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Our body produces many waste products as a result of the metabolic activities that take place inside it. We need to get rid of these waste products as they can be toxic for our body, if they get accumulated inside it. In this chapter, we will learn about an important life process called excretion that helps us remove waste substances from our body.

EXCRETIONThe process of removal of metabolic waste substances from the body is known as excretion. Specialised organs called excretory organs present in our body help in the removal of waste products. Before studying these organs, let us fi rst know about the different kinds of waste substances or excretory products that our body produces.

Types of Excretory ProductsThe following are the various excretory products produced in our body.

1. Nitrogenous waste products: Nitrogenous wastes are produced in the body as a result of the breakdown of excess proteins. This produces urea, uric acid and ammonia. Our kidneys help to remove these waste substances.

2. Water: We drink water and take in other fl uids such as milk and juices, which also contain water. The body uses some amount of this water, while excess water is removed either by the kidneys as urine or by the skin in the form of sweat.

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Learning Objectives

• Know about excretion and its importance• List the types of excretory products produced by

human beings• Study the human excretory system

• Identify other excretory organs in our body• Learn about artifi cial kidney• Know about common disorders of the urinary

system

Human Excretory System

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Fig. 4.1 Human excretory system

Kidneys

Ureter

Urinary bladderUrethra

3. Bile pigments: The liver helps to break down the haemoglobin of dead RBCs, leading to the formation of bile pigments. These pigments are excreted in urine and faeces.

4. Extra salts and vitamins: Our body needs salts for carrying out certain functions. Any excess amount is removed from the body along with urine. Similarly, our body retains the required quantity of water-soluble vitamins and excretes the extra quantity with the help of kidneys.

HUMAN EXCRETORY SYSTEMThe excretory system (Fig. 4.1) in human beings consists of a pair of kidneys, two ureters, urinary bladder and urethra. Let us know more about these organs and their functions in detail.

KidneysOur body has two kidneys located on either side of the backbone. Reddish-brown in colour and bean-shaped, kidneys fi lter waste products from the blood.

UretersTwo narrow tubes called ureters come out of each kidney. They carry urine from the kidneys to the urinary bladder.

Urinary BladderThe urinary bladder is a muscular pouch-like structure that serves to store the urine before it is passed out of the body.

UrethraThe urinary bladder opens into a tube called urethra that acts as the passage through which urine is passed out of the body.

1. Fill in the blanks.a. The breakdown of excess proteins in the body produces ____________, uric acid and

____________.b. ____________ are narrow tubes that carry urine from the kidneys to the urinary bladder.c. Kidneys are present on either side of our ____________.d. ____________ pigments are formed due to the breakdown of dead RBCs in the liver.e. ____________ stores the urine temporarily before it is passed out of the body.

Quick Check

Did You Know?

Male urethra is about 20 cm long, while female urethra is 3–5 cm long.


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Structure of the KidneyInternally, each of our kidneys has two regions—cortex and medulla (Fig. 4.2). While cortex is the outer dark region, medulla is the inner lighter region. Each kidney has millions of microscopic tubes called nephrons or renal tubules. Nephrons fi lter metabolic wastes from the blood. Thus, a nephron is the structural and functional unit of a kidney .

Urine is a transparent fl uid with a yellowish tinge. Water makes up the majority part of urine, while urea, uric acid and other salts are present in small quantities.

From the kidney, the urine enters the ureters that carry it to the urinary bladder. The urinary bladder temporarily stores the urine, from where it is passed out of the body through the urethra.

Other Excretory OrgansEarlier in this chapter, we learnt about the various type of waste substances produced in our body. Besides the kidneys, there are other organs that help in the elimination of these waste products. These are the skin, the lungs and the liver.

Skin: The skin has sweat glands present beneath it. Sweat not only helps to remove excess water, salts and urea from the body, but also has a cooling effect on our body.

Lungs: Lungs help to remove the carbon dioxide produced in our body as a result of respiration. From the lungs, carbon dioxide is exhaled through the nose.

Liver: The liver not only breaks down amino acids into urea, but also produces bile pigments from the haemoglobin of dead RBCs. These waste products and excess vitamins are eliminated from the body along with urine.

