ROLE OF THE CIRCULATORY SYSTEM IN BODY DEFENCE MECHANISM

INTRODUCTION Pathogens:

harmful & disease-causing microorganisms Defense mechanism - against the invasion

of these pathogens Human body has 3 lines of defence

mechanism: 1st line 2nd line 3rd line

LINE OF DEFENSE MECHANISM

Inborn, nonspecific defense

mechanism

FIRST LINE DEFENSE

Skin Mucous membrane

SECOND LINE DEFENSE

White blood cell (phagocytes)

Acquired, specific defense

mechanism

THIRD LINE DEFENSELymphocytes

Antibodies

FIRST LINE DEFENCE

1st line defense

The 1st line defense is:1. Skin 2. mucous membrane

INBORN: natural built in defense Provide immediate protection against invading

pathogens NONSPECIFIC :

Use the same barrier against all microbes & foreign matter

Are not directed against any particular pathogens

The Skin provides a continuous layer that protects the

body Few microorganisms can penetrate the dead

skin layer on the surface of the skin Blood clot :

When skin is cut, blood clots to plug the wound & prevent the entry of microorganism

Mucous membraneThin & less protective than skinAct as a barrier against the entry of microorganism

Secretes mucus, Thick slippery liquid that protects

the membrane & keep it moist and soft

Mucous membrane Protects the interior surfaces of the

body that may be exposed to pathogens

Lines all tissues & organs E.g. respiratory & digestive tracts

SECOND LINE DEFENDS

2nd line defence Come into play when pathogens succeed in

penetrating the skin / mucous membrane Non specific immune system:

Use same method of defence used as the type of infecting agent is not discriminated

Process of phagocytosis

a)Ingestion : pseudopods encircles the bacterium

a)

b) Formation of phagosome (phagocytic vessicles)

c)Fusion of a phagosome & a lysosome to form phagolysosome

d) Digestion of bacterium by enzymes

e) Discharge of waste material

Non specific immune response include

1. Phagocytosis- Carried out by

WBC (neutrophils, macrphages, eosinophils)

2. Natural cell killers

-destroy infected cells

3. Inflammation- Involves redness,

heat, swelling & pain

4. Fever - Fever stimulates phagocytosis, kills certain bacteria by

denaturing their protein & helps in healing process

Nail penetrates into skin

Blood clot plugs up injury

a) Skin is punctured with the bacteria entering the injured tissue

b) Inflammation response with the phagocytes and plasma moving to the injured tissue

c) Phagocytes ingesting bacteria and foreign particles

THIRD LINE DEFENCE

3rd line Responds in specific ways to specific

types of toxins, microb & other foreign substances

E.g: a specific type of antibody is produced by lymphocytes to fight against definite pathogen

Need to be developed; takes longer time to be effective

“remember” past infections

Immunity The ability of the human body to resist infection

Immune response Body’s defence reaction whereby an antigen is

recognised & specific antibodies are produced by lymphpocytes

Antigen: Foreign molecule that when introduced into the

body, stimulates the production of antibodies

Antibody: Protein substances produced by immune system in

response to the recognition of a specific antigen Y shape Aka immunoglobulin Forms the basis of immune response

Two main groups of WBC involved in immune response: Lymphocytes : makes antibodies to destroy foreign

pathogens; activate the immune response Macrophages : mop the pathogens by

phagocytosis

Primary and secondary immune response

Ways antibodies defend the body

Agglutination

Antibodies bind the antigens and

clump microorganism together in large numbers

making the antigens harmless

Opsonisation

Antigen is covered with antibodies -easier for ingestion by phagocytes

An antibody-coated pathogen can be made to burst, killing it before ingested by phagocytes

Neutralization Antibody bind to the

toxins neutralizing the

poison by disabling the chemical action of the toxin

Precipitation Antibodies bind to

the soluble antigens & cause them to precipitate

They can then be ingested by the phagocytes

Primary and secondary immune response

Various types of immunity

Mumps (Beguk)

Measles (Demam Campak)

Diphtheria (Difteria) upper respiratory tract

illness caused by Corynebacterium diphtheriae

sore throat, low fever, and an adherent membrane on the tonsils, pharynx, and/or nasal cavity

infectious disease spread by direct physical contact or breathing 

Rubella

Poliomyelitis