Blood vessels and their functions

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  • Created by: Eema003
  • Created on: 15-05-16 16:28

Arteries

Function:

  • Carry blood away from the heart and into the arterioles

Structure:

  • Tough fibres outer layer- resists pressure changes within and outside
  • Muscle layer is thicker than veins- can be constricted and dilated in order to control the volume of blood passingthrough them.
  • Elastic layer is thicker than veins- able to stretch and recoil to maintain high BP
  • Thin inner layer- smooth to reduce friction and thin for short diffusion pathway.
  • No Valves- due to constant high pressure
  • Lumen 
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Arterioles

Function:

  • Smaller arteries that control blood flow from arteries to capillaries

Structure:

  • Tough fibrous outer layer- resists pressure changes
  • Muscle layer is relatively thicker than arteries- Retricts blood flow and so controls its movement
  • Elastic layer (tinner than arteries)- because the BP is lower.
  • Thin enothelium- smooth, reduces friction, short diffusion pathway
  • Lumen- blood flows through here.
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Capillaries

Function:

  • Tiny vessels that link arterioles to veins

Structure:

  • Walls consist of epithelium lining- extremely thin for short diffusion pathway
  • Hughly branched- large surface area for exchange
  • Narrow diameter- short diffusion pathway
  • Lumen  is narrow- red blood cells are squeezed flat against the side reduces diffusion distance.
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Veins

Function: 

  • Carry blood from the capillaries back to the heart

Structure:

  • Tough fibrous outerlayer
  • Thin muscle layer- carry blood away from tissues doesnt cannot control flow of blood
  • Elastic layer relatively thin- BP too low to cause recoil action
  • Thin epithelium layer- Smooth, and short diffususion pathway
  • Valves at intervals throughout to prevent backflow of blood
  • Lumen
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