Artificial KidneyYou now know that kidneys help to fi lter toxic wastes from the blood. However, sometimes kidneys are not able to carry out their function due to an infection, illness or injury. The build-up of toxins in the blood could prove to be fatal for a person. A person may continue to lead a normal life, even if one of the kidneys fails while the other functions properly. However, if both kidneys fail, then either a kidney transplant can be carried out or an artifi cial kidney (dialyser) (Fig. 4.3) is used. Dialysis is a procedure by which blood from the patient is cycled through a machine to remove nitrogenous metabolic wastes.

Fig. 4.2 Structure of a kidney

CortexMedulla

Ureter

Renal artery

Renal pelvis

Renal vein

Fig. 4.3 Dialysis


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COMMON DISORDERS OF URINARY SYSTEMWe have just now read how kidneys can sometimes fail to function properly. Apart from this, there are certain disorders or diseases that could affect our urinary system. Let us know more about them.

Kidney StonesA common disorder of the urinary system is the formation of kidney stones (Fig. 4.4). Sometimes, when the concentration of certain salts or minerals increases in the urine, it leads to the formation of hard stones within the kidney or the urinary tract. Dehydration is a major risk factor for kidney stone formation. People with certain medical conditions and those who take certain medications are also at the risk of developing this disorder.

A person with kidney stones may not always display signs and symptoms of the disorder.Thisisbecausethestonesmaybeverysmallinsizeandtheypassoutofthe body along with urine, without causing any pain or discomfort. However, when large kidney stones block the fl ow of urine, the condition can be extremely painful. Pain is felt in the back and/or abdomen. Such patients are put on medications for pain control and are advised to take plenty of fl uids to facilitate the passage of kidney stones.

Urinary Tract InfectionCommonly known as UTI, a urinary tract infection can affect any organ of the excretory system—urethra, urinary bladder, ureters or kidneys. Escherichia coli (or E. coli), the bacteria found in our colon and around the anus, cause this infection in a majority of people. These bacteria cause infection when they enter the urine and begin to multiply. The infection starts from the urethra and may progress up the urinary tract, sometimes even reaching the kidneys.

Poor personal hygiene, blocked fl ow or urine, diabetes, etc., are among the many factors that pose a risk of developing a UTI. The symptoms include frequent urge to urinate, painful urination, cloudy appearance of urine or urine containing blood, nausea and vomiting.

the formation of kidney stones (Fig. 4.4). Sometimes, when

Know Your Scientist

Willem Johan Kolff (1911–2009) is known as the ‘Father of Dialysis’. He was a Dutch physician, credited with the invention of the dialyser (artifi cial kidney) in 1943. Kolff was also a pioneer in the fi eld of artifi cial organs. He was widely recognised for his scientifi c contributions.

Fig. 4.4 Kidney stones


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Connecting the Dots

Human Excretory System

Lungs LiverKidneys Skin

Made up of nephrons

KEYWORDS

• Excretion: the process of removing waste substances from the body

• Ureters: a pair of narrow tubes that carry urine from the kidneys to the urinary bladder

• Nephron: the structural and functional unit of a kidney

• Dialysis: the process by which metabolic wastes in the blood are removed by a dialyser

ASSESSMENT TIMEA. Choose the correct answer.

1. Which one of the following is a nitrogenous waste?

a. Urea b. Carbon dioxide

c. Ammonia d. Both (a) and (c)

2. ____________ serves to temporarily store urine in the body.

a. Urinary bladder b. Urethra

c. Ureter d. Kidney

3. Which of the following organs produces bile pigments?

a. Lungs b. Skin

c. Liver d. Kidneys

4. _________ helps to remove extra water-soluble vitamins from the body.

a. Liver b. Kidneys

c. Skin d. Lungs

5. Which of the following statements about kidney stones is not true?

a. They are formed due to a large amount of salts present in the urine.

b. Theycanbesmallorlargeinsize.

c. The bacteria E. coli can also cause kidney stones.

d. Dehydration is a major risk factor for kidney stone formation.

B. Answer in one word.

1. The form in which the skin removes excess water from our body

2. The inner, lighter region inside a kidney

3. The waste product removed by lungs

4. The passage through which urine is passed out of the body


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C. State whether the following are true or false.

