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White blood cell Other pathogensHIVHuman body

1 2

3 4

This cartoon is a symbolic illustration of a fight taking place inthe human body. Analyse the cartoon and note down the conceptsthat can be drawn from it.

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Why don’t we get infected always, though we live amidst anumber of pathogenic microorganisms?

There are several mechanisms in the human body which preventthe entry of germs. What are these mechanisms? Examine Figure6.1 and the indicators given.

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Fig - 6.1.Defence mechanisms in the human body

Find the indications that match best with the organs marked and note down the numberof the indication in the box given against the respective organ.

Indications1. The waxlike substance seen here has

germicidal effect.2. Since hydrochloric acid is present here,

the germs that enter through food andwater are destroyed.

3. The inner membrane of this organ isalways wet due to a fluid called mucusand germs are eliminated through theflowing mucus.

4. The alkalinity and germicidal effect ofthe digestive juice produced by theglands here prevent germs.

5. The fluid that moistens and frequentlywashes this organ contains a germicidecalled lysozyme.

6. Germs cannot break this coveringeasily. Since it is waterproof and oily,germs cannot grow here.

Among these mechanisms to preventgerms skin constitutes the largest organ.Analyse the given figure and thedescription following it, and prepare anote on the mechanisms in the skin toprevent germs.

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Illustration-6.1.

Degreecelsius

37

15

0

62

100

7

75

bacteria

The Power of a Fort

Different types of tissues are seen indifferent layers of the skin. The outermostkeratin layer blocks the entry of germs.Secretions like sweat and sebum havegermicidal effect. Since sebum is oily,water does not stick on to the skin. Thecovering of hair protects the body fromheat and cold, and also prevents the entryof foreign bodies. In the ears, eyes, nose,mouth, urinary duct etc. a thin mucusmembrane is present instead of a thickskin. This covering has severalmechanisms to prevent germs.

If by any means, the skin is injured, germsmay enter the body through the wound.Note down such possibilities from theexperiences in your day to day life.

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Persons who suffer severe burns getinfected easily. Guess the reason and writeit down.

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You know that germs can multiply veryfast if conditions are favourable. What aresuch favourable conditions inside thebody?

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Observe Illustration 6.1. which shows howthe difference in temperature affects theproliferative potential of germs.

How far is the normal temperature of thehuman body suitable for themultiplication of germs? Note down yourinferences.

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Fig.-6.2. Skin

keratin layer hair epidermis

sebaceousglandblood vessels

sweat gland

dermis

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Illustration - 6.2. Inflammatory response

How does an increase in body temperatureaffect the multiplication of germs?

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When germs get inside the body severalreactions take place in the body to preventtheir increase and spreading. Don't wehave fever when wounds swell andbecome sores and when infection oftonsils occurs? Is it beneficial or harmfulto the body when the body temperaturerises in such situations? Note down yourinferences.

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Though the body can control themultiplication of germs through

mechanisms like raising bodytemperature, diseases can be preventedonly when the germs which have enteredthe body are destroyed. This is facilitatedby various activities of the white bloodcells. We have learnt that there aredifferent types of white blood cells. Writedown their names.

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White blood cells like neutrophils andmonocytes can destroy germs byengulfing them. This process is known asphagocytosis. Observe Figure 6.3. and findout how phagocytosis takes place and fillup the boxes.

You must have seen that when a wound occurs in the hand or leg, that area swells.What might be the reason for such swellings? This is another safety measure taken bythe body against germs. How can germs be prevented by this? This activity is calledinflammation. Given below is an illustration which explains how this occurs.

With the help of the indicators, analyse it and prepare a note on how this activitybecomes useful to the body.

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wound

wound

blood capillary

red blood cell

white blood cell

germsphagocytosis

A

Fig-6.3. phagocytosis

B C D

................................... ................................... ...................................

.......

neutrophil

lysosome nucleus

bacteria

Neutrophil nearthe bacteria

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Indicators« What change is seen in the capillary

wall? What is its advantage?« What is the advantage of excess inflow

of blood?

