The heart!

• Smallest vessell in the body.
• Connect small arteries to small veins
• Blood flow is slow
• One cell thick
• Very narrow

Allows oxygen and food to pass easily out of the capillary to the cells and for CO2 and other waste to pass easily from the cells into the capillary.

• Carry blood towards the heart
• Carry blood under low pressure
• Deoxygenated blood (except the pulmonory vein)

• Carry blood away from the heart
• Carry blood under high pressure
• Carry oxygenated blood (except the pulmonary artery)
• Wall is thick ad elastic to withstand high blood pressure
• Force of blood through the arteries can be felt as a pulse.