Communicable Diseases/ Infectious Diseases

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Communicable Diseases/ Infectious Diseases
 

• Diseases that are spread from one living organism
  to another through the environment.

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What causes infectious diseases?

• Microscopic organisms, pathogens, invade the body
  and attack its cells and tissues.  When the
  pathogens multiply and damage body cells it is
  called having an infection. Most pathogens are
  considered parasites, organisms that live in or
  on another organism and derive nourishment from
  it.  
• Examples of pathogens are
• bacteria
• viruses
• rickettsias
• protozoans
• fungi

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Viruses

• Viruses are the smallest pathogens, they are a
  ball of genes wrapped in a protein coat.
• Viruses must have a host to survive, grow, and
  reproduce.
• Once inside the body viruses spread but infecting
  cells.

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Bacteria

• Bacteria is found everywhere on Earth. 
•  
• Bacteria are single celled organisms.
•  
• Some bacteria is harmful but most are harmless or
  helpful. 
• Disease causing bacteria can produce toxins,
  which kill cells or interfere with cell
  functions.

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Protozoans, Fungi, and Rickettsias

• Protozoans
•  Single-celled organisms that are larger than
  bacteria and have a more complex cell structure. 
  Mostly harmless but some can cause disease in
  humans.
•  
• Fungi
• Multi-celled plant-like organisms.  They thrive
  in damp, warm environments.  Most commonly invade
  hair, nails, and skin and cause infections
• Rickettsias  
• Look like small bacteria but like viruses must
  invade a cell.  Passed on through bites and feces
  deposited on the skin.

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How are Pathogens Spread?

• Pathogens are spread to people in various ways...
•  

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What do Pathogens do to the Body?

• Immunity, the body's natural defense against
  infections, is what helps protect us from being
  sick.  
• The immune system is a network of cells, tissues,
  organs, and chemicals that help fight off
  pathogens.  
• The body does many things to prevent pathogens
  from getting into the body.
• Physical Barriers  skin, mucous membranes, tiny
  hairs.  Prevents pathogens from entering the
  body.
• Chemical Barriers Enzymes in tears and saliva
  that can destroy bacteria.  
• Body Cells  White blood cells called
  Phagocytes.  Phagocytes travel through the blood
  and group together to destroy the pathogens. 
• Inflammatory Response  Occurs when tissue damage
  occurs.  The blood vessels open up and allow more
  phagocytes to the infected area.  Antigens are
  substances that can trigger an immune response.
•  
• When these first efforts don't work, the specific
  resistance goes into effect.

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Specific Resistance

• Lymphocytes, a special type of white blood cell
  that fights pathogens.  They flow through two
  networks of vessels.
• Blood Vessels
• Lymph Vessels
•  
• There are two major types of Lymphocytes.
• B Cells  turn into plasma cells that produce
  antibodies.  Antibodies are proteins that destroy
  or neutralize invading particular pathogens.
• T Cells  two major types, killer and helper
  cells.  Attach to abnormal body cells and destroy
  them.  
•  
• Together these cells help control the Immune
  System.

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Preventing Infectious Diseases

• Immunity The body's natural resistance to many
  pathogens
• Active Immunity  immunity your body develops to
  protect you from disease.
• Passive Immunity  temporary immunity that an
  infant acquires from its mother.
•  
• Immunization
• Passive Immunization  immediate, short-lived
  protection against specific disease causing
  pathogens.  
• Active Immunization  aka vaccination.  The
  introduction of the pathogen into the body.  A
  vaccine contains a preparation of dead or
  weakened pathogens that are introduced to the
  body to stimulate an immune response.