13.13 Solid Waste Management
Solid waste management refers to the collection, transportation, processing and reuse of waste
materials. Various communicable diseases may spread if solid wastes are not managed and
disposed properly. Therefore, solid wastes should be managed properly and carefully. Various
ways of solid waste management are given below:
1. Collection and transportation
Collection and transportation is the first step
in solid waste management. The solid waste
produced in every household should be
collectedandthenitistransported toaproperplace.
The waste should be transported away from the
residential area for their proper management.
2. Segregation and waste management Fig. 13.8
After collection solid wastes should be segregated into biodegradable and non-biode-
gradable wastes. We should manage biodegradable wastes and non- biodegradable
wastes separately. We should classify non-biodegradable wastes. On the basis of their
nature, we should separate wastes for reuse and recycle. Biodegradable wastes should
be used to prepare compost manure.
3. Landfill dumping
After processing, the solid waste should be
taken to the landfill site. The landfill site should
be constructed away from the residential area,
and the site should be selected only after an
environment impact assessment.
4. Incineration Fig. 13.9
Incineration is the method of burning solid waste at very high temperature. Incineration
should be carried out only at the dumping site.
Fig. 13.10
CHEMISTRY Oasis School Science - 10 243
SUMMARY
• Cement is a fine grey powder of calcium silicate and calcium aluminate. It is used to
make roads, buildings, dams, bridges, etc.
• The raw materials of cement are limestone (CaCO3) and a special type of clay (Al2O3 .
SiO2). Some gypsum (CaSO4 . 2H2O) and oxides of iron are also added to increase the
quality of cement.
• The mixture of cement, sand and water is called cement mortar. It is used for
plastering.
• The mixture of cement, sand, gravel and water is called cement concrete. It is used in
roofing and flooring.
• Glass is a homogeneous mixture of different metallic silicates. It is a transparent and
super cooled liquid.
• Quartz glass is obtained by heating pure silica at about 1600°C. It is used for making
laboratory instruments like a crucible.
• Borosilicate glass has boron silicate as an additional compound. So, it has high ther-
mal resistant power.
• Sodium silicate or potassium silicate is called water glass. It is water soluble in nature.
• The sodium salt of long chain fatty acid is called soap. It is used for bathing and
washing purpose.
• Sodium salt of alkyl hydrogen sulphate or alkyl benzene sulphate is called detergent.
• Fibers are long, strong and elastic thread-like structures which may be natural or
man-made.
• Polymers are formed by repeating many small and simple molecules.
• Plastics are man-made chemical substances which are obtained by repeating simple
molecules.
• Thermoplastic becomes soft on heating, but thermosetting plastic does not
become soft on heating.
• Bakelite is an example of thermosetting plastic, which is formed from carbolic acid
and formaldehyde.
• Insecticides are those chemical substances which are used to kill or control insects.
• DDT (dichloro diphenyl trichloroethane) and BHC (benzene hexa chloride) are
chlorine containing insecticides.
• Fertilizers are those organic or inorganic substances which are added to the soil to
increase its fertility.
• Chemical pollution is caused by unwanted chemicals in the environment.
244 Oasis School Science - 10 CHEMISTRY
Exercise
Group-A
1. What is cement?
2. What are the materials necessary for the manufacture of cement?
3. Name the chemical which increases the setting time of cement.
4. What are the two chief raw materials required to prepare cement?
5. Write down raw materials used in the preparation of ordinary glass.
6. Which glass is called lead crystal glass?
7. Which metallic oxide is mixed in ordinary glass to make red and black glass each?
8. Which substance is used to increase refractive index of glass?
9. Write any two properties of ceramics.
10. What is NPK fertilizer?
11. What is soap?
12. Write any two functions of organic fertilizer.
13. What are the raw materials used to prepare water glass?
14. Write down the full form of BHC.
15. Write the full form of DDT.
16. Write two raw materials which are used to make soap.
17. Which type of chemical fertilizer increases disease resistance capacity of plants?
18. Name a chemical fertilizer that supplies nitrogen in the soil.
19. State any two causes of chemical pollution.
20. Write a name of each chemical fertilizer containing nitrogen and phosphorus.
21. Write the names of two insecticides, one containing chlorine and another containing
phosphorus.
22. What is chemical pollution?
Group-B
1. Write any two differences between mortar and concrete.
2. Write any two differences between soft glass and hard glass.
3. Write any two differences between pyrex glass and lead crystal glass.
4. Write any two differences between recycled fibres and synthetic fibres.
5. Write any two differences between thermoplastic and thermosetting plastic.
6. Write any two differences between soap and detergent.
7. Write any two differences between compost manure and chemical fertilizers.
8. Write any two differences between bakelite and polythene.
CHEMISTRY Oasis School Science - 10 245
9. NPK fertilizer is called a complete fertilizer, why?
10. Environmentalists request for avoiding the use of plastics, why?
11. Bakelite is used to cover the handle of a pressure cooker, why?
12. We should be careful while using insecticides, why?
13. Detergent is called soapless soap, why?
14. Plastic materials are widely used in comparison to other materials, why?
15. Detergent is better than soap for washing clothes, why?
16. The organic fertilizer is better than chemical fertilizers, why?
17. Mention any two properties of ceramics due to which it is suitable for making false teeth.
18. Write any two differences between biodegradable solid wastes and non-biodegradable
solid wastes.
