Vasesblood they are tubular structures through which blood circulates, present throughout the body. These vessels form a large system of tubes that ensure that the blood pumped by the heart travels to the body and later returns to the heart.
Read too:Difference between vein, artery and capillary
→ blood vessel structure
Blood vessels are made up of the tunica intima, media and adventitia. The tunics are nothing more than layers in which there is an association of different tissues. Below are some of the main features of each of the tunics that make up blood vessels.
Underwear: This layer, which is the innermost, is formed by endothelial cells that are supported by a loose connective tissue layer, which may have some muscle tissue cells not striated. It is also possible to observe the presence of an internal elastic lamina, separating the tunica intima from the tunica media. This lamina is seen in arteries and is not usually seen in veins.
Middle tunic: This tunic, which is the median layer, is made up mainly of non-striated muscle tissue cells. Among these cells, there is a variable amount of extracellular matrix, which has, among other components, elastic and reticular fibers.
Adventitious tunic: This tunic, which is the outermost layer, is mainly made up of collagen and elastic fibers.
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→ Types of Blood Vessels
The three main types of blood vessel are: arteries, veins and capillaries. Let's learn more about each of them:
Did you know that the total length of an adult's blood vessels is approximately twice the circumference of the Earth at the equator? |
What are arteries?
The arteries are vessels that guarantee the transportofbloodofheartforyoufabricsand body organs. Contrary to what many people think, the arteries do not guarantee the exclusive transport of arterial blood (blood rich in oxygen gas and low in carbon dioxide). The pulmonary arteries, for example, are an exception and ensure the transport of blood rich in carbon dioxide.
Arteries carry blood under high pressure. This happens because they depart from the heart, pumping blood drives it in the form of a fast flow. Due to this characteristic, it is essential that the artery walls are strong, elastic and resistant. The walls of these vessels, therefore, are quite thick. Inside the organs, the arteries branch into smaller-caliber vessels, which are called arterioles.
Look closely at the structure of the different types of blood vessels.
Read too: Heart
What are capillaries?
Capillaries are blood vessels that have only one endothelial cell layer and a very small diameter. Its thin walls guarantee the exchange of substances between the blood and the interstitial fluid present around the cells.
What are veins?
Veins are blood vessels that ensure that blood from organs and tissues is transported back to the heart. Veins are the result of the convergence of capillaries. Capillaries converge to venules, which converge to veins. Veins, contrary to what many people think, do not only carry blood rich in carbon dioxide, popularly called venous blood. The pulmonary veins, for example, are an exception to this rule and ensure the transport of oxygen-rich blood.
Blood flowing in veins is under lower pressure than that seen in arteries. To ensure unidirectional blood flow, the veins have valves that prevent the reflux of blood. Furthermore, to ensure adequate blood flow, skeletal musculature plays an important role. Contraction of skeletal muscles compress the veins, ensuring flow. That's why sitting or standing for a long time causes swelling in the lower limbs.
Like arteries, veins have the three tunics. However, unlike the arteries, the tunica media of the veins has a smaller amount of muscle tissue and is therefore less thick.
Read more: Cardiovascular system
→ Summary
Blood vessels | ||
arteries |
veins |
capillaries |
|
Vessels that carry blood from the heart to tissues and organs in the body. Blood transported under high pressure They have the tunica intima, the tunica media and tunica adventitia. |
Vessels that transport blood from tissues and organs to the heart. Blood transported under low pressure. Have valves that prevent blood reflux They have the tunica intima, the tunica media and tunica adventitia. |
Small-caliber blood vessels that guarantee the exchange of substances by diffusion. They have a thin and thin wall. They do not have the tunic media and adventitia. |
By Ma. Vanessa Sardinha dos Santos
Would you like to reference this text in a school or academic work? Look:
SANTOS, Vanessa Sardinha dos. "Blood vessels"; Brazil School. Available in: https://brasilescola.uol.com.br/biologia/vasos-sanguineos.htm. Accessed on June 27, 2021.
