Blooming Science-10-2077- final press

Role of compost manure
a. It supplies most of the nutrients like nitrogen, potassium and phosphorus to the soil.
b. It helps to conserve water in soil.
c. It does not pollute soil and water.
d. It helps to increase the soil organism.
e. It increases the nutrients of soil and makes the soil porous .

Inorganic Chemical Fertilizers
These are chemical compounds manufactured in the factories which are added to the soil to
provide the essential nutrients necessary for the growth of plants. Nitrogen, phosphorus and
potassium are the three principal elements. The chemical fertilizers contain one, two or more
of these elements along with oxygen. Fertilizers having more than one plant nutrient elements
are called mixed fertilizers. For example, Potassium nitrate contains potassium and nitrogen.
Ammonium sulphate, ammonium nitrate, sodium nitrate, urea, etc. are mixed fertilizers.
To provide three most vital elements to the soil, there are three main types of chemical fertilizers:
i) N-type, ii) P-type and iii) K-type.

N-typeFertilizers (Nitrogenous Fertilizers)
N-type fertilizers contains salts of nitrogen. Nitrogen element helps in the synthesis of protein,
protoplasm and chlorophyll for rapid growth of the plants. Its deficiency in soil causes reduction
in yield. The leaves turn from green to yellow. Urea (NH2CONH2), an organic compound also
found in the urine of animals, is an excellent nitrogenous fertilizer containing high percentage
of nitrogen. Ammonium sulphate (NH4)2SO4, ammonium nitrate (NH4)NO3 and calcium nitrate
Ca(NO3)2 are other nitrogenous fertilizers.

P-type Fertilizer (Phosphorus Fertilizers)

P-type fertilizer contains salts of phosphorus. It is essential element for the development of roots
of the plants, it accelerates seeding or fastens the ripening of fruits. It helps the plant in cell
division. It increases the content of starch in potatoes and yield of grains. It helps the plants to
resist disease. Powdered bones are used in soil. Bones are mainly calcium phosphate which is
slightly soluble in water. Super phosphate fertilizer is obtained by treating calcium phosphate
with concentrated sulphuric acid. It is a mixture of calcium dihydrogen phosphate and calcium
sulphate.

Common p-types fertilizers are: Ammonium phosphate (NH4)3PO4, Super phosphate Ca(H2PO4)2.
2CaSO4 and triple super phosphate 3Ca(H2PO4)2.

The triple super phosphate contains about three times more phosphorus than in super phosphate
and can be easily absorbed by plants.

K-type Fertilizer (Potassium Fertilizers)

K-type fertilizer contains salts of potassium. It is also essential for the growth of the plants. It
increases vigour and disease resistance, makes the plants strong and helps in the development of
healthy roots. It also helps in the formation of carbohydrates, fats and proteins. It is also essential
for protein synthesis and cell division. The common potassium fertilizers are potassium chloride
(KCl), potassium sulphate (K2SO4) and potassium nitrate (KNO3). Ash also contains potassium.

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A fertilizer that supplies all three essential nutrients, nitrogen, phosphorus and potassium is
called NPK fertilizer. It is a complete fertilizer.

Plastics

A polymer is an extremely large molecule that is formed by linking a large number of small
molecules together. The starting small molecules are called monomers. Example are ethene,
ethyne, vinyl chloride, etc.

The process by which two or more simple molecules are joined together to form a giant compound
is called polymerization.

The properties of the polymer are far superior to that of the monomers. They are generally carbon
molecules(monomers). Polythene is a polymer which is obtained when thousands of ethene
(CH2 = CH2) molecules unite together. Polyvinyl chloride, polystyrene, etc are other examples
of polymere.

n(CH2 = CH2) Polymerization (-CH2 - CH2 -)

Ethene Polyethene
Polymers are of two types
Natural polymers
Proteins, starch, cellulose, silk, wool, rubber etc. are examples of natural polymers.

Synthetic Polymers
Plastics, synthetic fibers (terylene, nylon) etc. are example of synthetic polymers.

Plastics

Several items made from plastics are used in our daily life. The raw materials for most plastics
are chemicals obtained from crude oil. Besides the chemical from crude oil, small quantities of
other substances are often added to modify its properties.

Types of Plastics 2. Thermosetting plastics

There are two types of plastics:
1. Thermoplastics and

Thermoplastics

Thermoplastics are polymer which become soft on heating. It is because the long linear chains of

molecules lie close to each other but are not strongly connected. They harden again on cooling.

So, they can be moulded over again and again into different shapes. Polythene is the most

common thermoplastic. The other thermoplastics are polystyrene, polyvinyl chloride (PVC), etc.

Polythene

n(CH2 = CH2) Polymerization (-CH2 - CH2 -)n

Ethene Polyethene

It is a polymer of ethylene which can be made by heating ethylene under high pressure. It is
tough but flexible and strong. It is used for making pipes, laboratory apparatus, buckets, kitchen
wares, toys, wrappers and several other household items.

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Polyvinyl Chloride (PVC) (-CH2 - CH -)n
(CH2 = CHCl)

Cl (pvc)

It is the polymer of vinyl chloride. It is used for making pipes, raincoats, boots, curtains, hand
bags, floor covering, covering for suitcase, seats, furniture, soles of shoes, bottles for oils, grease
and other chemicals, buckets and electrical insulating cover for electrical wiring.

Polyster
It is largely used in textile. It is used for making food packaging and soft drink bottles.

Polystyrene
It is a polymer of styrene molecule. It is used to pack fragile materials like TV, glass articles, etc.

Thermoplastics and their uses

Polythene Polythene bags, sheets

Polyvinlyl (PVC) chloride Pipes, raincoats, soles of shoes, handbags, boots, floor covering,
bottles for oils

Polystyrene Packing material, thermocole is used as an insulating material

Polyster Packing materials, soft drink bottles

Thermosetting Plastics

Thermosetting plastics are usually hard and strong. They do not bend easily and are resistant to
heat. They cannot be softened again once setting has taken place on heating. So these plastics
cannot be moulded a second time and the change is irreversible.

On heating, the long chain molecules react together and links are formed between the molecules
in the chains which stop the chains from moving one another.

Bakelite: It is a thermosetting plastic. It is made by condensation and polymerization of
formaldehyde and carbolic acid. It is used for making radio and T.V. cabinets, switches, plugs
and other electrical fittings, cable, handles of cookers and tea kettles and ashtrays etc.

Melamine: It is made from melamine and formaldehyde so, it is also called as melamine-formal
dehyde (MF) plastic. It is used for making cups and bowl.

Teflon: It is widely used in non-sticky frying pan. It can hold very high temperature.

Differences between Thermoplastic and Thermosetting Plastics

S.N Thermoplastics S.N Thermosetting Plastics
1. They soften on heating readily. 1. They do not soften on heating.
2. They can be reshaped. 2. They cannot be reshaped and reused.

They are usually soft and weak. They are usually hard, strong and brittle.
3. 3.

e.g. : PVC, polythene, polyster etc. e.g. : Bakelite is a thermosetting plastic.

Blooming Science Book 10 203

Advantages of plastic
1. They can be easily shaped and moulded.
2. They are quite cheap. They are produced as by- products of oil refining.
3. They are durable. They do not rot, carrode in air or water. They are not affected by acids

or alkalies.
4. They are lighter than steel, wood or stone.
5. They can be used as thermal and electrical insulators.
6. They can be made very strong and coloured.

Disadvantages of plastic

1. They are not biodegradable. This means they do not rot.

2. Some plastics catch fire very easily.

3. Many plastics often produce poisonous gases and smoke. Plastics are thus very dangerous
than fibres.

Soap and Detergent

Soap: Soaps are sodium salt of fatty acids.

Soaps are the chief cleansing agents. Soap are used to clean our body, clothes, utensils and
several other household objects. There are various types of soaps made for special purposes.

The quality of soaps depends upon the raw materials used in their preparation. Soaps are basically
a fatty acid salt. Stearic acid, palmitic acid and oleic acids are found in oils and fats. These are
long chain carboxylic acids containing 16 to 18 carbon atoms.

Manufacture of Washing Soap

The main raw material required for the manufacture of ordinary soap are animal fats or vegetable
oils, sodium hydroxide and sodium chloride.

Animal fats or vegetable oils are heated with sodium hydroxide solution. The fats or oils react
with sodium hydroxide to form sodium salt of higher fatty acid and glycerol. Glycerol is the
trihydric alcohol.

Fats or oil + Sodium hydroxide D Soap + Glycerol

C3H5(OOCR)3 + 3NaOH D 3NaOOCR + C3H5(OH)3, Where R = C15H31
(Glyceryl palmitate) (an alkali) (Sodium salt of higher fatty acids)

Washing soaps, therefore, are sodium salts of higher fatty acids having cleaning property in water.

Sodium stearate (C17H35COONa), sodium oleate (C16H33COONa) and sodium palmitate
(C15H31COONa) are the examples of such soaps.

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Activity

To prepare soap and observe its washing effect.

1. Take about 20cc of any vegetable oil (castor oil) in a beaker.

2. Take about 6 grams of sodium hydroxide in 30 cc of water and make sodium hydroxide
solution.

3. Add an equal volume of sodium hydroxide solution into oil slowly and with constant
stirring.

4. Boil the mixture of oil and sodium hydroxide with constant stirring till a thick paste is
formed.

5. Add small quantity of sodium chloride into the thick paste.

6. Put it into mould of any shape and allow it to harden.

7. Take out the soap cake and wash a small piece of cloth.

Soaps prepared from liquid oils are comparatively soft to those prepared from solid fats.
Soaps, prepared from caustic soda are usually hard and are called hard soaps. Soaps prepared
from caustic potash (potassium hydroxide) are usually soft and more water soluble and are
called soft soaps. The process of soap formation by hydrolysis of fats or oils with alkali is called
saponification. On completion of saponification NaCl is added to separate the soap from solution
and then Na2CO3 is added to make soap hard.
Detergents:

Detergents are the sodium salts of long chain benzene sulphonic acid.

Detergents are not prepared from vegetable oils and fats. Most detergents are made from
hydrocarbons extracted from petroleum but they have better cleansing action than soap so they
are also called soapless soap. For example, a common detergent is made from kerosene oil
through a complicated chemical process. Sodium lauryl sulphate, alkyle benzene sulphonate
and sodium pyrophosphate etc. are detergents. They do not form insoluble calcium and
magnesium salts with hard water, hence, they are used to wash clothes when the water is hard. In
powder form they are called detergent powder.

Differences between Soaps and Synthetic Detergents

Soap Synthetic detergents

1. Soaps are the sodium or potassium salts of 1. Synthetic detergents are the long chain
the long chain fatty acids. benzene sulphonic acids or long chain
alkyle benzene sulphonate.

2. They are not suitable for washing in hard 2. They can be used for washing even in the

water. hard water.

3. Animals fats or vegetable oils are used in its 3. Hydrocarbons of petroleum are used in

preparation. its preparation.

4. They are biodegradable. 4. Some of the detergents are non-
biodegradable. So cause water pollution.

5. They have relatively weak cleansing action. 5. They have a strong cleansing action.

Blooming Science Book 10 205

Chemical Pollution

Pollution is an undesirable change in the physical, chemical
or biological characteristics of air, land, and water that may
or will harmfully affect human life or that of desirable
species industrial processes, living conditions and cultural
assets. In other word, pollution is the unfavourable change
of our environment, largely as a result of our own activities.
The pollution caused by various types of chemicals is called
chemical pollution.

Causes of Chemical Pollution

Different types of chemicals: Organic or inorganic, such as chemical fertilizers, pesticides, detergents,
fuels, synthetic fibres, dyes, etc. are used in our daily life. These materials have added some pollutants
in our environment and causes pollution called chemical pollution.

i. Pesticides and Chemical Fertilizers

The pesticides are used to control crop diseases by killing the pests and, hence, to increase
the productivity. The pesticides used are toxic not only to pests, but also to other plants and
animals including human beings.

The most hazardous property of the pesticides is their persistence in the soil which cause long
term effects. They are retained in soil for long time.

ii. Domestic Sewage

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The domestic sewage includes food wastes, detergents, urines, human excreta etc. They are
thrown untreated into the rivers, which are one of the most common sources of pollution in
urban areas, like Kathmandu.

iii. Solid Wastes and Plastics

Solid wastes are probably the most visible forms of pollution. People throw away tons of
solid wastes. Much of this waste ends up littering roadsides, boating in lakes and streams and
collecting in ugly dumps.

The collected solid wastes provide homes for disease carrying animals such as cockroaches
and rats. These solid wastes when burnt to destroy, produce smoke that cause air pollution.
When they are dumped in water, they contribute to various forms of water pollution.

