The document discusses the body's defense mechanisms against pathogens. It describes three lines of defense: non-specific defenses as the first line (skin, mucous membranes); phagocytosis by white blood cells as the second line; and the specific immune response involving antibodies produced by lymphocytes as the third line. It defines key terms like antigens, antibodies, immunity, and different types of immunity including active and passive immunity acquired naturally or through vaccination and immunization.

2. 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

3. 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.

4. MAIN LINES OF DEFENCE
• Non-Specific
Defence : First line
defence & Second
line defence
• Specific Defence :
Third line defence

5. BODY’S DEFENCE MECHANISM
NON-SPECIFIC SPECIFIC
1ST LINE 2ND LINE 3RD LINE
SKIN : sweat, sebum Phagocytosis by Antibodies produced by
phagocytes lymphocytes
MUCOUS
MEMBRANES :
secretion of mucus

6. FIRST LINE of
DEFENCE
• S k in – p h ys ic al b arrie r (d e ad k e ratinis e d laye r
 d iffic u lt to p e ne trate
• I f th e re is a c u t, th e b lood c lots q u ic k ly  to
p re ve nt b lood los s & e ntry of m /org anis m s
• T e ars s e c re te d b y te ar g land & ac id ic s e b u m
(s e b ac e ou s g land ) – c ontain lys oz ym e s w h ic h
d e s troy s om e b ac te ria
• M u c u s (m u c ou s m e m b rane ) in nas al c avity &
trac h e a trap s d u s t p artic le s & m ic rob ial s p ore s
• T h e c ilia (re s p iratory trac t) s w e e p th e trap p e d
p artic le s to th e p h arynx  s w allow into
s tom ac h (s e c re te s H C l)

7. S E C OND LINE of DE FE NC E
• Th e p h agocytic wh ite b lood ce ll are attracte d
b y ch e m icals p rod u ce d at th e s ite s of
infe ction and m ove to th e s e s ite s .
• E ngu lf & d ige s t th e p ath oge ns
• Th e s olu b le p rod u cts are ab s orb e d &
as s im ilate d b y th e p h agocyte s
• M ay als o b e d e s troye d b y toxins p rod u ce d b y
th e p ath oge ns
• N u m b e r of le u cocyte s incre as e s to try to
d e s troy th e p ath oge n & ne u tralis e th e toxin

8. THIRD LINE of ME C HA NIS M
• 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.

9. THIRD LINE of ME C HA NIS M
(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

10. MECHANISM TO DESTROY
ANTIGENS
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.

11. • 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

12. Defence system
Non specific Divided into
specific
is
Divided into
3rd line
1st line 2nd line through
eg are produce
lymphocyte antibody
Phagocyte
•Skin Carry out gives
immunity
•mucous Phagocytosis
Divided into
membrane passive active immunisation
Divided into Divided into
artificial natural natural artificial

13. V A R IO U S T YP E S O F
IM M U N IT Y
• 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)

14. • Artificial Active Immunity : can b e
e s tab lis h e d u p on im m u nis ation or
vaccination. (m u m p s , ru b e lla,
m e as le s & p oliom ye litis )

15. V A R IO U S T YP E S o f
IM M U N IT Y
• 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

16. • Artificial Passive Immunity : ready-made
antibody or serum is injected into the
individual. Prepared from cows or horses.
(rabies, hepatitis, tetanus & snakebites)

17. 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!!!