Blood Vessels 

The tubes (or pipes) through which the blood flows are called Blood vessels.

What are the 3 Types of Blood Vessels

There are three main types of blood vessels involved in blood circulation

1. Arteries
2. Veins
3. Capillaries

Also Check – 7 Structural and Functional Difference Between Arteries Veins and Capillaries

These all 3 Vessels are connected to form one  continuous closed system.

 Arteries

 Characteristics of Arteries

 They have thick muscular and elastic walls to withstand the high pressure of the blood emerging from the heart. 

They do not have valves.

Also Check – 15 Important Differences Between Arteries and Veins

 Veins

Characteristics of Veins

 They have thin valves than the arteries and carry blood at low pressure.

 Have valves to prevent the backflow of blood to maintain uni directional flow.

.

 Capillaries 

Characteristics of Capillaries

 Artery divides into smaller vessels known as capillaries on reaching an organ or tissue.

 The walls of capillaries are one cell thick. 

They also have valves to prevent the backflow of blood.

Also Check – Transportation in Human Beings

7 Important Functions of Blood Vessels -Arteries, Veins and Capillaries

1. Arteries carry oxygenated blood from the heart to various organs of the body except palmonary artery.
2. Veins collect the deoxygenated blood from different organs of the body and bring it back to the heart except pulmonary vein.
3. Capillaries allow outward diffusion of oxygen into the intercellular fluid and from there into the tissue cells.
4. Capillaries allow inward diffusion of carbon dioxide from the intercellular fluid.
5. Capillaries allow inward and outward diffusion of substances like glucose, amino acids, urea, hormones, etc.
6. Capillaries allow leukocytes (WBCs) to squeeze out through the capillary walls by means of amoeboid movement.
7. Capillaries help in exchange of materials between blood and surrounding cells that takes place across the thin walls of capillaries.