To state another function of the circulatory system To identify the three lines of defence mechanism To describe phagocytosis To state the meaning of antigen & antibody

WHY DO WE NEED THE BODY’S DEFENCE MECHANISM? To defend the body against disease-causing microorganism (pathogens) Pathogens are bacteria, viruses & parasites Transmitted by air, contaminated food & water, animal (vector) & contaminated needles. Also by contact.

Non-Specific Defence : First line defence & Second line defence Specific Defence : Third line defence

BODY’S DEFENCE MECHANISM NON-SPECIFICSPECIFIC 1 ST LINE2 ND LINE3 RD LINE SKIN : sweat, sebum MUCOUS MEMBRANES : secretion of mucus Phagocytosis by phagocytes Antibodies produced by lymphocytes

Skin – physical barrier (dead keratinised layer  difficult to penetrate If there is a cut, the blood clots quickly  to prevent blood loss & entry of m/organisms Tears secreted by tear gland & acidic sebum (sebaceous gland) – contain lysozymes which destroy some bacteria Mucus (mucous membrane) in nasal cavity & trachea traps dust particles & microbial spores The cilia (respiratory tract) sweep the trapped particles to the pharynx  swallow into stomach (secretes HCl)

The phagocytic white blood cell are attracted by chemicals produced at the sites of infection and move to these sites. Engulf & digest the pathogens The soluble products are absorbed & assimilated by the phagocytes May also be destroyed by toxins produced by the pathogens Number of leucocytes increases to try to destroy the pathogen & neutralise the toxin

In higher group of animals have a more specific immune defence mechanism against pathogen  IMMUNE SYSTEM Two main types of lymphocytes : B-lymphocytes  produce antibodies T-lymphocytes  attack cells infected by pathogen or which produce certain chemicals to coordinate the immunes response. ANTIGENS – large complex molecules (proteins/polysaccharides) that the immune system recognises as foreign found on the cell membrane of m/organisms/dissolved in the blood plasma/interstitial fluid.

ANTIBODIES – A protein produced by lymphocytes in response to the entry of an antigen into the body. IMMUNE RESPONSE – interaction between antibody & antigen which result in the antigen being eliminated from the body

AGGLUTINATION : the clumping of antigens  easy targets for phagocytes to destroy NEUTRALISATION : toxin are made non-toxic by reaction with the antibodies LYSIS : lysin (antibodies) bind to antigens  cause antigens/pathogens to rupture OPSONISATION : The binding of antibodies to antigens stimulate phagocytes (macrophage) to destroy the antigens.

IMMUNITY : The state in which the body is resistant to infection by a disease-causing the ability of an animal or plant to resist infection by pathogens IMMUNISATION : The process of inducing immunity by administering a vaccine VACCINE : A preparation of weakened, dead or non-virulent forms of a pathogen

Defence system specific Non specific 1st line2 nd line 3 rd line Skin mucous membrane Phagocyte Phagocytosis lymphocyteantibody passive active naturalartificialnaturalartificial immunisation immunity Divided into is through produce gives Divided into are Carry out eg

ACTIVE IMMUNITY : when an individual’s own immune system produces its own antibodies to defend against specific antigens Natural Active Immunity : after recovered from certain disease (examples : mumps, measles & chicken pox)

Artificial Active Immunity : can be established upon immunisation or vaccination. (mumps, rubella, measles & poliomyelitis)

PASSIVE IMMUNITY : when an individual is given the antibodies required to defend against the pathogen Natural Passive Immunity : when antibodies produced by the mother are passed across the placenta to the foetus during development or in early infancy through breast milk (breast feeding). Colostrum (1 st formed milk) – rich in antibodies

Artificial Passive Immunity : ready-made antibody or serum is injected into the individual. Prepared from cows or horses. (rabies, hepatitis, tetanus & snakebites)

Ooo…sleeping in Biology class ek? So stubborn la. Let me ‘teach’ U first before Mr. FAZLI become angry!!! Waa….mama! Help me…. I don’t want to fall asleep in the class anymore!!! I SWEAR!!!