Plastics form a major constituent of solid wastes. It is non-biodegradable and remain in
environment for long time. Plastics on burning produce toxic gases.

iv. Industrial and Vehicular Emissions

Industrial and vehicles such as car, buses, trucks etc. emit gases and fumes as the products of
combustion of various types of fuels. The gases emitted from the industries and vehicles are
carbon monoxide, carbon dioxide, sulphur dioxide, sulphur trioxide etc. All these gases pollute
the air in and around the city.

Carbon-monoxide is a poisonous gas which causes respiratory problems in human. This gas
combines with haemoglobin of blood to form carboxy-haemoglobin which reduces its oxygen
carrying capacity. Carbon dioxide enchances the green house effect leading to excessive
heating of the earth and its atmosphere. Sulphur dioxide and sulphur trioxide get oxidized to

206 Blooming Science Book 10

sulphuric acid in air. This sulphuric acid falls to the earth with rain. The rain containing this
sulphuric acid is called acid rain. The acid rain increases the acidity of soil in agricultural
land, reducing the agricultural production. The acid rain also accelerates the corrosion of most
building materials used in the construction of historic buildings and other important cultural
objects. It too corrodes the marbles of historical monuments, statues made from bronze,
bridges, fences and railings.

v. Metallic Particles

Air contain, metallic particles such as lead (Pb), chromium (Cr), arsenic (As), cadmium (Cd)
and mercury (Hg).

Exhausts of automobiles give out lead oxides and salts to the air, form where they are directly
inhaled by human beings.

vi. Dyes

Dyes are released out from textile and leather industries. These consist of peroxides,
hypochloride, caustic soda and some other bleaching agents. These pollutants have been found
to cause serious water pollution by destroying the natural quality and composition of water.

vii. Detergent

The use of detergents have been responsible for a marked increases in the phosphorus
released in domestic wastes. Detergents usually consist of complex phosphates, which
eventually break down into phosphates usable by aquatic plants. The phosphates are
responsible or the growth of undesirable algae population which deplete dissolved oxygen
content of water.

Control of Chemical Pollution
It is not really easy but rather challenging to get a pollution free environment. The quantity of
dirt extremely goes up owing to uncontrolled growth of population. On the more profound level,
urbanization together with industrialization is upgrading the pollution level. Farmers are using
insecticides and other chemicals regardless of its effect on environment. Despite all these anti
environment activities, we are meant to save our environment. It is important to make strong
efforts for preservation of environment.

Some measures to control chemical pollution are:

a. Noxious smokes from industries should not be allowed to spread in the air.

b. Use of pesticides, insecticides, plastics must be reduced and should focus on use of
environmental friendly substances.

c. Unnecessary use of chemical fertilizers must be reduced.

d. We must give emphasis for recycling and reusing of dirt as fertilizers.

e. Unnecessary use of synthetic cleangers must be reduced.

f. Public awareness must be given to people to make them conscious of the results of using
harmful substance in environment and in food.

Solid Waste Management

The thing which is solid and generated in the daily activities of the human beings as a by-product is
generally termed as a waste material. The wastes are produced from houses,offices,hospitals or simply
we can say that from the place where there is human settlement. There may be the different types of
wastes on the basis of the composition or nature; some may be combustible or non combustible,
metallic or non metallic, biodegradable or non –degradable etc. Here we are going to discuss only
about bio-degradable and non-biodegradable solid wastes.

Blooming Science Book 10 207

Degradable wastes

Those unwanted substances which can get easily decomposed in nature and can get broken down
into smaller forms by natural scavengers are called degradable waste. Kitchen wastes, agricultural
residues, paper, cotton bags, vegetable leftovers, animal excreta etc are some of the examples of
degradable wastes. These types of wastes can be easily decomposed by bacteria which get mixed
with soil and changed into the humus. There are several ways for the management of the degradable
wastes. However best way to manage it is to decompose them into manure pit and cover them with
soil. In this way it can be also used as compost manure.

Non – Degradable solid wastes

Those unwanted substances which can’t be decomposed by natural scavengers are called non
degradable solid wastes. Polythene bags, chemical fertilizers, plastic pipes, plastic bottles, pieces of
glasses etc are some common examples of non degradable solid wastes. These types of solid wastes
never get mixed into nature or decay. Molecules of these solid wastes can never be broken down into
smaller forms by natural scavengers such as bacteria. If we bury a polythene bag under soil it remains
in the same state up to millions of year. If we burn plastic, it produces harmful gases such as carbon
monoxide, sulphur dioxide etc which create air pollution and if we mix it in soil, it degrades the
quality of soil. Thus, the best way to manage non degradable solid waste is to apply 3R i.e. reduce,
reuse and recycle. To manage non degradable wastes properly, we should decrease their use, reuse
them and recycle them. For example we can use paper bags instead of polythene bags.

Let's Learn

1. It is essential to use chemical fertilizers with organic fertilizers because organic fertilizers
have nutrients in very less amount which are not sufficient.

2. Use of pesticides is not advantageous because it causes different type of diseases in human
beings, kills also useful insects and pollutes the environment.

3. Use of chemical fertilizers is not advantageous because they imbalance-pond ecosystem,
pollute the soil and water.

4. Use of plastics is disadvantageous also because they are not degradable chemicals and do
not decay. Their burning also produces harmful smoke that may cause many diseases.

5. Gypsum salt is also added in manufacture of cement, which decreases the period of setting
cement. It makes convenient to use the cement.

6. Sodium chloride is added during the preparation of soap in order to precipitate out all the
soap from its aqueous solution.

7. Little amount of boron oxide is added during preparation of ordinary glass as it make the
glass resist to heat and chemicals.

8. Na2CO3 are added during preparation of soap. The Na2CO3 makes the soap hard.
9. Soap is better than detergents because soap is biodegradable and does not pollute the

environment. But, detergents are non-biodegradable and it pollutes the environment.

10. PVC is a thermoplastic because it is affected by heat and melts on heating.

208 Blooming Science Book 10

Points to Remember

1. Plastics, glasses, fibres, soaps, detergents, ceramics, cement, insecticides, pesticides,
fertilizers etc. are some important substances of daily use.

2. Cement is a mixture of calcium and aluminium silicates made by fusing limestone and
special type of clay containing aluminosilicates.

3. Glass is an amorphous substance. It is transparent rigid homogenous mixture of silicates
of alkali and alkaline earth metals.

4. The properties of glass depend upon the chemical components added to the silica during
the process of the manufacture of glass.

5. The trade name of borosilicate glass is pyrex. A mixture of silica, sodium carbonate,
calcium carbonate and boric oxide are heated at high temperature to make it.

6. Coloured glass is prepared by adding small amount of metal oxides.
7. Ceramics is used in making attractive things.
8. Clay used in ceramic industries is mainly a hydrated aluminium silicate.
9. Very pure clay is white and is called kaolin. Chinese wares are made from kaolin.
10. Plastics are transparent, light, less brittle, non-decaying, colourfulness, flexibile and non-

conductor of heat and electricity.
11. Plastics is an artificial polymer. Plastics are two types: thermoplastics and thermosetting

plastics.
12. Thermosetting plastics are hard and cannot be remoulded. It does not become soft on

heating. It is used to make handles of pressure cookers, switches, plugs etc.
13. Thermoplastics soften on heating and can be used again. It is used for making polythene

bags, pipes, electrical insulators, floor covering, radio cabinets, toys, house wares, etc.
14. Polymers are large molecules formed by joining together large number of identical

molecules.
15. The process of making soap by the hydrolysis of fats and oils with alkali is called

saponification.
16. Detergents are sodium salts of long chains benzene sulphonic acid and are mostly non-

biodegradable.
17. Fertilizers are chemicals added to soil, to replace the minerals used by the plants.
18. Fertilizers are of two types. They are organic and inorganic.

19. Chemical fertilizers are chemicals manufactured in industries to form nitrogen,
phosphorous and potassium compounds.

20. Organic fertilizers are made from plants and animals. Compost manure is an example.
21. N, P and K are collectively known as NPK fertilizer. It is a mixed fertilizer.

Blooming Science Book 10 209

22. The use of fertilizers has polluted the environment. So the use of chemical fertilizer should
be minimized.

23. Various types of insecticides are used to control harmful insects.
24. Household wastes, plastics, gases and smokes and wastes from industries etc cause

pollution.

Project Work
Visit about 10-15 households in your community. Make a survey of household solid waste
management methods. Write down a report with your conclusion and present in your class.

Exercise
1. What is cement? What are cement clinkers ? Describe how cement is manufactured.
2. What is glass? What is the natural sources of silica?
3. What happens when a little amount of lead monoxide is added before heating the

ingredients of soda glass?
4. How is an ordinary glass made? Name two things made from it.
5. What is borosilicate glass? Write its important characteristic feature.
6. How is coloured glass made? Name the compound to be added for imparting blue colour

in glass. Write one use of coloured glass.
7. What is ceramic? Mention its two properties and two uses.
8. Name the following

a) The industrial chemical formed by limestone and special type of clay.
b) The industrial chemical formed by silica and sodium carbonate.
c) The industrial chemical formed by silica and potassium carbonate.
d) The industrial chemical formed by silica, lead oxide and potassium carbonate.
e) Two natural fibres
f) A type of plastic used in making handle of cooker
g) The chemical, which is formed as the by-product of soap manufacture
h) The industrial chemical, which is formed by fatty acid and caustic soda.
9. How is glazing done in ceramics? How can you obtain colourful ceramics articles?
10. Define polymer. What do you mean by polymerization?
11. What is plastic? What is the main source of raw material to make plastic.

12. Write three advantages of plastics.

13. Why are plastics considered as the major cause of chemical pollution? Give two causes.

14. Distinguish between thermosetting plastic and thermoplastic. Give one example for each.

210 Blooming Science Book 10

15. What are fibres? Why are natural fibres considered more environment friendly than
synthetic fibres?

16. What is saponification?
17. What type of plastic is PVC? Give important characteristic of it and write two things made

from it.
18. Plastic has been more popular than other materials, in spite of its bad effects to the

environment. Explain.
19. What is soap? How is soap prepared?
20. What is detergent? Write with an example. Why is it called as soap less soap.
21. What is pesticide? Write any one disadvantage of DDT.
22. What is insecticide? Write down advantages and disadvantages of using insecticides.
23. Write the full form of BHC and DDT and mention their functions.
24. What is a fertilizer? Name two chemicals used as fertilizers in the field.
25. What is NPK fertilizer?
26. What is manure? Why are fertilizers used in soil? Name two elements commonly supplied

to plants by means of fertilizers. Why are farmers encouraged to use more organic
fertilizer than chemical fertilizer? Give reasons.
27. Write the importance of nitrogen, phosphorus and potassium rich fertilizer to plants. Also
write two examples of each of such fertilizers.
28. The use of compost manure is far better than the use of chemical fertilizers. Give two
reasons to justify the statement.
29. What is chemical pollution? Write three major causes of it and three measures to reduce it.
30. Differentiate between:
a. Soap and detergent
b. Chemical and organic fertilizer
c. Water glass and ordinary glass
d. Biodegradable and non-biodegradable wastes
e. Natural and synthetic fibres
f. Bakelite and PVC

Blooming Science Book 10 211

31. Choose the correct alternatives from the following options.

i. The important raw material for manufacturing cement is;

a. Silica b. Gypsum c. Limestone d. Polymer

ii. Which one is an example of thermoplastic?

a. PVC b. Bakelite c. Polythene d. Both ‘a’ and ‘c’

iii. Detergent is widely used in cleaning clothes than the soap, because it:

a. Pollutes the water b. Works in hard water also

c. It is easy to use d. All of the above

iv. Which fertilizer is used for proper growth and development of plants?

a. Nitrogen b. Potassium c. Phosphorus d. None of them

v. The major cause of chemical pollution is:

a. Plastic b. Detergent c. Soap d. Glass

212 Blooming Science Book 10

Chapter Invertebrates Hsi Ling Shi
Chines emprees who
14 discovered silk fibre

in 27th century BC

Learning Outcomes Estimated Periods: 4+2

On the completion of this unit, the students will be able to:
 explain about life cycle of bee and silkworm.
 tell about stages of life cycle of bee and silkworm.
 list the uses of insects.
 describe the structure of bee and silkworm.

A. Bee Forewing
Classification

Kingdom - Animal THORAX Hind wing
Phylum - Artropoda Ocelli
Class - Insecta HEAD ABDOMEN
Genus - Apis Compound Eye Spiracle
Species - mellifera, cerana, etc.
Type - Honey bee Antenna Sting

Jaw Pollen Press

Tongue Middle leg Hind leg
Foreleg Antennae
Introduction cleaner

Honey bee is the insect that lies under the phylum of Arthropods. It is believed that honey bee
was evolved when the flowering plants were evolved on the earth surface i.e. in the cretaceous
period. They can be found all over the world however tropical climates and temperate climates
with gardens, availability of water resource and the heavy forest areas are best suited for them.
Climate directly effects the life cycle of honey bee but now a days they can be domesticated for
the production of honey.

