Post on 06-Apr-2018
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1.5: The role of circulatory system in the bodys defencesystem
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Bodys Defence Mechanism Circulatory System (CS) also defends the body against
disease abolition of the disease causingmicroorganisms (pathogen)
Humans have 3 lines of defence against pathogens:
FIRST LINE OFDEFENCE
THIRD LINE OFDEFENCE
Skin
# sweat# sebum
Phagocytosisby phagocytes
SECOND LINEOF DEFENCE
MucousMembranes#Secretion of
mucus
Antibodiesproducted bylymphocytes
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First line of defence
-prevent of pathogen entering the body
(i) Skin
-as a physical barrier
-is made up of a dead keratinised layer- tough enough for pathogen topenetrate
If there is a scratch/cut , the blood clotsto seal the wound & avoids infection
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-as a chemical barrier (a) sweat gland secretes sweatwhich contains salt ,
& lysozyme ( destroy bacteria)
(b) Sebaceous gland secretessebum-which contains acid &oil
## All these substances areunfavourable for growth of
microorganisms
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(ii) Tears & Saliva
-Contain lysozyme - protect theeyes & mouth from pathogeninvasion
(iii) Gastric juice in stomach
-contain hydrochloric acid destroys most pathogens in foods &drinks
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(iv) Mucous membranes
-secrete mucus in nasal cavity &tracheas to trap the dustparticles & spores
- The cilia in the respiratory tractsweep the trapping particles
to the pharynx & stimulatesneeze /cough to expel out the
pathogens
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Second line of defence (non-specificdefence)
-killing the pathogens that entered our body byaction ofphagocyticwhite blood cells(neutrophill & monocyte)
known as phagocytes(process: phagocytosis)
-occur when the pathogens get through the first
line of defence .-Phagocytes move to the infected area due to the
stimulation by chemicals released by damaged
cells example cut skin.
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The third line of defence (antibody)
1)is a kind ofprotein released bylymphocytes
in response to the presence of foreignsubstances, called antigen in our body
2)Lymphocytes (WBC) :
-found in lymph nodes & in the blood circulatorysystem
-2 types :
B- lymphocyte T-lymphocytesSecretes antibody Helps B-lymphocytes
in antibody
production
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3)Antigen
-is a substance (usually protein) normally found
on the outer surface of pathogen.-different types of pathogen act as different types
of antigen.
4)It is a specific defence because when a specificantigen invades the body, lymphocytes isstimulated & produces specific antibodytodestroy these specific antigens.
5)This response is known as immune responsebecause it resists the body from pathogens ordisease
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6) After any infection, some lymphocytesremain in the body as memory cells, which
may last for several months /years.#This memory cells help to defend the body
against next infection by the same
antigen.#During this period, someone is said to be
immuned for that particular disease.
7) Definition of immunity
The ability of an organism to defend
itself against infection by pathogens.
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Types of Immunity