1. Both kidneys and skin help remove excess water from the body.

2. A person cannot lead a normal life with only one kidney functioning properly.

3. Cortex is the inner, dark region of the kidney.

4. The liver breaks down excess amino acids into urea.

5. An artifi cial kidney is also known as a dialyser.

D. Label the picture given below and answer the following questions.

1. Name the nitrogenous wastes that our kidneys remove from the body.

2. Which blood vessel carries blood to the kidneys?

E. Answer in brief.

1. Defi ne excretion. Name the excretory organs present in the human body.

2. What is the difference between urinary bladder and urethra?

3. How do the following organs help in waste removal from our body?

a. Liver b. Skin c. Lungs

4. What is a nephron? What is its role in the kidney?

5. What is dialysis?

6. What are kidney stones? Name the major risk factor for their formation.

F. Answer in detail.

1. Discuss any three types of excretory products produced in our body.

2. Explain the structure of a kidney with the help of a labelled diagram.

3. Why do kidneys of some people fail to function properly? What treatment is given to such patients?

4. What is urinary tract infection? Discuss its causes and symptoms.

APPLICATION-BASED QUESTIONS

Sonia does not drink enough water. Her overall fl uid intake per day is also very less. For the past 3–4 months, she has started complaining of severe abdominal and back pain. Could Sonia be suffering from a disorder of the urinary system? What might be the cause of it?

LET US EXPLORE

Field trip: Visit a nearby hospital to see the dialysis process taking place. Discuss the process with the doctor and prepare a brief report.


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Have you ever thought how do the lungs inhale and exhale? How do the stomach and intestines digest food? How does the heart beat? How does the tongue perceive different tastes? How do the ears help us to hear? How do the eyes see objects? Our body carries out several functions at the same time in a well-coordinated and systematic manner. All of this is controlled and regulated by the nervous system (Fig. 5.1) of our body.

NERVOUS SYSTEMThe human nervous system consists of the brain, spinal cord and nerves (Fig. 5.1). Of these, the brain is the most important part of the nervous system. It regulates the processes of breathing, respiration, vision, hearing, digestion, movement, speech, recognition as well as reflexes such as sneezing, coughing, vomiting andswallowing. In this chapter, we will learn the importance of the nervous system and its functioning.

NeuronOur nervous system is made up of highly specialised cells known as neurons (Fig. 5.2). Also known as nerve cells, neurons are the structural units of the nervous system.

A neuron is made up of three parts—a cell body called cyton, dendrons and an axon.

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Learning Objectives

• Describe the human nervous system• Study the structure of the brain and its parts

• Learn about spinal cord, nerves and their functions

Human Nervous System

Fig. 5.1 Human nervous system

Brain

Spinal cord

Nerves

Fig. 5.2 Structure of a neuron

Cell body

Dendrite

Axon

Nucleus


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• Thecytoncontainsthenucleus.

• Fromthecytonariseshortfibrescalleddendrons, which further branch into dendrites. Dendrites receive messages from other neurons.

• Axonis thesingle, longfibrethatarisesfromthe other end of the cell body. The axon helps to carry messages from the cyton of one neuron to the cyton of the next neuron.

Let us now study the parts of the nervous system and their functions.

BrainThe human brain (Fig. 5.3) is a large, soft, slightly fl at structure present in the head region. It is enclosed by the skull that serves to protect this vital organ. The brain is the control centre of our body. It is divided into three main regions—cerebrum, cerebellum and medulla oblongata. Each of these regions performs a specifi c set of functions.

Cerebrum

CerebellumMedulla

oblongata

Fig. 5.3 The human brain

CerebrumIt is the largest part of the brain. The cerebrum (Fig. 5.3) controls all the voluntary actions of our body. Besides controlling our thoughts, reasoning ability, perception of touch, temperature, sight, sound and pain, the cerebrum is also the seat of memory and intelligence.

CerebellumThe cerebellum (Fig. 5.3) is a small part of the brain that lies under the cerebrum. It plays a key role in maintaining the balance of the body. The cerebellum is also responsible for coordinating activities that involve voluntary muscles.

