blood

blood

1. Blood is a connective tissue formed in the red bone marrow

2. functions of blood

   • transport
     • - blood gases: oxygen and carbon dioxide
     • - nutrients from the digestive system
     • - heat and waste products from cells
     • hormones from endocrine cells to target tissues
   • Regulation
     • - pH (acid/base) by buffers
     • - temperature by vasodilation and vasoconstriction, supply of blood to sweat glands
     • blood osmotic pressure and water content of tissues (involves protein and dissolved ions)
   • protection
     • - blood clotting - preventing blood loss
     • white cells, antibodies and other proteins (interferon, complement etc.) protect against disease

3. Composition of Blood

   • Plasma 55%
     • water
     • protiens
     • other solutes
   • - Formed elements 45%

4. Erythrocytes – red blood cells

   • contain no nuclei (lost in their development)
   • • are biconcave discs
   • contain haemoglobin, a pigment used for carrying oxygen

5. Production of formed elements

   • • Occurs in the redbone marrow
   • Haemopoiesis
     • - is the production of formed elements
   • Erythropoiesis
     • is the production of red blood cells also known as erythrocytes

6. Leucocytes – white blood cells

   • five types
     • neutrophills
       • Phagocytise bacteria
     • monocytes
       • Phagocytises debris
     • lymphocytes
       • Forms plasma cells which produce antibodies
     • eosinophils
       • Allergies and kills parasites
     • basophil
       • Mast cells of connective tissue, release histamine, heparin etc., involved in inflammation

7. Platelets - thrombocytes

   • • are essential for blood clotting

8. blood groups

   • Blood groups are determined by the antigens found on the plasma membrane (remember one function of the plasma membrane is cell recognition)
   • There are many blood grouping systems based on the antigens found on the plasma membrane of red blood cells
   • The best known ones are ABO and Rhesus

9. Rhesus blood group

   • Rhesus is another antigen found on the surface of red blood cells
   • • Rhesus positive means you have the antigen (and you do not produce rhesus antibodies)
   • Rhesus negative means you do not have the antigen on the surface of the red blood cell (you do produce rhesus antibodies)
   • Rhesus negative individuals are different to the ABO grouping in that the antibody only appears after exposure to the antigen

10. Haemostasis

    • • Is a series of responses to stop bleeding from a damaged blood vessel
    • • Loss of blood from a vessel is known as haemorrhage
    • • Haemostasis involves three steps:
      • 1. vascular spasm (vasoconstriction)
      • 2. platelet plug formation
      • 3. blood clotting (coagulation)
        • Blood normally remains liquid in the blood vessels
        • Once outside coagulation takes place
        • Coagulation is the formation of a clot made up of protein fibres (fibrin) which traps the formed elements
        • The plasma is now without its clotting proteins and forms a yellow liquid called serum