Blood Clotting too – a DefenceMechanismYou know that when there is a wound inthe body, blood flows out through it and

if the wound is small, the flow of bloodstops within a short time. Blood clottingis a defence strategy adopted by the bodyto prevent the dangers due to excessiveloss of blood. How is this possible?Analyse Illustration 6.3. given below andthe following description. Learn how ablood clot is formed and the flow of bloodcontrolled. Prepare a note in the Sciencediary.

Indicators

« What is the role of platelets in the formation of blood clot ?« How does the relatively large size of the red blood cells help in the formation of

blood clot?« What is the cause of the recurrence of blood flow even when there is a slight force

on the wounded portion?We have learnt that certain white blood cells engulf pathogens and destroy them.However a number of germs may survive phagocytosis and enter the body. Theymultiply and spread very quickly. In such conditions, certain special defencemechanisms become active in the body to encounter the germs. These reactions aregoverned by lymphocytes.

How do lymphocytes fight germs? Analyse the given description and prepare a noteon their defence mechanism.

Illustration 6.3. Blood clotting

Ca2+

RBC

Certain chemical substances are produced from plateletsas well as cells in the wounded part. They synthesizethe enzyme thrombin from a substance calledprothrombin.

Fibrinogen in the blood

Thrombin

Fibrin

Platelets

blood clot

Prothrombinenzyme

Fibrin filaments formfine network. Redblood cells andplatelets get trapped inthis network andblood clot is formed.

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Louis PasteurEdward Jenner

Lymphocytes and Immunity

Any foreign substance reaching the body can be called an antigen. Germs are importantamong them. The white blood cells called lymphocytes can recognize specificcharacteristics of germs and can act against each germ in a specific manner.Lymphocytes are of two types- B-Lymphocytes and T-Lymphocytes. Though they differin their activity, immunity of the body is made possible by the combined action of both.Lymphocytes destroy pathogens both directly and by antibodies. Antibodies are proteinmolecules that can destroy antigens by acting against them.

All defence actions against pathogens takeplace naturally after their entry into thebody. Hence all of these can be said to benatural immune systems. But even beforesuch responses are evolved, somepathogens proliferate profusely andspread widely. Then the body becomesmorbid. The body can be protected fromdisease only if it can respond promptly

against even mild attack of germs. Howcan the body be equipped for such aresponse? It was this search that led manto the concept of vaccine. It was the keenobservation skills and the ability to thinkin diverse ways that helped thesescientists for this. Let us get acquaintedwith some of these geniuses. Gather moreinformation about them.

Seeking Artificial Means of Defence

It was Edward Jenner, arural doctor in England,who first testedvaccination. What ledhim to this invention wasan observation that no

one else had noticed during the time ofthe acute small pox disease. He noticedthat the rate of death due to the infectionof small pox was higher among the urbanpopulation when compared to ruralfarmers who were engaged in cattlerearing. He also observed that all thesevillagers were cured of the disease calledcowpox. He thought of using cowpox virusto destroy small pox virus. Subsequently,he conducted a series of experimentsthrough which the first vaccine wasdeveloped. As a result it has beenpossible to wipe out smallpox from theearth.

In the ancient society,many superstitionsprevailed about theincidence of diseases.However, Louis Pasteur,a French scientist, couldprove substantially thatdiseases are caused by microorganisms.This concept of germ theory initiated agreat revolution in the field of medicalscience. He found that milk, wine etc.become stale due to bacterial activity andthat they can be preserved in tact by aprocess called pasteurisation. It is he whoinvented an effective vaccine against theanthrax disease that affects cattle andhuman beings. The invention of rabiesvaccine is also a notable achievement ofPasteur.

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You might have heard of various types of vaccines. List a few which are familiar toyou.

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What are vaccines?How is defence against diseases possible by using vaccines?

On the basis of indicators, analyse the description given below and form inferencesabout immunity to diseases through vaccines.

Indicators« How can lymphocytes act against dead

pathogens and inactivated toxins?« When live germs are used as vaccine,

why do they need to be speciallyprocessed?