Know Your Scientist

Santiago Ramon y Cajal (1852–1934) was a Spanish neuroscientist and pathologist. A Nobel laureate and known as the ‘Father of Modern Neuroscience’, he found that the brain and the spinal cord are made up of neurons.

Think Through

If a person takes too much alcohol, he /she is neither able to walk properly nor perform other activities in a coordinated manner. Can you tell why?


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Medulla oblongataThe medulla oblongata (Fig. 5.3) is the lowermost part of the brain that extends up to the spinal cord. It controls the involuntary actions of our body, such as breathing, swallowing,sneezing,coughingandheartbeat.

Spinal Cord The medulla oblongata continues as the spinal cord (Fig. 5.4) that runs through the backbone or vertebral column. The backbone acts as a protective structure for the delicate spinal cord.

NervesYou now know that neurons or nerve cells are the structural units of the nervous system. A nerve is an aggregation of nerve cell fi bres, bound together by connective tissue. Nerves run throughout our body. They connect various organs to the brain and the spinal cord. Their function is carry messages to and from the brain as well as the spinal cord.

Connecting the Dots

Human Nervous System

Brain Spinal cord Nerves

Cerebrum

Parts of the Brain

Cerebellum Medulla oblongata

Fig. 5.4 Spinal cord

Spinal cord


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KEYWORDS

• Neuron: a specialised cell of the nervous tissue involved in impulse transmission

• Cerebrum: the largest part of the brain that is the seat of memory and intelligence

• Cerebellum: the part of the brain that maintains the balance of the body and coordinates body movements

• Medulla oblongata: the part of the brain that regulates involuntary actions of the body


1. Which of the following is not a part of a neuron?

a. Dendron b. Cyton

c. Nephron d. Axon

2. Which of the following are parts of the nervous system?

a. Nephron b. Brain

c. Spinal cord d. Both (b) and (c)

3. __________ contains the nucleus in a neuron.

a. Dendron b. Axon

c. Cyton d. Dendrite

4. This part of the brain that controls breathing.

a. Cerebellum

b. Cerebrum

c. Medulla oblongata

d. None of these

5. Which of the following parts of the brain controls our voluntary actions?

a. Medulla oblongata

b. Cerebrum

c. Cerebellum

d. Both (a) and (b)

B. Match the following:

1. Cerebellum a. Arises from the cyton

2. Dendron b. Seat of memory and intelligence

3. Nerves c. Lowermost part of the brain

4. Cerebrum d. Maintains the body’s balance

5. Medulla oblongata e. Aggregation of nerve cell fi bres

C. Fill in the blanks.

1. __________ is the largest part of the brain.

2. The __________ coordinates activities that involve voluntary muscles.

3. The __________ carries messages from one neuron to another.

4. The medulla oblongata continues as the __________ running through the backbone.

5. The brain is enclosed by the __________.

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D. Look at the picture of the brain given below and answer the questions that follow.

1. Identify and label the part of the brain that lies under the cerebrum.

2. Name the part that controls heartbeat.

E. Answer in brief.

1. Name the main parts of the human nervous system. What is its importance in our body?

2. Which is the largest part of the brain? Which all actions does it control?

3. Describe the following:

a. Cerebellum b. Medulla oblongata

4. What is spinal cord? Name the bony structure that encloses it.


1. What is a neuron? Explain its structure and function with the help of a well-labelled diagram.

2. What are nerves? What is their function in our body?

3. Describe the structure of the human brain. List the key functions that its main parts perform.


Why could an injury to the medulla oblongata be dangerous?

CROSS-CONNECTIONHistory: It was in the nineteenth century that the electrical nature of the nerve impulse was established. The neuron was also recognised as the basic unit of our nervous system. These and many more interesting facts about the history of the nervous system can be read by accessing the following link.

http://georgi-georgiev.com/demo/websites/nervous-system/04GG01.html

LET US EXPLOREField visit: Visit a neurologist and learn more about the situations that could lead to brain damage. Prepare a questionnaire prior to your visit. Give special importance to road accidents and alcoholism in the questionnaire. Cover the need to avoid sugar- and fat-rich food, too.