External structure

The honey bees are ovals shaped insects and size that varies from (15-17)mm. Their bodies
have different types of colours. Some are dark brown in color and others have the golden yellow
colors and dazzling colors of the body reflects their stinging nature. The body of the honey bee
is divided into three parts

1. Head 2. Thorax 3. Abdomen

Blooming Science Book 10 213

Head

The head of honey bee consists of two types of eyes, antennae and feeding structure.

Eyes

There are five eyes which can be found on the head of honey bees. A pair of compound eyes used
to identify color and directional information and three simple eyes also called Ocelli are used to
locate amount of light in the environment.

Antennae Scan for practical experiment

The head consists of a pair of antennae which can move freely in every
direction. They help to smell and detected the odors.

Mouth parts: The mouth parts of honey bee are chewing and lapping
types.

Thorax

The thorax of the honey bee can be categorized into three parts : visit: csp.codes/c10e16

1. Prothorax 2. Mesothorax and

3. Metathorax

Each part carries a pair of legs and last two parts support two pairs of wings. Larger pair of wings
is called forewings and smaller pair is called hind wings. The forewings help in flight and hind
wings help to cool the hive. The legs are jointed and contain 6 segments with brushes in some
segment; the brushes in 5th segment of the fore limbs are used for sweeping pollen and other
particles from the head or mouth parts.

Abdomen

The abdomen is six segmented and contains different sensitive organs like hearts (simple having
5 pairs of muscles with one way opening valves), reproductive organs, intestine, and the sting.
It is connected with thorax by a narrow projection called petiole the sting which lies at the last
segment is used to bite the enemies.

The honeybees are trimorphic as they are found in three different forms in a colony. They are;
workers drones and queen.

Workers

Workers are female honey bees who perform different work in the colony. They live
for (5-7) weeks and laid sometimes infertile eggs from which drones are developed.
They are the largest in number among other adult castes. They have special body
structures such as scent glands, wax glands and pollen baskets which allow them to
perform all the necessary works like to clear and polish the eggs, collecting nectars,
maintain air condition inside the hive etc.

The workers decide the fate of the queen. If they find queen is not working properly for the
colony, they will replace her immediately either by starvation or by killing her.

Drones

Drones are male honey bee developed from unfertilized eggs produced by queen or
sometimes by female workers. They have larger body structures than workers but

214 Blooming Science Book 10

smaller than queens and die after mating with queen. They act as guards of hive and make
mating with queen according to her desires. When queen flies for mating drones follow her with
the help of the scent (pheromones) of queen and mating occurs and at the time of mating, the
endophalus is removed from the abdomen along with ejaculation hence their rips of abdomen
open and drones die.

Queen

The queen bee can be easily located by their body structure which is larger than other
adult castes. The life span of queen is about 5 years. They produce egg after mating
flight with drones. The mating of queen can be easily known by watching her red head
i.e. head becomes reddish after mate with drones. They can produce special types of
scent or pheromones which even help to mobilize the worker bees. This scent is passed
from queen to worker such that members of colony can recognized each other. When
queen becomes aged or unable to produce egg, she is immediately replaced by other
queens and pervious queen is killed by workers. The main difference between workers and queen
are, they laid fertilized and unfertilized eggs and feed the royal jelly throughout their life while
worker only lay infertile eggs and feed on the mixture of honey and pollens.

When the number of bees increases in the colony than its capacity, the worker bees make new
queen by feeding only royal jelly to a selected larva hatched from the fertilized egg. When a new
queen is made ready anuther colony is formed at new place. The queen bee flies either only for
mating which is called nuptial flight or for migration. Otherwise the queen remains inside the
comb laying eggs and eating honey.

Life cycle of honey bee

The life cycle of honey bees is perennial and shows the complete meta -morphosis. It completes
into four stages viz, egg, larva, pupa and adult.

Eggs

The colony of honey bee is formed by 3 types of adult bees: queen, female workers and drones
(male honey bee). A colony has a single queen at the maturity it flies away for mating with
drones and after mating she returns to the hive and lays the eggs. The queen mates with drones
throughout her life, collects more than 5 millions of sperms even at the single mate and lays
about 2000 eggs per day however the numbers of egg laying of the queen depends upon the
weather and food.

Eggs are oval and white in color whose size varies from 1 to 1.5mm which are laid in each cells
of the hive in such a way that honey can be passed through them because it makes easier to
nourish the larvae with a royal jelly or different other foods in future. There are two types of egg
laid by a queen; fertilized eggs from which female worker and queen are developed if necessary
and unfertilized eggs from which drones are developed. According to the need of the hive, queen
lays the eggs i.e to maintain the number of workers or drones. The female worker gives infertile
eggs which later changed in drones. Each egg are attached to the bottom by a mucus strand, after
3 days eggs are hatched into small white worm having mouth only called larvae.

Larvae (Instar)

The larvae of the honey bee are voracious in nature. They are fed initially by royal jelly for 2

Blooming Science Book 10 215

days and then by the mixture of honey and pollens. However, for queen larvae only royal jelly is
used. Larval stage ends in 5.5 days for queen,6 days for workers and 6 days for drones. Nearly
after a week, the cells containing larva is closed. During this whole time the larva moults four
times and enters the pupal stage.

Pupa

During the 5th moult, all the parts like body, head and wings are developed completely but the
outer skin or pupal case is only removed after 6th moult and changed into the adult, the time
period of pupal stage for queen is 7 days, for workers 12 days and for drones 14.5 days.

Adults

After pupa stage, all three types of adults are developed. The drones need 24 days for proper
growth from eggs to adult, worker needs 21 days and queen needs 16 days.

The duration of egg, larva, pupa and adult of all three forms of bees is shown in the given table:

Bee Egg Larva Pupa Adult From egg to pupa

Queen 3 days 5.5 days 7.5 days 2-5 years 16 days

Drone 3 days 6 days 14.5 days upto 4 months 23.5 days

Worker 3 days 6 days 12 days 6-7 weeks 21 days

Utility of honey bees

1. By the help of honey bee honey and honey bread can be produced which is rich in vitamins
and functions as anti-oxidants.

2. The honey can be used for medicine of ulcer, sore throat and blood purifier.

3. Bee wax used for lotions and creams, lip-sticks, polishes for boots.

4. All the flowering plants continue their life cycles by the process of pollination in which honey
bees act as a carrier of pollen grains from one flower to another or between same flowers.

5. Enzymes, vitamins, minerals and water can be found in honey.

Formation of Honey
The nectar is collected by the worker bees and it is stored in the comb. The sucross present in
nectar is changed into fructose and glucose by various chemical changes. The honey contains
fructose, glucose, water and amino acid. It is the very good source of vitamins, protein and

minerals.

Points to Remember

1. Honey bee is the insect that lies under the phylum of Arthropods.

2. The body of the honey bee is divided into three parts

a. Head b. Thorax c. Abdomen

3. The mouth parts of honey bee are chewing and lapping types.

216 Blooming Science Book 10

4. The thorax of the honey bee can be categorized into three parts :

a. Prothorax b. Mesothorax c. Metathorax

5. The life cycle of honey bees is perennial and shows the complete Meta -morphosis.

6. The colony of honey bee is formed by 3 types of adult bees' queen, female workers and
drones (male honey bee).

7. The larvae of the honey bee are voracious feeder. They are fed initially by royal jelly for
2 days and then by the mixture of honey and pollens

8. Workers are female honey bees who perform different work in the colony.

9. Drones are male honey bee developed from unfertilized eggs produced by queen or
sometimes by female workers.

10. The queen bee can be easily located by their body structure which is larger than other adult
castes. The life span of queen is about 5 years.

Project Work

Visit a nearby 'Bee farming' or a beehive found in your locality and take the reports of various
types of bees, the structure of beehive and formation of honey with the availabe expert.

Exercise

1. Classify bee with any three features.
2. Draw the diagrams of queen bee, workers and drone.
3. Explain the external structure of bee briefly.
4. In which climate does bee farming suit for?
5. Write three parts of thorax.
6. What are four stages of life cycle of bee? Explain.
7. The larvae of honey bee are voracious feeder, Justify.
8. Write the role of workers bee, drones and queen.
9. What are advantages of honey bee?
10. Honey is popular and useful for every people, explain.
11. Workers are laborious to produce honey, Why?
12. Draw a labelled diagram of life cycle of bee.

B. Silkworm
As the worm produces silk, it is called silkworm. Silkworm is a very useful insect to human
beings since it is the source of pure silk. Silk is smooth, shiny, light and durable compared to
artificial silk fibres. The art of obtaining silk moth was originated in China in 3500 BC. It was
great secret for some 3000 years. It is believed that, later it was smuggled out of China through
some monks. It was introduced in Europe in 552 AD.

The body of silkworm is slightly bigger than butterfly and silkworm can be identified by looking
antennae which is different from butterfly.

Blooming Science Book 10 217

In Nepal, mainly two types of silkworms are reared. They are Seri silk moth (Bombyx mori) and
Eri silk moth (Attacus ricinii). Seri silk moths feed on mulberry leaves and Eri silk moths feed
on caster leaves. The mulberry is a perennial deciduous plant.

Classification

Kingdom - Animal

Sub-kingdom - Invertebrata

Phylum - Arthropoda

Class - Insecta Male moth Female moth

Common name - Seri silk worm

The farming of silk worm on commercial scale to obtain silk is called sericulture.

External Structure

Adult silkworm is creamy white in colour and is about 2.5cm long. Body is divided into head,
thorax and abdomen. Head bears a pair of compound eyes, a pair of antennae and mouth parts.
Thorax bears three pairs of legs and two pairs of wings. Abdomen is hairy and contains ten
segments. The body of female is wider due to the eggs it contains.

Life Cycle

The female silkworm mates with male silkworm so fertilization is internal. The silkworms
complete their life cycle in about 45 days. The life cycle is completed in four stages - eggs, larva,
pupa and adult.

Eggs adult female male female

After fertilization, each female cocoon chrysalis
lays about 300 eggs on the head
leaves of mulberry trees and cocoon
dies. The egg is white and very cut open
small as a size of pin head.
Female produces a gelatinous eggs on eggs
secretion which sticks eggs. mulberry leaf dorsal horn
When mulberry leaves are not
available, the eggs are stored mature caterpillar
and preserved in cold places to
avoid their hatching. When eggs thoracic true legs spiracles abdominal pseudolegs
are placed at the temperature
of 18-25oC, they develop into
larvae within 10 to 12 days.

Larva Life cycle of Silkworm

Larvae are voracious feeders and they feed on mulberry leaves upto 25 to 32 days. They moult

four times. After every moulting, they stop feeding for 20 to 24 hours. This condition is called

instar. After full growth (after fourth moulting i.e. in fifth instar) larvae develop a pair of salivary

218 Blooming Science Book 10

glands in the lateral sides of the body. These glands secrete a sticky substance which forms solid
silk thread in contact with air. The thread becomes wrapped around the body of caterpillar forming
a pupal case of cocoon. The cocoon is a white or yellow, thick oval capsule. The caterpillar larva
changes into pupa or Crysalis. The larval stage of silkworm completes in about 28 to 32 days.

Pupa

Inactive pupa does not take any food. This stage lasts for 12 to 14 days. Pupae are killed by
treating with hot water or hot air to extract silk. A single cocoon yields 1000 metre of unbroken
silk fibre. If pupa develops into adult, the silk fibre produced turns into pieces. The pupa is the
inactive stage in which its body is protected in cocoon but undergoes very important active
changes called metamorphosis. It now stops feeding but shows internal developments.

Adult

The pupa develops into adult. Adult silkworm has three pairs of legs and two pairs of wings.
Adult survives about 5 to 6 days. It cannot fly immediately, so it dries its wings and flies. Adult
silkmoth lays eggs after its maturity. The life cycle completes within 45 to 50 days.

Stages and duration in the Life Cycle of Silkworm

Stages Duration
Egg (Incubation period) 10-12 days
Larva 25-32 days
Pupa 12-14 days
Adult 4-5 days

Importance of the Silkworm fibre

Silkworm provides natural silk which is smooth, shiny, light and durable compared to artificial
fibres. It has high commercial value. It is elastic and absorbs water readily. Silk clothes can be
used in all seasons and it is possible to dye them in different colours. Due to these characteristics
possessed by silk, it is often called queen of fibres. The economic importance of silk is as follows:

1. Silk is used in making clothings, curtains etc.

2. Silk is used with other natural and synthetic fibres to achieve new effects in fabrics.

3. Another economic value of silkworm is the preparation of gut, used for surgical and
fishing purpose. For preparing the gut, the intestine of silkworms are extracted, made into
strings, dried treated and packed.

4. Sericulture helps to improve the economic condition of individual and the nation.

Usefulness of Silk

Silk fibre has the following use. Silk is used in the manufacture of woven materials and the
knitted fibrics of making of mens’ and womens’ fashionable clothing, fishing lines, sieves for
flour mills, insulation coil for telephone, wireless receivers and tyres of racing cars.

