They transport blood from the heart to all the body organs.
All the arteries carry oxygenated blood except for the pulmonary artery.
The deoxygenated blood from the ventricle to the lung is carried by the pulmonary artery.
They have thick, elastic, and muscular walls.
They branch into arterioles and finally end in capillaries.
They are deeply situated and carry blood under pressure.
They have lumen without valves.
There are three layers of the arteries namely tunica externa, tunica media, and tunica interna.
The smallest tubes of the arterial system are called arterioles.
Veins:
It carries blood toward the heart.
They carry blood from various parts of the body toward the heart.
All the veins carry deoxygenated blood except for the pulmonary vein.
They have thin and less muscular walls.
They can be seen on the surface of the skin as they are situated on the upper surface of the skin.
Blood flows smoothly through them.
There are internal valves to prevent the backflow of blood.
Venules are small veins.
From the capillaries, venules arise and then they join to form veins.
Capillaries:
They are small veins that carry blood from arterioles to small veins.
The capillary wall is formed of a single layer of endothelial cells.
They lie in close contact with body tissues.
Their function is to supply food and nutrients to the tissue cells and remove the injurious wastes.
Leukocytes squeeze out through the capillary walls into the surrounding tissue to attack the invading bacteria, a phenomenon that is called diapedesis.