The word ‘disease’ means “without ease or not at ease” and is the opposite of health. The condition of malfunctioning of the organ system or systems is called disease.There are numerous diseases that affect our health.
Causes of the diseases
Diseases are caused due to various factors such as pathogens, environmental factors, nutritional factors, genetic factors, metabolic factors, etc.
Based on the causative agent, diseases are classified into two categories:
1. Diseases that are not caused by organisms.
2. Diseases that are caused by organisms.
Diseases not caused by organisms – Non-communicable diseases
1. Organic diseases or Metabolic disorders: A healthy body maintains a constant blood sugar level, which is normally 80-120 mg/dl of blood under fasting conditions. When large quantities of glucose enter the blood stream, as it happens after a meal, the excess glucose is converted into insoluble glycogen and is stored in liver and muscles for future use. Later when required, glycogen is reconverted into glucose and reintroduced into the blood stream.
All these processes are controlled by the hormones, insulin and glucagon secreted by beta cells and alpha cells of Islets of Langerhans in the Pancreas. If insulin is not produced in sufficient quantity, excess of sugar cannot be stored in the liver and cannot be utilized. As a result, sugar gets
accumulated in the blood and is subsequently expelled through the urine.
This leads to other complications and results in diabetes mellitus. Diabetes mellitus is a state of expulsion of excess unused glucose in the urine due to less production of insulin.
Similarly, Diabetes insipidus, coronary heart diseases, Renal failure, hypertension, obesity, Alzheimer’s disease, stroke affecting the functions of the brain, etc., are all caused due to metabolic disorders.
2. Hereditary diseases or Genetic disorders: The genetic disorders are caused due to defective or mutated genes. Albinism is an inherited disorder of melanin metabolism, characterized by the absence of melanin in the skin, hair and eyes. The recessive mutant genes cause this disorder. The clinical symptoms
of Albinism are milky white-coloured skin and marked photophobia (high sensitivity to light). Haemophilia, Sickle cell anaemia, Thalassemia, Down’s syndrome, Colour blindness, Bubble boy syndrome, etc. are a few other genetic disorders.
3. Nutritional Deficiency Diseases:A diet which contains all essential nutrients in correct proportion, is indispensable for maintaining good health. Deficiency in certain food constituents causes various kinds of diseases. Protein deficiency causes Marasmus and Kwashiorkar. In Marasmus, the child loses weight and suffers severe diarrhoea and it will appear as though bones are covered by skin. In Kwashiorkar, the child develops an enlarged belly with face and feetswelling.
Diseases caused by organisms
Robert Koch and Louis Pasteur were the first to establish the Germ Theory of Diseases. A germ or microbe gains entry into the host, such as man, multiplies so fast that it increases in large numbers, produces poisonous substances called toxins and interferes with the host metabolism and
produces a characteristic set of symptoms by which, the disease can be diagnosed.
Parasitic Microorganism: The causative organism of a large number of diseases in man, are microorganisms belonging to different groups. They are viruses, bacteria, fungi and protozoans.
1. Viruses and viral diseases in man: Viruses are living substances inside the host cell and behave as dead particles outside the host cell. The Viral body consists of a nucleic acid, DNA or RNA and a protein cover. All the known viruses
are parasitic and some of them cause deadly diseases such as polio, rabies,
hepatitis, meningitis, encephalitis (brain fever), etc.
2. Bacteria and Bacterial Diseases:Bacteria are unicellular prokaryotes and visible under a compound microscope. Though many bacteria are harmless,some are parasitic and produce diseases. Bacteria can enter the host body through the mouth, nostrils, cuts and bruises on the skin. They multiply rapidly, producing toxins in high concentration to affect health. Some bacterial diseases in man are Tuberculosis, Leprosy, Cholera, Typhoid, Diphtheria, Pertusis, Tetanus, Plague, Pneumonia, Syphilis, Gonorrhoea, etc.
3. Fungi and Fungal Diseases:Fungi are non-green saprophytic or parasitic plants that subsist on dead and decaying organic matter or living organisms. Certain species of fungi are parasitic on man and cause Ringworm attacking the keratinized layer of skin, destroying it in circular patches. Dandruff and Athletes’ foot are other fungal diseases that attack man.
Protozoan and Protozoan Diseases:Protozoans are unicellular animalcules. Some parasitic protozoans in man cause diseases such as malaria, amoebic dysentery, sleeping sickness, etc.Parasitic macro-organisms: Infestations of the body with tapeworm, liver fluke, round worm, filarial worm, etc. cause diseases in man like Taeniasis, Ascariasis, Filariasis, etc.