Silk garments are extremely light and are warmer than cotton. Silk cloth can be dyed very easily
and also be ironed easily.

Blooming Science Book 10 219

Characteristics of Silk Fibre
1. Silk is strong and shiny fibre.
2. The silk clothes are best suited for wearing in all seasons.
3. Silk is the strongest of all natural fibres.
4. Silk is highly elastic. It can be stretched and will still return to its original shape.
5. Silk garments are light in weight and warmer than other clothes.
6. Silk does not decay easily so it is used in Surgical stitching.

Some Interesting Facts about Silkworm
1. Bombyx mori is popularly called the Chinese silkworm because the importance of

silkworm in silk production was first known in China.
2. Silk-glands are modified salivary gland develops at the lateral sides of the body of larva.
3. One cocoon yields about 1000 metres of silk thread. It requires about 25,000 cocoons to

prepare a half kilogram of silk. About 40 to 50 million kilograms of raw silk is consumed
in the world annually.

Let's Learn
1. A silkworm is called queen of the fibre, because it forms a quality fibre, which is shiny,

strong, long and attractive.
2. Cocoon of silk moth is kept in hot water/woven, to destroy the gelationus substance.

Because in this way only the silk thread can be unwounded from the cocoon.
3. Farmers keep silkmoth’s egg in cold place, when mulberry leaves are not available. It

avoids the hatching of larvae from eggs.

Points to Remember

1. The silkworms are useful insects. They produce silk.
2. Seri-silkworm and Eri-silkworm are two major kinds of silkworm cultivated in Nepal.
3. Farming of silkworm on a commercial basis is called sericulture.
4. Eggs of silk moth hatch in a suitable temperature i.e. about 18-25oC.
5. The larvae of seri-silkworm feed on mulberry leaves and eri-silkworm on castor leaves.
6. Mulberry is the main food of silkworm.
7. Larvae of silkworm produces silk.
8. The life cycle of the silkworm is completed in four stages- egg, larva, pupa and adult.

Whole process takes 45-50 days.
9. The pupa of silkworm is called cocoon. Silk is obtained from the cocoon after killing the

pupa inside.
10. Silk thread is long and shiny. It is used to make cloth.

220 Blooming Science Book 10

Project Work

Extracting silk thread
(a) Collect the larvae of silkworm from a silk farm.
(b) In a cardboard box (or in a wooden box), put some mulberry leaves and the larvae.
(c) Observe the feeding habit of larvae on mulberry leaves and thread produced by
them.
(d) After some days, you will get cocoons. Shake the cocoons to see whether a pupa is
there.
(e) Boil the cocoon in water. You can extract a thread from cocoon.
If you leave the cocoon on the tray, a silk moth will be produced. The new born silk
moth is called Imago.

If collecting larvae is not possible visit a silkworm farm, observe and make a
report.

Exercise

1. Classify silkworm with any three features.
2. In which stage of the life cycle does the silkworm produce silk fibre?
3. Does larva eat mulberry leaves during skin change? What is the process of shedding off

old skin called?
4. Can silkworm farming be done at home if mulberry leaves are available?
5. Why are the eggs of silkworm kept in a cold place for many days? What are its advantages?
6. Silkworm lays eggs on the leaves of mulberry bush, why?
7. How many times does a larvae moult?
8. How many days do the eggs of silkworm need to hatch out larvae?
9. What is the use of cocoon?
10. Why do we kill pupa?
11. What is sericulture? Name the types of silkworm found in our country.
12. How do you manufacture silk thread, if you are given silk eggs?
13. Why is silk called queen of fibres?
14. In which stage does silkworm not take food? In which stage does it produce silk?
15. What is the covering of pupa called?
16. Describe the life cycle of silkworm with clear diagram.
17. Justify the statement that silk farming upgrades the economic condition of individual and

nation.
18. Sketch neat and labelled diagrams of
a. Larva b. Crysalis c. Female silk moth.

Blooming Science Book 10 221

19. Study the diagram and answer the following questions. b
a
(a) Label ‘a’ and ‘b’.

(b) Which part of them consists of silk?
(c) What is the process called by which the ‘b’ is farming?


(d) What is cause of keeping the stage in boiling water before unwinding the silk fibre?
BA

C
20. The given figure shows the adult larva stage of silkworms. Label the parts A, B and C.

21. Choose the correct alternatives from the following options.

i. Honey bee can lay how many eggs at a time?

a. 200 b. 2000
ii.
c. 20000 d. 20

iii. Which bee is deployed only for mating with queen?

a. Drone b. Workers
iv.
c. Both ‘a’ and ‘b’ d. None of the above

v. In which stage of silkworm, it starts to produce silk thread?

a. Pupa b. Adult

c. Larva d. Imogo

Which fibre is called as queen of fibre?

a. Synthetic b. Rayon

c. Wool d. Silk

The capsule like structure made from silk in pupa stage of silkworm is called:

a. Chrysalis b. Cocoon

c. Larva d. None of the above

222 Blooming Science Book 10

Chapter Human Nervous Allssandro Benedetti

15 System and 1450-1512 AD
A.B is a surgeon is the author of book

'The History of the Human body.'

Glandular System

Leaning Outcomes Estimated Periods: 5+2

On the completion of this unit, the students will be able to:
 describe the function and relation of brain and nerves (sensory and motor).
 describe importance of hormones in human body.
 distinguish endocrine and exocrine glands.

Introduction

There are various kinds of organisms around us. Living organisms response to their
environment. Survival of all living organisms depends on the communication with the external
environment, communication among the various parts of the body and their co-ordinative
funtioning. The ability to respond to stimuli is a fundamental characteristic of living organisms.

At all the moment, living organism is subjected to many influences that come from the
surroundings. We can get information about them with the help of sense organs. In addition
to these organs, nerves, brain and hormones play vital role for the proper functioning of body
systems. Living organisms are sensitive towards different stimuli. Living organisms usually
respond to stimuli for food, habitat, protection, reproduction and suitable environment.

Nervous System

The system which consists of brain, the spinal cord and nerves is called nervous system. This
system is responsible for the adjustment of the external and internal functioning of our body.

The nervous system of human beings is divided into following three types:

1) Central Nervous System(CNS): It includes the brain and the spinal cord. It lies in the body
axis.

2) Peripheral Nervous System(PNS): It includes 12 pairs of cranial nerves and 31 pairs of
Spinal nerves.

3) Autonomic Nervous System (ANS): It includes a pair of chains of ganglia and the nerves
which regulate the function of involuntary muscles.

A. The central nervous system
1. The Brain

Brain consists of soft mass of nervous tissue. It is 1.2kg to 1.4kg around 2% of our body weight.
It is protected by skull bone. The external part of brain is covered with three layers. They are
called meninges. They are outer (duramater), middle (arachnoid mater) and inner (piamater)
layer. Durameter is a thick and tough layer that protects the brain from jerk. Middle layer is thin

Blooming Science Book 10 223

and soft and contain blood vessels. Piameter covers whole brain. In between arachnoid and

piameter, there is a cavity called sub-arachnoid cavity, which is filled with cerebrospinal fluid.

This fluid protects the brain and spinal cord from jerks Cerebrum
and shocks and nourishes the brain and spinal cord.

The brain consists of two types of matter ie. grey

matter and white matter. The outer surface is made of

grey matter which is made up of cell bodies of

neurons. The inner part of brain is of white matter Cerebellum
which is made up of axons. The brain consists of three Ponsvarolli Spinal cord
medulla
parts: cerebrum, cerebellum and medulla oblongata. oblongata

a. The Cerebrum (The forebrain)

It is the largest part of the brain which occupied about 4/5 part of brain. It contains right and left
halves called cerebral hemispheres. Cerebrum consists of different centers to control different
activities like motion, vision, hearing, thinking, imagination, memory, smell, speech, sense
(touch, pain, pressure, temperature, smell), anger, emotion, learning etc. The right cerebral
hemisphere controls the left part of the body and the left cerebral hemisphere controls the right
part of the body. The functions of cerebrum are as follows:

1. Cerebrum is the centre of intelligence, memory, imagination and emotions.

2. Cerebrum is responsible for ordinary sensations like touch, pain, heat and cold and
special sensations like sight, hearing , smell, etc.

3. Cerebrum controls the functions of other parts of the brain.

4. It also helps to conduct different types of motor action of muscles.

Any sort of injury in cereberum could lead person into coma.

b. The Cerebellum (Hind brain)

It lies beneath the cerebrum. The main function of cerebellum is to maintain balance of
body and to co-ordinate voluntary movements. It consists of outer grey matter and inner
white matter.

The major functions of cerebellum are as follows:
1. It maintains equilibrium and controls posture of the body.
2. It makes body movement smooth, steady and co-ordinated.
3. It also regulates and co-ordinates contraction of skeletal muscles.
Any sort of injury in cerebellum, effects the involuntary movement of muscles which
develops disabilities in a person.

c. Brain stem (The Pons Varoli and Medulla Oblongata)

The Pons is a structure located on the brain stem named after the Latin word meaning
“bridge” and the 16th Century Italian anatomist and surgeon CostamzoVarolio. So name
became Pons Varolii. It is superior to the medulla oblongata, inferior to the mid brain and
ventral to the cerebellum. This means it is above the medulla, below the fore brain and
anterior to the cerebellum.

The Pons measures 2.50cm in length. The function of Pons Varolii can be listed as:

224 Blooming Science Book 10

1. It serves as conduction pathway between the spinal cord and other parts of brain.

2. It forms a bridge of nerves fibres.

Posterior part of the brain, medulla oblongata connects spinal cord with brain. It
controls heart beat, respiration, blood circulation, swallowing, salivation, sneezing,
vomiting, coughing etc. Medulla oblongata is the lowermost part of the brains.
It lies just above the spinal cord and made by both grey matter and white matter.
Damage of medulla oblongata causes instant death. The main functions of medulla
oblongata are listed below:

a. Medulla oblongata receives and integrates signals from spinal cord and sends
resulting impulses to the cerebrum and cerebellum.

b . It contains different centres that regulate heart beat, blood pressure, breathing,
swallowing, salivation, sneezing, vomiting, coughing and some other involuntary
movements.

Cerebral hemisphere Parietal lobe
Occipital lobe Cerebrum
Frontal lobe

Cerebellum Mid brain
Spinal cord
Pons varolli
medulla
oblongata

2. Spinal Cord

Spinal cord is part of central nervous system. It is the rope like long bundle of nervous tissues and
lies inside the neural canal of vertebral column. It extends from the base of medulla oblongata
of the brain and runs down to the sacral vertebrae. Spinal cord is also protected by three layered
membranes called meninges (dura matter, arachnoid layer and pia matter) and the cerebrospinal
fluid. Cerebrospinal fluid is clear and colourless fluid that gives cushioning effect and protection
against mechanical injury to brain and spinal cord. Spinal cord contains white matter out side and
gray mater inside. The gray matter is in the shape of extended wings of butterfly in cross section
of the spinal cord. White mater is mainly composed up of myelinated axons and the grey mater
consists mainly of cell body (cyton) of neurons, unmyelinated motor neurons and interneurons.
Grey matter cells emerge out of the spinal cord in form of bundles known as dorsal and ventral
horns which become the part of spinal nerves.

Spinal cord works as the main pathway between brain and peripheral nervous system. It also
takes part in reflex action. It conducts sensory impulses from different parts of body to brain
and motor impulses from brain to different parts of body like muscles, glands, skin etc. It also
participates in conscious actions of body parts like arms, leg, fingers, toes, skin and voluntary
organs. The serious injury to spinal cord can lead to paralysis of the part of body below the point.

The main functions of the spinal cord are as follows:

1. It acts as the main centre of reflex actions.

2. It acts as a link between spinal nerves (PNS) and brain.

Blooming Science Book 10 225

brain stem Back Disk
Spinal cord Spinal Vertebra
vertebra nerves
Front
Spinal cord

Sensory nerve pathway
sensory(posterior)
root

Cauda equina spinal nerve Motor nerve
pathway
Motor
(anterior) root
Fig: spinal cord structure

Reflex Action

The involuntary action performed by muscles under the direction of spinal cord in response to the
stimulus is called reflex action. Reflex actions are immediate actions and are not judged by brain.
For examples blinking of eyes, shivering when there is cold, watering of mouth after smelling
food, the knee jerk and with drawl of hands from a hot object. The stimulation of reflex action
undergoes conduction in the following ways.

• a receptor - receives stimulus and initiates a sensory nerve impulse. It is usually a sense
organ like skin, eye, etc.

• a sensory nerve fibre - conducts impulse from receptor to spinal cord.

• an intermediate nerve fibre - changes sensory impulse into motor impulse.

• a motor nerve - conducts impulse from spinal cord to effector organ.

• an effector - responds to the impulses received. It is usually the muscles of body.

