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Diseases

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28
Notes

SOME COMMON HUMAN DISEASES
In the previous lesson you have read about the diseases due to nutritional
deficiencies. In this lesson, you will learn about diseases caused due to other
reasons.

OBJECTIVES
After completing this lesson, you will be able to :
l

define a disease and learn its types;

l

differentiate between parasite and pathogen;

l

differentiate between infection and infestation;

l

list the symptoms, causative agents, prevention and control of influenza,
measles, polio, hepatitis, tuberculosis, diphtheria, leprosy, malaria, filariasis
and dengue.

l

identify certain diseases that are caused due to improper functioning of some
organs of the body system;

l

describe the causes, symptoms and prevention and cure for hypertension;

l

list the symptoms of and methods for diagnosing coronary heart disease and
suggest preventive measures;

l

describe the cause, the symptoms, preventive and curative methods of diabetes
mellitus and osteoporosis;

l

recognize cancer as a cell-regulation disorder;

l

define and differentiate between benign and malignant tumors;

l

interpret the category of allergies as immune system related disorders;

l

define the special category of sexually transmitted diseases;
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l

list the causative agents, symptoms, prevention and control of syphilis,
gonorrhea and AIDS;

l

define drug abuse and its prevention.

28.1 DISEASES

Notes

28.1 What is a disease?
Any condition which interferes with the normal functioning of the body is called
a disease. In other words, disease may be defined as a disorder in the physical,
physiological, psychological or social state of a person caused due to nutritional
deficiency, physiological disorder, genetic disorder, pathogen or any other reason.
28.1.1 Types of Diseases
The diseases may be classified into two broad categories (Table 28.1).
Table 28.1 Classification of human diseases
Diseases

Congenital diseases
(Present since birth)

Acquired diseases
(Develop after birth)

Communicable diseases
(Spread from infected person
to healthy person

Non-communicable diseases
(do not spread from one person
to another)

Degenerative
diseases
(caused due to
malfunctioning
of vital body
organ)

Deficiency
diseases
(caused due to
lack of nutrients
in diet)

Allergies
(caused due to
hypersensitivity
of the body to
certain foreign
substances)

Cancer
(caused due to
uncontrolled
growth of cells/
tissues)

Other diseases
(caused due to
various physical
agents or any
other reason)

A. Congenital disease : The disease which is present from birth (e.g. hole in the
heart in infants). They are caused by some genetic abnormality or metabolic
disorder or malfunctioning of an organ.
B. Acquired disease : The disease which may occur after birth during one’s
lifetime.
Acquired diseases may generally be classified into :
(i) Infectious diseases : The diseases which can be transmitted from person to
person e.g. measles.
(ii) Degenerative diseases : The diseases caused by the malfunction of some vital
organs of the body e.g. heart failure.
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(iii) Deficiency diseases : These are caused due to nutritional deficiency such as
that of minerals or vitamins in the diet e.g. anaemia (Fe, Beri- beri (vitamin
B). You have read about such diseases in an earlier lesson 27.

Notes

(iv) Cancer : This is an abnormal, uncontrolled and unwanted growth of cells. e.g.
breast cancer.
Acquired diseases are studied under two categories (Table 28.2).
(i) Communicable diseases : The diseases which can be transmitted from
an infected person to a healthy person.
(ii) Non-communicable diseases : These diseases do not spread from an
affected person to a healthy person.
Table 28.2 Differences between communicable and
non-communicable diseases
Communicable diseases

Non-communicable diseases

1. Caused by some biological agents or
pathogens, such as viruses, bacteria,
protozoans, helminths (worms) etc.

Caused to some specific factor, such
as malfunctioning of some vital organ,
deficiency of nutrients, etc.

2. Spread from one person to another
through contact, water, air, food, etc.

Do not spread from one person to
another by contact.

3. The concern of society as these are
related to community health.

The concern of the individual only.

28.1.2 Modes of Spread of Communicable Diseases
Communicable diseases spread from the infected person to a healthy person in the
following ways.
Direct transmission
The pathogens of diseases infect a healthy person directly without an intermediate
agent. It can take place by various means such as,
(i) Direct contact between the infected person and the healthy person :
Diseases like small pox, chicken pox, syphilis, gonorrhoea spread through
direct contact.
(ii) Droplet infection : The infected person throws out tiny droplets of mucus by
coughing, sneezing or spitting. These droplets may contain the pathogen. By
inhaling the air containing the droplets, a healthy person may get the infection.
Diseases like common cold, pneumonia, influenza, measles, tuberculosis and
whooping cough spread through droplet infection.
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(iii) Contact with soil contaminated with disease-causing viruses, bacteria etc.
(iv) Animal bite : Viruses of rabies are introduced through the wound caused by
the bite of rabid animals, especially dogs. The virus is present in the saliva
of the rabid animals.
Indirect transmission
The pathogens of certain diseases reach the human body through some intermediate
agents. It can take place by various means, which are as follows :