There may be a scar on your hand nearthe shoulder due to an injection takenshortly after your birth. What is the nameof this injection? Against which disease isthis vaccine administered?

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Which other vaccines were given to you?Enquire at home and gather information.Complete the given table either visiting ahealth centre or collecting data throughsome other means.

Disease VaccineTuberculosisPolioLiver cirrhosisMumpsTetanusDiphtheriaWhooping cough

Today we are aware of the importance oftaking vaccinations at the proper time.

Attempts to provide the whole populationwith vaccinations to defend certaindiseases which are very common in India,have been widely organised throughoutthe country. An immunisation awarenessschedule itself has been charted for this atthe national level. This is available evenin Primary Health Centres. Complete thefollowing table analysing the NationalImmunisation Schedule.

Vaccines

The principle of vaccination is the use of pathogens themselves to destroy pathogens.Vaccination prepares the white blood cells beforehand to act against pathogens.Lymphocytes can sense the presence of antigens and get activated against them. Germs,both alive and dead, are used as vaccines. Dead germs are utilized in rabies vaccinewhich act against rabies, and in salk vaccine against polio infection. Live but inactivatedgerms are utilized in BCG vaccine against tuberculosis. Active cowpox virus were usedas vaccine against small pox infection. In some vaccines, the toxins produced by thegerms are inactivated and used. e.g., TT (Tetanus toxoid) vaccine.

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We have been able to survive manydiseases through vaccination. Howevervaccines are yet to be developed againstmany other diseases. It is also to be noticedthat many diseases emerge afresh.Decrease in our natural immunity due tochanges in the natural environmentalconditions and life style, and the increasein resistance of germs are reasons for theemergence of new diseases. What can wedo to enhance our natural immunity?Organise a discussion in the class.

Immune DisordersLymphocytes are cells which have aspecial ability to recognize one's own bodycells. However in some individuals,lymphocytes identify the body cells asantigens, and react against them. Suchconditions are called autoimmunedisorders. Rheumatic fever is an example.

Hyper Activity of Immune SystemIs there any extra advantage to the body ifthe immune system works excessively?Many factors which are commonly foundaround us act as antigens in our body. Inmost individuals they do not produce anynotable defence reactions. But in somepeople the body reacts excessively tothese factors, causing many health

problems. Asthma, allergy etc. areexamples of this. Enlist the factors causingsuch disorders.

� Dust� Pollen grains� Food items�

Discuss the symptoms and methods oftreatment of asthma and prepare notes.

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Organ Transplantation and ImmunityYou might have heard of the technologyof transplanting new organs as asubstitute for damaged organs.

Notice this advertisement.

30 year old man critically ill due to thefailure of both the kidneys needs suitablekidney from individuals with O-ve bloodgroup

Which are the organs that can betransplanted? Note down the ones youknow.

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Collect more information about organtransplantation.

Immunisation

Age Vaccine Disease

� ........................................ � ........................................................... � ..........................................................

� ........................................ � ........................................................... � ..........................................................

� � �

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When organ transplantation is done, thenewly grafted organ is a foreign body asfar as the body is concerned. The body mayreact against the grafted organ. What maybe the reason for this? What is the necessityof using immuno suppressants duringsuch operations? Why does this conditionrequire special concern in nursing?Through discussions form inferences andnote them in yours Science diary.

Donate an Organ, Donate LifeOnly if somebody iswilling to donateperfectly functionalorgans, a person's life canbe saved through organtransplantation. Certainorgans can be donated bya live donor whereassome others can bedonated only after thedeath of the donor. Mostpeople hesitate to donateorgans because they arenot sufficiently aware oforgan donation. Isn’t it anoble thing that ourorgans live throughanother person even afterour death? Collect moreinformation on thegreatness of organdonation. Observe thedetails of eye donationgiven as a model.

Eye Donation,a Noble Deed

The cornea of a personcan be donated upto sixhours after his death. The

eyes are taken only when the person givesthe consent for eye donation. The letter ofconsent is to be signed in presence oftwo witnesses. If the relatives and friendsare also informed in advance of one’sdecision to donate eyes, it would be easyfor them to intimate the death to thoseconcerned. As soon as the intimation isreceived, doctors arrive, remove the eyesand fix artificial eyes in their place. Therewill be no deformity on the dead body.

