Arteries, Capillaries, Veins and Arterioles

A set of notes on stucture and function of Arteries, Capillaries, Veins and Arterioles. Suitable for AQA AS Biology.

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  • Created by: lizzie
  • Created on: 08-04-10 12:00

Artery

Artery

  • Every cell in the body needs oxygen in order to respire.
  • Oxygenated blood is carried within the arteries this is generally the flow of blood going away from the heart, the exception being the Pulmonary Artery.
  • When the blood leaves the heart it is under very high pressure and arteries need to be string enough to contain the high pressure blood.
  • In order to do this the Arteries have thick muscular walls with elastic fibres to withstand the pressure which recalls as the heart beats.

Stucture

  • The Arteries have a small lumen compared to that of a vein, maintaining a high blood pressure.
  • The walls surrounding the lumen are made up of layers of muscle and elastic fibre.
  • The total diameter of the artery is large comapared to a vein.
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Arterioles

Arterioles

  • Arterioles are able to control blood flow by restricting and opening the lumen.
  • The muscle layer is thicker than in the Arteries:
    • when the muscle contracts in the Arterioles, the lumen constricts and blood flow becomes restricted.
  • The elastic layer is thinnner than in the Arteries:
    • there is lower blood pressure in Arterioles so does not need to expand as much.
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Veins

Veins

  • Veins carry deoxygenated blood, generally back towards the heart with exception to the pulmonary vein.
  • Veins have thinner walls that are flexible and can expand holding large volumes of blood.
  • The blood contained within the veins is at a much lower pressure than in the Arteries.
  • Veins that run within or close to skeletal muscles have blood squezed as the muscles contract.
  • Movement of the blood is assited by valves which prevent backflow of blood.

Stucture

  • Veins have a very large lumen and thin walls surrounding the lumen.
  • there are valves within the veins preventing back flow.
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Capillaries

Capillaries

  • Arteries and veins are linked by a series of capillaries.
  • These are tiny blood vessels with walls one cell thick, to allow exchange of oxygen, carbon dioxide, nutrients and waste between the blood and tissue.
  • The capillary walls have small pores in the wall through which tissue fluid and White blood cells can pass.

Substance movement

  • Diffusion of lipid soluble subtances passes through the plasma membrane.
  • Diffusion of lipid Insoluble substances passes though pores in capillary wall.
  • Bulk flow of water with dissolved substances also passes though pores in capillary walls.
  • Osmosis of water passes out of the capilary.
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Comments

Fool

Nice resource! :)

This is the first one I tried using the sound file on that reads it out, so I could listen while I read it.... and it was so funny that I don't think I'm gonna forget this bit xD thanks!

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