Notes

(i) By vectors such as houseflies, mosquitoes, and cockroaches. Examples:
Houseflies carry the causative organisms of cholera on their legs and mouth
parts from the faeces and sputum of infected persons to food and drinks and
contaminate them. When this contaminated food is taken by a healthy person,
he gets the infection. Similarly, mosquitoes carry virus of dengue and malarial
parasite which causes malaria.
(ii) Air-borne : The pathogens may reach humans with air and dust. The epidemic
typhus spreads by inhalation of dried faeces of infected fly.
(iii) Object borne (Fonite borne) : Many diseases are transmitted through the use
of contaminated articles, such as clothes, utensils, toys, door handles, taps,
syringes and surgical instruments, etc.
(iv) Water borne : If potable water (drinking water) is contaminated with
pathogens of diseases such as cholera, diarhhoea, hepatitis or jaundice, it
reaches a healthy person upon consuming such water.
28.2 SOME IMPORTANT TERMS TO REMEMBER
Pathogen : A living organism which causes a disease.
Parasite : An organism which gets food and shelter from host.
Host : The living body on or inside which the disease-producing organism takes
shelter.
Infestation : A large number of parasitic organisms present on the surface of body
of the host or on the clothings.
Vector : It is an organism which harbours a pathogen and may pass it on to another
person to cause a disease (Mosquitoes harbour malarial parasite and transmits it
to humans).
Carrier : It is an organism which itself does not harbour the pathogen but physically
transmits it to another person (Housefly is the carrier of cholera germs).
Reservoir : An organism which harbours pathogen in large numbers and does not
suffer itself.
Epidemic : Spreading of a disease among a large number of people in the same
place for some time e.g. plague.
Endemic : A disease which is regularly found among a particular group of people
e.g. goitre.
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Pandemic : A disease which is found all over the world e.g. AIDS.
Interferon : Type of proteins produced by infected cells of the body when attacked
by a virus, which act to prevent the further development of the virus.
Notes

Inoculation : Introduction of antigenic material inside the body to prevent suffering
from a disease.
Vaccination : Injection of a weak strain of a specific bacterium (Vaccine) in order
to secure immunity against the corresponding disease. It is also called immunisation.
Incubation period : The period between entry of pathogen inside a healthy body
and appearance of the symptoms of the disease.
Symptoms : Specific expressions which appear on the deseased and help in the
identification of the disease.

INTEXT QUESTIONS 28.1
1. Define the term disease. .........................................................................
2. Give appropriate terms for
(i) the kind of disease which is present from birth.. .......................
(ii) disease caused by malfunctioning of vital organs. ......................
3. Name any two communicable and any two non-communicable diseases in
humans
..................................................................................................................
4. What does infestation mean?
..................................................................................................................
28.3 COMMUNICABLE DISEASES (INFECTIOUS DISEASES)
The diseases which spread from one person to another through contaminated food,
water or contact or through insecticides, animals etc. are called the communicable
diseases. These are caused by different causative agents (pathogens).
28.3.1 Diseases caused by viruses
1. Chicken pox
Pathogen : Chicken pox virus (varicella)
Mode of transmission : By contact or through scabs
Incubation period : 12-20 days
Symptoms
(i) Fever, headache and loss of appetite
(ii) Dark red-coloured rash on the back and chest which spreads on the whole
body. Later, rashes change into vessicles.
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(iii) After few days these vessicles start drying up and scabs (crusts) are formed.
(v) These scabs start falling (infective stage)
Prevention and cure
There is no vaccine against chicken pox as yet. But precautions must be taken as
follows:
(i)

Notes

The patient should be kept in isolation.

(ii) Clothings, utencils, etc. used by the patient should be sterilised.
(iii) Fallen scabs should be collected and burnt.
One attack of chicken pox gives life long immunity to the person recovered from
this disease.
2. Measles
Pathogen : Virus (Rubeola)
Mode of transmission : By air
Incubation period : 3-5 days
Symptoms
(i) Common cold
(ii) Appearance of small white patches in mouth and throat.
(iii) Appearance of rashes on the body.
Prevention and cure
(i) The patient should be kept in isolation.
(ii) Cleanliness should be maintained.
(iii) Antibiotics check only the secondary infections which can easily occur.
3. Poliomylitis
Pathogen : Polio Virus
Mode of transmissions : Virus enters inside the body through food or water.
Incubation period : 7-14 days
Symptoms
(i) The virus multiplies in intestinal cells and then reaches the brain through blood.
(ii) It damages brain and nerves and causes infantile paralysis.
(iii) Stiffness of neck, fever, loss of head support.
Prevention and Cure
Polio vaccine drop (oral polio vaccine, OPV) are given to children at certain
intervals.
Pulse polio programme is organised in our country to give polio vaccine to
children.
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4. Rabies (also called hydrophobia)
Pathogen : Rabies virus
Mode of Transmission : Bite by a rabid dog.
Notes

