Defense against Diseases

1
Defense against Diseases
2
Physical and Chemical Defenses

• Your bodys first line of defense against
  infectious disease includes both physical and
  chemical defenses that prevent pathogens from
  entering your body.
• Skin
• Your skin serves as both a physical and a
  chemical barrier against pathogens
• Sweat acts as a chemical barrier.
• Old skin cells are shed constantly, and the
  pathogens on these cells are shed, too.

3
Physical and Chemical Defenses

• Mucous Membranes
• The openings into your body, such as your mouth,
  eyes, and nose, are covered by protective linings
  called mucous membranes
• Mucus traps many pathogens and washes them away.
• Cilia
• Some of your bodys mucous membranes are lined
  with tiny hair like structures
• Saliva and Tears
• trap pathogens and wash them away.

4
Digestive System and Inflammation

• Chemicals in your digestive system kill many
  pathogens
• motions of the digestive system move pathogens
  out.
• substances within that can harm or kill invading
  bacteria.
• Inflammation
• is your bodys general response to all kinds of
  injury, from cuts and scrapes to internal damage.
• is your bodys general response to all kinds of
  injury, from cuts and scrapes to internal damage.

5
Phagocytes

• Within seconds after your body is injured, the
  damaged cells release chemicals that cause blood
  vessels in the injured area to enlarge.
• Blood, other fluids, and white blood cells called
  phagocytes leak out of the enlarged vessels.
• engulf and destroy pathogens and give off
  substances that cause healing to begin.

6
The Immune System

• Immunity is your bodys ability to destroy
  pathogens that it has previously encountered
  before the pathogens are able to cause disease.
• The immune system fights disease by producing a
  separate set of weapons for each kind of pathogen
  it encounters.
• White blood cells called lymphocytes carry out
  most of the immune systems functions.
• immune system will quickly recognize a
  re-occurring pathogen and launch an immediate
  attack

7
T Cells

• T cells (lymphocytes) perform several functions.
• Killer T cells destroy any body cell that has
  been infected by a pathogen.
• Helper T cells produce chemicals that stimulate
  other T cells and B cells to fight off infection.
• Suppressor T cells produce chemicals that turn
  off other immune system cells when an infection
  has been brought under control.

8
B Cells

• The B lymphocytes, or B cells, produce
  antibodies.
• Antibodies are proteins that attach to the
  surface of pathogens or to the toxins produced by
  pathogens.
• This binding action keeps the pathogen or toxin
  from harming the body.
• The memory capacity of B cells explains why you
  develop immunity to some diseases youve already
  had.

9
The Lymphatic System

• The lymphatic system is a network of vessels that
  collects fluid from your tissues and returns it
  to the bloodstream.
• The fluid flowing through the lymphatic system is
  called lymph
• The lymphatic vessels have hundreds of small
  stations, called lymph nodes.

10
Passive and Aggressive Immunity

• Passive Immunity
• acquired by receiving antibodies from a source
  other than ones own immune system
• Temporary
• Babies receive it from the mother
• Passive immunity can be artificially acquired.

• Active Immunity
• Active immunity results from either having a
  disease or from receiving a vaccine.
• immunizations
• The substance that is injected is called a
  vaccine
• contain small amounts of dead or modified
  pathogens or their toxins