Blood

• Functions of Blood:

  1. Transport:

  • Delivers nutrients, oxygen and hormones to the tissues
  • Removes wastes such as carbon dioxide and urea.

  1. Regulation

  • Helps to keep the body's pH within its homeostatic range
  • Helps in regulating the body's temperature

  1. Protection

  • Prevents blood loss if blood vessels are damaged
  • Protects the body against pathogens and toxins.
• Plasma blood cells:

  • Makes up 55% of the blood volume
  • 91% water
  • 9% dissolved substance
• Red Blood Cells - Erythrocytes

  • Transport respiratory gases
  • Biconcave discs with no nucleus -> Providing larger surface area and room for haemoglobin
  • Produced in the bone marrow
  • Destroyed by the spleen and liver
• White Blood Cells - Leucocytes

  • Remove dead or injured cells and invading micro-organisms.
  • Types:

  1. Granulocytes: granular cytoplasm and a lobed nucleus
  2. Monocytes and lymphocytes: spherical nucleus and agranular cytoplasm.
• Blood clotting:

  • When a blood vessel is damaged it is important a blood clot forms to prevent blood loss

  1. Walls of blood vessels constricts
  2. Damage to vessels creates rough surfaces, which platelets stick to
  3. Sticking platelets attract more platelets creating a plug, reducing blood flow.
  4. Platelets release vasoconstrictors, which make walls constrict more and for a longer time.
  5. Clotting factors are released by platelets and fibrin is formed
  6. This fibrin forms a mesh that traps blood cells, platelets and plasma. This is known as a clot.
• Clot Retractions

  1. The threads in the clot contacts pulling the damaged vessel parts together.
  2. The fluid in the clot (called serum) is forced out, drying out the clot. This is the scab.
• Nutrient Transport - Oxygen

  • 3% carried in solution in the blood plasma.
  • 97% carried as oxyhaemoglobin.
• Nutrient transport - Carbon Dioxide

  • 8% of carbon dioxide is dissolved  in the plasma and carried in solution
  • 22% carries as carbamionhaemoglobin.
  • 70% is carried in the plasma as bicarbonate ions.
• ABO Blood groups

  • An antigen is a substance that is capable of stimulating the formation of a specific protein called antibody.
  • Antibodies are produced in response to an antigen and are able to combine with the antigen that initiated the response
  • Antigen-antibody reactions are the basis for various classifications of blood groups
  • 2 antigens involved in the ABO classification of blood groups: antigen A and B.
  • The antibody that reacts is called the Anti-A and Anti-B
  • A group A person can only produce anti-B and vice versa.
• RH Blood Groups

  • A person with Rh antigens is said to be positive
  • A person without Rh antigens is said to be Rh negative
  • Rh negative people can produce an anti-Rh antibody that reacts against those antigens
• Blood Transfusions

  • The transfer of blood or blood components to another person.
  • Most the time it is vital that blood groups are to be matching otherwise the blood can clump together.
  • The ABO blood group of the donor is always matched to the receiver when the transfusions are given.