LEARNING OUTCOMES

• 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.

MAIN LINES OF DEFENCE

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

• Specific Defence : Third line defence

BODY’S DEFENCE MECHANISM

NON-SPECIFIC SPECIFIC

1ST LINE 2ND LINE 3RD LINE

SKIN : sweat, sebum

MUCOUS MEMBRANES : secretion of mucus

Phagocytosis by phagocytes

Antibodies produced by lymphocytes

FIRST LINE of DEFENCE

• 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)

SECOND LINE of DEFENCE

• 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

THIRD LINE of MECHANISM

• 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.

THIRD LINE of MECHANISM (cont…)

• 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.

MECHANISM TO DESTROY ANTIGENS

• IMMUNITY : The state in which the body is resistant to infection by a disease-causing pathogens @ 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

specificNon specific

1st line 2nd line3rd line

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•mucous membrane

Phagocyte

Phagocytosis

lymphocyte antibody

passive active

naturalartificial natural artificial

immunisation

immunity

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VARIOUS TYPES OF IMMUNITY

• 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)

VARIOUS TYPES of IMMUNITY

• 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 (1st 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!!!