Group-C
1. Write any three uses of cement.
2. Write any three uses of glass.
3. Write down the uses of each soft glass and hard glass.
4. Write any three uses of ceramics.
5. Explain in brief the method of making utensils from ceramics.
6. Write any three uses of plastics.
7. Write down the method of making soap with chemical equation.
8. How does smoke released from vehicles and factories cause environmental pollution?
Describe.
9. Why are the following chemicals added to make following materials?
i) Gypsum in cement
ii) Lead monoxide in ordinary glass
iii) Salt in heated ceramics
10. Write down one use of each of the given industrial chemicals:
i) Ammonium sulphate
ii) Aldrin
iii) Sodium lauryl sulphate
11. Write down one use of each of the given industrial chemicals:
i) Sodium separate
ii) Potassium nitrate
iii) Bakelite
246 Oasis School Science - 10 CHEMISTRY
12. Write any three ways to get rid of chemical pollution.
Group-D
1. Describe the method of making cement in brief.
2. Explain the method of making ordinary glass.
3. Write short notes on:
i) Borosilicate glass ii) Lead crystal glass
4. Describe the process of making utensils from ceramics in brief.
5. Synthetic detergents are better than soaps. Justify this statement by giving three reasons.
Write any two uses of plastics.
6. How is pollution caused by insecticides and chemical fertilizers? Describe.
7. Write various steps of solid waste management.
8. Write short notes on:
i) Landfill dumping ii) Incineration
CHEMISTRY Oasis School Science - 10 247
Part 3 : Biology
Scope and sequence of the subject matter
Area Unit Syllabus
Living Beings 14. Invertebrate • Structure and life cycle of silkmoth and honeybee
Animals • Utility
Physical Processes 15. Human Nervous • Nervous system
and Glandular • Glandular system
System
16. Blood • Structure of blood and functions
Circulation in • Blood circulation
Human Body • Blood pressure
• Blood sugar
• Uric acid
17. Chromosome • Introduction to chromosome
and Sex • Sex determination
Determination
18. a) Asexual • Asexual and sexual reproduction in living beings
and Sexual
Reproduction • Grafting
• Layering
b) Artificial • Tissue culture
vegetative
propagation in
plants
Evolution 19. Heredity • Mendel's experiment
• Introduction to monohybrid cross
• Variation and mutation
Nature and Environment 20. Environmental • Air pollution
Pollution and • Water pollution
Management • Soil pollution
• Conservation and management of forest and water
SEE Specification Grid-2074
S.N. Unit (K) (U) (A) (HA) Total Remarks
14 Invertebrates 5×1 4×2 2×3 1×4 23
15. Human Nervous and Glandular System
16. Blood Circulatory System in Human Body
17. Chromosome and Sex determination
18. Artificial Vegetative Propagation in Plants
19. Heredity
20. Environmental Pollution and Management
248 Oasis School Science - 10 BIOLOGY
UNIT 14 Estimated teaching periods
Theory 5
Practical 2
INVERTEBRATES
Objectives
After completing the study of this unit, students will be able to:
• explain the body structure and life cycle of the silkworm and Honeybee.
• state the utilities of the silkworm and Honeybee.
A. Silkmoth
14.1 Introduction
A silkworm is an insect larva that produces silk thread which is used to make silk clothes. Raw
silk is obtained from the cocoons of a silkmoth.
Sericulture, or silk farming is the rearing of silkworms for the commercial production of
silk fiber. It is a technique of silk production, which is an agro-industry. Sericulture plays an
eminent role in the rural economy of many countries. Historically, sericulture was introduced
for the first time in China, around 2700 BC. Sericulture was considered to be a national secret
by the Chinese government, and as an industry it was not known in other countries. Later it
was introduced in Europe and other Asian countries.
Fig. 14.1 Silkworm
Sericulture has become one of the most important cottage industries in a number of countries,
like China, Japan, Korea, India, Brazil, Russia, Nepal, etc. Today, China and Japan are the two
main producers, together manufacturing more than 50% of the world production each year.
In Nepal, sericulture was introduced for the first time in Khopasi, Kavre. Altogether, there
are eight branches of sericulture in Nepal. They are located in Syangja, Pokhara, Bandipur,
Dhading, Bhandara, Itahari, Dhankuta and Chitapur.
BIOLOGY Oasis School Science - 10 249
14.2 Silkmoth
The adult of silkworm is called the silkmoth. Silkmoths are found in many indigenous varieties
across the world. The species of silkmoths commonly reared in Nepal are listed below:
Common name Scientific name Food of larva
1. Seri silkworm Bombyx mori Mulberry leaves
2. Eri silkworm Attacus ricini Castor leaves
Among them, Bombyx mori is the most common species of silkmoth found in Nepal. It is a
blind, flightless moth with a life span of 9-10 days. Eri silkworm is reared indoors, which is
not easily susceptible to diseases.
