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
cell-mediated immunity
The T-lymphocytes mediate CMI
transplant procedure
Grafts from just any source – an animal, another primate, or any human beings cannot be made since the grafts would be rejected sooner or later. Tissue matching, blood group matching are essential before undertaking any graft/transplant and even after this the patient has to take immuno–suppresants all his/her life. The body is able to differentiate
‘self’ and ‘nonself’ and the cell-mediated immune response is responsible for the graft rejection
active immunity
When a host is exposed to antigens, which may be in the form of living or dead microbes or other proteins, antibodies are produced in the host
body Active immunity is slow and takes time to give its full effective response. Injecting the microbes deliberately during immunisation or infectious organisms gaining access into body during natural infection induce active immunity
passive immunity
When ready-made antibodies are directly given to protect the body against foreign agents
Do you know why mother’s milk is considered very essential for the newborn infant?
The yellowish fluid colostrum secreted by mother during the initial days of lactation has abundant antibodies (IgA) to protect the
infant. The foetus also receives some antibodies from their mother, through the placenta during pregnancy
vaccination
a preparation of antigenic
proteins of pathogen or inactivated/weakened pathogen (vaccine) are introduced into the body. The antibodies produced in the body against these antigens would neutralise the pathogenic agents during actual infection. The vaccines also generate memory – B and T-cells that recognise the pathogen quickly on subsequent exposure and overwhelm the invaders with a massive production of antibodies
passive immunisation.
If a person is infected
with some deadly microbes to which quick immune response is required as in tetanus, we need to directly inject the preformed antibodies, or antitoxin (a preparation containing antibodies to the toxin). Even in cases of snakebites, the injection which is given to the patients, contain preformed antibodies against the snake venom
allergy
The exaggerated response of the immune system to certain antigens
present in the environment
allergens
The substances to which
such an immune response is produced
Allergy is due to the release of chemicals like
histamine and serotonin
from the mast cells
how to control allergy symptoms
The use of drugs like anti-histamine, adrenalin and
steroids quickly reduce the symptoms of allergy. Somehow, modern-day
life style has resulted in lowering of immunity and more sensitivity to
allergens
auto-immune disease
sometimes, due to genetic and
other unknown reasons, the body attacks self-cells. This results in damage to the body, eg: Rheumatoid arthritis
The human immune system consists of
lymphoid organs, tissues, cells
and soluble molecules like antibodies
Lymphoid organs
These are the organs where origin and/or maturation
and proliferation of lymphocytes occur. The primary lymphoid organs
are bone marrow and thymus where immature lymphocytes differentiate into antigen-sensitive lymphocytes.
secondary lymphoid organs
After maturation the
lymphocytes migrate to secondary lymphoid organs like spleen, lymph nodes, tonsils, Peyer’s patches of small intestine and appendix. The secondary lymphoid organs provide the sites for
interaction of lymphocytes with the antigen, which then proliferate to become effector cells
The bone marrow
the main lymphoid organ where all
blood cells including lymphocytes are produced.
thymus
The thymus is a lobed organ located near the heart and beneath the breastbone, The thymus is quite large at the time of birth but
keeps reducing in size with age and by the time puberty is attained it reduces to a very small size. Both bone marrow and thymus provide micro-environments for the development
and maturation of T-lymphocytes.
the spleen
The spleen is a large bean-shaped organ. It mainly contains lymphocytes and phagocytes.
It acts as a filter of the blood by trapping blood-borne microorganisms. Spleen also has a large reservoir of erythrocytes.
lymph nodes
small solid structures located at different
points along the lymphatic system. Lymph nodes serve to trap the micro-organisms or other antigens, which happen to get into the lymph and tissue fluid. Antigens trapped in the lymph nodes are responsible for the activation of lymphocytes present there and cause the immune response.
mucosa-associated lymphoid tissue (MALT)
There is lymphoid tissue also located within the lining of the major
tracts (respiratory, digestive and urogenital tracts
cancer cells
In our body, cell growth and differentiation is highly controlled and regulated. In cancer cells, there is
breakdown of these regulatory mechanisms
contact inhibition
Normal cells show a property called contact inhibition by virtue of which contact with other cells inhibits their uncontrolled growth. Cancer cells appear to have lost this property. As a result of this, cancerous
cells just continue to divide giving rise to masses of cells called tumours
Tumors are of two type
: benign and malignant. Benign tumors normally
remain confined to their original location and do not spread to other parts of the body and cause little damage. The malignant tumors, on the
other hand, are a mass of proliferating cells called neoplastic or tumor cells.
