Functions of Blood

Transport
1. Digested Food Substances
  1. from intestines
    1. to other parts of the body
2. Excretory Products
  1. NItrogenous Wastes
    1. urea, uric acid & creatinine
  2. Carbon Dioxide
    1. carried as hydrogencarbonate ions in plasma
  3. from all parts of the body
    1. to kidneys
    2. to lungs where hydrogencarbonate ions are converted to carbon dioxide
  4. excess mineral salts from intestines
3. Hormones
  1. from glands
    1. to target organs
4. Heat
  1. from respiring body tissues
    1. e.g. muscles
    2. to all parts of body
      1. to maintain a uniform body temperature
5. Oxygen
  1. from lungs
    1. to all parts of the body for cellular respiration
Protect
1. Blood Clotting
  1. blood exposed to air will soon clot
    1. seals the wound
      1. prevent excessive loss of blood
      2. prevent foreign particles from entering bloodstream
    2. blood vessels are damaged
      1. damaged tissues & blood platelets release thrombokinase (enzyme)
        thrombokinase converts prothrombin (protein present in plasma) into thrombin (enzyme)
        calcium ions must be present
        thrombin catalyses the conversion of fibrinogen (soluble protein) to fibrin (insoluble threads)
        fibrin threads entangle blood cells & the whole mass forms a clot
  2. heparin (produced in liver) is an anti-clotting substance
2. Phagocytosis
  1. process of engulfing or ingesting foreign particles, such as bacteria, by the white blood cells
  2. can destroy foreign particles that enter the blood (e.g. bacteria that enter a wound)
    1. engulfs the bacteria by flowing over them & enclosing them
      1. ingested bacteria will be digested in the phagocyte
    2. dead phagocytes killed by bacteria
      1. dead phagocytes + dead bacteria = pus
3. Production of Antibodies
  1. disease-causing organisms (pathogens) e.g. bacteria & viruses enter bloodstream
    1. stimulate lymphocytes to produce antibodies
      1. destroy bacteria e.g. attaching to them, causing the bacterial surface membrane to rupture
      2. cause bacteria to clump together or agglutinate so that they can be easily ingested by phagocytes
      3. neutralising harmful substances (toxins) produced by bacteria
  2. antibodies may stay in blood long after disease has been overcome
    1. thus, person who has recovered becomes immune/resistant to that infection
  3. some types of dead bacteria are sometimes injected into the bodies of certain animals
    1. to induce formation of antibodies in the blood
      1. antibodies are extracted from animal's serum & injected into humans to protect them from certain diseases
  4. may also be directly induced in the human body by exposing the person to dead/weakened forms of pathogen (immunisation/vaccination)
    1. dead/weakened form of pathogen stimulates the person's system to produce antibodies against the pathogen
Organ Transplant & Tissue Rejection
1. tissue or organ transplant involves replacing damaged/diseased tissue/organ with healthy tissue/organ from the same person or donor
  1. recipient's lypmphocytes may produce antibodies to destroy the transplanted organ
  2. e.g. liver, kidney & heart
  3. tissues must be as genetically close as possible to reduce risk of rejection
  4. use of immunosuppressive drugs
    1. inhibit the responses of the recipient's immune system
    2. will cause problems
      1. lower resistance to many kinds of infection
      2. recipient has to continue taking the drugs for the rest of their lives

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	Creado por Caramel Kitty hace más de 8 años