14.3 External Morphology
The silkmoth, Bombyx mori, is a medium-sized insect with a robust body of creamy-white
color. Its body can be divided into three parts, they are: head, thorax and abdomen.
The head bears a pair of compound eyes, a pair of feathery antennae and sucking mouth parts.
The thorax bears two pairs of wings covered with scales, three pairs of jointed legs and two
pairs of spiracles for breathing purpose.
Adult male Adult female
Fig. 14.2
The abdomen consists of a few segments, which contain seven pairs of spiracles. The abdomen
of the female is larger than that of the male.
14.4 Life Cycle
The life cycle of the silkmoth shows complete metamorphosis. The life cycle completes in four
different stages: eggs, larvae, pupae and adults. The silkworm is dioecious, i.e., the sexes are
separate. Copulation takes place in air, and the fertilization is internal. The male dies after
mating and the female dies after laying eggs.
250 Oasis School Science - 10 BIOLOGY
Adult
Pupa Eggs
Larva
Fig. 14.3
Eggs
A female silkmoth after copulation lays nearly 300-
400 eggs in clusters on a mulberry leaf. The moth
secretes a sticky secretion on the eggs, which glues
them on to the leaf so that they do not fall off. The
eggs are small, rounded and yellowish-white in color.
On favorable condition, at a temperature of 18°C to
25 0C, eggs hatch into larvae within 10 to 12 days.
Larvae Fig. 14.4
The eggs hatch into small caterpillars within 11 days Fig. 14.5
on favorable condition. The larva is creamy-white and
about 6 mm long, which moves on the leaf in a looping
movement. The larva is a voracious feeder, feeding on
mulberry leaves for about 25-32 days.
The body of the larva contains a head with biting and
chewing mouth parts, which can easily cut the mulberry
leaves. The thorax is three-segmented with three pairs
of true legs. The abdomen is ten segmented, which
contains five pairs of pseudolegs and a dorsal anal horn
on the 8th segment.
BIOLOGY Oasis School Science - 10 251
The larva moults four times. The stage of a larva between two successive moultings is called
an instar. The newly born larva falls in the first instar. This larva feeds for three days and
sleeps for about 20 to 24 hours. After the sleep, it moults.
The second instar larva is bigger than the first instar, which eats for three days and sleeps for
about 24 to 26 hours. After the sleep, the larva moults for the second time. The third instar eats
for three days and sleeps for 26-30 hours. Similarly, the fourth instar eats for three days and
sleeps for about 20-36 hours. After the sleep, it moults and becomes the fifth instar larva.
The fifth instar larva is 100 times bigger than the first instar larva. It eats for 7 days and sleeps
for 36-42 hours. When fully grown, the caterpillar stops feeding. The body color changes. It
develops a pair of salivary glands which secrete liquid silk. The liquid silk flows into two
ducts to a common exit tube in the worm's mouth. On emerging, the liquid silk hardens and
forms silk fibers. The silk fibers wrap around the body of the caterpillar to form the pupal case,
or cocoon.
A single caterpillar is said to produce nearly 1000-1500 meters of silk thread in a period of
about 3-4 days. Within a fortnight the caterpillar develops inside the cocoon and becomes a
pupa, or chrysalis.
Pupae
The pupa is the third stage of the life cycle which is inactive. Fact File - 1
The pupa does not eat and move, but active metamorphosis
takes place inside the cocoon involving the processes of The pupa of a silkmoth
histolysis and histogenesis, and becomes, adult, or imago. remains inside the cocoon. It
The imago secretes an alkaline fluid to moisten one end of does not take food.
the cocoon in order to escape outside. This stage lasts for
about 12-14 days.
Cocoon
Pupa
Fig. 14.6 Fig. 14.7
Adults
On favourable condition, an imago, or adult, comes out by tearing the cocoon. It contains a
head, thorax and abdomen, with two pairs of wings and three pairs of jointed legs. It flies
away after drying the wings. Soon after emergence, the male and female moths mate. The
female lays eggs and then both die after 3-4 days.
In this way, on favorable condition, the life cycle of the silkmoth completes within 45 days.
252 Oasis School Science - 10 BIOLOGY
Precautions During Sericulture
• In sericulture, or silk industry, the eggs of a silkmoth are stored at a temperature below
18°C for long term storage when mulberry leaves are not available. Mulberry is a
deciduous tree, and leaves are not available throughout the year. But the larvae of the
silkmoth are voracious feeders, which need mulberry leaves immediately after hatching,
and they die in the absence of mulberry leaves.
• When mulberry leaves are available, the eggs are kept in an incubator for hatching. When
the temperature is raised from 18°C to 25°C, eggs hatch into tiny caterpillars within a
week.
• Clean and dry mulberry leaves are fed to the larvae because if wet leaves are given, they
may die.
• For obtaining commercial silk, the cocoons are treated with hot water or placed in a hot
oven. It is done to kill the pupae inside the cocoon; for if allowed to hatch, they would
cut the silk thread on emerging. It also helps to enable the hard sericin portion to get
softened and make the unwinding easy without breaks.
