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to microbial growth. The pH of gastric juice is low
enough to kill microbes directly. Other secretions
(tears, saliva) wash microbes away, preventing
them settling on surfaces, sweat contains an
enzyme that destroys some types of bacterial cell
walls, urine flushes potential pathogens from the
(e) Antimicrobial properties prevent multiplication of
microbes (especially viruses).
(f) Produced against specific pathogens, antibodies
bind and destroy pathogens or their toxins.
(g) Fever raises general body temperature and
metabolic rate which speeds up the blood flow
and the rate of delivery of white blood cells to the
site of infection. Fever also intensifies the effect of
(h) T cells recognize and destroy specific target
pathogens directly on contact. Other T cells assist
in the process, for example, by regulating the
activity of other lymphocytes.
(i) Heat inhibits the activity of the pathogens at
the site of infection. Swelling and pain help to
confine the infection to a limited area by limiting
movement, increased blood flow speeds up the
delivery of white blood cells and speeds healing. 4. The Action of Phagocytes (page 134)
1. Neutrophils, eosinophils, macrophages. 2. By looking at the ratio of white blood cells to red
blood cells (not involved in the immune response).
An elevated white blood cell count (specifically a high
neutrophil count) indicates microbial infection. 3. Microbes may be able to produce toxins that kill
phagocytes directly. Others can enter the phagocytes,
completely filling them and preventing them
functioning or remaining dormant and resuming
activity later. Inflammation (page 135)
1. (a) Increased diameter and permeability of blood
vessels. Role: Increases blood flow and
delivery of leukocytes to the area. Aids removal
of destroyed microbes or their toxins. Allows
defensive substances to leak into the tissue
(b) Phagocyte migration and phagocytosis. Role: To
directly attack and destroy invading microbes and
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This document was uploaded on 01/28/2014.
- Winter '13