Incubation period : 10 days to 1-3 months depending upon the distance of bite
from Central Nervous System (CNS), that is the brain or spinal cord.
Symptoms
(i) Severe headache and high fever.
(ii) Painful contraction of muscles of throat and chest.
(iii) Choking and fear of water leading to death.
Prevention and Cure
(i) Compulsory immunisation of dogs.
(ii) Killing of rabid animals.
(iii) Anti-rabies injections or oral doses are given to the person bitten by a rabid
animal.
5. Hepatitis
Pathogen : Hepatitis B virus.
Mode of Transmission : Mainly through contaminated water.
Incubation Period : Generally 15-160 days.
Symptoms
(i) Bodyache.
(ii) Loss of appetite and nausea.
(iii) Eyes and skin become yellowish, urine deep yellow in colour (due to bile
pigments).
(iv) Enlarged liver.
Prevention and Cure
(i) Hepatitis B vaccine is now available in India.
(ii) Proper hygeine is to be observed.
(iii) Avoid taking fat rich substances.
6. Influenza
Influenza, commonly known as ‘flu’ is an illness caused by viruses that infect the
respiratory tract. Compared to common cold, influenza is a more severe illness.
Causes
Influenza is caused by a virus which attacks our body’s cells, resulting in various
effects depending on the strain of the virus.
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There are many strains of influenza virus. The virus mutates all the time and new
variations (strains) arise. This constant changing enables the virus to evade the
immune system of its host. Unfortunately immunity against one strain (which is
conferred by exposure or immunisation) does not protect against other strains. A
person infected with influenza virus develops antibodies against that virus; as the
virus changes, the antibodies against the virus do not recognize the changed virus,
and influenza can recur, caused by the changed or mutated virus.

Notes

Symptoms
Typical symptoms of influenza include:
(i) fever (Usually 100° F to 103° F in adults and often even higher in children).
(ii) respiratory tract infection symptoms such as, cough, sore throat, running
nose, headache, pain in the muscles, and extreme fatigue.
Although nausea and vomiting and diarrhoea can sometimes accompany Influenza
infection, especially in children, gastrointestinal symptoms are rarely prominent.
Most people who get flu, recover completely in 1 to 2 weeks, but some people
develop serious and potentially life-threatening complications, such as pneumonia.
Treatment and Control
(i) Much of the illness and death caused by influenza can be prevented by annual
influenza vaccination. Influenza vaccine is specifically recommended for those
who arc at high risk for complications with chronic diseases of the heart, lungs
or kidneys, diabetes, or severe forms of anemia.
(ii) The persons suffering from influenza should
l
l

drink plenty of fluids
take symptom relief with paracetamol, aspirin (not in children under the
age of 16) or ibuprofen etc. as recommended by the doctor.

l

Consult doctor immediately for treatment.

7. Dengue
Dengue is an acute fever caused by virus. It is of two types: (i) Dengue fever, (ii)
Dengue hemorrhagic fever.
Dengue fever is characterized by an onset of sudden high fever, severe headache,
pain behind the eyes and in the muscles and joints.
Dengue hemorrhagic fever is an acute infectious viral disease. It is an advanced
stage of dengue fever. It is characterized by fever during the initial phase and other
symptoms like headache, pain in the eye, joint pain and muscle pain, followed by
signs of bleeding, red tiny spots on the skin, and bleeding from nose and gums.
How does Dengue spread?
Dengue spreads through the bite of an infected Aedes aegypti mosquito. The
transmission of the disease occurs when a mosquito bites an infected person and
subsequently bites a healthy person. In doing so, it transmits blood containing the
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virus to the healthy person and the person becomes infected with dengue. The first
symptoms of the disease occur about 5 to 7 days after the infected bite.

Notes

Aedes mosquito rests indoors, in closets and other dark places, and is active during
day time. Outside, it rests where it is cool and shaded. The female mosquito lays
her eggs in stagnant water containers such as coolers, tyres, empty buckets etc.,
in and around homes, and other areas in towns or villages. These eggs become adults
in about 10 days.
Incubation period
The time between the bite of a mosquito carrying dengue virus and the start of
symptoms averages 4 to 6 days, with a range of 3 to 14 days.
Diagnosis
Diagnosis is made through blood tests by scanning for antibodies against dengue
viruses. In addition the blood platelets counts also drastically reduce in the infected
person.
Symptoms
Symptoms of Dengue fever
(i)

Sudden onset of high fever, generally 104-105 °F (40 °C), which may last 45 days.

(ii) Severe headache mostly in the forehead.
(iii) pain in the joints and muscles, body aches.
(iv) Pain behind the eyes which worsens with eye movement.
(v) Nausea or vomiting.
Symptoms of Dengue hemorrhagic fever
These include symptoms similar to dengue fever, plus other symptoms such as:
(i)

Severe and continuous pain in the abdomen.

(ii) Rashes on the skin.
(iii) Bleeding from the nose, mouth, or in the internal organs.
(iv) Frequent vomiting with or without blood.
(v) Black stools due to internal bleeding.
(vi) Excessive thirst (dry mouth).
(vii) Pale, cold skin, weakness.
Prevention
Following steps can be taken to prevent spread of dengue fever:
(i)

Avoid water stagnation for more than 72 hours so that the mosquitoes do not
breed there.

(ii) Prevent mosquito breeding in stored water bodies, like ponds, wells etc.
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(iii) Destroy discarded objects like old tyres, bottles, etc. as they collect and store
rain water.
(iv) Use mosquito repellents and wear long sleeved clothes to curtail exposure.
(v) Use mosquito nets, also during daytime.
(vi) Avoid outdoor activities during dawn or dusk when these mosquitoes are most
active.
(vii) Patients suffering from dengue fever must be isolated for at least 5 days.
(viii) Report to the nearest health centre for any suspected case of Dengue fever.

