turn out to be extensions of arteries and veins and that allow oxygen and nutrients to reach the cell or to return the blood from the organ or cell to the vein. The great vessels are the arteries and veins, which carry and direct the blood either to the organs (arteries) or to the heart (veins) and are inserted into them through the capillaries.

Main differences between veins and arteries

Although from the above we can already deduce one of the main divergences between both, this and other differences between arteries and veins are indicated below.

1. Main function

One of the main differences between arteries and veins, and the most well known, is that they perform opposite functions: while arteries carry blood from the heart to the organs, veins carry blood from the organs to the heart.

2. Composition of the blood they carry

Another of the main differences, linked to the previous one, is the type of blood they carry: while blood with a high level of oxygenation travels through the arteries, the blood carried by the veins has very low levels of this component and residues of organic functioning, such as CO2, are abundant in it .

The only exception is in the heart-lung communication, where arteries and veins carry out the opposite functions to the usual ones: the arteries carry the blood with carbon dioxide and without oxygen to the lungs (from which the CO2 will be expelled and the blood reoxygenated through breathing) while the veins take care of carrying the oxygen-rich blood to the heart.

This is linked to its function: the oxygenated blood from the heart is sent to the organs , which allows them to function, and subsequently returns to it so that it can and is enriched with the oxygen from the lung activity and through the same medium expel the CO2 produced by the body’s activity.

3. Pressure at which its contents circulate

Another major difference between arteries and veins is the pressure with which the blood circulates. There is a high blood pressure in the arteries, which is due to their thickness, their ability to contract and their elasticity, among other things. On the other hand, the venous pressure is much lower and it takes longer for blood to reach the heart from the organs than the other way round.

4. Presence or absence of valves

The arteries do not have any type of valve, and their high level of pressure is due to their size, thickness and elasticity and causing the movement of blood in the heart . In the case of the veins, there are small pumps and internal valves that allow the blood to be directed towards the heart and prevent it from flowing back to the organs.

5. Size, thickness and fragility

Veins and arteries also differ in their strength and the thickness of their walls . The arteries have a thick wall and the capacity to contract, being very resistant. In contrast, a vein is much more fragile and brittle, with much thinner and weaker walls. Also, veins tend to be larger than arteries.

6. Structure

This is due to its structure. Both large vessels have an inner layer of endothelial tissue, an intermediate layer of muscular tissue and an outer layer of connective tissue . In the arteries the muscle layer is much thicker than in the veins, which makes them more rigid.

7. Interpersonal Variability

Another difference can be found in that while veins have a highly variable pattern and arrangement depending on the person, arteries generally appear in the same locations in most humans.