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Parts of the Immune System
Skin, hair, mucus, and acids are firstline defenses which help keep germs
from reaching the parts of your body
where they can make you sick.
Your skin keeps dirt and germs from
entering your body.
Sweat and acids from skin cells kill some
bacteria, and natural oils make skin
waterproof so you can easily wash it.
Parts of the Immune System (cont.)
• Hairs in your nose and hairlike
structures called cilia trap
pathogens in the upper
respiratory system and move
them out of your body.
• The digestive system is effective
at stopping pathogens that enter
your body on or in the food you
eat.
Parts of the Immune System
(cont.)
• Stomach acids destroy many pathogens.
• Pathogens can be moved through the
circulatory system to organs that fight
infections.
• The nervous and circulatory systems
work together to produce a fever.
• The high temperature kills many
pathogens and stimulates white blood
cell production.
Parts of the Immune System
(cont.)
• White blood cells and inflammatory
response make up your body’s
second-line defenses.
• Some white blood cells surround and
destroy bacteria directly and others
release chemicals that make it easier
to kill the pathogens.
• Another type of white blood cell
produces proteins that destroy
viruses and other foreign substances.
Parts of the Immune System
(cont.)
Inflammation is a process that causes
the area around an injury to become red
and swollen.
Parts of the Immune System
(cont.)
The inflammatory response cleans
the area of the injury and keeps the
infection from spreading, enabling
the damaged tissue to heal.
Parts of the Immune System
(cont.)
• Third-line defenses are specific to
foreign substances.
• An antigen is a substance that
causes an immune response.
• Proteins called antibodies can
attach to the antigen and make it
useless.
• Certain white blood cells, called B
cells and T cells, form antibodies.
Parts of the Immune System
(cont.)
• B cells form and mature in the
bone marrow and secrete
antibodies into the blood.
• T cells form in the bone marrow
and mature in the thymus gland,
producing a protein antibody that
becomes part of a cell membrane.
• Antibodies match with specific
antigens.