Human Health and Diseases


Table of Content

Health is affected by different factors such as:

  • Genetic disorders

  • Infection caused by any bacteria, viruses, fungi etc

  • Life style of an individual such as food habits, sleeping habits, exercise etc

What are different common Human Diseases?

Disease causing organism is known as Pathogen. It can be bacteria, virus, fungi, nematode, etc. Examples of common human diseases:

  • Typhoid - This disease is caused by a bacteria Salmonella Typhi. It is a type of fever that affect different individuals. They enter the small intestine via contaminated food and water and then reaches to the blood. The common symptoms include Stomach Pain, Headache, Loss of Appetite, Constipation. It can be fatal in severe cases. Widal Test is used to confirm Typhoid fever.

  • Pneumonia - It is a bacterial disease which is caused by Streptococcus Pneumoniae and Haemophilus Influenza. These bacteria affect the lungs of the person. Alveoli is the smallest unit of the lungs which helps in gaseous exchange. These Alveoli are blocked by the mucus. The common symptoms include Fever, Coughs, Chills etc.

  • Common Cold - It is caused by a group of viruses known as Rhino Viruses. They do not affect the lungs but affect the respiratory system including nose. The common symptoms include Cough, Headache, Congestion, Hoarseness, Sore Throat etc. This last for about 3 to 7 days.

  • Malaria - It is caused by Protozoan which is a different Plasmodium species. There are different species of Plasmodium that Causes Malaria, such as Plasmodium Falciparum, Plasmodium Ovale, Plasmodium Malariae and Plasmodium Vivax.

The most severe malaria is caused by Plasmodium Falciparum.

 Life Cycle of Malaria

The Plasmodium infects the human body by sporozoites through the bite of female mosquito Anopheles.

  • Ascariasis- Ascaris is a common roundworm that causes Ascariasis. It includes internal bleeding, fever, muscle pain, intestinal blockage.

  • Filariasis - Wuchereria Bancrofti is a filarial worm that causes Filariasis or Elephantiasis. It causes chronic inflammation in the lower limbs. The infection is transmitted to healthy individuals via bite of the Anopheles mosquito.

  • Ringworms - These are caused by Fungi such as Microsporum, Trichophyton and EpidermophytonThere is appearance of dry, scaly lesions on different parts of the body such as skin, scalp, nails etc. The symptoms include severe itching in the affected area. Personal hygiene is very important for prevention of these infections.

  • Amoebiasis - It is caused by the Pathogen Entamoeba Histolytica. The parasite destroys the mucus membrane. The symptoms include pain in abdomen, nausea, fever, etc.

What is Immunity?

Immunity is defined as the ability of a body to resist an infection.

What are different types of Immunity?

There are two types of Immunity – Innate Immunity and Adaptive Immunity.

Innate Immunity refers to the non-specific defense mechanism that works immediately when a person is encountered by an antigen. There are different barriers of innate immunity-

  • Skin and mucous membranes forms the physical barriers

  • Hydrochloric acid in stomach and tears acts as physiological barriers

  • White blood cells such as monocytes acts as cellular barrier

Different types of immunity.

Adaptive Immunity refers to the specific defense mechanism. It involves two types of cells:

  • B cells which are formed in bone marrow. They are involved in forming antibodies in blood. Thus this type of immune response is known as humoral immune response.

  • T cells are formed in bone marrow but matures in thymus. They involve activation of phagocytes but do not form antibodies. This type of response is known as cell mediated immune response.

What are the differences between Innate Immunity and Adaptive Immunity?





present, reaction is against foreign

present, reaction is against foreign

Lag phase

absent, response is immediate

present, response takes at least a few days


limited, the same response is mounted to a wide variety of agents

high, the response is directed only to the against that intiated it.


limited, hence limited specificity

extrensive, and resulting in a wide range of antigen receptors.


absent, subsequent exposures to agent generate the same response

present, subsequent exposures to the same agent induce amplified response

There are other two types of immunity on the basis of production of antibodies:

  • Active Immunity is the production of antibodies in response to a particular antigen.

  • Passive Immunity is the artificial introduction of antibodies from some outside source. For Example: Transfer of antibodies from mother to baby during pregnancy.

Watch this Video for more reference

Course Features

  • Video Lectures
  • Revision Notes
  • Previous Year Papers
  • Mind Map
  • Study Planner
  • NCERT Solutions
  • Discussion Forum
  • Test paper with Video Solution