Dec 23, 2015
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