The malignant tumor
These cells grow very rapidly, invading and damaging the surrounding normal tissues. As these cells actively divide and grow they also starve the normal cells by competing for vital nutrients. Cells sloughed from such tumors reach distant sites through blood, and wherever they get lodged in the body, they start a new tumor there. This property called metastasis
carcinogens
Ionising radiations like X-rays and
gamma rays and non-ionizing radiations like UV cause DNA damage leading to neoplastic transformation. The chemical carcinogens present in tobacco smoke cause lung cancer. Cancer-causing viruses called oncogenic viruses have genes called viral oncogenes
cellular oncogenes
(c-onc) or proto oncogenes
in normal cells which, when activated under certain conditions, could lead to oncogenic transformation of the cells
Cancer
detection
n biopsy and histopathological studies of the tissue
and blood and bone marrow tests for increased cell counts in the case of leukaemias, Antibodies against cancer-specific antigens are also used for
detection of certain cancers
biopsy
a piece of the suspected tissue cut into thin sections
is stained and examined under a microscope (histopathological studies) by
a pathologist
detect cancers of the internal organs
Techniques like radiography (use of X-rays), CT (computed
tomography) and MRI (magnetic resonance imaging
Computed tomography
uses X-rays
to generate a three-dimensional image of the internals of an object
MRI
MRI uses strong magnetic fields and non-ionising radiations to accurately detect
pathological and physiological changes in the living tissue
Treatment of cancer
surgery, radiation therapy, chemotherapy and immunotherapy
radiotherapy
radiotherapy,
tumour cells are irradiated lethally, taking proper care of the normal tissues surrounding the tumour mass
chemotherapy
Several chemotherapeutic drugs are used
to kill cancerous cells. Some of these are specific for particular tumors.
The majority of drugs have side effects like hair loss, anaemia
α-interferon
Tumor cells have been shown to avoid detection and destruction by the immune system. Therefore, the patients are given substances called biological response modifiers such as α-interferon which activates their immune system and helps in destroying the tumor
The drugs
opioids, cannabinoids and coca alkaloids. Majority of these are obtained from flowering plants. Some are obtained from fung
opioids
Opioids are the drugs, which bind to specific opioid receptors present
in our central nervous system and gastrointestinal trac
heroin
Heroin commonly called smack is chemically diacetylmorphine which is a white, odourless, bitter crystalline compound. This is obtained by
acetylation of morphine which is extracted from the latex of poppy plant Papaver somniferum (Figure 8.8). Generally taken by snorting and injection, heroin is a depressant and slows down body functions
cannabionoids
Cannabinoids are a group of chemicals, which interact
with cannabinoid receptors present principally in the brain. Natural cannabinoids are obtained from the inflorescences of the plant Cannabis
sativa
cannabis plant
The flower tops, leaves and the resin of cannabis
plant are used in various combinations to produce marijuana, hashish, charas and ganja. Generally taken by inhalation and oral ingestion, these are known for their effects on cardiovascular system of the body
Coca alkaloid
cocaine is obtained from coca plant Erythroxylum coca, native to South America. It interferes with the transport of the neuro-transmitter dopamine. Cocaine, commonly called coke or crack is usually snorted. It has a potent stimulating action on central nervous system, producing a sense of euphoria and increased energy. Excessive dosage of cocaine causes hallucinations
plants with
hallucinogenic properties
Atropa belladona and
Datura
drugs, that are used as medicines to help patients cope with mental illnesses like depression and insomnia
barbiturates, amphetamines,
benzodiazepines
. Morphine
a very effective sedative and painkiller, and is very useful
in patients who have undergone surgery
Tobacco
It is smoked, chewed or used
as a snuff. Tobacco contains a large number of chemical substances
including nicotine, an alkaloid. Nicotine stimulates the adrenal gland to release adrenaline and nor-adrenaline into blood circulation, both of
which raise blood pressure and increase heart rate
diseases caused due to smoking
increased incidence of cancers of lung, urinary bladder and throat,
bronchitis, emphysema, coronary heart disease, gastric ulcer, etc. Tobacco chewing is associated with an increased risk of cancer of the oral cavity.
Smoking increases carbon monoxide (CO) content in blood and reduces the concentration of homebound oxygen. This causes oxygen deficiency
in the body
