Veins, arteries and capillaries share a common characteristic: all three are blood vessels.. Blood vessels carry and distribute blood throughout the body, forming the circulatory system.
This system, in humans, is closed; thus, the blood circulates inside this system of ducts, which we call blood vessels.
These three blood ducts can be confused. However, they have notable differences in terms of their characteristics and functions. In this article we will learn the 6 differences between veins, arteries and capillaries.. In addition, we will explain in detail what each of them is and what function it exerts in our body.
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Differences between veins, arteries and capillaries: what is each one?
In order to understand the differences between veins, arteries and capillaries, we will define what each of these blood vessels is (and what it is like). We will learn about their most relevant characteristics and their functions.
Veins are the blood vessels responsible for transporting blood from the different organs to the heart. to the heart. The first difference between veins, arteries and capillaries is that the wall of veins is thinner and less resistant than that of arteries, as we will see later. However, capillaries are even thinner than veins.
This is so (that the wall of the veins is thinner and less resistant) because the blood that circulates through the veins does so with less pressure than that exerted in the arteries.
Inside the veins there are valves, called venous valves (or semilunar valves), which prevent the blood from flowing back to the organs of origin. As we shall see, in the arteries there are also valves that perform the same function (preventing the backward flow of blood).
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The arteries are those blood vessels in charge of carrying the blood that leaves the heart to the different parts of the organism (i.e. to the different organs). (i.e., to the different organs). So, we have just found another difference between veins, arteries and capillaries: veins go from the organs to the heart, and arteries do just the opposite (they go from the heart to the organs).
What are arteries like and what are their characteristics? They are formed by an elastic yet resistant wall. This wall allows them to withstand the pressure with which the blood leaves our heart. When the heart contracts, the blood rushes out and accumulates in the artery. This artery, upon receiving the blood, swells.
Then, the walls of the arteries put pressure on the blood, which cannot flow back towards the heart, since there are valves that prevent this: the sigmoid valves. Thus, the blood is pushed forward, and begins its journey throughout the body. We can say, then, that it is thanks to this pressure that the blood can circulate and be distributed throughout the organism.
Finally, the walls of the arteries have a series of holes through which the blood flows to the different tissues of the body.
Finally, capillaries are the blood vessels responsible for exchanging different substances between the lumen of the capillaries and the cellular interstitium of the tissues.. Their thickness is extremely thin (as we saw, another difference between veins, arteries and capillaries is that capillaries are the thinnest blood vessels).
In fact, their name (“capillary”) comes from this very thin thickness, being assimilated to the thickness of a hair.
As for the capillary wall, it is formed by the endothelium, a single layer of cells. This layer allows the components of the blood to filter into the cells and the waste products of the cells to filter into the blood.
Every organ in our body has its own capillary system. Technically, the arteries “become” capillaries, because as they move away from the heart, they branch out into finer vessels, reaching the organs in the form of capillaries. These capillaries join and originate thicker and thicker vessels, which are the veins and have the function of returning the blood to the heart, as we have seen above.
The 6 differences between these blood vessels
Now that we have learned the definitions and characteristics of each of these blood vessels, as well as some of the differences between them, we will summarize the most important differences between veins, arteries and capillaries (some of which we have already mentioned).
1. Blood pressure
The blood flowing through the arteries has a certain pressure (the pressure that “comes” from the heart); in the case of veins and arteries, on the other hand, there is no such pressure..
2. Origin and destination
Another difference between veins, arteries and capillaries is the origin and destination of the blood: while in the veins the blood leaves the organs towards the heart, in the arteries it leaves the heart for the organs; finally, in the case of the capillaries, it leaves the heart for the organs.Finally, in the case of the capillaries, these are in fact the “terminations” of the arteries, which have branched off at the end of the organs (destination).
3. Wall thickness
The next difference between veins, arteries and capillaries is found in the thickness of their walls.. Thus, while arteries have the thickest walls of all, the walls of veins are slightly thinner, and those of capillaries are the thinnest of all. In addition, capillary walls are not associated with muscular tissues.
Degree of flexibility
While the walls of arteries are thick and resistant (they have the flexibility to return to their original shape when crushed), this is not the case in arteries and capillaries, this is not the case in arteries and capillaries.. Thus, arteries are the only blood vessels capable of recovering their original shape in the face of deformity or external force.
5. Presence of valves
The fifth of the differences between veins, arteries and capillaries refers to the presence of valves.. Both veins and arteries have valves inside them, which have the function of preventing the blood from flowing backwards.
The valves in arteries are called sigmoid valves and those in veins are called venous or semilunar valves. In the case of capillaries, they do not have valves.
6. Oxygenation of the blood
The blood carried by the arteries and capillaries is oxygenated blood (with oxygen); in contrast, the blood in the veins is not oxygenated. (with oxygen); on the other hand, the blood in the veins is not oxygenated.
This is because the veins carry blood to the heart from other organs; therefore, this blood has already transported oxygen through the organism, that is, this oxygen has been “lost” (distributed) along the way.