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
These all Vessels are connected to form one continuous closed system.
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.
Functions of Arteries
- They carry oxygenated blood from the heart to various organs of the body except palmonary artery.
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.
Functions of Veins
- They collect the deoxygenated blood from different organs of the body and bring it back to the heart except pulmonary vein.
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.
Functions of capillaries :
- To allow outward diffusion of oxygen into the intercellular fluid and from there into the tissue cells.
- To allow inward diffusion of carbon dioxide from the intercellular fluid.
- To allow inward and outward diffusion of substances like glucose, amino acids, urea, hormones, etc.
- To allow leukocytes (WBCs) to squeeze out through the capillary walls by means of amoeboid movement.
- They help in exchange of materials between blood and surrounding cells that takes place across the thin walls of capillaries.