• A few cocoons of good quality are kept as seeds for the next crop.
14.5 Economic Importance of Sericulture
• A silkworm is a useful insect which produces valuable silk fiber. The silk fiber is extracted
from the cocoon and is used to make silk clothes, like saris, shirts, vests, socks, ties, nets,
etc. These clothes are shiny, durable, attractive and very expensive. Raw silk and silk
clothes can be exported to improve the economic status of farmers.
• Women constitute over 60% of those employed in down-stream activities of sericulture
in the country.
• Sericulture can be practiced with very low land holding. About 0.75 acre of mulberry
garden and silkworm rearing can support a family of three without hiring labor.
• All the things used in sericulture can be sold. The pupae are fed to animals. Similarly,
spoilt cocoons can be used as food for fishes in fish farms.
14.6 Features of Natural Silk Thread Fact File - 2
• Natural silk is very shiny, light and durable as • Silk fiber is commonly known as
compared to artificial silk. the king of fibers.
• Natural silk fiber is longer and more elastic than
artificial silk.
• Natural silk can be colored easily and silk clothes can be worn in all climates.
• Natural silk absorbs water readily and can be dried easily.
Activity-1
• During the spring season, visit a nearby silk industry, if possible. Observe the mulberry
plants and various stages of the life cycle of the silkworm. Draw well-labeled figures.
• Observe the technique of extraction and reeling of silk thread carefully.
• Prepare a short report of your field trip.
BIOLOGY Oasis School Science - 10 253
B. The Honeybee (Apis mellifera)
14.7 Introduction
Honeybees are social insects, i.e., they live in colonies where all the individuals are of the same
family, often the offspring of one mother. There is a division of labor in which individuals
carry out particular duties. Honeybees produce honey. Honeybees live in discipline, and their
life is very busy.
14.8 Structure
The bodies of bees are divided into the head, thorax and abdomen. The thorax consists of three
pairs of jointed legs and two pairs of wings. The head consists of a pair of antenna, a pair of
compound eyes and mouth parts.
Drone Queen Worker
Fig. 14.8 Honeybees
The mouthparts consist of a tongue, or labium, which can be enclosed near the head by the
labial palps and maxillae. Nectar can be drawn up the grooved surface of the labium in the
head. When not in use, these elongated mouthparts are folded back under the head, leaving
the shorter, stouter mandibles free in front. The abdomen is elongated and segmented. The
ovipositor through which the queen lays her eggs in the wax cell is modified in the workers
to form a sting.
14.9 Organization of the Colony Fact File - 3
There are three types of bees in a colony. They are: • The drones are very lazy. They
1. The queen, or egg-laying female (one in a colony) mate with the queen.
2. Drones, or males (a few hundred in a colony)
3. Workers, or sterile females (20 to 80 thousand in a colony)
254 Oasis School Science - 10 BIOLOGY
The Queen
Generally, there is only one queen in a colony. The queen is larger
than the drones and workers. The abdomen of the queen is large
and slender. The head of the queen is smaller than that of the other
types of bees, and its proboscis is shorter. The queen has a special
smell in its body. All the drones and workers identify their colony
on the basis of the smell of the queen.
A queen bee may live from two to five years and, except for a
short period at the end of her life, when one of her daughters
takes over the colony. The queen is the only egg-laying female.
All the members of the family, whether drones or workers, are
her offspring. The queen spends all her time laying eggs, perhaps Fig. 14.9
upto 1500 a day, each one being placed in a wax cell made by the
workers. The queen can feed herself, but in the hive the nearest workers turn towards her, lick
her body and feed her a special secretion of their salivary glands, called royal jelly.
The queen usually mates only once in her life and stores the sperms received from the drone
in a sperm sac in her abdomen. The store of sperms lasts for two or more years of egg-laying.
When the store of sperms is used up, she may continue to lay eggs but they are all unfertilized
and will become drones. By this time, one of her daughters has been reared as a queen and is
ready to take over the egg-laying.
14.10 Life Cycle
The life cycle of the Honeybee completes in four stages: egg, larva, pupa and adult. The queen
bee emerges from the hive after 3 to 5 days and mates with the males (drones). The flight
of the queen bee and drones outside the hive for mating is called nuptial flight, or mating
flight. After mating, the queen start laying eggs after 2-3 days. Each egg is laid in one of the
hexagonal wax cells and hatches into a tiny, white legless larva. The larva feeds on substances
deposited in the cell by the workers. The larva grows, pupates in the cell, hatches as an adult
bee and finally emerges from the cell into the hive. The eggs hatch after three to four days
and by nine days are fully grown and ready to pupate. The workers put a capping over the
cells at this time. When the capping is bitten away, the adult emerges. The time given above
varies with the changes in the temperature and according to whether the bee is becoming a
drone, worker or queen. The duration of development of the three types of bees on favourable
condition is tabulated below:
Type of bee Egg Larva Pupa Adult
1. The queen 3 days 5.5 days 7.5 days 16 days
2. Drone 3 days 6 days 14.5 days 23.5 days
3. Worker 3 days 6 days 12 days 21 days
BIOLOGY Oasis School Science - 10 255
Egg
Adult
Larva
Pupa
Fig. 14.10 Life cycle of Honeybee
Drones Fig. 14.11
Fig. 14.12
The drone bee is smaller than the queen bee and larger than the
worker bee. Its body is black and hairy. It does not have a poison
gland, nectar gland and pollen sac. The drones live for about four
to five weeks and do not work inside the hive. They are fed by the
workers. Their function is to fertilize the new queen. In the autumn,
or when conditions are poor, they are turned out of the hive where,
unable to find food for themselves, they die.