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When Immunity is LostWe have learnt that it is by the combinedactivity of various systems that the bodyis protected from germs. We have alsolearnt that lymphocytes are the chiefwarriors in this fight. However, certaingerms are capable of destroying thelymphocytes themselves. How might theattack of such germs affect the body?

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We have noticed the illustration at thebeginning of the lesson, whichsymbolically explains how AIDS virusesact on the body. Analyse that picture andthe indications given below. Prepare a noteon AIDS.

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PathogenHIV – (Human ImmunodeficiencyVirus)

Mode of transmissionThrough body fluids, unprotectedsexual relationship, unsterilizedinjection needles, blood transfusion, etc.

Activity of the virusHIV attack destroys the lymphocytes. Itcauses considerable reduction in theirproduction.

SymptomsFor a long time after infection, nospecific symptoms appear. Butimmunity gradually decreases sincelymphocytes are destroyed. Even minordiseases become critical and may leadto death.

Unlike other diseases, AIDS can becompletely prevented by taking the rightprecautions. This is a peculiarity of AIDS.

Discuss the precautions to be adoptedagainst AIDS.

Even though there are such powerfulimmune systems in the body somefavourable situations may arise, in whichgerms resist all these and enter the bodymaking it morbid. List such situations.

� Abundance of pathogens� Failure of body functions� Difference in temperature levels� Atmospheric humidity�

If infected, what must we do to save thebody?

Treatment- the Ultimate DefenceStrategySeveral modes of treatment have beendeveloped according to the situations indifferent countries. List the more popularsystems of treatment prevailing in ourcountry.

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Of these, note down the systems oftreatment which originated in India.

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Ayurveda

It is a system of treatment which prevailedin India from the ancient times.

Beyond being an urgent treatmentmeasure against some diseases,Ayurveda gains acceptance as a life styleto maintain the body fit.

Given below are certain indications fromthe Science bulletin “Lessons on Nature’’prepared by Jolly and friends, based onthe origin, development, treatment,methodology, advantages, limitations etcof Ayurveda. Making use of this andcollecting more information, prepare ascience magazine.

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Item

Page

$ The Veda of life

5

$ The contribution of Sages9

$ The balance of 'Tridoshas'12

$ Methods of diagnosis- 'darshanam, 15

sparshanam, prashnam'

$ Medicinal plants - Methods of

treatment

$ Depletion of biodiversity

Lessons on Nature

Hippocrates

Shouldn’t this great system of treatmentbe made more popular? What steps couldbe adopted towards this? Discuss.

The system of treatment like'Sidhavaidyam', 'Panchakarma' etc. whichare based on Ayurveda and systems like'Unani' and Naturopathy are also widelypractised. Gather more information onthem also.

Homeopathy

This is a system of treatment introducedby Samuel Hanniman, a German doctor.Homeopathy gives great importance tothe symptoms in each individual since itaims at treating not the disease but thepatient.

The main principle behind homeopathy isthat the causative factor of the diseasecan itself effect the cure. Anothersignificant principle of this system oftreatment is that the more the medicineis diluted the more is its potency.

Either by interviewing a homeo doctor orutilizing some other source, gather moredata on homeopathy.

Allopathy and Modernmedicine

This is a cosmopolitanmedical practicewidely used all over theworld. This branch ofmedicine, introducedby the ancient Greekphysician Hippocrates,gives much importance

to diagnosis, treatment, medicines etc.Most hospitals in our country function onthe basis of modern medicine.

Given below is a table which indicatescertain specializations of modernmedicine and the area to which they arerelated. Complete the table and find moreareas.

Specialisation Related Area

Paediatrics Treatment of diseasesin childrenTreatment of heartdiseases

Geriatrics

Oncology

Treatment of diseasesof the eye

Neurology

Urology

Treatment ofgynaecological diseases

Radiology

ENT

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Fig - 6.4. Devices for diagnosis

AlexanderFlemming

Diagnostic ToolYou may be familiar with the instruments seen in the figure. Note down the name anduse of each.

