4.2

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sg

Cards (8)

  • First line of defence
    SKIN
    • The human skin is made of a tough layer and is difficult to be penetrated by microorganisms
    • Microorganisms can only get into the body if there is a wound or if the skin is injured
    • Sweat and sebum secreted by the skin contain chemicals that can kill microorganisms
  • First line of defence
    MUCOUS MEMBRANE
    • Mucous membrane is a membrane that lines the digestive tract and respiratory tract
    • Microorganisms that enter the respiratory tract are filtered by nasal hairs and trapped by mucous lining the nasal cavity.
    • Earwax, tears and vaginal secretions also function as an antiseptic that kills microorganisms
  • Second line of defence
    PHAGOCYTOSIS
    • White blood cells engulf and digest the pathogens using enzymes through phagocytosis
  • Third line of defence
    BODY IMMUNE SYSTEM
    • Immunity is the ability of the body system to resist pathogens before it is infected
    • It involves the production of antibodies when pathogens enter the body
    • Antibody is a protein produced by white blood cells into the bloodstream in response to antigens
    • An antigen is a foreign substance that comes from outside the body and induces the production of antibodies. Examples of antigens are pathogens, toxin molecules and blood cells from other blood groups.
  • NATURAL PASSIVE IMMUNITY
    • Obtained when a baby receives antibody from breast milk or from the mother's blood that flows across the placenta
    • The immunity is temporary and short-lived lasts for a few months after the birth of the baby
  • ARTIFICIAL PASSIVE IMMUNITY
    • Obtained when an antiserum is injected into the patient's body
    • The antiserum fights against pathogens without interrupting the patient's immune system
    • Antiserum is a clear liquid in the blood that contains antibodies to prevent diseases
    • The immunity is fast and temporary
  • NATURAL ACTIVE IMMUNITY
    • Occurs when a person recovers from an infection
    • THe immunity lasts long after the infection
  • ARTIFICIAL ACTIVE IMMUNITY
    • Occurs when a vaccine that contains a dead or weakened pathogen is injected into the body and the immune system responds by producing antibodies
    • The immunity lasts long after the infection