Workers
Workers are the smallest bees in the colony. Their body can be
divided into the head, thorax and abdomen. Their mouth is modified
for chewing and lapping.
The workers are female bees whose reproductive organs do not
function. They collect food from outside the hive and store it, make
the wax cells and feed the developing larvae. They are very laborious.
Workers have pollen baskets to collect the nectar.
256 Oasis School Science - 10 BIOLOGY
14.11 Division of Labour in the Honeybee on the Basis of Their Type:
S.N. Type and Age Functions / Duties
1. The Queen bee - To lay eggs
- To control and guide the colony by releasing special odor
2. Drone - To fertilize the queen
- To keep the hive warm
3. Worker (1 to 3 days) - To learn walking
- To give warmth to egg, larva and pupa
- To clean the cells
4. Worker (4 to 6 days) - To feed mature larva workers who also take a lot of food
5. Worker (7 to 11 days) - To feed royal jelly produced by the salivary glands to the
larvae below 3 days and the queen bee. Workers also
take a lot of food.
6. Worker (12-17 days) - To secrete wax from 4 pairs of wax glands in the
abdomen
- To build a honey comb using wax
- To close the cells of the larvae and honey
7. Worker (18-20 days) - To protect the beehive from enemies with their
poison glands and sting
8. Worker (21 days) - To be busy in outdoor works, i.e. to collect nectar
from flowers, to collect pollen, water, etc. from crop
fields and forests
Activity-2
Draw a neat and labeled figure showing the life cycle of the Honeybee.
Activity-3
Visit a nearby area having apiculture. Ask the owner to open a beehive and observe it.
Identify the queen, drones and workers. Study their structure and draw a neat and labeled
figure of each.
14.12 Origin of the Three Types of Bees
The wax combs are built hanging vertically with a gap of about half an inch separating each
one. The cells in each comb thus lie horizontally. The workers prepare three types of cells.
Worker cells are about 5mm across, drone cells are about 6mm across, and the queen cells are
larger and made individually.
BIOLOGY Oasis School Science - 10 257
Eggs are laid by a queen in a broad area. This is done where the temperature is about 320C,
kept so by the heat given out by the bees' bodies. The queen moves over a broad area, laying
eggs in any of the three types of cells by placing her abdomen in the cell and depositing a
single egg. The eggs placed in the larger, drone cells, are not fertilized, and this results in the
eggs developing into a male bee or drone. In the queen and worker cells, fertilized eggs are
laid.
For the first three days after hatching, all the larvae are fed on a protein rich, milky secretion,
called royal jelly, which comes from the salivary glands of the workers of certain age. The
larvae in the queen cells continue to be fed on the royal jelly for the rest of their lives. The
larvae in the drone and worker cell are fed on a mixture of dilute nectar and pollen.
Fact File - 4
If a 'one to three day old larva' is transferred from a worker to a queen cell, it will receive a
diet of royal jelly and develop into a queen.
14.13 Swarming
When the size of the colony reaches a certain stage,
usually in spring or summer when the nectar flow
is at its greatest, the queen and many workers leave
the hive in a swarm. The swarm comes to rest in a
great cluster on a tree branch. In the old hive, one
new queen hatches out, mates and takes over the
colony that is left.
Fig. 14.13 Swarming in honeybees
14.14 Advantages of Honeybees
1. Honeybees produce honey, which is a protein-rich diet.
2. Honey is used for making medicines, for treating allergies, healing wounds, fighting
infections, etc.
3. Honeybees help in pollination while collecting nectar and increase the productivity of
crops.
4. They help in environmental balance.
258 Oasis School Science - 10 BIOLOGY
SUMMARY
• A silkworm is a useful insect which produces silk fiber in the last stage of the larva
after 4th moulting.
• The rearing of silkmoths in order to obtain silk for commercial purpose is called
sericulture.
• Bombyx mori and Attacus ricini are the common species of domesticated silkmoths
found in Nepal.
• A caterpillar is the second stage of the life cycle of a silkmoth, which produces
valuable silk thread in the fifth instar.
• The period of a larva between two successive moultings is called an instar.
• A cocoon is a spherical cover of the pupa of a silkworm. It is made up of a very
long (about 1000-1500 m) silk thread.
• Silk fiber is extracted from the cocoon by killing the pupae inside it.
• During winter, mulberry leaves are not available. So, eggs of the silkworm are
kept below 180C to prevent them from hatching.
• Clean and dry mulberry leaves are fed to the larvae.
