Arteries

Carry oxygenated blood from the heart to the cells. Exceptions are:

• Pulmonary artery - carries oxygen from the heart to the lungs
• Umbilical cord - carries deoxygenated blood from the fetus to the placenta

Artery walls must be able to withstand the pressure of blood flow so it has elastic fibres in the walls to allow it to stretch during surges of blood. Between surges they return to original length, squeezing the blood for continuous flow.

Arteries far away from the heart are called peripheral arteries. In these, muscle fibres contract or relax to change the sixe of their lumen controlling blood flow.

• External layer of tough tissue 
• Smooth lining allows easy blood flow