Blood and Circulation

Blood Cells
1. Red and white blood cells and platelets in liquid plasma
  1. Red blood cells carry oxygen
    1. Bioconcave discs: round and flattened with a central indentation
      1. Red due to red blood pigment HAEMOGLOBIN which absorbs oxygen
        Mature red blood cells are unusual
        Lost their nucleus
        More space for HAEMOGLOBIN
      2. Increases surface area for absorption of oxygen
  2. White blood cells form part of the immune system
    1. Some produce antibodies while others engulf bacteria
      1. Phagocytosis
    2. Phagocyte ingests bacteria
      1. Contain lysosomes which contain enzymes which digest the bacteria
    3. Can change shape and can also move
      1. Allows them to squeeze through tiny gaps in capillary walls and enter the tissue fluid
  3. Platelets help the blood to clot
    1. Deep vein thrombosis
  4. Plasma transports food, carbon dioxide and wastes
William Harvey
1. English physician who was first to accurately describe the circulation of the blood (1628)
  1. Before Harvey, it was thought that blood was formed in the liver and was used up
  2. Scientific approach by:
    1. Dissection of humans and other animals
    2. Study of the structure of the heart
    3. Observation of living hearts in fish
    4. Experiments on human circulation
    5. Mathematical models
2. Double circulation
  1. One circulation takes blood to the lungs and back; the other takes it to the rest of the body
  2. The right half receives blood from the body and sends it to the lungs
  3. The left half receives blood from the lungs and pumps it around the body.
  4. Aorta - takes blood from the heart to the body
  5. Pulmonary artery - takes blood from the heart to the lungs
  6. Vena cava - brings blood back to the from the body
  7. Pulmonary vein - brings blood back to the heart from the lungs
Blood Vessels
1. Arteries, Veins and Capillaries
  1. Arteries - away from the heart to the organs A AWAY
    1. Blood returns to the heart from the organs in veins IN TO HEART veINs
      1. Veins do not have a pulse - blood moves in veins due to surrounding muscles squeezing them
        They have valves which ensure the blood only travels in one direction
  2. Capillaries - connect the arteries and veins
    1. Capillaries are small blood vessels with walls one cell thick
      1. Oxygen and food leave the capillaries and enter cells.
      2. Carbon dioxide and wastes leave the cells and enter the capillaries
    2. Capillaries form extensive networks so every cell is near to one
2. Arteries have a pulse, created by the pumping of the heart which moves the blood along them
The Heart
1. Pumps blood around the body
2. Made of muscle
3. Own external blood supply via the coronary artery and vein
  1. Walls are so thick that blood from inside the heart cannot supply nutrients and oxygen to outer parts
    1. Right side of heart receives blood from the body and to the lungs
      1. Left side of heart receives blood from the lungs to the rest of the body
        Right side therefore deals with de-oxygenated blood and vice versa
        Pumped to the body via aorta - pumped to the lungs via pulmonary artery
        Returns to heart from body in vena cava - returns to heart from lungs in pulmonary vein
  2. Coronary vein - blue
  3. Coronary artery - red

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Blood and Circulation

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