human health and diseases Flashcards
infectious diseases
Diseases
which are easily transmitted from one person to another, are called infectious diseases.
pathogens
A wide range of organisms belonging to bacteria, viruses, fungi, protozoans, helminths, etc., could cause diseases in man
Salmonella typhi
Salmonella typhi is a pathogenic bacterium that causes typhoid fever in human beings. These pathogens generally enter the small intestine
through food and water contaminated with them and migrate to other organs through blood. Sustained high fever (39° to 40°C), weakness, stomach pain, constipation, headache and loss of appetite are some of the common symptoms of this disease. Intestinal perforation and death may occur in severe cases
may occur in severe cases
typhoid fever confirmation
Widal test
Streptococcus pneumoniae and Haemophilus
influenzae
responsible for the disease pneumonia in humans which infects the
alveoli (air-filled sacs) of the lungs. As a result of the infection, the alveoli
get filled with fluid leading to severe problems in respiration. The symptoms
of pneumonia include fever, chills, cough and headache. In severe cases,
the lips and fingernails may turn grey to bluish in colour. A healthy person acquires the infection by inhaling the droplets/aerosols released
by an infected person or even by sharing glasses and utensils with an infected person
Rhino viruses
represent one such group of viruses that cause one of the most infectious
human ailments – the common cold. They infect the nose and respiratory
passage but not the lungs. The common cold is characterised by nasal congestion and discharge, sore throat, hoarseness, cough, headache, tiredness, etc., which usually last for 3-7 days. Droplets resulting from cough or sneezes of an infected person are either inhaled directly or transmitted through contaminated objects
protozoans
Plasmodium, a tiny protozoan is responsible for malaria. Different
species of Plasmodium (P. vivax, P. malaria and P. falciparum) are responsible for different types of malaria. Of these, malignant malaria caused
by Plasmodium falciparum is the most serious one
and can even be fatal
life cycle of Plasmodium
Plasmodium enters the human body as sporozoites (infectious form) through the bite of infected female Anopheles mosquito. The parasites initially multiply (asexually) within the liver cells and then attack the red blood cells (RBCs) resulting in their rupture. The rupture of RBCs is associated with the release of a toxic substance, haemozoin, which is responsible for the chill and high fever recurring every three to four days
When a female Anopheles
mosquito bites an infected person
sexual stages develop in the RBC that form gametocytes. the female mosquito takes up the gametocytes with blood meal, fertilization and development take place in the mosquito’s gut, mature infective stages(sporozoites) escape from the gut and migrate to the mosquito salivary glands
Entamoeba histolytica
a protozoan parasite in the large intestine of
humans which causes amoebiasis (amoebic dysentery). Symptoms of this disease include constipation, abdominal pain and cramps, stools with excess mucous and blood clots. Houseflies act as mechanical carriers
and serve to transmit the parasite from the faeces of an infected person to food
Ascaris
the common round worm,Ascaris, an intestinal
parasite causes ascariasis. Symptoms of these disease include internal bleeding, muscular pain, fever, anaemia and blockage of the intestinal passage. The eggs of the parasite are excreted along with the faeces of infected
persons which contaminate soil, water, plants, etc. A
healthy person acquires this infection through
contaminated water, vegetables, fruits, etc
Wuchereria
a (W. bancrofti and W. malayi), the filarial
worms cause a slowly developing chronic inflammation
of the organs in which they live for many years, usually
the lymphatic vessels of the lower limbs and the disease is called elephantiasis or filariasis. The
genital organs are also often affected, resulting in gross deformities. The pathogens are transmitted to a healthy
person through the bite by the female mosquito vectors.
ringworms
fungi Microsporum, Trichophyton and Epidermophyton are responsible for ringworms.
Appearance of dry, scaly lesions on various
parts of the body such as skin, nails and
scalp are the main symptoms of
the disease. These lesions are accompanied
by intense itching. Heat and moisture help
these fungi to grow, which makes them thrive
in skin folds such as those in the groin or
between the toes. Ringworms are generally
acquired from soil or by using towels, clothes
or even the comb of infected individuals
protection from insect vectors that transmit diseases
, introducing fishes like Gambusia
in ponds that feed on mosquito larvae
recent widespread diseases in India
the vector-borne (Aedes mosquitoes) diseases
like dengue and chikungunya in many parts of India
use of vaccines
A large number of other infectious diseases
like polio, diphtheria, pneumonia and tetanus have been controlled to a the large extent by the use of vaccines
immunity
the ability of the host to fight the disease-causing organisms conferred by the immune system
2 types of immunity
innate and acquired immunity
innate immunity
non-specific type of defence, that is present at the time of birth, gained by providing different types of barriers to the entry of the foreign agents into our body
physics barriers
the skin on our body is the main barrier that prevents entry of the microorganisms, the mucus coating of the epithelium lining the respiratory, gastrointestinal and urogenital
tracts also help in trapping microbes entering our body
Physiological barriers :
Acid in the stomach, saliva in the mouth,
tears from eyes–all prevent microbial growth.
Cellular barriers
Certain types of leukocytes (WBC) of our body
like polymorpho-nuclear leukocytes (PMNL-neutrophils) and monocytes and natural killer (type of lymphocytes) in the blood as
well as macrophages in tissues can phagocytose and destroy
microbes.
Cytokine barriers
Virus-infected cells secrete proteins called
interferons which protect non-infected cells from further viral
infection
Acquired immunity
pathogen-specific. It is
characterised by memory. This means when our body encounters a
pathogen for the first time it produces a response called primary
response which is of low intensity. Subsequent encounter with the same
pathogen elicits a highly intensified secondary or anamnestic response.
This is ascribed to the fact that our body appears to have the memory of the
first encounter
lymphocytes that help in primary and secondary responses
two special types of
lymphocytes present in our
blood, i.e., B-lymphocytes and
T-lymphocytes
The B-lymphocytes
produce an army of proteins in response to pathogens into our blood to fight with them. These proteins are called antibodies.
T CELLS
The T-cells themselves do not secrete
antibodies but help B cells to produce them
antibody
Each antibody molecule has four peptide chains, two small called light chains and two longer called heavy chains. Hence, an antibody is represented as H2L2
types of antibodies
.IgA, IgM, IgE, IgG are some of them
antibody-mediated response
humoral immune response