• The cocoons are treated with hot water or hot air to kill the pupae inside them for
obtaining unbroken silk thread.
• Silk clothes are light, strong, lustrous, attractive and have tensile strength.
• Raw silk and silk clothes can be exported to earn foreign currency, and hence the
economic status of farmers can be improved.
• Honeybees are social insects, i.e., they live in colonies where all the individuals
are of the same family, often the offspring of one mother.
• The bodies of bees are divided into the head, thorax and abdomen.
• The queen usually mates only once in her life and stores the sperms received from
the drone in a sperm sac in her abdomen.
• The life cycle of a Honeybee completes in four stages which are: egg, larva, pupa
and adult.
• The drone bee is smaller than the queen bee and larger than the worker bee. Its
body is black and hairy.
BIOLOGY Oasis School Science - 10 259
Exercise
Group-A
1. What are invertebrates? Give one example.
2. Name two species of silkmoths reared in Nepal.
3. What is the food of the larva of Seri silkmoth?
4. Write down the scientific name of Seri silkworm and Eri silkworm.
5. In how many stages does the life cycle of silkmoth complete?
6. Write any two characteristics of eggs of silkmoth.
7. What is the food of larva of silkmoth?
8. In which stage of life cycle does the silkmoth produce silk thread?
9. What is cocoon? Write its function.
10. Write any two characteristics of pupa of silkmoth.
11. How many types of honeybees are there in the hive? What are they?
12. Write down three characteristics of drone bee.
13. In how many stages does the life cycle of silkmoth complete?
14. Write any two characteristics of egg of honeybee.
15. What is royal jelly?
16. In how many days the life cycle of honeybee complete?
17. What is metamorphosis?
Group-B
1. Why are eggs of silkmoth stored below 18 0C in winter season?
2. Why is the larva of silkmoth called varacious eater?
3. Write any two differences between larva and egg of silkmoth.
4. Why are cocoons kept in hot air before the extraction of silk fibre?
5. Write any two differences between male silkmoth and female silkmoth.
6. Write any two differences between pupa and cocoon.
7. Why is honeybee called social insect?
8. Write any two differences between queen bee and drone bee.
9. What is meant by mating flight or nuptial flight?
10. Write any two similarities between queen bee and worker bees.
11. Write any two differences between worker bee and queen bee.
12. Write any two differences between drone bee and worker bee.
Group-C
1. Give a brief account of silkmoth.
2. Write any three characteristics of larva of silkmoth.
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3. How does silkworm produce silk fibre? Describe in brief.
4. Write a short note on pupa of silkmoth.
5. Describe in brief the advantages of silkmoth.
6. How is sericulture done? Explain in brief.
7. Give a brief account of honeybee.
8. Write any three characteristics of queen bee.
9. Write any three characteristics of worker bee.
10. Mention the importance of royal jelly for queen bee.
11. Describe in brief the uses of honeybee for human beings.
Group-D
1. Describe the external structure of silkmoth with a labeled figure.
2. Draw a neat and labeled figure showing the life cycle of silkmoth.
3. Describe the life cycle of silkmoth in brief.
4. Describe the structure of silkworm with a labeled figure.
5. Write a short note on adult silkmoth.
6. Explain the method of extraction of silk fibre from silkworm.
7. Describe the structure of queen bee in brief.
8. Draw a neat and labeled figure showing the life cycle of honeybee.
9. Write short notes on:
a) Lava of honeybee b) Pupa of honeybee
10. Show the development of different types of honeybees in a table.
12. Why should we study the life cycle of honeybee? Explain.
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UNIT 15 Estimated teaching periods
Theory 5
Practical 2
HUMAN NERVOUS AND
GLANDULAR SYSTEM Human brain
Objectives
After completing the study of this unit, students will be able to:
• describe the structure of the brain, nerves (sensory and motor), their functions and
their relationship in human beings.
• describe the reflex action in human beings.
• introduce the endocrine system and explain its functions in the human body.
15.1 Introduction
Living organisms are sensitive to their environment. They respond and react to changes in the
environment. The change in the environment to which the living beings respond and react is
called stimulus (pl.–stimuli). Stimuli provoke the physiological or behavioral response in an
organism. A response is a change in the activity of an organism due to stimuli. Living beings
show response to stimuli, such as light, heat, cold, sound, pressure, touch, taste, smell, etc. The
response shown by organisms is usually in the form of some movement of their whole body
or body parts. Any external factor or change in the environment which brings about a response
in an organism is called stimulus.
Living organisms show response towards or
away from a stimulus. The response shown by
an organism towards or away from a stimulus
is called a reaction. The reaction to stimuli is a
characteristic of living organisms. For example,
if a man touches a very hot object accidentally,
he quickly withdraws his hand from the hot
object. Here, heat is the stimulus, and the quick
withdrawal of hand is the reaction shown by the
man. Similarly, a sunflower always turns towards Fig. 15.1
the sun. Here, the presence of the sun is the
stimulus, and the movement of the sunflower towards the sun is the reaction.
