Download Body Defenses: Innate Defenses

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The body has two defense systems for
foreign materials that form the immune
system
Immunity—specific resistance to disease
(such as bacteria, virus, fungus)
◦ Provided for by the adaptive defenses
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Innate (nonspecific) defense system
◦ Mechanisms protect against a variety of invaders
◦ Responds immediately to protect body from foreign
materials
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Adaptive (specific) defense system
◦ Specific defense is required for each type of invader
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mechanical barriers that include:
◦ Body surface coverings
◦ Specialized cells
◦ Chemicals produced by the body
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See Table 12.1 for a more detailed summary
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 first
line of defense:
◦ Skin and mucous membranes
1.
2.
3.
4.
Acidic pH of the skin inhibits bacterial growth
Stomach mucosal secretions kill pathogens (HCl)
Saliva and lacrimal (eyes) fluid contain lysozyme
Mucus traps microogranisms
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 second
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line of defense:
Natural killer (NK) cells
Inflammatory response
Phagocytes
Antimicrobial proteins
Fever
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Found in blood and lymph
Release perforin (lytic chemicals)
◦ Does not discriminate
◦ targets abnormal cell’s membrane and nucleus
◦ causes disintegration of cancer or virus-infected
cells
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http://biology-animations.blogspot.com/2010/04/nk-cellanimation.html
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Takes place when tissues are
injured/damaged
Functions:
◦ Prevent spread of damaging agents
◦ Phagocytosis eliminates cell debris and pathogens
◦ Sets the stage for tissue repair
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Begins with redness, heat, swelling, pain
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Release of inflammatory chemicals causes:
1. Blood vessels dilate and leak
2. Pain receptors to be activated
3. Influx of neutrophils and macrophages
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Neutrophils devour foreign materials
Macrophages replace spent neutrophils and
dispose of cell debris
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Inflammatory
chemicals diffusing
from the inflamed
site act as chemotactic
agents
Neutrophils
1 Enter blood from bone marrow
and roll along the vessel wall
Capillary wall
3 Positive
chemotaxis
2 Diapedesis
Endothelium
Basement membrane
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Implored when pathogens get through the
first line of defense
Macrophages or neutrophils will:
1. Engulf foreign material into a vacuole
2. Vacuole fuses with a lysosome
3. Enzymes from lysosomes digest the material
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(a) A macrophage (purple) uses its
cytoplasmic extensions to pull
spherical bacteria (green) toward it.
Scanning electron micrograph (10,800×).
1 Phagocyte
adheres to
pathogens.
2 Phagocyte
Phagosome engulfs the
(phagocytic particles, forming
a phagosome.
vesicle)
Lysosome
Acid
hydrolase
enzymes
(b) Events of phagocytosis
3 Lysosome
fuses with the
phagocytic
vesicle, forming a
phagolysosome.
4 Lysosomal
enzymes digest
the pathogens or
debris, leaving a
residual body.
5 Exocytosis
of the vesicle
removes
indigestible and
residual material.
Slide 1
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Complement proteins
◦ Complement Fixation: proteins become fixed to
sugars/proteins (antibodies) on a foreign cell’s
surface
◦ Membrane Attack Complexes (MAC): lesions
produced by fixation
 Creates holes in the cell’s surface
 Water enters and cell bursts
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Membrane attack
complex forming
Antibodies
attached to
pathogen’s
membrane
Pore
Activated complement proteins attach to
pathogen’s membrane in step-by-step sequence,
forming a membrane attack complex
(a MAC attack).
MAC pores in the
membrane lead to
fluid flows that cause
cell lysis.
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Virus infects cell
Cell secretes proteins called interferons
Interferons bind to receptors on healthy cell
surfaces
◦ Interfere with the ability of viruses to replicate DNA
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ation_quiz_2.html
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Abnormally high body temperature
◦ Up to 104°-106° - depends on the individual
◦ systemic response to invasion by microorganisms
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Regulated by hypothalamus
Inhibits reproduction of bacteria
Increases speed of repair processes
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