Notes

Treatment for dengue and dengue hemorrhagic fever
There is no specific treatment for dengue fever. Persons with dengue fever should
rest and drink plenty of fluids. Dengue hemorrhagic fever is treated by replacing
lost fluids. Some patients need blood transfusions to control bleeding.

INTEXT QUESTIONS 28.2
1. How does chicken pox spread?
..................................................................................................................
2. Mention the most obvious symptom of measles.
..................................................................................................................
3. Which organ system of the body is affected by the polio virus?
..................................................................................................................
4. Name the causative organism of hydrophobia.
..................................................................................................................
5. Which mosquito spread dengue?
..................................................................................................................
28.3.2 Diseases caused.by Bacteria
1. Tuberculosis
Pathogen : A bacterium (Mycobacterium tuberculosis).
Mode of Transmission : airborne-discharged through sputum, cough, sneeze, etc.
of the infected person.
Incubation period : 2-10 weeks during which the bacteria produce a toxin,
tuberculin.
Symptoms
(i) Persistent fever and coughing.
(ii) Chest pain and blood comes out with the sputum.
(iii) General weakness.
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Prevention and Cure
(i) Isolation of patient to avoid spread of infection.
(ii) BCG vaccination is given to children as a preventive measure.
(iii) Living rooms should be airy, neat and with clean sorroundings.
Notes

(iv) Antibiotics be administered as treatment.
2. Typhoid
Pathogen : A Bacillus rod-shaped bacterium (Salmonella typhi)
Mode of transmission : Through contaminated food and water
Incubation period : About 1-3 weeks
Symptoms
(i) Continuous fever, headache, slow pulse rate.
(ii) Reddish rashes appear on the belly.
(iii) In extreme cases, ulcers may rupture resulting in death of the patient.
Prevention and Cure
(i) Anti-typhoid inoculation should be given.
(ii) Avoid taking exposed food and drinks.
(iii) Proper sanitation and cleanliness should be maintained.
(iv) Proper disposal of excreta of the patient.
(v) Antibiotics should be administered.
3. Cholera
It often breaks out among crowded and areas with poor sanitary conditions.
Pathogen : Comma shaped bacterium (Vibrio cholerae)
Mode of transmission : Contaminated food and water. House - fly is the carrier.
Incubation period : 6 hours to 2-3 days.
Symptoms
(i) Acute diarrohoea, rice watery stool.
(ii) Muscular cramps.
(iii) Loss of minerals through urine.
(iv) Dehydration leads to death.
Prevention and cure
(i) Cholera vaccination should be given.
(ii) Electrolytes (Na, K, sugar, etc.) dissolved in water should be given to the
patient to check dehydration (In market it is available as ORS–oral rehydration
solution).
(iii) Proper washing and cooking of food.
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(iv) Proper disposal of vomit and human excreta.
(v) Flies should not be allowed to sit on eatables and utensils.
4. Diphtheria
This disease generally occurs in children of 1-5 years of age.

Notes

Pathogen : Rod-shaped bacterium (Cornybacterium diphtherea)
Mode of Transmission : Through air (droplet infection)
Incubation period : 2-4 days
Symptoms
(i) Slight fever, Sore throat and general indisposition.
(ii) Oozing semisolid material in the throat which develops into a tough membrane.
The membrane may cause clogging (blocking) of air passage, resulting into
death.
Prevention and cure
(i) Immediate medical attention should be given.
(ii) Babies should be given DPT vaccine.
(iii) Sputum, oral and nasal discharges of the infected child should be disposed
off.
(iv) Antibiotics may be given under doctor’s supervision.
(v) Isolation of the infected child.
5. Leprosy
Pathogen : A bacterium (Mycobacterium leprae)
Mode of transmission : Prolonged contact with the infected person. Nasal
secretions are the most likely infectious material for family contacts.
Incubation period : 1-5 years
Symptoms
(i) Affects skin.
(ii) Formation of nodules and ulcer.
(iii) Scabs and deformities of fingers and toes.
(iv) Infected areas lose sensation.
Prevention and Cure
(i) The children should be kept away from parents suffering from leprosy.
(ii) Some medicine may arrest the disease and prevent from spreading.
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INTEXT QUESTIONS 28.3
1. Name the causative bacterium of (i) TB (ii) Typhoid (iii) Cholera.
Notes

..................................................................................................................
2. State the most obvious symptom of diphtheria.
..................................................................................................................
3. What is the mode of transmission of leprosy.
..................................................................................................................
28.3.3 Diseases caused by protozoans
1. Malaria
Pathogen : Malarial parasite (different species of Plasmodium)
Mode of transmission : By bite of female Anopheles mosquitoes
Incubation period : Approximately 12 days
Symptoms
(i) Headache, nausea and muscular pain.
(ii) Feeling of chilliness and shivering followed by fever which becomes normal
along with sweating after some time.
(iii) The patient becomes weak and anaemic.
(iv) If not treated properly secondary complications may lead to death.
Prevention and cure
(i) Fitting of double door and windows (with “Jali” i.e. wire mesh) in the house
to prevent entry of mosquitoes.
(ii) Use of mosquito net and mosquito repellents.
(iii) No water should be allowed to collect in ditches or other open spaces to
prevent mosquito breeding.
(iv) Sprinkling of kerosene oil in ditches or other open spaces where water gets
collected.
(v) Antimalarial drugs to be taken.
2. Amoebiasis (Amoebic dysentery)
Pathogen : Entamoeba histolytica
Mode of transmission : Contaminated food and water
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Symptoms
(i) Formation of ulcers in intestine.
(ii) Feeling of abdominal pain and nausea.
(iii) Acute diarrhoea and mucus in stool.
Prevention and cure
(i) Proper sanitation should be maintained.
(ii) Vegetables and fruits must be properly washed before eating.
(iii) Antibiotics may be given to the patients.

