Medical brain notes 25

  Introduction   The Latin term “immunis” meaning “exempt” gave rise to the English word “immunity”, which refers to the mechanism used by the body to protect against environmental agents that are foreign to the body. These agents may be microorganisms or their products, foods, chemicals, drugs, pollen or animal hair.

  Infections   The invasion and multiplication of a parasite in or on the surface of host tissue constitute infection . Infection and immunity involve interaction between thebody (host) and the infecting microorganism. Based on their relationship to their host, microorganisms classified as saprophytes (free living microbes that subsist on dead or decaying organic matter, mostly found in soil). Parasites (establish themselves and multiply in hosts (it may be pathogens - disease producing) or commensals (without causing any damage to the host-normal flora). Infections may be classified in various ways.   Primary infection      :   First time infection with a parasite in a host. Secondary infection : When new parasite sets up an infection in a host  whose  resistance  is  lowered  by  a  pre-existing infectious disease. Focal infection          :   Inf...

  Immunity Disease spreads from one person to another is called as infectious disease. Infectious diseases are caused by foreign substances like fungi, bacteria, virus or parasite, when they enter in to the human body. Though the disease by such pathogen affects the body for a shorter duration, the person may survive after loosing functions of some of the organ (eg. Poliomyelitis). Some times, when the infection or disease is severe the person has to die. Yet many of the human beings are able to lead a normal life because of the immune system. The immune system provides such freedom enjoyed by an individual, in order to keep them free from diseases.   The immune system has the following functions,   ·                Recognition and defense against foreign substances (antigen) irrespective of the route of entry.   ·               ...