Download Topic 19 - Roslyn Public Schools

Topic 19
Immune System
I. Lines of Defense
• A. First Line of Defense – Physical Barriers
– 1. Skin - consists of three layers
• a. epidermis – outermost layer – protects the body
from disease by preventing microbes from entering the
body – also contains melanocytes which produce the
pigment melanin that protects the body from the
damage caused by ultraviolet light from the sun
• b. dermis – this layer of skin contains sweat glands and
oil glands – this area helps with thermoregulation
• c. hypodermis – fat cells insulate the body against the
cold
• 2. Mucous glands and hairs that line the nose
and trachea – trap pathogens
• 3. Hydrochloric acid – destroys some of the
pathogens that enter the digestive system
• B. Second line of Defense
– 1. phagocyte –white blood cells engulfs pathogens
and destroys them by the process of phagocytosis
– several types of phagocytes - nonspecific
– a. macrophages – develop from monocytes – engulf the
microbe into a vacuole which fuses with a lysosome
– b. eosinophils – position themselves alongside the parasite
and discharge destructive enzymes from cytoplasmic granules
– C. neutrophils – first to arrive – attracted to chemical signals
by infected tissue – self-destruct while destroying invaders –
life span is short
– 2. antimicrobial proteins – variety of proteins – function in
nonspecific defense – attack microbes and impede their
reproduction
– 3. interferons – set of proteins – nonspecific defense –
secreted by virus-infected cells – induce neighbors to
produce chemicals that inhibit viral reproduction
– 4. inflammatory response – capillaries respond to
damaged area by increased dilation and permeability –
leads to increased redness, heat and swelling
• 5. Histamine release – inflammation sets off histamine release
– released by special leukocytes called basophils and by mast
cells – increased dilation and permeability of nearby
capillaries
• 6. enhanced blood flow – damaged tissues release
prostaglandins which promote blood flow to the injured site –
increases clotting, blocks spread of microbes, and enhances
the migration of phagocytic cells
• 7. fever – systemic response – inhibits growth of microbes,
facilitates phagocytosis, and speeds up repair of tissue
• Septic shock – overwhelming systemic inflammatory response – high
fever and low blood pressure – can lead to death
• C. Third line of defense – lymphocytes
– 1. lymphocytes – two types
• (a) B-cell – produce antibodies that destroy invading
microbes or pathogens (including viruses, bacteria, and
parasite) – each pathogen triggers a different response
– there are millions of different pathogens so there are
millions of different B-cells in the blood
• (b) T-cells – there are two types of T-cells –
1. Helper T-cells – helps B-cells and other T-cell multiply and
coordinate their actions
2. Killer T-cells – directly destroy a pathogen
immune response
D. Lymphatic system – transports materials in only
one direction from body tissues back to the blood
through lymphatic vessels
• A. lymph nodes – contain lymphocytes so that
pathogens can be destroyed as they pass through the
lymphatic system – when confronted with a large
number of pathogens, the lymphocytes will multiply
and as a result lymph nodes get larger or swollen which
indicates an infection
Lymphatic System
II. Active and Passive Immunity
• A. active immunity – occurs when the body makes its own
antibodies against a particular antigen – can occur as a result
of having a particular disease and recovering from it or from
getting a vaccination for a particular disease
– 1. vaccines – an injection of a weakened or deadened form of a
disease causing microorganism that can no longer cause the
disease but can still stimulate antibody production by white
blood cells – lasts a long time
– 2. memory cells – remember the antigen so the next time the
microbe invades, it is destroyed before it can make you sick
vaccines
• B. passive immunity – a temporary immunity to a
disease produced by the injection of antibodies into
the body – the antibodies can be produced by
another person or by an animal – will last only a
short period of time – used to temporarily increase
the body’s defense against a particular disease – a
person who has been exposed to hepatitis is given
injections containing antibodies to hepatitis
– 1. no memory cells are created
III. AIDS
• A. AIDS – acquired immune deficienty
syndrome – caused by a virus called HIV
(human immunodeficiency virus) – this virus
destroys the body’s immune system so that it
is unable to fight off even small infections –
spread during sexual contact or blood and
fluid contact
IV. Allergic reaction
• A. Allergies are an overreaction of the body's natural defense
system that helps fight infections (immune system).
• B. The immune system normally protects the body from
viruses and bacteria by producing antibodies to fight them.
• C. In an allergic reaction, the immune system starts fighting
substances that are usually harmless (such as dust mites,
pollen, or a medicine) as though these substances were trying
to attack the body.
• D. The body produces histamines which can be counteracted
by an anti-histamine(Benadryl).