What are Blood vessels?

The human circulatory system consists of the heart, blood cells, lymphatic system and network of blood vessels. These four main organs have specific roles and functions, which work together to keep us active and healthy.

Have you ever imagined what would happen if the blood vessels stopped functioning for a few seconds?

Yes, we would die from SCA – Sudden Cardiac Arrest.

Let’s learn more in detail about blood vessels and their types.

Angiology is the branch of anatomy or human science that deals with the study of the circulatory system, blood cells, arteries, veins and diseases related to the circulatory system.

Read more: Blood and Blood Vessels

Blood Vessels

The networks of hollow tubes like pipes, which carry blood to and from all parts of the body, are called blood vessels. These vessels carry blood in both the directions, i.e. one from the heart to all other parts and another from all body parts to the heart.

Types of Blood Vessels

The three types of blood vessels are:


Arteries are the main blood vessels that carry and transport oxygenated blood or oxygen-rich blood from the heart to other parts of the body. They are the strongest blood vessels with thicker walls and are muscular in nature. It consists of three distinct layers, which are rigid, thicker and highly muscular. Arteries are located deep within the body and are red in colour. These blood vessels are with high pressure and move in a downward direction from the heart to the body tissues.

Also refer: Why arteries have thick walls.


Veins are thin, tube-like elastic blood vessels, present closer to the surface of the skin. These translucent blood vessels are blue in colour and carry impure or deoxygenated blood from all parts of the body to heart. These blood vessels are with low pressure and move in an upward direction, i.e. from the cells, tissues and other organs to the heart. Compared to the arteries, veins are thin-walled.

Also refer: Difference between arteries and veins.


Short and tiny blood vessels, found within the tissues are called capillaries. Capillaries bring about the exchange of substances between blood and tissues. These blood vessels also function by connecting arterial systems to the venous system and help in exchange of substances across cells.

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Layers of Blood Vessels

Both arteries and veins consist of three layers.

  • Tunica Intima: It is the innermost and thinnest layer of arteries and veins, which have a direct contact with the blood flow.
  • Tunica Media: It is the middle layer of an artery or vein, which is made up of smooth-muscle cells.
  • Tunica Externa: It is present adjacent to the tunica media and is composed of collagen and functions by supporting the elastic lamina in arteries.

Explore more: Blood and the Circulatory System

Functions of Blood Vessels

  • Blood vessels play a vital role in the gaseous exchange.
  • Blood vessels help in maintaining a constant internal temperature of an organism.
  • The vital function of the blood vessels is protecting against the loss of blood during injuries.
  • Blood vessels are also involved in circulating both oxygenated (poor) and deoxygenated (impure) blood from and to the heart.
  • Blood vessels help in the transportation of nutrients, water, minerals, hormones and all other essential components required for the different body metabolism.

This article concludes the introduction to blood vessels, their types and functions. Stay tuned with BYJU’S to learn more in detail about blood vessels, blood, blood cells, blood groups and any other related topics, at BYJU’S Biology.

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