biology chapter 5 form 5

8/13/2019 biology chapter 5 form 5

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The Role of the

Circulatory System in theBodys Defence

Mechanism

Subtopic 1.5


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Bodys defence mechanism against diseases

3 lines of defence mechanism in the body:

First Line

of Defense

Second

Line of

Defense

Third Line

of Defense


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Includingskin

mucous membranes

Function

to prevent pathogens from entering the body.

Mucous Membrane

consists of cells lining the respiratory tract andopenings of the urinary and reproductive systems.

The membrane secretes a protective layer ofmucus.

Mucus

stickyand traps pathogens and other particles


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The Second Line Of Defence

Deals with pathogens(microorganisms that causeddisease) that have bypassed the

first line of defence.

Phagocyte(phagocytic white blood

cells) digests the pathogensbyphagocytosisin order to destroythe pathogens.


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The Third Line Of Defence

Lymphocytes in the bloodproduce chemicals calledantibodiesthat destroy bacteriaand viruses before they getinside the body cells.


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Immunity

ability of an organism to resistinfection.

Antigen

a foreign substance capable ofstimulating an immune response orthe formation of antibodies.

Examples of antigens are pathogens,toxic substances, and variousharmless molecules and cells.


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Antibodies

proteinsthat interact with the antigens andthereby rendering them harmless. Specificantibodies interact with specific antigens.

Immunisation

a technique used to induce immunity to aspecific disease in humans or other animalsby exposing the individual to an antigen in

order to stimulate the production of specificantibodies.

achieved through injection a vaccine thatcontains killed or severely weakened antigeninto the body of an individual.


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Antibodies

are proteins

are produced by lymphocytesare in response to specificantigens

provide immunity against certainmicroorganisms or their toxins


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HIVHuman Immunodeficiency Virus)


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HIVvirus that attacks the human immune

system.

leads toAIDS(Acquired Immunodeficiency

Syndrome).

A person who has AIDS is vulnerable tovarious infections because the immune

system is being destroyed progressively.

The infected person eventually diesofsecondary infections because the immune

system collapses and is unable to defend

the body against pathogens.


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There are four main ways that HIV can be

transmitted:

Through any form of sexual intercourse

with an infected person.

Through contact with blood products ofan infected person.

Through shared needles or syringes

that are contaminated with blood of an

infected person.From an infected mother to child, either

during pregnancy, birth or breast

feeding.


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Infection of HIV virus in the blood

stream

biology chapter 5 form 5

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