DISEASES CAUSED BY MICROBES AND THEIR PREVENTION
A disease caused by a parasitic organism and transmitted from one person to another by the transfer of the parasite is known as an infectious disease.We shall study the cause, spread and prevention of a few selected infectious diseases prevalent in our country so that we will know how to guard ourselves against them and other similar diseases.
Viral diseases(Common Cold)
More than a hundred strains of viruses are responsible, for causing common cold in man. Children are more susceptible to common cold than adultsSymptoms
1. Inflammation of upper respiratory passage – nasal epithelium.
2. Flow of mucous.
3. Headache, slight rise in temperature, etc.
It lowers body resistance, leading to a number of secondary infections like pneumonia, bronchitis, etc.
Transmission
i) It spreads mostly through the nasal and oral discharge of the patient in the process of talking, laughing, sneezing, etc.
ii) It may also spread through contaminated objects like handkerchief, bedding, clothes, utensils, toilet articles, etc.
(called fomites)Control and prevention: There are no effective measures to control common cold. However, eating nutritious food, avoiding contact with patients and wearing suitable clothing are suggested, to avoid common cold.
Influenza: It was once a dreadful disease and spread worldwide (pandemic) in 1970s.Causative agent: A(H1N1) Virus, is
spherical in shape and highly contagious, causing influenza.
Symptoms
Sudden onset of fever accompanied by aches and pains in the back and limbs.
Transmission
It spreads through the patient’s nasal and oral secretions and enters into the respiratory tract of a healthy person. It also spreads through fomites.
Prevention
i. Avoid contact with the patients and cover your mouth when sneeze or cough.
ii. Wash hands to maintain good personal hygiene.
Bacterial diseases
Bacteria are prokaryotic organisms. Some of the bacteria are parasitic, causing diseases like Tuberculosis, Cholera, Typhoid, Dysentery etc. in man.
Tuberculosis
It is an airborne disease affecting the lungs and other parts of our body such as bones, joints, lymph glands, alimentary
tract, liver, kidney, etc.
Causative agent: Mycobacterium tuberculosis, a rod-shaped bacterium causes tuberculosis (TB).
Symptoms
i) The affected parts develop lesions in the form of small nodules called tubercles from which, the disease gets its name.
ii) Persistent cough.
iii) Loss of body weight.
Transmission
Tuberculosis is transmitted through air. A large number of bacteria are expelled through the sputum of the patients while
eating, sneezing, talking, laughing and so on. The droplets containing viable germs may remain suspended in the air for a long time and the waxy cell wall of the tuberculosis bacillus prevents it from drying up and thus can remain viable outside the body for a long period. The germs suspended in the air may be inhaled by a healthy person.
Prevention
i) Keeping oneself healthy and avoiding unsanitary conditions, overcrowding and poor-ventilation.
ii) Sunlight and fresh air are important agents that act as natural disinfectants, readily destroying the germs.
iii) Isolation of the patients and frequent of articles used by them are also important.
iv) Incineration (burning) of cloth/ clothes droplets/ the sputum of the patients can prevent infection.
v) Immunization with BCG vaccine is an effective measure to prevent this disease.
vi) The patient should cover his/her mouth and nose while coughing and sneezing.
Typhoid
Causative agent:A short rod-shaped bacterium with numerous flagella – Salmonella typhicauses typhoid.
Symptoms
i) Persistent fever.
ii) Inflammation and ulceration of the intestine.
iii) Enlargement of spleen and a
characteristic red spot eruption on the abdomen.
TREATMENT AND PREVENTION OF DISEASES
Treatment means the medical management of the symptoms of a disease. Medical Management includes:
i) Treatment involving medicine.
ii) Treatment not involving medicine.
Treatment involving medicine:Medicines are generally used to treat infectious diseases. These medicines either reduce the effect of the disease or eliminate the cause of the disease. Antibiotics are used to block the disease without affecting the individual.
Treatment not involving medicine: For a person recovering from the effect of fracture or neurotic problem, yoga and physiotherapy can greatly help him to perfrom normal activities. People addicted to alcohol and drugs are given counselling to overcome the habit.
Prevention: Getting rid of disease causing germs is a means of prevention of the disease.
Prevention can be achieved in two ways:
i. General – preventing the infectious germs by keeping away from exposure to the germs. Hygienic life style, avoiding overcrowding, inhaling air, safe drinking water and good sanitary measures are the ways to prevent a disease causing germ, coming into contact with us.
ii. Specific – This relates to a peculiar property of the immune system that usually fights the microbial infections. e.g. Immunisation programme.
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