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Till a decade or two back, these instruments were the only important techniques usedby doctors for the diagnosis of diseases. However, now there are devices capable oftaking pictures of even minute internal organs and observing their functions live. Usingthe indications given and collecting more information, prepare an excerpt about themodern techniques used for the diagnosis and treatment of diseases.

Indications

� MRI scan � X ray � CT scan

� Pacemaker � ECG � EEG

� Angiogram � Artificial valves � Bypass surgery

� Telemedicine � Nanotechnology � Endoscopy

� Genetic engineering � Gene therapy

Medicines from Microorganisms

Scientists have been successful in transforming their failures toinventions through a creative outlook. The best example for this is theinvention of penicillin, the first antibiotic drug. Alexander Flemmingwas a scientist working on bacteria. In the laboratory he often failed inkeeping equipments clean. Once he went on a tour without properlycovering the petridishes in which staphylococus was grown for

MedicinesFrom olden days man depended mostlyon plants for medicinal requirements.Later chemical substances synthesizedartificially in laboratories establishedtheir monopoly in this field.

The names of such chemical substanceswill be written on the packets of thesemedicines. Examine them and prepare atable showing the names of medicines andtheir chemical composition.

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experimental purposes. When he returned to the lab, he found that all the bacteria grownin a particular petridish were destroyed due to fungal infection. At first he was sad, butsoon the thought that fungi might produce substances that are capable of destroyingbacteria awakened hope in his mind. The substance produced by the fungus penicilliumacts against bacteria. He called this substance penicillin. The finding of the first antibioticmedicine, penicillin, sowed the seeds of a great revolution in the field of health. Antibioticswhich were exemplified as the magical cure of the 21st century, still remain inevitable inthe field of medical science due to its diversity and effectiveness.

Prepare a table showing the names of antibiotics which are familiar to you and themicroorganism against which they act. Even though antibiotics are very helpful, manyside effects are likely to occur due to their use. Note the indications given.

� Constant use may develop resistance against them in bacteria.� Destroy the useful bacteria in the body.� Reduces the level of certain vitamins in the body.When some people have fever or headache, they use tablets and medicines boughtfrom medical shops without consulting a doctor.

Is this tendency right? Why? Conduct a discussion in the class and form inferences.

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Note Illustration 6.4.

Illustration - 6.4.

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A B C

............................................ ............................................ ............................................Fig - 6.5.

What are the reasons for such accidents?

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What can we do to reduce road accidents?Organize a discussion in the class andformulate practical suggestions. Inassociation with the Road Safety Clubconduct awareness campaigns on trafficrules.

When accidents occur, if urgent medicalcare is delayed, won’t it worsen the crisis?

Why do people hesitate to offer urgent aidto a victim of an accident? Discuss.

� Lack of sufficient awareness of first aid.� Legal intricacies.�

We can also help others if we have basicinformation about first aid and thepractical training on it. After observingFigures 6.5 A, B, C, find out the situationswhen each aid is administered and recordit. Prepare a science excerpt on first aidmaking use of previously learnt facts andcollecting more information and pictures.

Blood TransfusionThe transfer of blood from one person to another is called blood transfusion. Duringemergencies, is it possible to receive blood from any person in order to save one’s life?

Note down your opinion on this.

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What all things are to be considered while blood transfusion is done?

Based on the indicators given, conduct an enquiry and prepare a note.

� Possibility of transmission of diseases� Quantity of blood.� Age of the donor, sex, health condition etc.� Compatibility

What is meant by compatibility of blood? Note the description given below.

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Carl Landsteiner

Even though the compo-sition of blood isgenerally the same in allindividuals, there maybe differences in certaincomponents. It was CarlLandsteiner, a scientist,who suggested a means

to enable blood transfusion, in a researchpaper published in 1901. He proposedthat blood grouping is to be done on thebasis of the presence of antigens seenon the surface of the red blood cells. Thisfinding was accepted globally and he wasawarded the Nobel prize for thiscontribution.

