Arteries, capillaries and veins. Image credit

Arteries, capillaries and veins. Image credit

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
Differences between a vein and an artery.

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

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.

To access more topics go to the Combined Science Notes page.

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