Transport in humans Part 3

• Platelets and blood clotting

  • When blood vessels are damaged, damaged tissues and platelets release thrombokinase
  • Thrombokinase converts soluble prothrombin to thrombin.
  • Calcium ions are needed
  • Thrombin catalyses the conversion of soluble fibrinogen to insoluble fibrin
  • Fibrin entangles blood cells , forming blood clots
• Protective functions of blood

  1. Forms blood clots
  2. Phagocytosis
  3. Production of antibodies
  4. When disease causing organisms known as pathogens enter our bloodstream, blood stimulates lymphocytes to produce antibodies
• Haemophilia

  • Hereditary
  • Blood clotting mechanism greatly impaired
  • Slight injury could result in bleed to death
• Immunisation

  • Immune system
  • WBC and their products
  • Antibodies remain in bodies for long period of time after defeating diseases. Person who has just recovered will gain immunity from that disease
  • Two ways
  • Older way is to inject types of dead bacteria into animal bodies
  • Induces the formation of antibodies in the animal bodies
  • Antibodies then extracted and injected into human body
  • Newer way is to directly induce antibodies in humans by injecting disease causing organisms (pathogens) into human bodies
  • Stimulates the immune system to produce antibodies
• Organ/tissue transplant

  • Transplanted organs/tissue may be rejected by recipients immune system due to it being recorded as foreign body
  • Lymphocytes produce antibodies to destroy transplanted organs/tissues
  • Methods to prevent rejection
  • Genetic match of organs/tissue
  • Organ immuno-suppressive drugs for rests of life
  • X - ray radiation of bone marrow/lymphatic system
• Lymphatic system

  • For absorption and transportation of fats
  • At higher pressure, hydroelectric pressure higher than osmotic pressure
  • Causes the re entry of fluid back into the blood capillaries
  • Not all the fluid returns
  • 10 percent enters a separate lymph capillary
  • Fluid in blood = plasma
  • Fluid surrounding cells = tissue fluid
  • Fluid in lymphatic system = lymph
• Functions of lymphatic system

  1. Returns excess interstitial fluid to blood circulation
  2. Returns plasma proteins to maintain low interstitial fluid protein concentration and to maintain osmotic pressure gradient
  3. Transports wastes from tissue cells
  4. Acts as a filter for foreign particles and kills bacteria
  5. Absorption and transportation of fats from small intestine
• Lymph flow

  • Very slow
  • No pumping system
  • Depends on movement of skeletal muscles and valves
  • Only in one direction which is towards the heart