• Body coverings (Skin and mucous membrane)
  • Body secretions (Mucus, lysozyme in saliva, tears
    and urine, sweat, sebum, ear wax, HCl …)
  • Body fluids (Blood and lymph)
  1. Skin :- The outer most keratin layer (protein)
    prevents germs from entering it.
  • Sebum makes skin oily and water proof.
  • Sweat have disinfectants to destroy germs.
  1. Mucus and cilia in the respiratory tract prevent and
    wipe out germs and dust.
  2. Useful bacteria in skin and mucous membrane.
  3. Cough and sneezing to expel foreign bodies.
  4. Ear wax and hairs prevent the entry of substances.
  5. The enzyme, lysozyme, in the tears, saliva and urine
    destroy germs.
  6. HCl in the stomach fight against germs.
    Action of WBCs :-
  • Neutrophils – Engulfs and destroys bacteria,
    Produces chemicals against bacteria
  • Basophils -Stimulates the other white
    blood cells, Dilates the blood vessels.
  • Eosinophils – Destroys foreign bodies.
    Produces chemicals for inflammatory
  • Monocytes – Engulfs and destroys germs.
  • Lymphocytes (B and T) act specifically against

nflammatory Response
The dilation of the blood vessels by certain
chemicals, when a cut or wound occur, blood
flow increases to the wound site and more white
blood cells can reach there.

  1. Phagocytosis
    [the process of engulfing and destroying germs
    by certain white blood cells (phagocytes)]

Phagocyte reach near the

  • Engulfs the pathogen
    in the membrane sac.
  • Membrane sac combines
    with lysosome.
  • The enzyme in the lysosome
    destroys the pathogen.
  • Phagocyte expels the remnants
  1. Blood clotting
  • Tissues of the wounded part degenerate to form
    an enzyme, thromboplastin.
  • With calcium ions and vitamin K, thromboplastin
    converts prothrombin to thrombin.
  • Thrombin converts fibrinogen to fibrin.
  • In the fibrin net, RBCs and plateletes entangled
    to form the blood clot.
  1. Healing of wounds
    (When connective tissues form to heal the wound,
    scar remains there)
  2. Fever
    Toxins of pathogens stimulate WBC to produce
    chemicals for raising body temperature.
    Fever prevents the rapid multiplication of bacteria
    and increases the effect of phagocytosis

Action of
B Lymphocytes
B lymphocytes, (which mature in the bone marrow)
produce antibodies, which destroy germs by

  • disintegrating bacterial cell membrane,
  • neutralising their toxins and
  • stimulating the other white blood cells.
    Action of
    T Lymphocytes
    T lymphocytes,(which mature in the thymus gland)
    stimulate the other white blood cells and destroy
    cancer cells as well as virus affected cells.
    Lymph helps in defense mechanisms:
    Lymphocytes in the lymph nodes and spleen
    destroy bacteria
    B. VACCINES for Induced Immunity
    Vaccines are substances,given in advance to prevent
    certain diseases.
    Dead, inactive, alive but neutralized germs or toxins
    are used as vaccines.
    By the presence of these antigens, lymphocytes
    become activated and produce antibodies. These
    antibodies remain in the body for long time to
    provide immunity against antigens.
    [ Smallpox vaccine , the first vaccine, was invented
    by the scientist Edward Jenner.]
    BCG, OPV, Pentavalent, MMR, TT are vaccines.

Systems of medicine
• Allopathy (Modern Medicine) Hippocrates
• Ayurveda (A life style to maintain the body fit.
Majority of medicines are herbal. Indian)
• Homeopathy – Samuel Hanniman.
• Unani etc.
Some specialisation in Modern medicine :
Cardiology – (treatment of heart)
Ophthalmology – (treatment of eye)
Neurology – (treatment of brain or nerves)
Oncology – (treatment of cancer)
E.N.T – (treatment of ear, nose and throat)

  • Equipments (Stethoscope, Sphygmomanometer,
    Digital manometer, Thermometer, ECG, EEG,
    Ultra Sound Scanner, CT Scanner, MRI
    Scanner, …)
  • Lab tests (blood, urine …)
    Normal value of blood cells and haemoglobin :-
    Haemoglobin – 12-17gm/100ml of blood.
    RBCs count – 45-60 lakhs/ml of blood.
    WBCs count – 5000-10000/ml of blood.
    Platelets count – 2.5-3.5 lakhs/ml of blood.


  • Using Antibiotics
    Antibiotics are effective medicines used to resist
    bacterial diseases.
    The first antibiotics -penicillin – was synthesized by
    Alexander Fleming (in 1928).
    Side effects:
  • Regular use develops immunity in pathogens
    against antibiotics.
  • Destroy useful bacteria in the body.
  • Reduces the quantity of certain vitamins in the
  • Radiation Therapy (for cancer and eye disease)
  • Surgery
  • Transplantation of organs
  • Blood Transfusion
    Carl Landsteiner proposed A,B,AB, O blood
    grouping on the basis of A, B antigens seen on the
    surface of the RBC.
    Those blood with Rh factor (antigen D) on the
    surface of RBC are termed as positive group blood
    and those with out Rh are termed as negative group
    If blood is not compatible, the antigen in the
    received blood will react with the antibody in the
    recipient’s blood of so as to clot RBC

Defense Mechanisms in Plants
• Bark protects the inner cells.
• Cuticle and wax on leaves, defends the attack
of microorganisms.
• Cell wall, made up of cellulose, is rigid coat by
the deposition of lignin, cutin or suberin.
• Callose, a poly saccharide, prevents
the germs which have crossed the cell wall.


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