Stimulus (pin)

Receptor (in skin)

Sensory
nerve
Rely
nerve
Motor
nerve
Ventral
Muscle root
(effector)

226 Blooming Science Book 10

The rapid withdrawal of the hand when it is burned or pricked is as follows:

Stimulus - Sensory cells of a receptor organ → Dendron of the sensory neuron along the dorsal
roof → Cell body of a sensory neuron → Axon of the sensory neuron →Inter neuron in the spinal
cord → Axon of the inter neuron → Motor neuron → Axon of the motor neuron along the ventral
root - Effector organ (Muscles or glands).

The route taken by nerve impulses from the receptors to the effectors during involuntory action
is called reflex arc.

Neuron (The nerve cell)

The single unit of nervous system is dendrites
its nerve cell. Nerve cells are called

neurons. Nerve cell contains the

cell body (soma or cyton), axon and cell body receptor cell body
dendrites. The cell body is compact (cyton) cell (cyton)
structure with cell membrane and it
contains cytoplasm, cell organelles axon neurofibril node axon
and cell inclusions. Cell body of nerve (node of Ranvier)
cell contains more mitochondria than
other cells. Axon and dendrites are myelin sheath

the extensions arising from the cell cell body
body. Axon extends in the form of (cyton)

a stem like structure from the cell axon
body and ultimately branches into

numerous nerve endings. One nerve

cell normally contains one axon and it a. motor neuron c. interneuron
has more or less same diameter along (multipolar) (multipolar)
its lengths. Axons are wrapped by b. sensory neuron
some sausage like structures known (unipolar)

as myelin sheath. These sheaths work

as boosters to speed up the flow of electrical impulses along the axon fibre. The main function

of axon is to transmit electrical signals from cell body to the dendrites of neighbouring neurons.

Dendrites are tiny root like projections arising from the cell body. Numerous dendrites arise

from one nerve cell and they branch and retrench into thinner and tapering branches. The main

function of the dendrites is to receive the electrical signals from other nerve cells around them.

Nerve cells are of various shapes and sizes. Neurons are electrically excitable cells and they

receive, process and transfer information in form of electrochemical signals.

The bundle of axons from many nerve cells make the nerve fibre. On the basis of functions,
neurons are classified into three types: Afferent or Sensory neurons, Efferent of Motor neurons
and Inter neuron.

Afferent or Sensory neurons: These neurons carry and transmit sensory impulses from the
receptor sites at tissues and organs to central nervous system.

Efferent or Motor neurons: These neurons carry and transmit motor impulses from the brain and
spinal cord to the target tissues, glands and organs.

Blooming Science Book 10 227

Interneurons: They connect sensory neurons and motor neurons at specific regions like spinal
cord. They are also known as mixed neurons.

Synaptic bulbs on the ends of the axons make connection with other nerve cell, with tiny
gaps between the cells. These tiny gap between the nerve cells, through which the nerve cells
communicate with each other is referred to as synapse.

Dendrites

Nodes of ranvier Cell body (Cyton)

Myelin
sheath

Boutons
(Synaptic Bulbs)

Fig: Medullated Neuron Nucleus

Ganglia Fig: A basal root ganglion

The clusters of nerve cells linked by synapses are called
ganglia. They usually form swollen structures on nerve fibres.
Ganglion is made from cell bodies (somata) and the dendrites of
numerous sensory neurons or autonomic neurons. They connect
peripheral nervous system to the central nervous system (spinal
cord and brain).

B. Peripheral Nervous System

The nervous system arising from the central nervous system and transmitting information
between CNS and all the rest of body parts is called peripheral nervous system (PSN). It includes
cranial nerves and spinal nerves

The 12 pairs of nerves that arise directly from the brain are called cranial nerves. A pair of optic
nerves come directly from brain and remaining 10 pairs of cranial nerves like facial nerves and
olfactory nerves arise from the brain stem. The cranial nerves transmit information to and from
the brain and parts of head.

There are 31 pairs of spinal nerves arising from each gap between the bones of vertebral column.
The first spinal nerve arises from the gap between occipital bone of skull and the first cervical
vertebra, Atlas. Other spinal nerves originate from the space between the two consecutive
vertebrae known as inter vertebral foramen. They are grouped as cervical (8 pairs), thoracic (12
pairs), lumbar ( 5 pairs), sacral (5 pairs) and the coccygeal (1 pair) as they arise from. These
spinal nerves are bundle of nerve fibres. The dorsal roots (afferent roots) of these spinal nerves
are sensory nerves that carry information of stimuli from different body parts like finger tips, skin
etc. The ventral roots ( efferent roots) are made from motor neurons and carry motor impulses

228 Blooming Science Book 10

from brain and spinal cord to target sites like skin, muscles and glands. The spinal nerves
branch into many branches as they leave the vertebral column and transmit electrochemical
signals for sensory impulses and motor impulses.

C. Autonomic nervous system

The part of nervous system that is responsible for the control and coordination of functions of
body that are done with out conscious knowledge is called autonomic nervous system. It consists
of a chain of ganglia. It controls and coordinates the muscles, tissues and glands during awake
or sleep conditions. Heart beat, breathing, yawning, blinking of eyes and secretion of glands and
peristalsis are some examples of the activities controlled by autonomous nervous system. The
autonomic nervous system is of two types: Sympathetic and parasympathetic nervous systems.

Sympathetic nervous system stimulates and regulates the involuntary bodily activities like beating
of heart, breathing, churning movement of stomach, peristalsis movement of intestines, urinary
bladder and urinary tracts at their exited states. The involuntary organs become activated during
exited conditions like during fight-or-flight response. For example, the heartbeat accelerates,
blood pressure rushes up due to narrowing of blood vessels and the flow of blood increases in
brain when we are exited or nervous due to action of sympathetic nervous system.

Parasympathetic nervous system relaxes and controls the involuntary activities during the rest
and relaxing state. This slows down the heart rate, dilate the blood vessels and normalize the
blood flow to all the parts of body, regulate breathing rate, relaxes urinary bladder and intestines
at resting state or after passing of exited state.

Glandular System

Human body contains systems like nervous system and glandular system that maintain the
balance of body activities in coordination. The glandular system regulates various biological
activities like digestion, elimination, growth, metabolism, homeostasis, reproductive activities,
sleep pattern etc.

Various glands are found in our body. Some glands like liver and salivary glands pour their
secretions in ducts. So, called exocrine glands or ducted glands. Some glands like pituitary,
thyroid, adrenal pour their secretions (hormones) directly into blood. They are called endocrine
glands or ductless glands.

Differences between Exocrine and Endocrine Glands

S.N. Exocrine Glands S.N. Endocrine Glands

1. These glands have ducts. 1. These glands do not have ducts.

2. They secrete enzymes. 2. They secrete hormones.

3. Their secretions pass through the duct 3. Their secretions are discharged
to the related organ. directly into the blood stream.

4. Glands are present near the site of 4. Glands are present far away from the
action. site of action.

Exocrine glands are related to body Endocrine glands are related to

5. physiology like digestion, respiration, 5. physiology like growth, ovulation,

excretion etc. homeostasis, etc.

Blooming Science Book 10 229

6. The enzymes secreted by exocrine 6. The hormones secreted by endocrine
glands are relatively more in amount. glands are relatively less in amount.

7. Examples: Salivary glands, gastric 7. Examples: Pituitary gland, thyroid
glands, lachrymal glands, intestinal glands, adrenal glands etc.
glands etc.

Hormones are the chemical messengers (means of communication among various parts) that
are transported by blood from endocrine glands to the particular cell. Hormones regulate or
control, coordinate and integrate various physiological processes and activities of the body. Any
disturbance in the functioning of these glands result in dwarfism, tallness, obesity, sterility and
others.

Note: Hormones are chemical messengers.
Hormones are known as two edged sword.
Enzymes are known as bio-catalyst.

Pituitary Glands

Pituitary gland is a small pea-sized gland weighing just 0.5 gram and lies at the base of the brain
below hypothalamus. Pituitary gland is called the ‘master gland’ as it controls and activates the
other glands by secreting stimulating hormones. These stimulating hormones or tropic hormones
are the catalytic hormones which initiate and activate the activities of other glands. For example,
thyroid-stimulating hormone (TSH) produced by pituitary gland activates thyroid glands and
follicle stimulating hormone (FSH) stimulate follicles at gonads.

Besides the stimulating hormones, it also secretes non-tropic hormones to influence target
organs directly. For example, the growth hormones (GH) regulates the normal growth of human
body. Undersecretion (hyposecretion) of growth hormone leads to dwarfism and oversecretion
(hypersecretion) of GH result into excessive tallness or gigantism.

Similarly, the over and under secretions of catalytic hormones can lead to irregularities in other
glands’ functions and secretions that ultimately imbalance the well being of bodily systems and
the whole body.

Thyroid Glands thyroid epiglottis
gland hyoid bone
There are two thyroid glands on either side of larynx
trachea. The two lobes of thyroid glands are
connected by a thin band of connective tissue called (thyroid cartilage)
isthmus. Thyroid glands produce thyroid hormones pyramidal lobe
rich in iodine like thyroxine (T4 or thyrotrobin) and
triiodothyroxine(T3). These hormones regulate the lateral lobe
general metabolism by regulating carbohydrate, isthmus of
protein and fat metabolism. They also regulate thyroid gland
vitamin metabolism and coordinate with growth of
bones.

Over secretion of thyroxine (hyperthyroidism) results
into higher metabolism, excess hunger, faster heart
beats, mental irritability, weakness of muscles, over-sweating, sleeping problem, popping of
eyes, weightloss and swelling of thyroid glands.

230 Blooming Science Book 10

Under secretion of thyroid hormone (hypothyroidism) results into decreased metabolism, reduced
physical growth, less heart rate, mental retardation (cretinism), slurred and hoarseness in speech,
dryness of skin, less sweating, overweight, and enlargement of thyroid glands known as goitre.
It is caused by deficiency of iodine in food.

Thyroid glands also produce hormone called calcitonin that regulates calcium and phosphorus
metabolism. Calcitonin reduces calcium level in blood and deposits calcium in bones.

(Iodine is provided to public by adding iodine in common salt known as iodized salt.)

Hypothalamus Pineal
Body

Pituitary

Thymus

Thyroid and
parathyroids

Heart Adrenal
gland

Kidney

Pancreas

Testis Ovary

Male Female

Fig: Endocrine System

Parathyroid Glands

There are four tiny glands over the thyroid glands, one pair on each of the thyroid glands. They
are called parathyroid glands. They are smallest of the endocrine glands. They produce hormone
called parathyroid hormone or parathormone. This hormone is responsible for balancing calcium
and phosphate in blood. It helps in normal growth of bones, teeth and normal muscles contraction.

Undersecretion of parathyroid hormones causes blood level of calcium to drop dramatically. This
leads to contraction of skeletal muscles. This disease is called parathyroid tetany (twitching of
uncontrolled contraction of the muscles of the larynx, face, heads and feet). It causes extensive
decalcification of the bone. The bone becomes soft and porous. This may lead to deformities and
fractures.

Hyper secretion causes the calcium level in the blood plasma rises and deposit of calcium in soft
tissues specially in the kidneys may occur. If calcium salts precipitate in kidneys and ureters,
kidney stone results and renal insufficiency develops.

Blooming Science Book 10 231

Pancreas

The pancreas is a mixed gland because it has both endocrine and exocrine functions. It produces
pancreatic juice through duct so it is exocrine gland and produces hormones so called endocrine
gland. It produces insulin and glucagon. It is situated in the abdominal cavity. The islets of
Langerhans are special group of cell which secrete hormones directly into the blood. So, this part
is endocrine.

Insulin controls the sugar level in blood by changing glucose to glycogen. Its deficiency results
in high sugar content in blood (hyperlycemia) and the person suffers from diabetes mellitus. Its
symptoms are increased sugar level in blood, increased thirst, feel more hungry, loss of body
weight, tiredness, frequently urination, presence of sugar in urine and delay in wound healing.

Over secretion of insulin causes low sugar level in blood (hyperlycemia) and may lead to
weakness, sweating convulsions, hunger and unconsciousness. Glucagon works opposite of
insulin, when sugar is low, glucagon breaks the stored fat of body into blood sugar to balance
sugar level in our body.

Adrenal Gland Adrenal Gland

At the top of each kidney there is a gland known as adrenal
gland. It secretes adrenaline noradrenalie and cortisone.
Adrenaline prepares the body to face emergency conditions
of emotional stress like fall in blood pressure, pain, cold,
injury, anger, fear etc. So, this gland is also called gland of
emergency. Noradrenaline maintains blood pressure under
normal conditions.
Cortisone regulates the metabolism of fat, protein

and carbohydrate to address stress.

In danger approach of stressful situation like, speaking in public, the heart beats faster and skin
develops goose bumps. These reactions are part of the "fight or flight" syndrome stimulated
by the secretion of hormone adrenaline. The hypersecrection of adrenaline increases the blood
pressure and heartbeat rate whereas its hyposecretion causes weakness, nausea, low blood
pressure, vomiting ,etc.

