Question
What are blood vessels? Explain their types.

Answer

  • The close hollow tubes, transporting the blood from the heart to different organs and from different organs of the body to the heart, are called blood vessels.
  • The blood circulates in the entire body through the blood vessels.
  • There are three types of blood vessels:
  • $(1)$ Arteries, $(2)$ Veins and $(3)$ Blood capillaries.
  • $(1)$ Arteries:
  • Arteries are blood vessels that carry blood from the heart towards other organs.
  • Herein, the blood flows at higher pressure.
  • So the walls of the arteries are thick and more elastic.
  • The artery finally ends in capillaries.
  • The arteries carry oxygenated blood, except the pulmonary arteries that carry deoxygenated blood to the lungs.
  • $(2)$ Veins:
  • Veins are blood vessels that carry blood from different organs of the body towards the heart.
  • Herein, the blood flows at somewhat lower pressure, so, their walls are somewhat thin and less elastic.
  • The capillaries join together to form veins.
  • The veins carry deoxygenated blood, except the pulmonary veins that carry oxygenated blood from the lungs.
  • $(3)$ Blood capillaries:
  • On reaching an organ or tissue, the artery divides into smaller and smaller vessels to bring the blood in contact with each of the individual cells.
  • The smallest vessels have one cell layered thick walls are called capillaries.
  • Exchange of material between the blood and surrounding cells takes place across thin wall.

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