3 edit lecture_13_defense.ppt
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BODY DEFENSE MECHANISMS
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Body Defense Mechanisms
The body has three lines of defense
Physical Barriers
Defensive Cells & Proteins, Inflammation, and
Fever
The Immune System
Lymphatic System
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The First Line of Defense:
Physical Barriers
Skin
Cells filled with keratin, making skinimpenetrable, waterproof, and resistant to
disruptive toxins and enzymes of most would-
be invaders
Dead cells are shed and replaced (1 million
every 40 min), taking with them any microbes
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The First Line of Defense:
Physical Barriers
Mucous Membranes
The inner surfaces of the body are guardedby mucous membranes that line the
respiratory, digestive, urinary, and
reproductive systems.
Mucous membranes are more vunerable than
skin
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The First Line of Defense:
Chemical Barriers
Sweat and oil produced by glands in the
skin wash away microbes and their acidity
slows bacterial growth. Some oils contain
chemicals that kill bacteria.
Mucous membranes produce sticky
mucous that traps many microbes
Saliva and tears contain an enzyme called
lysozyme that kills bacteria by rupturing
their cell walls
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The Second Line of Defense:
Defensive Cells
Phagocytes
Engulf pathogens, damaged tissue, or deadcells
Neutrophils Macrophages
Eosinophils
Discharge destructive enzymes to destroypathogens too big for phagocytes (e.g.,parasitic worms)
Natural Killer Cells
Seek out abnormal cells (e.g., cancer cells)
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The Second Line of Defense:
Defensive Proteins
Interferon Protein-A virus enters a cell
-The infected cell produces interferon
-The interferon binds with an uninfectedcell
-The interferon protects other cells that
become infected with a virus by
stimulating the cell to produceantiviral proteins that prevent the
virus from making copies of itself
-The interferon attracts and stimulates
natural killer cells and macrophagesto kill cells infected with the virus
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The Second Line of Defense:
Defensive Proteins
Complement System
-Complement bindingcomplements the
ability of antibodies and phagocytic cells
to clear pathogen from an organism
-Small proteins in blood stimulates
protease to cleave to specific proteins to
release cytokines
-Activate massive amplification responseand cell-killing membrane attack complex
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The Second Line of Defense:
Defensive Proteins
Complement System
-Destruction of pathogen
-Enhancement of phagocytosis
-Stimulation of inflammation
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The Second Line of Defense:
Inflammation
When body tissues are injured or damaged, a series of
events called the inflammatory responseoccurs
Redness: caused by increased blood flow to the
damaged area
Heat:increased blood flow elevates the temperature in
the area of injury, increasing metabolic rate of the body
cells
Swelling:histamine makes capillaries more permeablethan usual
Pain:causes person to protect the area and prevent
additional injury
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The Second Line of Defense:
Fever
A fever is an abnormally high body
temperature caused by pryogens
(chemicals that set the thermostat in the
brain to a higher set point)
A mild or moderate fever helps the body
fight bacterial infections by slowing the
growth of bacteria and stimulating body
defense responses
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The Third Line of Defense:
The Immune System
The immune system
has two characteristics:
1. It is specific
2. It has a memory
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The Third Line of Defense:
The Immune System
How does the body recognize specific
targets?
Substances that trigger an immune response
are called Antigens. Antigens provoke animmune response because they are not
recognized as belonging in the body
Large molecules (proteins, polysaccharides,or nucleic acids) on the surface of the invader,
embedded in the plasma membrane of a
bacterium, or part of the protein coat of a virus
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The Third Line of Defense:
The Immune System
What about specificity and memory of the
immune system?
Lymphocytes are responsible for both
specificity and memory
There are two types:
B lymphocytes (B cells)
Mature in bone marrow T lymphocytes (T cells)
Mature in the thymus gland
Recognize MHC markers
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AGGLUTINATION: the clumping of antigens easytargets for phagocytes to destroy
NEUTRALISATION: toxin are made non-toxic by
reaction with the antibodies
LYSIS: lysin (antibodies) bind to antigens causeantigens/pathogensto rupture
OPSONISATION: The binding of antibodies toantigens stimulate phagocytes (macrophage) todestroy the antigens.
MECHANISM TO DESTROY
ANTIGENS
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IMMUNITY :The state in which the bodyis 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
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BODYS DEFENCE MECHANISM
NON-SPECIFIC SPECIFIC
1STLINE 2NDLINE 3RDLINE
SKIN : sweat, sebum
MUCOUSMEMBRANES :
secretion of mucus
Phagocytosis by
phagocytes
Antibodies produced by
lymphocytes
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V RIOUS TYPES OF IMMUNITY ACTIVE IMMUNITY:when an individuals
own immune system produces its own
antibodies to defend against specific antigens
Natural Active Immuni ty:after recovered
from certain disease (examples : mumps,
measles & chicken pox)
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Art i fic ial Ac t ive Immun i ty:can be
established upon immunisation or
vaccination. (mumps, rubella,
measles & poliomyelitis)
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V RIOUS TYPES of IMMUNITYPASSIVE IMMUNITY
:
when an individualis given the antibodies required to defendagainst the pathogen
Natural Passive Immunity:when antibodiesproduced by the mother are passed across theplacenta to the foetus during development or in
early infancy through breast milk (breastfeeding). Colostrum(1stformed milk)rich inantibodies
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Art i f ic ial Pass ive Immun ity:ready-made
antibody or serum is injected into theindividual. Prepared from cows or horses.
(rabies, hepatitis, tetanus & snakebites)
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Defence system
specificNon specific
1st line 2ndline3rdline
Skin
mucous
membrane
Phagocyte
Phagocytosis
lymphocyte antibody
passive active
naturalartificial natural artificial
immunisation
immunity
Divided into
Divided intois
through
produce
gives
Divided into
Divided into Divided into
are
Carry out
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