Notes

28.3.4 Diseases caused by worms (helminths)
1. Filariasis
Pathogen : Filarial worm (Wuchereria bancrofti)
Mode of transmission : Bites of mosquitoes - Aedes and Culex.
Symptoms
(i) Fever
(ii) Collection of endothellial cells and metabolites in the wall of lymph vessels.
(iii) Swelling takes place in certain parts of the body like legs, breasts, scrotum,
etc.
(iv) Swelling of legs which appear as legs of elephant, so this disease is also called
elephantiasis (Fig. 28.1)

Fig. 28.1 Patient suffering from Elephantiasis.

Prevention and cure
(i) Mesh doors and windows in the house to check the entry of mosquitoes.
(ii) The water collected in tanks or other articles should be properly covered.
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(iii) Sprinkling of kerosene in ditches, etc.
(iv) Drugs may be administered.

Notes

INTEXT QUESTIONS 28.4
1. Which mosquito carries stages of life history of the malarial parasite?
..................................................................................................................
2. Which protozoan causes amoebic dysentery?
..................................................................................................................
3. Name the disease cause by Wuchereria bancrofh.
..................................................................................................................
28.4 NON-COMMUNICABLE DISEASES
1. Diabetes mellitus
The disease can be diagnosed by blood test or urine test.
Causes
(i) Less secretion of insulin hormone from the pancreas.
(ii) Mental stress
(iii) Through heredity from parents to children.
Symptoms
(i) More glucose in blood.
(ii) Excessive and frequent passing of urine.
(iii) Feeling thirsty and hungry frequently.
(iv) Reduced healing capacity of injury.
(v) General weakness of the body.
(vi) In extreme cases diabetic coma can take place making the patient unconscious.
Prevention and cure
(i) Control the excessive weight of the body.
(ii) A regulated and controlled diet is to be taken.
(iii) The food should not contain sugar and much carbohydrates.
(iv) Injection of insulin before meals, if required (only on doctor’s prescription).
2. Cardio vascular diseases
Common Causes
(i) Deposition of cholesterol (a kind of fat) in the walls of coronary arteries which
restrict the flow of blood to the heart muscles. This leads to heart attack.
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(ii) Due to reduced blood supply, oxygen available to the muscles, heart’s
efficiency is affected.
(iii) Due to stress and strain.
(iv) Obesity (over weight).
(a) Hypertension : (high blood pressure)

Notes

Symptoms
(i) Persistent high blood pressure (BP)
(ii) It may damage the arteries of kidney.
(iii) In extreme cases the arteries may burst or blindness may be caused.
(iv) It may also cause paralysis.
Prevention and Cure
(i) Do not build up mental tension.
(ii) Low fat diet should be taken.
(iii) Weight of the body must be kept under control.
(iv) Good eating habits should be cultivated
(v) Medicines may be taken as per doctor’s advise.
(b) Coronary heart disease
Symptoms
(i) Severe pain in the chest gasping for breathe.
(ii) Intense nausea and vomiting.
(iii) Lot of sweating takes place.
(iv) Blood clot may be formed within the blood vessels.
Prevention and Cure
(i) A diet low in saturated fats may control the formation of cholesterol.
(ii) Sound eating habits should be developed.
(iii) Over weight should be checked.
(iv) Avoid smoking, alcoholic drinks and drugs.
(v) Take treatment under a qualified doctor.
(vi) Electrocardiogram (ECG) can diagnose the disease.
(vii) By-pass surgery is performed in extreme cases.
3. Osteoporosis
Osteoporosis is an age dependent disorder with loss of the normal density of bone.
The bones become fragile and are easily fractured. Bones that are affected by
osteoporosis can fracture with only a minor fall or injury. Elderly men and women
are most susceptible because of hormonal changes which occur with advancing age.
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Symptoms
(i) The persons suffering from osteoporosis may not know about their condition
for a long time, because osteoporosis doesn’t cause clear cut symptoms and
one may not realise till a bone fracture.
Notes

