Human Diseases - Part 2

HUMAN DISEASES - PART 2

THE IMMUNE SYSTEM

•    Immunity : The ability of the body to protect against all types of foreign bodies like bacteria, virus, toxic substances etc. which enter the body.

•    The science dealing with the various phenomena of immunity, induced sensitivity and allergy is called immunology.

•    Immune Response :  Third line of defence.  Involve production of antibodies and generation of specialized lymphocytes against specific antigens.

•    Antigens: Substances which stimulate the production of antibodies, when introduced into the body.

•    Antibodies: Immunoglobulins (Igs) which are produced in the body in response to the antigen or foreign bodies.

•    All antibodies are immunoglobulins but all immunoglobulins are not antibodies.

•    There are two major types of immunity: Innate or Natural or Non-specific immunity and Acquired or Adaptive or Specific Immunity.

TYPES OF DISEASES

ACUTE AND CHRONIC DISEASES
•    Some diseases last for only very short periods of time, and these are called acute diseases. We all know from experience that the common cold lasts only a few days.
•    Other ailments can last for a long time, even as much as a lifetime, and are called chronic diseases. An example is the infection causing elephantiasis, which is very common in some parts of India.

COMMUNICABLE DISEASES
•    Microbial diseases that can spread from an infected person to a healthy person through air, water, food or physical contact are called communicable diseases.
•    Examples of such diseases include cholera, common cold, chicken pox and tuberculosis.
•    Example of a carrier is the female Anopheles mosquito, which carries the parasite of malaria. Female Aedes mosquito acts as carrier of dengue virus.
•    Robert Köch (1876) discovered the bacterium (Bacillus anthracis) which causes anthrax
•    How do infectious diseases spread? Many microbial agents can commonly move from an affected person to someone else in a variety of ways. In other words, they can be ‘communicated’, and so are also called communicable diseases.
•    Such disease-causing microbes can spread through the air. Examples of such diseases spread through the air are the common cold, pneumonia and tuberculosis.
•    Diseases can also be spread through water. This occurs if the excreta from someone suffering from an infectious gut disease, such as cholera, get mixed with the drinking water used by people living nearby.
•    The sexual act is one of the closest physical contact two people can have with each other. Not surprisingly, there are microbial diseases such as Syphilis or AIDS that are transmitted by sexual contact from one partner to the other.
•    Other than the sexual contact, the aids virus can also spread through blood-to-blood contact with infected people or from an infected mother to her baby during pregnancy or through breast feeding.
•    We live in an environment that is full of many other creatures apart from us. It is inevitable that many diseases will be transmitted by other animals. These animals carry the infecting agents from a sick person to another potential host. These animals are thus the intermediaries and are called vectors. The commonest vectors we all know are mosquitoes.
•    In many species of mosquitoes, the females need highly nutritious food in the form of blood in order to be able to lay mature eggs. Mosquitoes feed on many warm-blooded animals, including us. In this way, they can transfer diseases from person to person.

To be Continued in Part 3