Animals use both the nervous system and endocrine system for co-ordination, but the nervous
system is absent in plants, and they use the endocrine system only for co-ordination. Therefore,
stimulus /ˈstɪmjələs/ - something that produces a reaction in an organism
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animals can respond quickly to a stimulus but plants cannot. The body parts of living
beings that detect stimuli are called receptors. In animals, receptors are often the parts of
a sense organ.
15.2 Nervous System
The nervous system is a network of organs and tissues that controls and co-ordinates
all the activities of the body with the help of nerves. A nerve is a long, slender, thread-
like structure which arises from the brain and the spinal cord. In human beings, the
nervous system is made up of three major divisions, which are: central nervous system,
peripheral system and autonomic nervous system.
Nervous System
Central Nervous Peripheral Nervous Autonomic Nervous
System System System
Brain Afferent (sensory) Efferent (motor)
Nerves Nerves
Spinal cord
15.3 Functions of Nervous System
i. The nervous system collects information both from inside the body and from the
outside world with the help of five sense organs.
ii. It transmits information to organs (effectors), muscles and glands so that they can
respond correctly.
iii. It processes information to determine the best response.
15.4 Nerves
Nerves are the communication lines for transmitting impulses from one part of the body to
another. They are elongated, slender, thread-like structures arising from the brain and spinal
cord. The nerves that arise from the spinal cord are called spinal nerves whereas the nerves
that arise from the brain are called cranial nerves. In human beings, there are 12 pairs of
cranial nerves and 31 pairs of spinal nerves.
15.5 Types of Nerves Fact File - 1
a. Afferent or Sensory nerves Electricity transmits at the speed
The nerves that carry impulses (messages) from of 1,50,000 km/s whereas nerve
impulse or stimulus transmits at
the body parts (receptors) to the spinal cord or the speed of 100m/s.
brain are called afferent or sensory nerves. They
impulse /ˈɪmpʌls/ - a force or movement of energy that causes an organism to react
BIOLOGY Oasis School Science - 10 263
are connected to the sensory cells or receptors. When our sense organs (eyes, ears, nose,
tongue and skin) are affected, they send the message to the brain in the form of nerve
impulses (electrical impulses) through the sensory nerves, e.g., optic nerve, auditory
nerve, etc.
b. Efferent or Motor nerves
The nerves that carry impulses from the brain or spinal cord to the effector organs
for action are called efferent (motor) nerves. The brain/spinal cord or both send out
instructions to the muscles of the concerned body parts for taking necessary action
through the efferent (motor) nerves, e.g., facial nerves.
c. Mixed nerves
Mixed nerves are those which consist of both afferent and efferent nerves, e.g., cranial
nerves and spinal nerves.
Note:
i. An impulse is a wave of electrical disturbances that sweeps over the nerve
cell, e.g., impulse of touch, impulse of heat, etc.
ii. Effector organs are the organs which become stimulated on receiving the
impulse, e.g., eye, tongue, etc.
15.6 Neuron and Its Structure
A neuron or nerve cell is a highly specialized cell which acts as the structural and functional
unit of the nervous system. A neuron basically consists of three parts: cell body, axon and
dendrites. The cell body contains a large central nucleus surrounded by cytoplasm. The
cytoplasm contains granules and neurofibrils along with mitochondria, endoplasmic
reticulum, golgi complex, etc.
Axon Dendrites
Nucleus
Cytoplasm
Myelin sheath
Motor end plates
Fig.15.2 Structure of a neuron
Numerous short, thread-like branches, i.e., dendrites (Gk., dendron–tree) arise from the cell
body. They carry impulses to the nerve cell. One of the branches of dendrites grows very large
in comparison to others, which is called axon. It carries impulses away from the cell body. The
myelin /ˈmaɪəlɪn/ - a mixture of proteins and fats that surrounds nerve cells
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axon remains covered by three layers, viz. Neurilemma (the outermost layer), Myelin sheath
(the middle layer) and Axolemma (the innermost layer).
Types of Neuron
On the basis of the structure and function, neurons are of three types. They are: Sensory
(afferent) neuron, Motor (efferent) neuron and Inter neuron.
The sensory neuron contains long dendrites and a short axon. It carries messages from the
sensory receptors to the brain or spinal cord.
Fig. 15.3 (a) Fig. 15.3 (c)
Fig. 15.3 (b)
The motor neuron contains a long axon and short dendrites. It carries messages from the brain
or spinal cord to the effectors.
Inter neurons are the neurons that convert the sensory stimuli into motor stimuli. Such neurons
are located in the brain and spinal cord.
15.7 Central Nervous System
The central nervous system consists of the brain and spinal cord. The brain and spinal
cord consists of white matter and gray matter. The white matter contains bundles of axons,
each coated with a myelin sheath, and the gray matter consists of masses of cell bodies and
dendrites, each covered with synapses.
meninges /ˈmə'nɪndʒi:z/ - the three membranes that surround the brain and spinal cord
synapse /ˈsaɪnæps/ - a connection between two nerve cells
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A. Human Brain
The human brain is a highly developed organ which acts as the highest co-ordinating center
in the body. It is a hollow organ located inside the skull. It is protected by a bony box called
cranium. In an adult human being, the brain weighs about 1200-1400 grams and contains
about 10,000 million nerve cells. The brain remains surrounded by three protective membranes
called meninges (singular–menix). These layers are - dura mater (outer tough and protective),
arachnoid mater (middle and delicate) and pia mater (inner thin and transparent layer).