(ii) The symptoms of osteoporosis are related to the location of the fractures.
(iii) Fractures of the spine can cause severe ‘band like’ pain that radiates around
from the back to the side of the body. Repeated spine fractures can cause
chronic lower back pain, as well as curving of the spine, which gives the
individual a hunched-back appearance.
(iv) Some patients with osteoporosis develop stress fractures of the feet while
walking or stepping off. Hip fractures typically occur as a result of a fall. With
osteoporosis, hip fractures can occur upon even minor accidents. Hip fractures
may take a very long time to heal because of poor bone quality.
Treatment
(i) Patients suffering from osteoporosis are generally treated with vitamin D and
calcium supplements. In addition they are advised bed rest so that the
condition does not worsen.
(ii) Changes to lifestyle and diet are also recommended. The patients are advised
to take calcium either via dietary means or via supplements in the form of
tablets. Since body absorbs about 500 mg calcium at a given time, the calcium
intake should be spread throughout the day.
(iii) Exercise also helps to protect persons from the risk of getting osteoporosis.
However, it is important to do exercises for osteoporosis under the guidance
of a professional physiotherapist.
4. Cancer
1t is the uncontrolled and unwanted growth of cells.
Cause
(i) No definite cause has been arrived at so far. However, it is found that body
has proto-oncogenes. These are activated by some substances or stimulus,
which convert these into active cancer-causing oncogenes.
(ii) Heavy smoking and alcoholism.
(iii) Chewing of tobacco.
(iv) Consistent irritation of skin or repeated injury at the same point.
Cancer is a kind of tumorous growth. Tumours can be classified into two categories :
(a) Benign tumour
It remains confined to the place of origin and does not spread to other body parts.
It is relatively harmless.
BIOLOGY

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(b) Malignant tumour
It spreads to other parts of the body and growth is rapid. This is serious and may
cause death of the patient.
Symptoms
(i) Persistent lump or thickening in tissues, specially in tongue, breast and uterus.

Notes

(ii) Any irregular bleeding or blood-tinged discharge from any body opening.
(iii) Any sore that does not heal quickly.
(iv) Change in the form of mole or wart.
(v) Persistent hoarseness in voice, cough or difficulty in swallowing.
Prevention and cure
(i) Cancer check up should be done once a year.
(ii) Treatment should be taken under medical advice.
(iii) Avoid smoking, taking alcohol and chewing of tobacco.
(iv) Observe regularity in life style to keep body healthy.
5. Allergy
(i) Includes a group of non-infectious diseases.
(ii) No definite cause is known
(iii) It is believed that they occur due to hypersensitiviness of certain individuals
to foreign matter (allergens) which may enter inside the body.
(iv) Symptoms may be sneezing, gasping, running of eyes, irritation of throat or
trachea, etc.
(v) Allergens may be pollen grains, feathers, some animals or insects, drugs,
medicines, odour etc.

INTEXT QUESTIONS 28.5
1. Why is diabetes called a hereditary disease?
..................................................................................................................
2. What happens to the blood pressure in persons with hpertension?
..................................................................................................................
3. State one point of difference between malignant and benign tumour.
..................................................................................................................
28.5 SEXUALLY TRANSMITTED DISEASES
The diseases that are transmitted through sexual contact are known as sexually
transmitted diseases. Sexually transmitted diseases are those infections that are
transmitted via the mucous membrane and secretions of the sexual organ, throat and
the rectum. Syphilis, gonorrhoea, AIDS, etc. are some sexually transmitted diseases.
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28.5.1 AIDS (Acquired Immuno Deficiency Syndrome)
It is a pandemic disease. The word “immuno deficiency” signifies that the immune
system becomes very weak. It is a disorder of cell-mediated immune system of the
body.
Notes

Lymphocytes are the main cells of the immune system i.e. T-lymphocytes and
B-lymphocytes. ‘Helper T’ lymphocytes play a great role in regulating the immune
system. Damages to or destruction of ‘Helper’ lymphocytes lead to the development
of a cellular immune deficiency which makes the patient susceptible to wide variety
of infections.

Fig. 28.2 Human Immunodificiency Virus (HIV)

Mode of transmission : AIDS may be transmitted through any of the following
means :
(i) Sexual contact with the affected person. In India, the most common route of
HIV transmission is through unprotected heterosexual sex.
(ii) Using the same syringe as that of affected person.
(iii) Blood transfusion which contains human immuno deficiency virus.
(iv) Organ transplantation of the affected person.
(v) Artificial insemination.
(vi) From mother to new born baby during the process of giving birth.
Incubation period : The average period is 28 months though it may range between
15 to 57 months
Symptoms : The sufferer may show one or more of the following symptoms :
(i) A type of lung disease develops (tuberculosis).
(ii) A skin cancer may be observed.
(iii) Nerves are effected.
(iv) Brain is badly damaged with the loss of memory, ability to speak and to think.
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(v) The number of platelets (thrombocytes) become less which may cause
haemorrhage.
(vi) In severe cases the patient shows swollen lymph nodes, fever and loss of weight.
A full blown (disease at its peak ) AIDS patient, may die within three years.
Prevention and cure
No medicine or vaccine is known to be available against HIV infection. Therefore,
care has to be taken through following measures:

Notes

(i) There should not be any sexual contact with the person who has HIV infection
or STI. Since STI causes some damage to the gemital area and mucous layer,
and thus facilitates the entry of HIV into the body.
(ii) Use disposable syringe and needle.
(iii) The blood to be transfused to the needy person, should be free from HIV germ.
(iv) Prostitution and homosexuality should be avoided.
(v) Condom should always be used during intercourse.
Control
AIDS can be detected by ELISA test.
There are three points which may be important to control STD.
(i) Partner notification : Identification of potential infected contact, examination
and treatment.
(ii) Education of STD : This should be a part of general education.
(iii) Screening for STD : Serological screening of groups, such as, blood donors,
women before giving birth.
Facts about HIV transmission
l HIV is a weak virus and hard to get infected with. It cannot be transmitted
through air or water outside the human body.
l A person cannot get AIDS by hugging or sneezing of an infected person, insect
bites (including mosquito), sharing the same comb, plates, glass, handkerchiefs,
knives or cutlery.
l A person cannot get AIDS by using public toilets, swimming pools, showers
and telephones.
l HIV does not transmit by being near to someone, touching someone or working
with someone who is suffering from AIDS.