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You might have heard or seen that a red-coloured rash appeared on a person’s body aftereatingsomething,orapersonstartedsneezingandcoughingseverelyonpassingby a dusty area. Have you ever wondered why does this happen and why do only some people experience such problems?

ALLERGYThe symptoms mentioned above are allergic reactions to certain substances. An allergy is a condition of high sensitivity of the body to certain substances. The substances that triggeran allergic reaction are called allergens. Certain food items such as peanuts, fi sh and eggs, dust particles, pollen and drugs might act as allergens. If a person sensitive to any of these things either consumes them or comes in contact with them, he or she could suffer an allergic reaction.

Even though there are several diseases and medical conditions that affect human beings, allergies are also among the most common medical conditions that people suffer from. Severe allergic reactions can hamper a person’s daily life and in some cases could also prove to be fatal. For example, hives (Fig. 6.1) is a severe allergic reaction characterised by the appearance of red, itchy and raised areas on the skin. Asthma, another type of allergy, can cause extreme diffi culty in breathing.

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Learning Objectives

• Defi ne the terms ‘allergy’ and ‘allergens’• Identify the symptoms produced by allergens• Infer that allergy can be seasonal or perennial

• Know the precautions to be taken if a person suffers from a particular type of allergy

Allergy

Fig. 6.1 Hives—a type of allergic reaction


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What Causes Allergy?An allergy is a hypersensitive reaction of our body to a harmless foreign substance called antigen, such as pollen and dust particles that enter the body. Our body has its own defence mechanism, which helps to fi ght off the germs that enter our body. However, when allergens (which are usually harmless for most people) come in contact with our body, they trigger an allergic reaction. This happens due to the fact that the natural defence mechanism of certain people is highly sensitive, which results in the production of antibodies. Antibodies are a type of proteins that the body produces to fi ght off germs. However, in the case of an allergic reaction, the body produces antibodies as a reaction to the entry of an allergen. This causes the appearance of signs and symptoms such as runny eyes, sneezingandrash.

ALLERGENSVarious types of substances can trigger an allergic reaction in people. A person may be sensitive to one or more types of allergens. The most common allergens are listed below.• Dustparticles• Dustmites (Fig.6.2) found inbedding,curtains,upholstered furniture, carpets,

etc.• Pollengrains• Drugssuchasantibiotics• Furofpetssuchasdogs,catsandrabbits• Fungalspores• Venomofinsectssuchaswaspsandbees• Strongsunlight• Somefooditemssuchaseggs,fish,milk,wheat,peanuts,nutssuchaspinenuts

and walnuts and shellfi sh (including shrimps and crab)

Entry Routes of AllergensAs there are many types of allergens, they enter our body in various ways. The symptoms of an allergic reaction depend not only on the allergen, but also on its route of entry. For example, when pollen come in contact with the skin, they may cause a mild reaction. However, if they are inhaled, they might trigger a strong allergic reaction affecting the respiratory tract. Similarly, when allergens enter the body orally (through the mouth) or are injected, they produce symptoms in areas that are remote from their point of entry. Let us know more about the entry routes of allergens.

usually harmless for most people) come in contact with our body, they trigger an

Know Your Scientist

Clemens Peter von Pirquet (1874–1929) was an Austrian scientist. He coined the term ‘allergy’ in the year 1906. He is renowned for this contribution to the fi eld of immunology.

Fig. 6.2 Dust mite

• Somefooditemssuchaseggs,fish,milk,wheat,peanuts,nutssuchaspinenuts

Did You Know?

Allergies caused due to cats are twice more common than those caused due to dogs. Cat’s dander (dead skin) is a major allergen that is found in the air, on the walls, carpets, etc.


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NoseWe breathe through our nose. Our nose has tiny, fi ne hair that trap dust particles present in the air. However, when people who are sensitive to dust and pollen inhale air laden with these allergens, it causes irritation of the nasal epithelium. This results in itchy nose, sneezing (Fig. 6.3), runny nose andother symptoms. Fungal spores can also trigger a similar allergic reaction, when inhaled through the nose.

