Recall

• Describe human circulation

  Double - blood passes through the heart twice in every circuit

  closed - in vessels
• Describe fish circulation

  Single - heart pumps deoxygenated blood to gills to load oxygen , flows to body and then returns to heart

  closed - in vessels
• Describe insect circulation

  Open - blood flows in body cavity - not always in vessels - segmented heart pumps haemolymph in a main artery - opens body cavity to flow around organs

  nutrients and hormones transported by haemolymph, oxygen is not
• Function of the blood

  • Transports oxygen, carbon dioxide, hormones , glucose
  • immune defence against pathogens
  • regukation if temperature - vasodilation/vasoconstriction
• Structure of blood

  euthrocytes - no nucleus, haemoglobin

  leycocytes - immune response

  platelets - clotting

  plamsa - serum liquid and clotting protein
• Describe serum

  Liquid of 90% water, glucose, AA, proteins like globulin and albumin, enzymes, antitoxins and hormones
• Describe tissue fluid

  Fluid derived from blood plasma which drains out of blood capillaries to bathe cells
• How is tissue fluid formed?

  Blood passes from Arterioles into carpillaries - hydrostatic pressure causes fluid to be pushed out through carpillary walls

  exchange occurs - most tissue fluid then re-enters at Venules by osmosis due to plasma proteins which caused oncotic pressure
• What is lymph?

  Fluid which doesn’t re-enter capillaries passes into open ended lymph capillaries - carried away from tissues to rejoin the blood in veins near heart
• Lymphatic system

  Lymph vessels (tubes) with valves containing lymph fluid and lymph nodes
• What protein is found throughout the system?

  Lymph contains antibodies , tissue fluid contains very little, serum contains soluble proteins

  plasma contains lots of proteins in forms of hormones, enzymes and globulin
• Red blood cell structure

  • No nucleus - more room for haemoglobin
  • bicomcave disc so large SA to volume ratio for absorption of oxygen
• Haemoglobin affinity for oxygen

  Each haemoglobin carries 4 molecules of O2

  Haemoglobin combines reversible with O2 to form oxyhb

  Hb‘s affinity for O2 is higher under higher ppO2 - readily associates and loads O2 in the lungs but dissociates and unloads in tissues
• Why are oxygen dissociation curves sigmoid?

  more difficult for Hb to associate with first molecule of oxygen but then change of haemoglobin a shape makes it easier to load molecules 2 and 3 - when saturated it’s difficult to pick up final O2 as less likely that an O2 will collide and right place to join to last haem group
• Bohr shift

  At high pPCO2 haemoglobin affinity for oxygen is lowered and dissociation curve shifts to the right
• Left shift - spenders

  some pigments have higher affinity for oxygen so at each PPO2 they are more likely to load O2
• How is carbon dioxide carried?

  mainly has HCO3 in plasma and red blood cells

  or simple solution of CO2 in plasma
• Describe the biochemistry of CO2 carriage as HCO3

  CO2 from respiration diffuses into red blood cells where it reacts with water to form carbonic acid - dissociates into H+ and HCO3- ions

  H+ causes oxyHb to unload O2 and Hb takes H+ ions to form haemoglobinic acid

  HCO3- ions diffuse out of RBC into plasma and Cl- diffuses in to balance charge

  lungs low pPO2 causes H+ and HCO3- to recombine into CO2 and water - CO2 breathed out