Download 7.4 Protecting the body – Questions and answers Q1. Bk Ch7 S7.5

7.4 Protecting the body – Questions and answers
Q1.
Bk Ch7 S7.5 Q1
a
b
Outline the difference between non-specific and specific defence mechanisms.
When do non-specific defence mechanisms operate, compared with specific defence mechanisms?
A1.
Bk Ch7 S7.5 A1
a
b
Non-specific defence mechanisms do not target particular pathogens. They are defences that
either stop pathogens from entering the body or a general response to the presence of a foreign
agent in the body. Specific defence mechanisms involve the production of antibodies against
particular pathogens.
Non-specific defence mechanisms can be divided into first-line and second-line defences. Firstline defences include barriers such as the skin and mucous membranes as well as the action of
cilia and chemical secretions from the stomach, vagina and urinary tract. These operate to keep
pathogens from entering the body. Second-line defences include inflammation and phagocytosis.
These methods operate once pathogens have managed to enter the body. Specific defence
mechanisms also operate after entry of pathogens but, instead of mounting a general attack on any
foreign invader, they target specific pathogens, producing antibodies to destroy them.
Q2.
Bk Ch7 S7.5 Q2
Explain what happens in the inflammatory response to help the body overcome invading pathogens.
A2.
Bk Ch7 S7.5 A2
During inflammation blood circulation to the affected area is increased. Blood vessels dilate and white
blood cells can leak out of the blood vessels into the surrounding tissue where they engulf foreign
materials, including cells and toxins. Histamines and prostaglandins produced by the damaged cells
encourage the inflammatory response.
Q3.
Bk Ch7 S7.5 Q3
Complete the table summarising the defence barriers in the body.
Defence barrier
Location in body
How defence barrier prevents entry of
pathogens
Skin
Mucous membranes
Cilia
Chemical barriers
Other secretions
A3.
Bk Ch7 S7.5 A3
Defence barrier
Location in body
How defence barrier prevents entry of
pathogens
Skin
Covers body
Physical barrier through which pathogens
cannot usually penetrate
Mucous membranes
Digestive, respiratory,
reproductive and urinary
tracts
Presence of antibody IgA in mucus reacts with
pathogens, stopping them from penetrating
through surface; lysozymes present—these
7.4 Protecting the body QA
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are chemicals that break down the cell walls of
some bacteria
Cilia
Respiratory passages
As cilia beat together they sweep mucus and
any foreign particles along, away from the
lungs and towards the nasal passages and
pharynx where they can be coughed out or
swallowed
Chemical barriers
Stomach and small
intestine
Acidic environment of stomach and alkaline
environment of small intestine usually destroy
potential pathogens
Other secretions
Mouth, eyes, nasal
passages
Saliva, tears and nasal secretions contain
lysozyme, a chemical that breaks down the cell
walls of some kinds of bacteria
Q4.
Bk Ch7 S7.5 Q4
What is phagocytosis? What types of cells are responsible for this activity in the body? In what
circumstances does this process occur?
A4.
Bk Ch7 S7.5 A4
Phagocytosis is the process in which specialised white blood cells called phagocytes engulf and destroy
foreign particles such as pathogens. Phagocytosis occurs whenever foreign materials enter the blood or
body tissues.
Q5.
Bk Ch7 S7.5 Q5
a
b
Is interferon an example of a non-specific or specific defence mechanism?
How does interferon operate to control infection in the body?
A5.
Bk Ch7 S7.5 A5
a
b
Interferon is an example of a non-specific defence mechanism.
Interferon is a protein that is produced by cells that have become infected by a virus. Once
produced by infected cells the protein attaches to nearby healthy cells, preventing replication of
the virus particles in those cells.
Q6.
Bk Ch7 S7.5 Q6
Define the term ‘antigen’.
A6.
Bk Ch7 S7.5 A6
An antigen is a molecule in the body that triggers an immune response, that is, the production of
antibodies against a specific pathogen.
7.4 Protecting the body QA
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© Pearson Australia (a division of Pearson Australia Group Pty Ltd)
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