Blood

Cards (29)

  • Vasoconstriction-
    • Contraction of arterial wall
    • Reduces diameter of artery
    • Reducing blood flow to organ
    • E.g. when you are cold/hypothermic
  • Vasodilation -
    • Relaxation of arterial wall
    • Increased blood flow to organ
    • E.g. when you overheat
  • Vasodilators
    • Carbon dioxide and lactic acid from cellular respiration act as vasodilators
    • E.g. when exercising muscle cells continually require energy so they produce extra CO2 and lactic acid
  • Oxy blood -
    Refers to blood that has been exposed to oxygen in lungs
    Also called arterial blood
    Oxygen concentration is high
    Carbon dioxide concentration is low
    Bright red
  • Deoxy blood -
    Refers to blood that has a low oxygen saturation relative to the blood leaving the lungs
    Venous blood
    Concentration is low
    Concentration Is high
    Dirty dark red
  • Oxyhaemoglobin = Haemoglobin + Oxygen (HbO2)
    • This is how oxygen gets the bright red colour
    • The more oxygen the brighter colour
  • Oxygen transport
    • Haemoglobin binds to oxygen as red blood cells travel through the lungs
    • Red blood cells transport circulating oxygen to organs where they need them
    • When red blood cells reach their target haemoglobin releases oxygen
  • Oxygen transport:
    • Oxygen is not very soluble in water and therefore only 3% is carried in solution in the blood plasma
    • The other 97% is carried in combination with haemoglobin molecules which are found only in red blood cells
    • Haemoglobin is able to combine with oxygen to form a compound called oxyhaemoglobin
    • The presence of haemoglobin increases oxygen carrying capacity by 60-70x
  • Carbon dioxide transport:
    • 7-8% in plasma
    • 22% combines with globin to form a compound called carbaminohaemoglobin
    • 70% is carried into the plasma as bicarbonate ions (CO2 reacts with water in plasma to form carbonic acid, carbonic acid then forms H+ and bicarbonate ions
  • Carbon dioxide transport -
    • CO2 from cells into plasma and air in alveoli
    • Carbaminohaemoglobin breakdown - diffuse into air in alveoli
    • H+ and bicarbonate ions recombine into carbonic acid
  • Blood Clotting:
    • Damage to blood vessels
    • Steps to minimise blood loss from broken vessel and prevent entry of infecting micro-organisms
    1. Vasoconstriction
    2. The muscles in the walls of the small arteries which have been damaged constrict to reduce blood flow and therefore reduce blood loss
    3. Vaso = vessel
    4. Constriction = contract
  • 2. Platelet plug
    1. Damage to the vessel creates a rough surface on a normally smooth surface
    2. Platelets stick to rough surface
    3. Sticking platelets attract others
    4. Plug gets built up at site of injury
    5. Plug helps reduce blood loss
    6. Platelets release substances that act as vasoconstrictors
    7. These enhance and prolong constriction of the damaged vessel
    8. For small tears in capillaries - plug and constriction of blood vessels is sufficient to stop any bleeding
  • 3. Coagulation
    1. Formation of a blood clot
    2. Large number of clotting factors in plasma form clot
    3. Complex series of reactions result in formation of fibrin threads
    4. Fibrin threads form a mesh that traps blood cells, platelets and plasma
    5. This mesh with the trapped material is known as a clot
    6. Threads stick to damaged walls of vessel, holding the clot in place
  • Clot retraction
    • After formation of a clot
    • Slow process
    • Threads contract becoming denser and stronger, pulling edges of damaged threads together
    • Serum - a fluid is then squeezed out
    • Clot dries forming scab over wound preventing entry of microorganisms
    • Antigen: surface of RBCs coated with sugar and protein molecules that can stimulate the immune system
    • Antibody: protein produced by the immune system
    • Antigen and antibody combine to form a complex and cause a reaction
    • 2 antigens – antigen A & antigen B
    • People may either have antigen A, B, both, or neither on the surface of their RBCs
    • Antibody that reacts against antigen A is called anti-A
    • Persons immune system recognises own antigens and will not produce antibodies for them
    • Will produce antibodies for antigens that are non-self
    • Rh antigens on surface of RBCs
    • Rh antigens are proteins
    • Person with Rh antigens are Rh positive
    • Person without Rh antigens are Rh negative
    • Person without Rh antigens is able to produce an anti-Rh antibody that reacts against those antigens
    • Rh positive individuals cannot produce an anti-Rh antibody
  • Transfusions:
    • Transfer blood or one of the components of blood from one person to another
    • Need to match blood group of donor to recipient
    • Mixing of blood types that are not compatible can cause RBCs to clump or agglutinate
    • If recipient blood contains or is able to make antibodies against the antigens on the donors RBCs, the foreign cells will clump together and disintegrate
    • ABO and Rh matched
  • Autologous transfusion:
    • Patients own blood used, blood collected form patient prior to operation that may require a transfusion
    • e.g. for elective surgery
  • In cases of severe blood loss:
    • Whole blood - has a chemical added to prevent clotting, transfused mainly in severe cases of blood loss
    • Red cell concentrates - the most widely used component, made by centrifuging whole blood to separate cells from plasma
    • Platelet concentrates - gives to patients with abnormal platelets or a reduced number of platelets
    • Plasma - the liquid part of the blood, may be given to patients needing extra clotting factors or to patients with severe liver disease
    • Immunoglobulins - a group of proteins that act as antibodies, extracted from plasma of suitable donors
    • Cryoprecipitate - obtained by freezing the plasma and thawing it slowly, when thawed it contains many of the substances needed for blood clotting remains solid
    • Agglutination: The mixing of blood types that are incompatible which causes the erythrocytes to clump together