BOSY_DEFENCE__ARISTO_
Download
Report
Transcript BOSY_DEFENCE__ARISTO_
Pathogens
Microorganisms
causing diseases
eg. bacteria
viruses
fungi
protozoa
Importance of having Body
Defense System
prevent pathogens from entering
the body
kill or inactivate any pathogens
that gain entry into the body
Ways of Pathogen
spreading
In Droplets
e.g. influenza, cold
By Touch
e.g. boils, athlete’s foot, AIDS,
anthrax
By Dust
e.g. diphtheria, scarlet fever,
anthrax, hay fever
Ways of Pathogen
spreading
In Faeces
e.g. cholera, hepatitis A
In Food
e.g. salmonella
By Insect
e.g. malaria
By Vertebrates
e.g. rabies
Nonspecific
Defences
Barriers
• physical barrier
Skin
the 1st line of defence of pathogen
Ciliated & Mucus Lining of respiratory
tract
mucus: trap bacteria
beating cilia: waft the trapped bacteria
towards the throat
Barriers
• chemical barrier
sebaceous glands of skin
produce oily secretion (sebum) which has
antiseptic properties
tears & saliva
contain lysozymes (enzyme) which
destroy bacteria
Barriers
• chemical barrier
gastric juice in stomach
contain acid which can destroy most
bacteria
acid secretions in vagina of women
reduce growth of pathogens
When you cut yourself carelessly,
why the wound stop bleeding
after a while ?
∵Blood Clotting occurs:
Platelets release a substance
to turn soluble fibrinogen into
insoluble fibrin which catches
blood cells & seal off the cut
Insoluble
fibrin
BLOOD CLOTTING is important
because this can …
Prevent the body from invasion of
pathogens
Stop excess bleeding (blood loss)
Nonspecific
(after infection)
• to localize & destroy the pathogens
• phagocytes involve in phagocytosis
– to engulf and digest the pathogens
macrophage
Nonspecific
(after infection)
• inflammatory response
– (before inflammation : skin arterioles constrict to
prevent excessive bleeding)
– skin arterioles in the infected area dilates so that
more blood flows to the area
– the permeability of skin capillaries increases so
that more phagocytes & fluid come into the
infected tissues
– the skin becomes red & swell up with pain
(because of high pressure)
Specific
Defences
What are Specific Defences ?
When a pathogen is able to get past
the nonspecific defences, immune
responses will be produced which
involve a series of specific defences
• After pathogens get into the blood & lymph :
• Antigens on the surface of pathogen stimulate
lymphocytes in the lymph nodes and the blood.
–
to produce specific antibodies which kill pathogen
by :
» lysis - burst the pathogen
» clump the pathogen together
• After pathogens get into the blood & lymph :
• Antigens on the surface of pathogen stimulate
lymphocytes
–
to produce specific antibodies which kill pathogen
by :
» stick to the surface of pathogen,
so that phagocytes can ingest
them easily (enhanced phagocytosis)
» neutralize the toxins from pathogens
Primary & Secondary
Immunity Responses
Primary Response: the 1st time
invaded by a certain pathogen which
stimulates the body to produce
antibodies
Primary & Secondary
Immunity Responses
Secondary Response: the invasion of the
same type of pathogen which stimulates
lymphocytes to produce much larger
amount of antibodies & much more quickly
primary
response
secondary
response
antibody
conc.
immune response
no immune response
Time (days)
first exposure
to antigen X
second exposure
to antigen X
Small pox (a killing disease)
Vaccine (Vaccination)
Vaccine (Vaccination)
From dead / weakened pathogens
– to stimulate the lymphocytes to produce
antibodies
Times of injection:
– first→ second → (booster) injection
From injection of a serum
It belongs to acquired immunity
Injection of a Serum
antibody
conc.
immune response
no immune response
injection of antibody
(in serum)
Time (days)
~END~