INTEXT QUESTIONS 28.6
1. How is HIV transmitted? Mention any three ways of infection.
............................................................................................................................
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2. Mention any two methods to prevent AIDS.
............................................................................................................................
3. Write full form of HIV.
............................................................................................................................
Notes

4. Give any two symptoms of AIDS.
............................................................................................................................
5. Mention three general points the knowledge of which may control STD.
............................................................................................................................
28.5.2 Syphilis
Causative organism
Treponema pallidum (a long corkscrew bacteria)
Mode of spread
Sexual contact with the infected person
Incubation period
Symptoms of the disease occur in about 10-90 days after contraction, but generally
noticed in 3-4 weeks after getting infected with the bacteria.
Symptoms
Symptoms of syphilis occur in stages. The common symptoms of syphilis include.
(i)

Fever, and sores on the skin, in the throat and urinogenital areas especially
vagina or penis, anus, rectum and mouth. Sores are firm, round and often
painless.

(ii) Rashes on hands, feet and palms.
(iii) White patches in the mouth.
(iv) Acne-like warts in the groin area.
(v) Hair fall in patches from infected areas.
(vi) The last three symptoms can be very serious. They often become internal and
affect organs like brain, nerves, liver, eyes, blood vessels, bones and joints,
which show up after about 10 years of getting the infection. It can lead to
paralysis, blindness, dementia and sterility.
Prevention and cure
(i) Having sexual intimacy with only one person.
(ii) Avoiding prostitution and homosexuality.
(iii) Practicing abstinence, and use condoms.
(iv) Taking appropriate medical treatment, and maintaing personal hygience.
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28.5.3 Gonorrhoea
Gonorrhoea is a sexually transmitted disease that often involves urethra, vagina or
penis, cervix, anus, and throat, as its target sites.
Causative organism
A gonococcus bacteria, Neisseria gonorrhoeae. It grows and multiplies quickly in
warm moist areas of the body, such as the cervix, rectum and mouth.

Notes

Modes of spread
Having multiple sex partners increases the risk of contracting it. Any kind of
unprotected sex is always a risk. Any kind of contact of sores with an infected
person is also risky.
Incubation period
About 2-5 days after getting infection.
Symptoms
(i) Inflammation of mucous membrane in the urinogenital tract.
(ii) Burning sensation while passing out urine and urithral discharge.
(iii) Rectal discomfort.
(iv) Pain in the joints.
(v) Rashes on palms, Mild sore throat
(vi) In females, it may cause sterility
Prevention and cure
(i) Having sexual contact with only one person.
(ii) Avoiding prostitution and homosexuality.
(iii) Taking antibiotics, such as penicillin injection or appropriate medicines at the
appropriate time as per Doctor’s advice.
In males, gonorrhoea primarily affects the urethra. anus, throat, joints and eyes.
Most victims of this disease are teenagers and young adults. One of the advanced
complications of gonorrhoea is gonococcal septicemia (blood poisoning).
28.6 DRUG ABUSE AND ITS PREVENTION
What is a drug
A drug is a chemical substance that changes the way our body and mind work. When
pharmaceutical preparation or a naturally occurring substance is used primarily to
alter the physical or mental functioning of an individual, it is called a drug.
What is drug abuse
When drugs are taken for medical reasons to treat or cure disease both physical
and mental, they are called medications or therapeutic drugs.
Drug abuse occurs when drugs are taken without medical reasons and without
medical supervision, especially when they are taken in an amount, strength,
frequency, or manner that damages the physical and mental functioning of the
individual. Cough syrups, pain killers, and tranquillizers are some common
medicines that are often abused.
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Drug abuse also occurs when certain chemicals that have no medical use or benefits
are taken, such as sniffing glue and solvents. The extent of drug abuse depends
on the quantity of the drug begin taken, and the method and frequency of its
consumption. Drug abuse leads to many serious physical, emotional, and social
problems.
Notes

What are the effects of drug abuse?
Drug abuse leads to a number of short-term and long-term effects that are
detrimental to health:
l

Short-term effects : These are the effects that appear instantly or a few minutes
after the intake of drugs. The effects include a sense of well-being and a pleasant
drowsiness.

l

Long-term effects : Constant and excessive use of drugs over a long period
can cause both physical and mental damage and illness. This includes failure
in academic studies, employment, and interpersonal relationship; financial ruin;
increased risk of contracting STIs; and increased risk of being involved in
vehicular accidents. Addicts stop thinking of everything in life except when and
how they will get their next drug dose. They will do anything for the dose,
including committing crimes such as theft and in certain case even number.

