ZIMSEC O Level Combined Science Notes: 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
- 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.
- 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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