Though there are various methods toclassify blood into groups, it is the ABOgrouping system which is more widelyused. Blood is classified into differentgroups based on the presence or absenceof antigens or agglutinogens in the redblood cells. Various antibodies oragglutinins are seen in blood plasma.

From the given table, form an idea aboutthe various antigens, antibodies, etc. ofdifferent blood groups.

Blood group Antigen AntibodyA A Anti-B

B B Anti-A

AB A, B Nil

O Nil Anti-A, Anti-B

Which is your blood group? Why areblood groups mentioned as positive,negative etc.?

During blood transfusion, presence ofanother type of antigen, called Rh factoris also to be considered along with A andB antigens. Though there are many Rhfactors, antigen D is the most important

among them. Those possessing Rh factorare known as Rh positive and those notpossessing it as Rh negative.

When blood having Rh factor is receivedby a person not having Rh factor, noproblem arises immediately. Butgradually, his body develops antibodiesagainst Rh factor. When the same factorreaches the body again, the antibodieswhich are already formed act against Rhfactor and destroy the RBCs in thetransfused blood. You might haveunderstood the importance of consideringthe Rh factor during blood transfusion.

The first child born to a woman of negativeblood group and a man of positive bloodgroup does not have any defect. Butduring parturition, when the placenta isseparated, the Rh factor in the blood of thebaby may reach the mother’s blood. Thenthe mother’s body forms antibodiesagainst this factor. During subsequentpregnancies, if the child is Rh+, theantibodies which are already formed, mayreach the embryo through placenta andcause coagulation of foetal RBCs,resulting in defective foetal developmentor even the death of the foetus. Thiscondition is known as erythroblastosisfoetalis. This can also be considered as adefence mechanism of the body.

There may arise several emergencieswhich demand blood transfusion to savelife. On such occasions, an adult candonate blood. How can we encourageblood transfusion?

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Defence Mechanisms in PlantsLike animals, plants also get infection dueto the attack of microorganisms. Plants

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Fig - 6.6.

When germs enter the body, the plantsrecognise the chemical substances presentin them and as a result substances likecertain proteins, salicylic acid andethylene are produced. Through thepresence of these substances, theinformation about the infection istransmitted to all parts of the plant body.Subsequently structural changes occur inthe cells of different plant tissues to fightgerms.

� Sudden destruction of infected cells.� Formation of layers of cork cell

separating the infected cell.

� Production of phenolic compounds

Immunization in PlantsIf the genes responsible for the productionof antibodies in animals are transplantedto plants through genetic engineering,plants also can synthesize antibodies.Antibodies in plants are called planti-bodies. Mosaic disease in tobacco plant iscaused by Tobacco Mosaic Virus (TMV).Certain tobacco plants into which somegenes of tobacco mosaic virus had beentransferred were found to developimmunity against this disease.

also possess mechanisms to prevent the entry of germs and attack them if they enter. Itis through structural and biochemical mechanisms that plants effect this defence.

You may have noticed that the leaves of plants like lotus and colocasia have a waxycoating on their leaves. This helps to prevent the entry of germs.

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Follow up Activities1. "When there is an infection, it is natural that the number of certain cells increases".

This was the reply given by the doctor to Rani who was anxious about the result ofthe blood test.a. Which type of blood cells is likely to increase in number when an infection

occurs?b. What advantage does the body have due to the increase in the count of this type

of blood cells?c. In what all ways do these blood cells perform their function?d. Use the indication given by the picture and prepare a note on the mechanism of

immunity.

...

2. Given below are certain indications regarding a deadly disease. Study them andanswer the following questions.

� Virus is the pathogen� Not transmitted through air, water, contact, parasites etc.� If infected, the body becomes easily susceptible to other germs.� No effective treatment.� Avoiding disease–causing situations is important.

a. Which is the disease? Which is the pathogen?b. What are the possibilities of germs reaching the body?c. How do the germs act in the body?d. If infected, even common cold may cause death. Why?

blood cell pathogen