Gonads

Testes of male and ovaries of female are called gonads. Testes lie in the scrotum and ovaries are
the female reproductive organs situated in the lower abdominal cavity. In addition to production
of sperm and ova, they produce sex hormones. Male hormones are androgen or testosterone.
They stimulate development of secondary sexual characters like development of mustache and
beard, hoarse voice, muscular body in male. Female hormones are oestrogen and progesterone.
The oestrogen stimulates the development of secondary sexual character like development of
breasts and enlargement of hips. The progesterone plays significant role in the maintenance of
pregnancy.

232 Blooming Science Book 10

Endocrine Glands, Hormones and Functions

Glands Location Hormones Functions Hyposecretion Hyper secretion
(number)

Growth hormones &

Pituitary Stimulating hormones Dwarfism Gigantism
glands -1 Just below [(Thyroid Stimulating Overall growth of body.
hypothalamus Hormones (TSH); Triggering the other Over activities of the
Thyroid in the skull Follicle Stimulating glands to activate them Inactivation of glands.
glands (2)
Hormone (FSH), other glands
Luteinizing hormone
(LH).

At the Adam’s Thyroxine T3 T3 & T4 normal Hypothyroidism: Hyperthyroidism:
(tri-iodo-thyronin) T4 metabolism and growth Goitre & Cretinism Irritability, muscle
apple on (Tetra-iodo- thyroxin), of body.
weakness, high
throat Calcitonin. Calcitonin: calcium (Low growth and metabolism,
deposition in bone. mental retardation.) tachycardia, sleeping

problem.

Para-thyroid Two on each Parathyroid hormone= Functions: Hypothyroidism: Hyperparathyroidism:
glands (4) thyroid gland Parathormone Low Ca in Hypercalcemia,
Balance of serum Blood,tetany Kidney stones,
Calcium between bone (twitching of
and blood. Vitamin D muscles)
production.

Pancrease In the Insulin by islets of Insulin: Glucose to Hyperglycemia Hypoglycemia (Low
(Islets of abdomen (High blood sugar) blood sugar)
Langerhans) below Langerhan (Beta cell) Glycogen Diabetes
stomach
and Glucagon by Alpha Glucagon: Glycogen to Vice versa Vice versa
cells Glucose

Maintains BP,

Adrenalin (Fight-or- Heartbeat,dilation of Hypersecretion:
blood vessels. Hypertension,
flight hormone) and Hypo secretion:

Adrenal One on top of Steroids Aldosterone (Fight or fight reaction.) Hyperkalemia tachycardia,
glands (2) each kidney and Cortisol.
Osmoregulation by (High K+ in blood) nervousness, blank

steroids. out, daredevilness.

Testosterone. Sperms production,

Male In scrotum at or secondary sex characters Infertility, lack
gonads: (Facial and body hair, of masculine
Testes (2) groin androgen beard and mustache, characters.
under arm and pubic

hair, hoarse voice, etc).

Secondary sex

Oestrogen-. characters), regulation of Infertility, upset
Progesterone:
Female Lower menstrual cycle menstruation

gonads: abdominal Female sexuality, lack of feminine

Ovaries (2) cavity conceiving, pregnancy, characters,

foetal development, and

lactation.

Exocrine Gland
Simple exocrine gland is tube-gland-like in structure. It is found on the wall of stomach and
inner part of intestine. Complex exocrine gland is found in liver, pancreas and salivary glands.
They produce different types of juices with many enzymes in different quantity. Mucus, sweat,
saliva and digestive juices are the examples. They transport the secretions with the help of tubes.

Blooming Science Book 10 233

Let's Learn
1. Pituitary gland is called master gland. It is because it activates other glands and control

their activities.
2. Hormones are called chemical messengers of the body because they are chemical in

nature and their site of action is away from the site of their secretion as well as the action
is specific.
3. Adrenal gland is called emergency gland of the body because it secretes a hormone called
adrenalin that prepares the body to face emergency conditions of emotional stress like fall
in blood pressure, pain, cold, injury, anger, fear, etc.
4. Gonads and pancreas are heterocrine or mixed gland because they produce hormone and
enzymes which are poured into blood eigher directly or through the duct.

Points to Remember

1. The system which consists of brain, the spinal cord and nerves is called nervous system.
2. Nervous system controls all other systems of the body.
3. Brain consists of cerebrum, cerebellum and medulla oblongata.
4. The nerves arising from brain are called cranial nerves and those arising from spinal cord

are called spinal nerves.
5. A set of nerves that carry message from receptors to brain are called afferent or sensory

nerves.
6. A set of nerves that carry message from brain to receptors are called efferent or motor

nerves.
7. Reflex actions are immediate actions and are not judged by brain.
8. Hormones are the chemical messengers that are transported by blood from endocrine

glands to the target organ.
9. Exocrine glands have ducts and secrete enzymes.
10. Endocrine glands have no ducts and secrete hormones.
11. Pituitary gland is called master gland because it activates other glands.
12. Undersecretion of insulin causes diabetes mellitus.
13. Thyroid gland secretes thyroxine.
14. Pancreas is a mixed gland. It secretes enzymes and hormones both.
15. Adrenal gland is called gland of emergency.
16. Testes of a male and ovaries of female are called gonads.

Project Work

1. Observe the various parts of human brain in a 'Model of Human brain.
2. Observe the brain of goat in a nearby meat shop if possible and find out various parts.

234 Blooming Science Book 10

Exercise

1. What is the main function of nervous system?

2. What is reflex action? Discuss by giving a suitable example.

3. A man afraid when he walked bare feet at dark over a soft and cool object and jumped.
What roles his parts of the body in this event played and what is this event called? Explain
with well lebeled diagram.

4. What is a gland? What is the main function of the gland in human body? What happens if
thyroid glands do not function well?

5. What is hormone? Write down one function of each of the following hormone

a. Growth hormone b. Parathyroid hormone c. Adrenalin

d. Insulin e. Glucagon f. Stimulation hormones

6. Name the glands which perform the functions mentioned below.

a. Physical and mental development.

b. Controls other glands.

c. Prepares body to face emergency.

d. Controls the amount of sugar in the blood.

7. Define the following.

a. Axon b. Dendrite

c. Sensory nerve d. Motor nerve

e. Neuron f. Cyton of neuron

g. Cerebrospinal fluid h. Myein sheath

8. Write the functions of the following.

a. Motor nerve b. Cerebellum

c. Medulla oblongata d. Spinal cord

e. Cerebrum f. Pituitary gland

g. Thyroxine h. Insulin

i. Meninges j. Sensory neuron

9. Distinguish between:

a. Axon and dendrite b. Exocrine and endocrine glands

c. Sensory and motor nerves d. CNS and PNS

e. Hormone and enzyme f. Cerebrum and cerebellum

g. Hypoglycemia and hyper glycemia h. Spinal cord and brain

10. Give reason.

a. Pituitary gland is called master gland.

b. Hormones are called chemical messengers.

c. Pancrease is called mixed gland.

d. Adrenal gland is called gland of emergency.

e. Iodine rich food must be included in our food.

f. Animals respond quickly than plants

Blooming Science Book 10 235

11. Draw a labeled diagram of the human brain and spinal cord.

12. Draw a labeled diagram to show the position of different endocrine glands in the human body.

13. Study the given diagram and answer the following question: A

a. Label A, B, C and D.

b. State the function of each of parts A and B. C B
A D
14. The diagram given is a typical reflex arc: B
Spinal cord
a. Name the parts labeled A, B, C and D?

b. Why is it called reflex arc? Dendrites

D

C

c. Which part of the central nervous system conducts this action? B
A C

15. Name the parts A, B, and C in the following diagram of a
neuron and write their functions.

16. What is the names of the hormones produced by the A
glands A, B and C shown in the diagram. Also name those B
glands.

17. Choose the correct alternatives from the following options. C

i. The largest part of brain is: d. Both ‘a’ and ‘b’
d. Cranial Nerve
a. Cerebellum b. Medulla Oblongata c. Cerebrum d. Both ‘a’ and ‘b’
d. All of them
ii. Which part of nervous system is related to reflex action? d. Parathyroid

a. Spinal cord b. Brain c. Ganglia

iii. Which chemical is called as a messenger?

a. Thyroxin b. Hormone c. Saliva

iv. The gland of emergency is called:

a. Gonad b. Pancreases c. Adrenal

v. Insulin is produced by:

a. Pancreas b. Thyroid c. Adrenal

236 Blooming Science Book 10

Chapter Circulatory
System in Human William Harvy
16
(1570-1657)
(discovered & published accurate
description of human circulatory system)

Learning Outcomes Estimated Periods: 5+1

On the completion of this unit, the students will be able to:
 describe the composition of blood.
 identify the types of blood cells and their functions.
 interpret the structure of heart and blood circulation.
 write the functions of blood.
 introduce heart beat , blood pressure, blood sugar and uric acid.

Every living cell requires the continuous supply of water, nutrients, hormones and oxygen to
sustain life. Also, metabolic wastes such as carbon dioxide, urea and uric acid need to be removed
regularly from their immediate environment. For this living organisms have a transport system.

Higher animals require an organized transport system for quick supply of nutrients to all the body
cells and to take wastes to the excretory organs for the removal from the body. To meet this need
blood circulatory (transport) system is developed. The blood circulatory system consists of an
extensive network of interconnecting tubes of varying sizes called blood vessels. The blood flows
through these vessels to the heart, which pumps it to the tissues and returns to the heart again. The
circulatory system is made by blood, blood vessels and heart.

Blood

Blood is a fluid connective tissue in which blood cells are suspended in the plasma. It keeps on

circulating in the blood vessels. A healthy person has about 5.5 litres of blood circulating through

the blood vessels. This comes to about 8% of the body weight. It is opaque, somewhat sticky and

slightly heavier than water. It is salty in taste and alkaline in nature. It consists of two parts:

Plasma and cells or Blood corpuscles. Scan for practical experiment

Blood

Plasma (55%) Blood Cells (45%)

Red blood cells White blood cells Platelets

1. Plasma: Blood plasma is a liquid portion of blood. It constitutes visit: csp.codes/c10e17

55% of the blood. It is a clear, straw coloured or pale yellow transparent liquid. It contains

mostly water (90%) and various organic and inorganic substances (10%).

The organic substances are the fibrinogen, albumin, globulin, nutrients like glucose,
amino acids and fatty acids, metabolic wastes like urea, uric acid and ammonia. It contains

Blooming Science Book 10 237

mineral salts and the hormones. It also Red Blood cells
contains heparin, which is anticoagulant. Plasma Platelets
Heparin prevents the blood circulating in Red Blood cells
the blood vessel from clotting.

Functions

1. Plasma transports digested food products Composition of blood
such as glucose and amino acids to various

parts of the body. In other words, it nourishes the living cells.

2. It transports urea from liver to kidney for the removal in the form of urine.

3. It transports carbon dioxide released during cellular respiration to the lungs.

4. It carries hormones secreted by endocrine glands to the target organs.

5. Fibrinogen, a kind of plasma protein, with platelets in blood helps in blood coagulation
thus prevents blood loss.

6. Some plasma proteins act as antibodies and destroy the germs that enter the body.

7. Plasma proteins also control the flow and the amount of water in the blood.

2. Blood Cells or Blood Corpuscles: Dispersed through blood plasma are three types of
cells: erythrocytes(RBC), leukocytes (WBC) and platelets. These blood cells are about
45% of the total blood volume.

a. Erythrocytes (Red Blood Cells): These are very small disc-shaped cells that is, circular
and biconcave. The biconcave shape of a red blood cell provides more surface area in
relation to its volume. This allows rapid absorption of oxygen to occur in the lungs and
rapid release of oxygen to occur in the tissue. Mature erythrocytes lose their nucleus
and most other organelles like mitochondria, endoplasmic reticulum during development.
They are bounded by a highly elastic membrane, which enables them to pass through fine
capillaries. They are so small that about 4.5 to 5 million of them are present in every cubic
millimeter of blood.

They are formed in the red bone marrow, especially in the ribs, vertebra, sternum and the
long bones of the arms and legs (Humerus and Femur). They have a life span of about 120
days (4 months) after which they are destroyed in the spleen and liver. They are formed at
the rate of 2.0 million per second and destroyed at the same rate.

They contain haemoglobin in their cytoplasm. Haemoglobin contains iron, which combines
with oxygen in the lungs to form oxyhaemoglobin. Oxyhaemoglobin will give its oxygen
to tissues. It is due to the presence of oxyhaemoglobin that has red colour. When oxygen
is lost, then the colour of these blood cells become purple and dark. Erythrocytes perform
the following functions:

1. They transport oxygen from the lungs to the body cells in the form of
oxyhaemoglobin.

2. The amino acids are absorbed by the surfaces of erythrocytes and transport them to
the cells from the alimentary canal.

