Biology Topic 10 Diseases

• A person in such condition will show signs (such as a raised in body temperature) and experience symptoms (such as feeling tired)
• Diseases is an abnormal condition of an organism in which one or more of its body parts fail to function properly.
• There are two main classes of disease — infectious and non-infectious
• Infection diseases are caused by living organisms called pathogens, which may spread in a number of ways.
• Example of pathogens include bacteria, virus, protoctists, fungus, worms.
• Infectious diseases are also known as transmissible diseases as the pathogens causing the diseases can be transmitted from one individual to another.
• Pathogen type : Virus

  Pathogen : Coronavirus, HIV

  Diseases in humans : Influenza , AIDS , Hepatitis
• Pathogen type : Bacterium

  Pathogen : Vibrio cholerae

  Diseases in humans : Cholera
• Pathogen type : Protoctist

  Pathogen : Plasmodium

  Diseases in humans : Malaria
• Pathogen type : Fungus

  Diseases in humans : Athlete’s foot
• Pathogen type : Worms

  Diseases in humans : Tapeworm infection
• Pathogens may be transmitted either through direct contact, e.g. through blood or other body fluids, or indirectly, e.g. from contaminated surfaces or food, from animals, or from

  the air.
• Non-infectious disease cannot be transmitted from person to person. These diseases may have a number of causes, such as deficiency in nutrition, allergy, environmental, genetics, mental, or self-induced like smoking. Some examples of non-infectious diseases include cancers, heart diseases and diabetes.
• Pathogens invade and attack the human body, causing infection.
• Body defence is important as it can prevent pathogens from entering our body and destroy pathogens that have entered our body.
• Non-specific defence mechanisms act against all types of invading substances.
• Non-Specific defense example 1

  Mechanism barriers to prevent the entry of pathogens

  • Skin is waterproof and impermeable to pathogens.
  • Hairs in the nose can filter large dust particles and the pathogens attached on these particles.
• Specific defence mechanisms act against specific pathogens.
• Example of Specific defence 1

  Substances that are "foreign" to the body is called antigens
• Non-specific defense example 2

  Chemical barriers to kill or inhibit the growth of pathogens

  • Gastric juice contains hydrochloric acid which kills most pathogens ingested with food.

  •Tears and saliva contain enzymes that kill bacteria.
• • Phagocytes are large white blood cells that have lobed nucleus
  • They surround the pathogens, engulf and digest them using enzymes

  • The process is called phagocytosis
• • Lymphocytes are white blood cells that produce antibodies
  • An antibody is a protein produced by the body in response to an antigen.
  • Antibodies can attack pathogens specifically.
• Vaccination :

  • Immunity is the body's use of antibodies to combat invasion by pathogens. It may be enhanced by a vaccine.
  • A vaccine is a chemical or cell which stimulates. the body's immune system to make the appropriate antibodies.
  • Vaccination reduces the spread of disease.