Some Basic Facts
Teenagers sometimes try a smoke or drink just to see how it
feels, but they do not start using drugs on a regular basis. What
is the harm in trying drugs just to see how it feels?
Ideally, there is no need to try out a smoke or drink.
But there is a great difference between “ trying out” smoking or
drinking as compared to drugs.
Smoking and drinking once only or very occasionally does not
always lead to addiction. But drugs are very powerful chemicals
that can cause profound alterations in the metabolism of the body
and in the chemistry of the brain. Even a single dose of a powerful
drug can start the addiction process. When one’s mind and body
becomes addicted to drugs, stopping drugs produces very unpleasant
and distressing mental and physical symptoms. This makes the
addict persist with the usage of the drug. Addicts cannot give up
their habit unless they get medical treatment and counselling.
You should not boast about your strong will power and assume that
you can experiment with drugs without becoming addicted. ALWAYS
KEEP AWAY from drugs. Do not allow yourself to succumb to
pressure by friends and acquaintances. If you remain firm in your
resolve, you can prevent your life from being ruined.
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Some Basic Facts
What are Reproductive Tract Infections (RTIs)?
RTIs are infections of the upper and lower reproductive tracts of
both sexes. Agents of infection include bacteria, viruses, and
protozoa. Not all RTIs are sexually transmitted; some may occur
due to an imbalance of the bacteria normally found in the reproductive
tract and poor personal hygiene.

Notes

Some Basic Facts
Is it possible for a person to have an STI and not know it?
Symptoms of STIs in men are visible, and hence they become aware
that their sexual organs have been infected.
However, STIs in women can be asymptomatic. This means that
signs or symptoms are not experienced even though the infection
is active. Hence women often do not know that they have an STI.

INTEXT QUESTIONS 28.7
1. Name the pathogen that causes syphilis.
..................................................................................................................
2. Mention any two symptoms of the disease gonorrhoea.
..................................................................................................................
3. Give the main method of checking syphilis.
..................................................................................................................

WHAT YOU HAVE LEARNT
l

Diseases are broadly classified into two categories–Acquired (Occur after birth)
and congenital (present from birth).

l

Infectious diseases are transmitted from person to person and degenerative
diseases are due to malfunctioning of some organs.

l

Cancer is uncontrolled growth of cells.

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Notes

l

Acquired diseases are studied in two categories of communicable and noncommunicable diseases.

l

Communicable diseases are transmitted and may be caused by virus, bacteria,
protozoa or helminths (worms).

l

Non-communicable diseases are not transmitted from person to person.

l

diseases which spread by sexual contact are called sexually transmitted diseases
(STD).

l

AIDS is caused by HIV.

l

Gonorrhoea is caused by a bacterium (Neisseria gonorrhoeae). Syphilis is
caused by a long, corkscrew bacterium (Treponema pallidum).

TERMINAL QUESTIONS
1.

What is a disease? How does it differ from disorder?

2.

Name the two categories of acquired diseases.

3.

Explain the term (i) parasitism (ii) reservoir.

4.

Give two symptoms of coronary diseases and of typhoid.

5.

What precautions should be taken to prevent malaria?

6.

Name the pathogen that causes diphtheria and cholera.

7.

Mention the four types of acquired diseases.

8.

Differentiate between :
(i) Communicable and non-communicable diseases
(ii) Pathogen and vector
(iii) Syphilis and gonorrhoea
(iv) HIV and AIDS
(v) Benign and malignant tumours

9.

How does polio virus enter human body? How does it paralyse limbs?

10. A nursing mother is given an immunization for BCG and DPT to the baby.
What are the diseases against which she would be protected?
11. Give the cause, symptoms and treatment of haemorrhagic dengue fever.
12. Give full form of STD.
13. Mention any two sympotms of syphilis.
14. State the means which may prevent and cure gonorrhoea.
15. What does the term AIDS stand for?
16. Write four possible symptoms of AIDS.
17. Mention three general points which may control sexually transmitted diseases.
BIOLOGY

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ANSWERS TO INTEXT QUESTIONS
28.1 1.
2.
3.
4.
28.2 1.
2.
3.
4.
5.
28.3 1.

2.
3.
28.4 1.
2.
3.
28.5 1.
2.
3.
28.6 1.
2.
3.
4.
5.

28.7 1.
2.
3.

BIOLOGY

Any condition which interfers with the normal functioning of the body.
(i) congenital (ii) degenerative
Refer text.
Presence of large number of organisms on the surface of body.
Contact or scabs
Appearance of rashes on the body
Nervous system
Rabies virus
Aedes aegypti
(i) Mycobacterium tuberculosis
(ii) Salmonella typhi
(iii) Vibrio cholerae
Oozing semisolid material in the throat, form a membrane which blocks
the air passage.
Prolonged contact with patient.
Female Anopheles
Entamoeba histolytica
Elephantiasis or Filariasis
It is passed down from parents to offspring.
The blood pressure remains persistently high.
Benign does not spread to other parts of the body, whereas malignant
tumor cells spread to other parts of the body.
Any three points mentioned under “mode of transmission”
Give any two points written under “prevention and cure”.
Human immunodeficiency virus.
Mention any two points given under “symptoms.”
(i) Partner-notification.
(ii) Education of STD.
(iii) Screening for STD.
Treponema pallidum
(i) Swelling of mucous membrane of urinogenital tract.
(ii) Burning sensation during passing of urine.
(i) Prostitution and homosexuality should be avoided.
(ii) Certain medicines may check the diseases.

Notes

261

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