Anaemia is caused either by less red blood cells in the blood or low concentration of haemoglobin

238 Blooming Science Book 10

in the red blood cells. Haemoglobin carries oxygen around the body. Thus, a person suffering from
anaemia does not like to work, feel tired in a short walk and can’t do the job efficiently.

Activeted Platelets

Red blood cells Nucleus Platelets
White blood cells

b. Leukocytes (White Blood Cells): Leukocytes are larger in size and fewer in number than
erythrocytes. Normally, one cubic millimeter of blood contains 6000 to 10,000 (about
8000) but the number increases whenever the body is fighting an infection. If its number
increases more than the necessary, the person will have blood cancer (leukemia). If WBC
decreases than the immunity power of our body decreases (leukopenia).

They have a changeable, Amoeba like shape that allows them to squeeze through the
capillary walls. These characteristics allow them to defend the body against invasions by
micro organisms and other foreign substances. They lack haemoglobin and have one or
more nuclei of different shapes and sizes.

Most of them are produced in bone marrow. They have a short life span that varies from 12
hours to 12 days. Generally they are destroyed at the site of infection. Leukocytes perform
the following functions:

1. Some of them destroy invading germs of diseases and other injurious agents. They do
so by engulfing.

2. Some of them produce antibodies against different antigens or pathogens and protect
the body against specific diseases. Some produce antitoxins that neutralise the
poisonous substances produced by the bacteria, making them harmless, so that they
can’t cause disease. In other words, they are responsible to provide immunity against
specific diseases.

3. Some of them remove the damaged cells or germs from the infected region of the body
and help in quick healing of the wound.

c. Thrombocytes (Blood Platelets): Platelets are extremely small, circular shaped cells or
‘pinched off’ segments of larger cells. They are smaller in size as compared to red and
white blood cells. They lack nucleus and have irregular shape. They are colourless and
produced in the red bone marrow. There are about 2 million to 4 million platelets in every
cubic millimetre of blood. They have a life span of 2-3 days. The important function of
the platelets is to help in blood clotting in injury thus prevent excessive bleeding and
also check entry of germs. If its number decreases, the blood does not clot quickly and
the person will have hemophilia. If increased, the blood thickens and disturbs the blood
circulation.

Blooming Science Book 10 239

Functions of Blood:

The blood circulation in the blood vessels performs the following three important functions
human body.

a. Transport functions
(i) Blood transports oxygen from the lungs to the tissues for cellular respiration and

the carbon dioxide from the tissues to the lungs for elimination. Most important is
the supply of oxygen to heart and brain.
(ii) Blood transports nutrients such as glucose, amino acid, etc absorbed from the
alimentary canal to the liver and then to the tissues.
(iii) Blood transports nitrogenous wastes such as urea and uric acids to the kidneys, skin
and liver for elimination from the body.
(iv) Blood transports hormones to the target organs where they produce the desired effects.

b. Reglulatory (control) Functions
(i) Blood transports heat from the deeper parts of the body to the surface where it can

be lost. In other words, it keeps the temperature of body uniform by distributing
heat energy and making us cool.
(ii) Blood maintains a constant environment in the body by regulating water and salts
concentration.
c. Protective Functions
(i) Certain white blood cells protect the body from diseases by engulfing bacteria that
have entered the body.
(ii) Certain white blood cells produce antibodies, which combat with the antigens
or pathogens and protect the body against specific diseases while other produce
antitoxins, which can neutralize the toxins produced by the germs.
(iii) It forms a clot wherever there is cut. Clotting is necessary to prevent an excessive
loss of blood when a blood vessel gets ruptured. But blood does not clot inside the
blood vessel as there is anticoagulant protein called heparin in the blood.

Activity -1

To observe the blood cells under the microscope.
Material needed:
Sterilized needle or lancent, cotton, spirit, glass slides, leishman stain, microscope.
Method:
1. Prick your fingertip with a sterilized needle in pessence of your teacher.
2. Put a drop of blood on a slide and spread it with the help of another slide and let it
to be dried.
3. Put a drop of leishman stain on it, leave it to dry and rinse it gently with water.
4. Dry it again and observe under the microscope.
What can you observe under the microscope? You can observe RBC, WBC and
Platelets.
Draw the diagram of your observation and show to your teacher.

240 Blooming Science Book 10

Blood Vessels

Blood vessels are network of tube-like structure of different sizes that carry blood away from the
heart, transport it to the tissues and then return it to the heart. The blood always flows in the same
direction in these vessels. There are three types of blood vessels: arteries, veins and capillaries.

Artery Capillary Vein

Endotheliun

Arteriole Venule

Connective Connective
tessue tessue

Smooth Smooth
muscle muscle
Endotheliun
Endotheliun
Valve

Arteries: Arteries carry blood away from the heart to different organs. Within these organs,
arteries branch into small branches called arterioles that give rise to capillaries. They are deep
seated and have thick and elastic muscular walls with a narrow lumen. Blood flows in them with
high pressure. They do not posses valves. Arteries and arterioles transport oxygenated blood
(except pulmonary arery)

Veins: Veins are normally blue blood vessels that are sometimes visible in different parts of
the body. They usually collect blood from the organs in the body back towards the heart under
extremely low blood pressure. They have thin walls with a wide lumen. The blood flows through
them very slowly. They have internal one-way valves throughout their length, to stop it flowing
backwards. The opening of the valves is in the direction of the heart, which cause the blood to
flow towards the heart only.

Veins contain deoxygenated blood except the pulmonary veins, which have oxygenated blood.
Pulmonary veins bring oxygenated blood from the lungs to the left auricle of the heart. The flow
of blood in veins is slow and steady. The pressure of the blood within it is less. The union of the
venules forms veins.

Capillaries: Capillaries deliver blood nutrients to body tissues under low pressure. They therefore
have only one thick cell wall that allows the exchage of material by diffusion between the blood
and the cells of the organs. They are miscroscopically small and extend into all body tissues,
forming networks.

Capillaries leave the organs and join up to form small vessels called venules. Venules join to
form veins.

Heart

The mammalian heart is a roughly conical shaped muscular pumping organ, which brings about
the circulation of the blood. It measures the size of one’s closed fist. It lies in the middle of the
chest cavity between two lungs with nearly two third of its structure (apex) towards the left of

Blooming Science Book 10 241

the midline. It is made up of thick cardiac muscles capable of strong contractions followed by
relaxation.

aorta

superior pulmonary
vena cava trunk

right left
atrium atrium
pulmonary
right veins
ventricle left
ventricle

inferior
vena cava

The heart is enclosed in double walled membranous sac called the pericardium. The inner
membrane invests the heart very closely. In between the two membranes is a narrow space called
pericardial cavity full of self-secreted fluid called pericardial fluid, the lubricant. The pericardial
fluid keeps the movements of the heart smooth, protects the heart from the mechanical injury and
shock and keeps the heart moist.

In its external view, the heart shows aorta, superior and inferior vena cava, a pair of coronary
arteries, a pair of pulmonary arteries. The upper broad part of the heart is darker in colour. It is
the auricular region of the heart. The lower narrow part of the heart is the ventricular region of
the heart. Blood moves through arterial vessels as a result of the pumping action of the heart,
which creates blood pressure.

Differences between Auricles and Ventricles

Auricles Ventricles

1. They are upper chambers. 1. They are lower chambers.

2. They are thin walled. 2. They are thick walled.

3. They are smaller. 3. They are bigger.

4. They receive blood from different parts of 4. They receive blood from auricles and

the body and push it into ventricles. pump it to different parts.

5. Veins are originated from auricle. 5. Arteries are originated from ventricles.

Internal Structure of the Heart

The human heart has four chambers. The two upper and smaller chambers are called the right
and left auricles. The two lower and large chambers are called the right and left ventricles. All
the four chambers have strong muscular walls, but of different thickness. The auricles have thin
walls because they receive blood from the body and force the blood into the ventricles. Auricles
are separated by an inter-atrial septum.

The ventricles have thick muscular wall because they pump blood to long distances. The
thickness corresponds to the pumping action performed by the chambers. The wall of the left
ventricle is more muscular than the right ventricle. This is because greater force is required to

242 Blooming Science Book 10

push oxygenated blood to distant parts of the body. The right ventricle has to pump blood only
to the lungs. Lungs are closed to the heart. There is a wall between the two ventricles, the inter-
ventricular septum. The wall separating the auricles and ventricles is called auriculo-ventricular
septum. Thus the heart chambers of right side are completely separated from those of the left
side. All the chambers function as distinct pumps.

superior vena cava aorta
pulmonary veins pulmonary artery

right atrium pulmonary vein
left atrium
right ventricle pulmonary valve
inferior vena cava (or semi-lunar valve

mitral vaive
left ventricle

cardiac muscle

Valves in the Heart: Valves are the muscular flaps, which allow unidirectional flow of blood i.e.
it prevents, back flow of the blood. There are four valves in the heart.

1. Right atrio-ventricular valve or Tricuspid valve is present between the right auricle and
the right ventricle. It allows the deoxygenated blood to flow from right auricle to right
ventricle only. It consists of three triangular leaf-like flaps (cusps) so called tricuspid
valves. When the ventricle contracts, this valve closes right atrio-ventricular aperture and
prevents the back flow of blood in the right auricle, then blood flows to pulmonary artery.

2. Left atrio-ventricular valve or Bicuspid valve also called mitral valve is present between
the left auricle and the left ventricle. It allows flow of oxygenated blood from the left
auricle to the left ventricles only. It consists of two cusps of flaps. When the ventricle
contracts, this valve closed left atrio-ventricular aperture and prevents the back flow of
blood in the left auricle, then blood flows to aorta.

3. Pulmonic valve lies in the opening of the right ventricle and the pulmonary artery. It
is made up of three half-moon shaped flaps attached to the inside of the arterial wall.
This valve allows the blood to flow from the right ventricle to the lungs only. When
right ventricle relaxes, this valve closes and will prevent the back flow of blood from the
pulmonary artery to the right ventricle.

4. Aortic valve lies in the opening of the left ventricle and aorta. This valve is also made up
of three half-moon shaped flaps. This valve allows the blood to flow from left ventricles
to the aorta during the ventricular contraction and prevents the backward flow of the blood
from the aorta to the left ventricle during ventricular relaxation.

Flow of Blood through the Heart

Deoxygenated blood from all parts of the body is returned to the right auricle of the heart through
two large veins, the superior and inferior vena-cava. The superior vena-cava brings the blood
from the head, the arms, and the upper parts of the body. The inferior vena-cava brings the blood
from the legs and those parts of the body that lie below the heart.

Blooming Science Book 10 243

Superior vena cava Arota Left pulmonary
(from upper body) Aortic artery to left lung
Right pulmonary valve
artery from left lung Left pulmonary
veins from left lung
Right pulmonary
veins from left lung Left atrium
Left AV valve
Right atrium
Left ventricle

Right AV valve Pulmonary
Interior vena cava valve
fron lower body Right
ventricle

From the right auricle, the blood passes into the right ventricle through tricuspid valve. From the
right ventricle the blood is pumped into the pulmonary trunk (the only artery in the body to carry
deoxygenated blood). Three pulmonary valves guard the opening of the pulmonary artery. These
valves prevent return flow of blood from the pulmonary artery to right ventricle when the ventricles
relaxes. The pulmonary artery divides into left and right pulmonary arteries. These arteries carry
deoxygenated blood to the left and right lungs where interchange of gases occurs: carbon dioxide
being given off and oxygen taken up. Now the blood is rich in oxygen i.e. oxygenated.

The oxygenated blood is carried from each lungs by two pulmonary veins. So four pulmonary
veins bring oxygenated blood into the left auricle. This blood passes into the left ventricle
through the bicuspid valve. From the left ventricle the blood is now pumped into the aorta and
subsequently into the general circulation. The opening of the aorta is guarded by aortic valve. It

is the largest artery.

Activity -2

To observe the structure of mammalian heart.
Materials needed: Goat heart, scissors, forceps dissectiny tray, globes, etc.
Method:
Take a heart of goat from a meat shop. Cut it longitudinally to observe the following
structures.
a) Auricles and ventricles
b) Tricuspid, bicuspid, pulmonic and aurtic valves.
Compare the size of two auricles walls of auricles and ventricles, etc. Draw the
diagram to show internal structure of heart, write finding of your observation and to
show your teacher.

Types of Blood Circulation

Humans have a double circulation of blood. The blood enters the heart twice through two separate
systems. One system is the pulmonary circulation, which carries blood from the heart to the lungs
and back. The other system is the systemic circulation, which carries blood from the heart to rest
parts of the body except the lungs and back.

