Keeping the blood flow

Types of blood vessels
1. Artery
  1. Arteries have a small lumen so that they have a large pressure to make sure the blood keeps flowing out of the heart. The thick elastic wall stops the artery wall from breaking under the pressure. The high pressure allows the arteries the carry large volumes of blood very quickly
2. Capillary
  1. Capillaries have a small, single celled wall so that they can diffuse materials easily through the call walls and deliver them to where they're needed
3. Veins
  1. Veins have a large lumen and small walls because they do not have to deal with large pressures, the blood instead passes easily through with little pressure as the veins carry the blood back to the hears
vessel structure
Blocked vessels
1. One reason vessels become blocked is due to a build up of cholesterol this can be due to: lack of exersize, bad diet, smoking, drinking and more
2. The formation of Atheroma
  1. As LDLs build up they can form a plaque and this can eventually form an ulcer which perpetuates the build up of LDLs that eventually block the artery.
3. Stents
  1. Stents help vessels to stay open when plaque has built up by holding the vessel open
  2. People have stents because their vessels have closed
Valves
1. Heart valves
  1. Heart valves stop blood from flowing back into the heart chamber after its been pumped out
    1. If blood was allowed to flow back into the heart then the heart would be less efficient and so cells would get less oxygen
2. Valves are needed in the veins because the relatively low pressure in them could mean that that there was a backflow of blood, arteries do not need valves because their high pressure means there is little chance of back flow
3. Valves could need to be replaced for two reasons: the valve could be restricting the flow of blood and the valve could be leaky meaning that there was a backflow of blood
4. Valve replacements
  1. Mechanical replacements
    1. Advantages
      1. Lifetimes durability
      2. Better survival rates
      3. Better efficience
    2. Disadvantages
      1. Must take blood thinner
      2. Noisy, can be bothersome to some patients
      3. Increased chance of bleeding
      4. Can cause a stroke
  2. Organic replacements
    1. Advantages
      1. 50% of patients do not need a blood thinner
      2. They are quiet and do not usually make much noise
    2. Disadvantages
      1. Decreaced survival rates
      2. Operation must be repeated every 10 - 15 years
      3. Can cause a stroke
  3. Overall I think that the best type of replacement valve is the mechanical valve because it lasts a lifetime and gives the patient the highest chance of survival

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Keeping the blood flow

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