The blood vessels

• Blood is circulated through a continuous network of vessels
• It is circulated away from the heart in vessels that are known as arteries
• These arteries continue to break into smaller arteries as they move away from the heart
• These  smaller arteries branch into smaller arterioles as they move further from the heart
• These arterioles are further divided into microscopic vessels called capillaries.
• These capillaries join to form up venules.
• The venules in turn join up to become veins

Differences between a vein and an artery.

• The blood that leaves the heart has greater pressure when compared to the blood that returns back to the heart
• This means that blood vessels have different characteristics.
• The differences between arteries and veins are shown in the diagram above.

A capillary

• The blood vessel network of a mammal is made of thousands of blood vessels.
• Every organ in their bodies has a network of capillaries which allow for the efficient diffusion to and from the blood.
• Each organ receives blood via a large artery
• This blood is then taken away via a large vein
• The liver however is an exception to this rule
• It receives blood through two vessels
• The hepatic artery  delivers  blood carrying oxygen and
• The  hepatic  vein  delivers blood carrying dissolved food from the small intestines.

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