244 Blooming Science Book 10

Double circulation means the flow of blood once from the heart to lungs and back and then from

the heart to the body and back i.e. blood circulates twice through the heart before the completion

of one full circuit. Circulation Head + Shoulders
1. Pulmonary

in which the impure

blood flows from the Pulmonary vein

right ventricles to the Lung
Left auricle
lungs and back to the Pulmonary artery Aorta
left auricles of the heart.
The deoxygenated blood Vena cava Left ventricle
from the right ventricle is Right auricle
pumped out through the Hepatic artery
pulmonary artery to the Right ventricle Stomach and Intestine
lungs. These arteries divide Hepatic vein
and subdivide into smaller Renal artery
arteries, subsequently into Liver
arterioles and capillaries in Renal vein Oxygenated blood
Lower parts of the body
Kidney (limbs+abdomen)

Deoxygenated blood

the lungs.

It is between the capillaries and the lung tissues that the exchange of gases occurs. There it
is purified and oxygenated. The capillaries now containing oxygenated blood join up with
one another and eventually form two veins.

Two pulmonary veins leave each lung, therefore four pulmonary veins, carrying
oxygenated blood at low pressure enter the left auricle of the heart. When the auricle
contracts the blood is forced into the left ventricles and during ventricular contraction the
blood is forced into the aorta for general circulation.

2. Systemic (Body) Circulation in which the oxygenated blood flows from the left ventricle
into the aorta which gives off branches to almost all parts of the body (except the lungs) such
as gut, kidneys, liver, sex organs, limbs, skin etc. The blood passes through capillaries in all
those organs where exchange of material takes place. From the capillaries the deoxygenated
blood is collected into the venules and then into the veins. Several veins from the different
organs collect the blood and unite and reunite to form two large veins - the superior
venacava and inferior venacava. These two vena cava empty their content into the right
auricle.

In human beings, the heart is distinctly divided into left and right sides separating
oxygenated and deoxygenated blood. The blood enters the heart twice, once the blood
from the general circulation of the body to the right auricle and via pulmonary circulation
to the lungs for oxygenation. Next from the lungs to the left auricles and via systemic
circulation to all parts of the body.

Heart Beat

One complete contraction and relaxation of the heart is called a heart beat. At the end of this
sequence, the heart relaxes while the auricles fill with blood once more. Each repeating sequence
is a heart cycle or heart beat. The heart beats about 72 or 76 times a minute at rest in the adult.

The number of beats per minute is the heart rate. The heart rate varies from person to person
with age, sex, and activity. It increases during exercise, so that oxygenated blood and glucose

Blooming Science Book 10 245

can be carried to the tissues more quickly. It is about 140 beats per minute in a newly born
child and gradually reduces in old people. Heartbeats increase during vigorous activity, anger,
emotion stress, anxiety, excitement, tension, fear and fever.

The heart on contraction forces the blood into the arteries. The arterial wall is stretched to accommodate
blood. In interval between the heartbeats, the arterial wall contracts, and forces the blood further. This
contraction and expansion of the artery, in time with the heart beat, is called the pulse. It is measured by
using stethoscopes.

Pulse can be felt easily in the radial artery at the wrist, emporal artery in front of the ear, common
carotid artery in the neck and facial artery in the corners of mouth.

Blood Pressure

It is the force with which blood pushes against the walls of the arteries. It is generally measured
in terms of how high it can push a column of mercury.

Blood pressure depends upon the force with which the heart pumps the blood, amount of blood
ejected from the heart and size of the blood vessels. It is the blood pressure that circulates the
blood in our body. When the heart contracts and relaxes, the blood pressure changes. Accordingly,
blood pressure is of two types: systolic blood pressure and diastolic blood pressure.

1. Systolic Blood Pressure:

When the ventricles contract, pressure of blood inside the arteries is the highest and this
pressure is called systolic blood pressure. In a healthy person, it varies from 90mm Hg
to 130mm Hg or about 120 mm Hg. The systolic blood pressure of a person is 120mm of
Hg, It means the blood pressure exerted on the wall of artery when ventricle contracts is
120mm of Hg.

2. Diastolic Blood Pressure:

When the ventricles relax, pressure of blood inside the arteries is comparatively less and
this pressure is called diastolic pressure. In a healthy person, it varies from 60mm Hg to
90mm Hg or about 80mm Hg. This pressure of blood is the minimum arterial pressure. The
diastolic blood pressure of a person is 80mm of Hg, It means the blood pressure exerted on
the wall of artery when ventricle relaxed is 80mm of Hg.

Thus, in a healthy person, the systolic pressure is 120 mm Hg. and diastolic pressure is 80mm
Hg. It is expressed by 120/80mm Hg. The blood pressure is measured by sphygmomanometer.
The blood pressure varies with age, sex, physical activities, exercise, etc.

Differences between Systolic and Diastolic Pressure

Systolic Pressure Diastolic Pressure

1. The pressure exerted on the walls of artery 1. The pressure exerted on the walls of arteries

when left ventricle pumps blood. when ventricles relaxed.

2. Average value - 120 mm Hg. 2. Average value - 80 mm Hg

3. Pressure exerted when heart contracts. 3. Pressure exerted when heart relaxes.

246 Blooming Science Book 10

High blood pressure

It is the condition in which person’s diastolic is above 90 mm of Hg and Systolic blood pressure
is above 140 mm of Hg.

Causes
a. Overweight of the body.
b. Smoking / Alcoholism.
c. Lack of physical exercise
d. Mental stress
e. Consumption of oily, salty and spicy foods.
f. Heredity

Symptoms of high blood pressure:
a. Headache
b. Nause and vomiting
c. Dizziness
d. Blurred vision
e. Nose bleeds
f. Breathlessness

Preventive measures
a. Take balance diet.
b. Do regular physical exercise.
c. Avoid smoking and drinking alcohol.
d. Maintain proper body weight.
e. Reduce mental stress.

Uric acid

Uric acid is the chemical which is produced from purine rich food like pulse, drinks, sea food etc.
Purines are the building blocks for RNA and DNA and can be found in all proteins. It is simply
aromatic organic compound having molecular formula C5H4N4O3.

When protein is broken down into their by products purine is produced and uric acid is the
metabolic by product of purine.

The uric acid produced in the body directly gets dissolved into the blood which passes to the
kidney for the filtration and uric acid is liberated out as a filtrate through the process of urination.
But sometimes due to the excessive purine rich food more amount of uric acid is produced inside
the body which can't be removed from the body through the urination and deposited in the joints
in the crystal forms.

This crystal form of uric acid creates painful arthritic condition which is known as gout. The high
amount of uric acid in the body is termed as hyperuricemia while for the lowering condition it is
termed as hypouricemia. The amount of uric acid must be balanced in the body to be a healthy
person. The normal level of uric acid in men (3.5-7.2) mg/dl and (2.1-6.1) mg/dl in women.

Causes of Hyperuricemia (high uric acid):
a. Consumption of high purine rich foods like red meat, legumes, sea food, etc.
b. Over weight of body.

Blooming Science Book 10 247

c. Lack of exercise
d. Drinking alcohol
e. Heredity

Symptoms of Hyperuricemia:
a. Pain in joints of ankles, heels and toes.
b. Swelling of joints.
c. Skin becomes red, swelling and burning sensation is felt in the skin.
d. It leads to kidney failure.

Preventive measures

To prevent from uric acid we should focus in our daily life style. The main point is that we have
to manage our diet (balance diet), regular exercise and if we suffer from it, take a blood or urine
test and consult with doctors. The following are frequently having the preventive measures of
Hyperuricemia.

1. Cherries which contain anthocyanins, which helps to lower uric acid.

2. Less consumptions of high purine rich foods like red meat, legumes, sea food, etc.

3. Drinking the solution baking soda helps to reduce the uric acid.

4. Taking sufficient water and have regular physical exercise.

Diabetes (Blood sugar)

The disease that occurs when the body is unable to regulate the amount of glucose (sugar) in the
blood is called diabetes. It occurs when the pancreas stops to produce insulin but inactive due
to the resistance of the body. The sugar or the glucose is the essential things for our body and is
made from the food or carbohydrate that we take. The digestive system breaks down the food
into various sugar molecules and one of them is sugar or glucose. It directly mixes with blood
and enters into the cells along with insulin and feeds the cells.

But when there is too much glucose or sugar in our blood in comparison to insulin produced
by pancreas, the sugar level is not maintained and it is the condition of diabetes. The average
amount of glucose level is approximately 70 to 140 mg/dl (mg means milligram and dl means
deciliter) at fasting while it is about 140mg/dl after having meals.

At the time having meal blood sugar rises, insulin is produced into the blood and sugar level
is maintained while at the fasting the hormone glucagon produced by pancreas actively breaks
down the stored glucose (glycogen) produced by liver into the sugar such that blood sugar is
maintained. There are two categories of diabetes:

1. Type first(Juvenile diabetes or diabetes mellitus)

This type of diabetes starts in people under the age of 20 or may occurs at any age.

Causes

This occurs because pancreas produces no insulin. The pancreas producing cells (called
beta cells) are destroyed by immune system.

248 Blooming Science Book 10

2. Type second diabetes (diabetes mellitus type 2)

This occurs usually in older people and begins gradually.

Causes

In this type of diabetes insulin is produced in the body but it is functionless because of the
body's against insulin. It may be caused due to overweight or being physically inactive
and also due to hereditary cause.

Symptoms:

Almost the symptoms of both type of diabetes are also same some of the symptoms of
diabetes are listed below:

Symptoms Becomes thirsty.
a. Frequent urination.
b. Excessive hunger.
c. Blurred vision.
d. Weight loss.
e. Fatigue and weakness.
f.

Preventive measures
a. Take balance diet.
b. Do regular physical exercise.
c. Avoid smoking and drinking alcohol.
d. Maintain proper body weight.
e. Reduce mental stress.
f. Include green vegetables and fruits in diet.

Note: Diabetes insipidus is another rare form of diabetes which is caused by deficiency of
pituitary hormone vasopressin or ant diuretic hormone.

Let's Learn

1. Heart beat is rhythmic contraction and relaxation of the heart. Each heart beat includes
one systole (contraction phase) and one diastole (relaxation phase) of the heart to
distribute and receive blood to and from the body. The heart of a healthy person beats
72 times per minute. During exercise both the number of beats per minute and the amount
of blood pumped per beat are greatly increased.

2. Pulse is caused by arteries, because blood flows at high pressure in arteries and wall of
arteries is elastic in nature.

3. Wall of left ventricle is thicker than the wall of right ventricle, because right ventricle
has to pump for a short distance i.e, from heart to the lungs. But the left ventricle has to
pump blood for a very long distance inside our body, for which a great pressure is required.
Due to it the wall of the left ventricle is the thickest.

Blooming Science Book 10 249

4. Arteries are deep seated but veins are superficial. It is because blood flows at high
pressure in arteries and at low pressure in veins. To balance the pressure in and out of the
blood vessels, they are found at different depth as mentioned above.

5. Colour of the blood in pulmonary artery is purple. The colour at oxygenated blood is
scarlet (bright red) and that of deoxygenated blood is purple. Because the pulmonary
artery carries deoxygenated blood from heart to lungs, the colour of blood in it is purple.

6. A person suffering from anemia feels weakness also after a short walk. It is because, such
people have very less number of RBCs in their blood. Due to it, their blood cannot carry
sufficient oxygen for the required amount of energy for the body.

7. Donated blood is treated with sodium citrate. It is because in the donated blood fibrinogen
is removed to avoid the blood clotting. Sodium citrate works as anticoagulant.

8. Injury in artery is more dangerous than in vein. It is because the blood flows at high
pressure and high velocity in the artery. In any sort of injury, it is difficult to stop the flow
of blood from artry which leads to excessive less of blood.

9. Himalayan people have red cheeks. It is because they have high amount of RBC as to
compensate the low oxygen in atmosphere.

Points to Remember

1. The flow of fluid in the body is called circulation and the organs concerned for this
transport constitute the circulatory system.

2. Blood is the liquid connective tissue. It contains plasma and blood cells.

3. Blood transports the nutrients and oxygen to different parts of the body.

4. Red blood cells are biconcave in shape. They lack nucleus.

5. Haemoglobin is present in RBC.

6. White blood cells do not have fixed shape. Their number is less than RBCs.

7. Platelets help in blood clotting.

8. Plasma constitutes about 55 percent of the blood.

9. The mammalian heart has four chambers. They are right auricle, left auricle, right ventricle
and left ventricle.

10. All veins except pulmonary artery carry oxygenated blood to different parts of the body.

11. All veins except pulmonary vein bring impure blood to the heart.

12. The heart of a healthy adult person beats 60 to 72 times per minute.

13. The human heart is a hollow, muscular organ and is somewhat conical in shape.

14. The heart is protected by a double-walled membranous sac called pericardium.

15. The human heart has four chambers. It is divided by a septa into two halves: the right and
the left. Each half consists of an upper, small sized, thin walled chamber called auricle and
a lower, larger-sized and thick walled ventricle.

250 Blooming Science Book 10