MouthWe take in food through our mouth. However, after eating certain food items symptomssuchashives,swellingofthefaceorhandsandfeet,coughingorwheezing,vomiting,abdominalpainandupsetstomachappear.Groundnuts,fish,eggs,spicyfood, etc., sometimes trigger allergic reactions. Some people are also allergic to the proteins present in milk. They experience symptoms, such as hives, fl atulence, acidity, diarrhoea and diffi culty in breathing.

SkinYou might have observed or experienced the appearance of rashes, blisters or felt an itchy sensation after using a soap, laundry detergents, etc. This happens when the skin comes in contact with an irritant or an allergen that causes an allergy, known as contact dermatitis. Fragrances present in perfumes, shaving creams and shampoos, some metals such as nickel found in jewellery, hair dyes and certain medications for application on the skin may also cause allergy in some people. Burning sensation and dry, scaly skin are also the signs of contact dermatitis.

SYMPTOMS OF ALLERGIC REACTIONSMost allergic reactions happen soon after contact with an allergen. While many allergic reactions are mild, some can be severe to the extent that they could prove to be fatal. An allergy can produce symptoms in one or more parts of the body, or in the entire body. Allergic reactions occur more often in people who have a family history of allergies.

The fi rst exposure to an allergen may produce only a mild reaction. Repeated exposure may lead to more serious reactions. Once a person has experienced an allergic reaction, even a limited exposure to a very small amount of allergen can trigger a severe reaction. Most severe allergic reactions occur within seconds or minutes of exposure to an allergen. Some reactions can occur after several hours, particularly if the allergen is a food item.

Fig. 6.3 Sneezing


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Common symptoms of a mild allergic reaction include itching, nasal congestion, rashes and watery, red eyes. A moderate allergic reaction is characterised by abdominal pain (Fig. 6.4), diarrhoea, tightness in the chest, heavy breathing, anxiety, nausea, vomiting, swelling of the face, etc.

In some cases, a severe allergic reaction called anaphylaxis occurs within minutes of exposure to an allergen. Its early symptoms include rash on the skin or a runny nose. If immediate medical attention is not provided, the symptoms mayworsentofainting,dizziness,shortnessofbreath,swellingofthelipsortongueand may even cause death.

TYPES OF ALLERGIESThere are certain types of allergies that can occur during any time of the year, while some allergies occur only during specifi c times in a year. Based on this, allergic reactions are of the following two types.

Perennial AllergiesAlso known as non-seasonal allergies, they occur during any time of the year. This is because the allergens are present in the environment all round the year. Allergies caused due to dust, dust mites, fur of pet animals (Fig. 6.5), some food items, etc., are grouped into perennial allergies.

Seasonal AllergiesThere are certain allergies that occur during specifi c seasons, such as spring and autumn. For example, during the spring season when fl owers bloom, the quantity of pollen (Fig. 6.6) considerably increases in the air. When a person sensitive to an allergen such as pollen inhales the air laden with pollen grains, he or she suffers an allergic reaction. Hay fever or allergic rhinitis is usually caused during the summer season when pollen grains of grasses are present in large quantities in the air. Fungal spores also cause seasonal allergies.

Fig. 6.4 Abdominal pain

Fig. 6.5 A dog’s fur is a common allergen

Fig. 6.6 Pollen grains on the stamens


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PREVENTION OF ALLERGIESThere is no permanent cure for allergies. Allergies can at best be prevented or controlled. Givenbelowaresomewaysbywhichallergicreactionscanbemanagedbetter.

• Thefirstandforemostwayofmanagingallergiesistoidentifythesymptomsthatare produced on exposure to certain allergens. One can make regular observations of the symptoms and the allergens that cause them. These can be noted down and discussed with a doctor. This would help minimise the frequency of allergic reactions and reduce the worsening of symptoms.

