Download Chapter 13 – Lessonn 2 – The Immune System

The Immune System
Sheila L. Jett, NBCT
Montevallo Middle School
Bell ringer
 What are some functions of your skin?
Keeping Pathogens Out
 You can’t escape pathogens; they are everywhere! Pathogens
are in the air you breathe, the water you drink, and on every
surface that you touch. There is nothing to be afraid of
because your body protects you most of the time. Your body
has 5 major barriers to block pathogens.
1. Tears
2. Saliva
3. Skin
4. Mucous membranes
5. Stomach acid
Immune System
 If pathogens get past the 5 barriers, then your immune system
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goes to work.
Immune system is a combination of body defenses made up of
cells, tissues, and organs that fight pathogens.
One mechanism that your body uses to help keep pathogens from
multiplying is to increase the temperature of your body.
The lymphatic system is a secondary circulatory system that helps
the body fight pathogens and maintains its fluid balance.
Macrophages surround and destroy foreign substances and then
help the lymphocytes identify the substance.
Lymphocytes are special white blood cells in the body that fight
pathogens.
Lymphocytes
 There are 3 main kinds of lymphocytes –
B cells – form in the bone marrow and produce antibodies
to fight pathogens.
2. T cells – form in the thymus gland and kill pathogens.
3. NK cells – stands for natural killer because the attack
cancers and viruses.
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Keeping your immune system healthy
Get regular exercise
2. Eat plenty of vitamin rich food
3. Manage stress
4. Get plenty of rest
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Antigens and antibodies
 Lymphocytes are activated when the body recognizes the part
of the pathogen called the antigen.
 Antigens are substances that send the immune system into
action.
 Antibodies are specific proteins that attach to antigens,
keeping them from harming the body.
Response to infection
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Pathogens get past the barriers and antigens trigger the immune
system.
Macrophages engulf the pathogens and present to the t cells. The
t cells identify the pathogens.
T cells divide and multiply and signal the b cells to respond.
The b cells divide and multiply.
Some of the b and t cells become memory cells and do not
respond to the first invasion.
The b cells that do respond then release antibodies. They tag the
pathogens for destruction by the t cells.
Memory cells respond quickly if the same pathogen enters again
Vaccinations and Immunity
 The CDC recommends that teens be given four vaccinations
– chicken pox, hepatitis B, measles-mumps-rubella, and
tetanus-diptheria.
 Vaccine – preparation of dead or weakened pathogens that is
introduced into the body to cause an immune response.
(immunization)
 Immunity is the ability to resist the pathogens that cause a
particular disease. Healthy mothers pass immunity to their
babies during pregnancy and through breastfeeding after
birth.