3 EDIT lecture_13_defense.ppt

8/14/2019 3 EDIT lecture_13_defense.ppt

1/24

BODY DEFENSE MECHANISMS


2/24

Body Defense Mechanisms

The body has three lines of defense

Physical Barriers

Defensive Cells & Proteins, Inflammation, and

Fever

The Immune System

Lymphatic System


3/24

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


4/24


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


5/24


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


6/24


7/24

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)


8/24


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


9/24


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


10/24


Defensive Proteins

Complement System

-Destruction of pathogen

-Enhancement of phagocytosis

-Stimulation of inflammation


11/24


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


12/24Menu


13/24


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


14/24

The Third Line of Defense:

The Immune System

The immune system

has two characteristics:

1. It is specific

2. It has a memory


15/24


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


16/24


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


17/24

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


18/24

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


19/24

BODYS DEFENCE MECHANISM

NON-SPECIFIC SPECIFIC

1STLINE 2NDLINE 3RDLINE

SKIN : sweat, sebum

MUCOUSMEMBRANES :

secretion of mucus

Phagocytosis by

phagocytes

Antibodies produced by

lymphocytes


20/24

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)


21/24

Art i fic ial Ac t ive Immun i ty:can be

established upon immunisation or

vaccination. (mumps, rubella,

measles & poliomyelitis)


22/24

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


23/24

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)


24/24

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

eg

Documents

3 EDIT lecture_13_defense.ppt