• Thebestwaytoavoidsufferinganallergicreactionistoavoidcomingincontactwith the allergen. Allergens such as certain food items, medicines, perfumes and detergents can be completely avoided. In some cases, appropriate substitutes or alternatives can be taken or used that do not affect a person with high sensitivity. Complete avoidance, however, may not be possible all the time. For example, in the case of seasonal allergies, allergens such as pollen are present in a large amount in the air. A person allergic to pollen when inhales the air containing pollen would suffer an allergic reaction. To avoid this, one should cover their nose especially while they are outdoors. Carpets and upholstered furniture are usually home to dust mites. These dust mites can cause contact dermatitis and produce symptoms such as rashes, redness and itching of the skin. To avoid this, one should avoid walking barefoot on carpets and get upholstered furniture cleaned regularly.

• Certainmedicinesgreatlyhelpinmanagingthesymptomsofallergy.Theyalsohelp in reducing the sensitivity of a person to the allergen. Thus, it is important that one should take medicines on time as prescribed by the doctor.

• Onemust also carry theirmedicines all the timewith them. In the case of anemergency, medicines can immediately be taken to avoid the worsening of symptoms.

KEYWORDS

• Allergy: a condition of high sensitivity of the body to certain substances

• Allergens: substances that trigger an allergic reaction

• Contact dermatitis: an allergic reaction of the skin that occurs when an allergen comes in contact with the skin

• Anaphylaxis: a serious life-threatening allergic reaction that requires immediate medical attention


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Connecting the Dots

Seasonal allergiesPerennial allergies

Types of Allergies

Allergy

Different Types of Allergens

Caused due to certain substances called allergens

Fungal spores

Certain food items

Dust particles and dust mites

Pollen grains

Certain drugs

Animal fur

Insect venom

Sunlight


1. Which of the following is an allergen?

a.Ginger b. Turmeric

c. Walnuts d. Coriander

2. Dust mites are found in __________.

a. carpets b. bedding

c. curtains d. all of these

3. Which of the following is a symptom of an allergic reaction?

a. Rashes b. Bleeding

c. Itching d. Both (a) and (c)

4. Which of the following is a cause of seasonal allergy?

a. Dust mites b. Pollen grains

c. Peanuts d. All of these

5. __________ is a strong allergic reaction.

a. Shortness of breath b. Vomiting

c. Anxiety d. Rashes

B. Fill in the blanks.

1. Milk and shellfi sh are examples of __________.

2. A severe allergic reaction called __________ occurs immediately on exposure to an allergen.

3. The __________ present in milk can cause allergy in some people.

4. Some medicines help to reduce the __________ of a person to an allergen.

5. __________ allergies can occur any time during the year.


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Riya was walking in the garden at her home. Her garden is full of beautiful fl owers. Suddenly, Riya startedsneezingbadly.WhatdoyouthinkhappenedtoRiya?Alsodiscussitscause.

LET US EXPLOREHealth awareness: Allergies affect large number of people across the world. Symptoms such as sneezingandcoughingmaynotappearveryseriousinthebeginning,buttheycanaggravateifthetype of allergy is not identifi ed and managed in time. In the wake of increasing air pollution, the cases of asthma are on a steep rise worldwide. Visit an allergist to know more about asthma and various other kinds of allergies, their probable allergens and the best ways to manage them. Have a discussion in the class and spread awareness among your family and friends.

C. State whether the following are true or false.

1. Antigens are proteins that help destroy germs.

2. Anaphylaxis can lead to death.

3. It is possible to completely avoid coming in contact with an allergen.

4. Hay fever is a seasonal allergy.

5. Repeated exposure to an allergen causes a mild allergic reaction.

D. Given below is the picture of pollen grains of a fl ower. Look at the picture carefully and answer the questions that follow.

1. What type of an allergy do pollen cause—perennial or seasonal?

2. What are the symptoms of an allergic reaction caused due to pollen?

E. Answer in brief.

1. Defi ne allergy.

2. What are allergens? Name any fi ve allergens.

3. Defi ne antibodies.

4. What is anaphylaxis? List its signs and symptoms.

5. Differentiate between perennial and seasonal allergies.


1. How is an allergic reaction caused in a person?

2. What is contact dermatitis? How is it caused? Discuss its symptoms.

3. What is the best way to avoid an allergic reaction?

4. Does the fi rst exposure to an allergen produce a severe reaction? Discuss the symptoms of mild and moderate allergic reactions.

5. How do the following organs act as entry routes for allergens?

a. Mouth b. Nose


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