Circulatory System

• The circulatory system comprise of: the heart, blood vessels & blood
• Blood contains several components namely: plasma, red blood cells, white blood cells, platelets.

  Blood transports nutrients, gases, waste, hormones and heat.

  These are about 5-7 liters of blood in an adult body

  The distribution is as follows:

  • 55% plasma which contains 90% water and 10% soluble materials
  • 45% are blood cells
• The blood is also the main defense against diseases and infection as it has platelets that form clots and they have white blood cells which have phagocytes which engulfs bacteria and lymphocytes which produce antibodies
• FUNCTIONS OF THE PARTS OF BLOOD

  • Plasma

  -transport of carbon dioxide, digested food, urea, mineral ions, hormones and heat energy.
• FUNCTIONS OF THE PARTS OF BLOOD

  • Plasma -transport of carbon dioxide, digested food, urea, mineral ions, hormones and heat energy.
  • Red blood cells- they transport oxygen around from the lungs to the cells which require it for aerobic respiration. they are red because they contain haemoglobin, it combines with oxygen to form oxyhaemoglobin.
  • White blood cells- They are larger than RBC. They have a nucleus. There are 2 types of WBC which are Phagocytes and Lymphocytes
  • Platelets- are involved in helping blood to clot
• BLOOD CLOTTING

  • When we cut ourselves we not only lose blood but we make it easier for bacteria to get inside our bodies. Therefore, the body must stop the flow of blood and block the breach in the skin to prevent blood loss & infection. For this to be effective it needs to be guided. Fibrin is sticky and forms long threads creating a net, which traps some red blood cells. This makes a plug called a blood clot.
• BLOOD VESSELS

  -Blood vessels are tubes through which blood flows

  -There are 3 main kinds of blood vessels: Arteries

  Veins

  Capillaries
• Arteries carry blood away form the heart. They divide again and again and eventually form tiny vessels called capillaries

  
  

  Capillaries gradually join up with one another to form large vessels called veins

  
  

  Veins carry blood towards the heart
• ARTERIES

  • Carry blood at high pressure away from the heart
  • Carry oxygenated blood (other than the pulmonary atery)
  • Have thick muscular walls containing elastic fibers
  • Have a narrow lumen
  • Speed of flow is fast
• VEINS

  • Carry blood at low pressure towards the heart
  • Carry deoxygenated blood (other than the pulmonary vein)
  • Have thin walls
  • Have a large lumen
  • Contains valves
  • Speed of BLOOD flow is slow
• CAPILLARIES

  • Carries blood at low pressure within tissues
  • Carry both oxygenated and deoxygenated blood
  • Have walls that are one cell thick
  • Have 'leaky' walls
  • Speed of flow is slow
• Arteries branch into smaller arteries called arterioles. These branch further into capillaries.
• After exchange of materials between capillaries and tissues, capillaries join up and form smaller veins called venules The venules join up to from veins
• MAIN BLOOD VESSELS IN THE BODY

  1. Heart and lungs: pulmonary artery & veins
  2. Between the heart & lungs: renal artery & veins
  3. Between the heart & liver: hepatric artery & veins

  • Hepatric portal vein connects the gut (intestines) with the liver
• Double circulation happens blood from the body passes through the heart twice before flowing back to the body.