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defence mechanism of body 4.pptx

  1. DEFENSE MECHANISM OF THE BODY Prepared By Ms. Beenish Tufail
  2. What is defense mechanism • The human body has three primary lines of defense to fight against foreign invaders, including viruses, bacteria, and fungi. The immune system's three lines of defense include • First line of defense • Second line of defense • Third line of defense
  3. First line of defense: physical and chemical barriers • Prevent all types of foreign agents from penetrating the outer layer of the body. • No specific foreign agent is targeted at this level.
  4. Physical Barriers Skin • Cells filled with keratin, making skin impenetrable, waterproof, and resistant to disruptive toxins and most invaders • Dead cells are shed and replaced ( 1 million every 40 min) taking microbes with them Mucous membrane • The inner surface of body are guarded by mucous membrane that line the respiratory, digestive, urinary, and reproductive systems and protect the internal lining Hair • hair in the nose act as a coarse filter
  5. Chemical Barriers Sweat produced by glands in the skin, wash away microbes and their acidity slows bacterial growth Mucous membranes produce sticky mucous that traps many microbes Saliva and tears contain an enzyme called lysozyme that kills bacteria by rupturing their cell walls Cerumen (ear wax) produced in the ear canal and protects the canal by trapping dirt and dust particles
  6. Second line of defense: Defensive cells If pathogens penetrate the first line of defense, these cells play a role in inhibiting or destroying the pathogen before it harms the body Phagocytes engulf pathogens, damaged tissues, or dead cells • Neutrophils • Macrophages Eosinophils discharge destructive enzymes to destroy pathogen too big for phagocytes Natural killer cells seek out abnormal cells
  7. Defensive proteins Interferon protein infected cells produced interferon • Binds with other cells that become infected with a virus, and protects it by stimulating the cells to produce antiviral proteins that prevent the virus from making copies of itself • Interferon attracts and stimulate natural killer cells and macrophages to kill cells infected with the virus
  8. Inflammation • When body tissues are injured or damaged, a series of events called the inflammatory response occurs Redness caused by increased blood flow to the damaged area Heat increased blood flow elevates the temperature in the area of injury, increasing metabolic rate of the body cells Swelling histamine makes capillaries more permeable than usual Pain causes person to protect the area and prevent additional injury
  9. Fever • A fever is an abnormally high body temperature caused by pyrogens (chemicals that set the thermostat in the brain to a higher set point) • A mild or moderate fever helps the body fight bacterial infections by slowing the growth of bacteria and stimulating body defense response
  10. Third line of defense: The Immune System • Immunity means protection from infections • When the first two line of defense of the body can not prevent the infection, the immune system acts to eliminate the infectious agent and prevent the body from infection • Immune response consists of two steps • Step 1 recognition of the pathogen or foreign molecule • Step 2 mounting reaction against pathogen
  11. Natural immunity • It is resistance to a disease possessed by an individual. • Nature has given certain individuals, species and races immunity against certain diseases. • For example, some individuals are more resistant to certain infections than others
  12. Acquired immunity • Only with natural immunity it is not possible to fight off each and every infection and survive. • Immunity is induced by certain ways. Acquired immunity is developed during persons lifetime • It is not inherited • This immunity can be acquired actively or passively
  13. Active immunity • Naturally acquired active immunity is acquired when a person is exposed to natural infections or to some antigen in the day to day life. Following the exposure the immune system responds by producing antibodies • Artificially acquired active immunity is acquired by administering specially prepared antigens which produced specific antibodies. This is also known as vaccination
  14. Passive immunity • Naturally acquired passive immunity is involves natural transfer of antibodies from a mother to fetus via placenta or breast milk and thus providing immunity to the newborn for a few days to few months. • Artificially acquired passive immunity antibodies are directly administered to body for stimulation of immune responses. These antibodies are either produced in animals or in human.
  15. Cont… • Immunity can be classified into two categories • Innate immunity • Adaptive immunity Innate immunity reflects the first and second line of defense against infections it is the defense mechanism which are present as inherent Adaptive immunity consists of defense mechanism which are stimulated by exposure to infectious agents
  16. Adaptive immunity • Humoral immunity is mediated by antibodies produced by B lymphocytes ( matured in bone marrow) It is principal defense mechanism against extracellular microbes and their toxins • Cell mediated immunity is mediated by cytokines, produced by T lymphocytes ( matured in Thymus Gland) defense mechanism against intercellular microbes
  17. Resistance and susceptibility • Susceptibility means they can't grow if the drug is present. This means the antibiotic is effective against the bacteria. • Resistance means the bacteria can grow even if the drug is present.
  18. Phagocytosis • The process by which a phagocyte (a type of white blood cell) surrounds and destroys foreign substances (such as bacteria) and removes dead cells. • Bacteria, dead tissue cells, and small mineral particles are all examples of objects that may be phagocytized.
  19. Process of phagocytosis