The space between the arachnoid and pia mater is filled with cerebrospinal fluid. This fluid
protects the brain from mechanical shocks. Twelve pairs of cranial nerves arise from the brain.
Cerebrum
Corpus callosum
Mid brain Cerebellum
Pons varoli
Medulla oblongata
Spinal cord
Fig. 15.4 Structure of human brain
The brain consists of three regions– fore brain, mid brain and hind brain. The fore brain
includes cerebrum and olfactory lobes. The hind brain consists of three centres called pons
varoli, cerebellum and medulla oblongata.
1. Fore Brain
The fore brain is the anterior region of the brain. It consists of two main parts, olfactory lobes
and cerebrum.
Olfactory lobes consist of a pair of very small, club-shaped bodies present in the ventral region
of the brain. Olfactory lobes act as the center of smell.
Cerebrum - structure and functions
The cerebrum is the largest part of the brain. It occupies about 80% of the total weight of the
brain. It is a dome-shaped part, which is divided into right and left cerebral hemispheres
by a deep median longitudinal groove called the corpus callosum. It transmits information
from one hemisphere to another. The cerebral hemispheres are covered by a thin layer of
gray, matter called cerebral cortex. The cortex is folded to form convolutions. The folds divide
the cortex into four lobes: frontal, parietal, temporal and occipital. The inner portion of the
olfactory /ɑlˈfækteri/ - connected with the sense of smell
convolution /ˌkɒnvəˈluːʃn/ - a twist or curve
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cerebrum consists of white matter, which consists of axons of neurons.
There are specific regions in the cerebrum for each kind of stimulus and its response. The
frontal lobe of the cerebrum is the region for speech, facial and muscular activities and higher
mental activities.
The parietal lobe is the region for taste, smell, touch, temperature and conscious association.
The temporal lobe is the region for auditory reception (hearing), and the occipital lobe is the
region for visual reception (sight).
In the cerebrum, there are some areas in each lobe called association areas, which control the
thinking and memory. These association centers (areas) store information and experiences.
Motor area
Higher Touch Vision
mental Smell
abilities Taste
Speech
Hearing
Fig.15.5 Areas of various functions of cerebrum
Functions
i. The cerebrum governs mental abilities like thinking, learning, reasoning,
memorizing and intelligence.
ii. It controls feelings of love, admiration and hatred.
iii. It also controls the will, anger, mood, emotions and speech.
iv. It enables us to observe things around us with the help of the sense organs.
2. Mid Brain
The mid-brain is a thick–walled structure which constitutes a small middle portion of the
brain. It is located between the cerebrum and pons varoli. It connects the anterior region of the
brain to the posterior region.
Functions
i. The mid-brain controls reflex movements of the head, neck and trunk in response
to the visual and auditory stimuli.
ii. It also controls the reflex movement of the eye muscles, change in pupil size and
shape of the eye lens.
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3. Hind Brain
It forms the posterior region of the brain. The hind brain consists of three main centers, viz.
cerebellum, pons varoli and medulla oblongata.
Cerebellum
Cerebellum is the second largest part of the brain, which occupies 10% of the total weight of
the brain. It consists of two deeply convoluted hemispheres. It is situated below the posterior
portion of the cerebrum and behind the pons varoli. A small injury to the cerebellum causes
dizziness, which disturbs the body balance.
Functions
i. The cerebellum maintains equilibrium (body balance) and controls posture.
ii. It makes body movements smooth, steady and co-ordinated.
ii. It regulates and co-ordinates the contraction of voluntary muscles, i.e., muscular
tone.
Pons varoli Fact File - 2
Pons varoli is located between the mid-brain and • Alcohol affects the cerebellum.
medulla oblongata. It forms the brain stem on the So a person cannot walk
floor of the hind brain. It forms a bridge of transverse properly after having alcohol.
nerve tracts from the cerebrum to the cerebellum.
Functions
i. The pons varoli serves as a relay station carrying signals from the cerebrum to the
cerebellum.
ii. It regulates respiration.
Medulla oblongata
The medulla oblongata is the lowermost part of the brain. It is located between the pons varoli
and upper end of the spinal cord. It encloses a cavity called the fourth ventricle. It contains
vital reflex centers like the cardiac centre and centers for coughing, sneezing, swallowing,
vomiting, etc. Damage to the medulla oblongata causes instant death.
Functions
i. The medulla oblongata controls breathing, blood pressure and heart beat.
ii. It acts as the regulating center for coughing, sneezing, swallowing, vomitting,
hiccupping, etc.
iii. It controls activities of the digestive tract, peristalsis, secretion of saliva, hormones
and enzymes.
iv. It controls contraction and relaxation of blood vessels.
peristalsis /ˌperɪˈstælsɪs/ - the wave-like movements of the intestine caused when the muscles contract and relax
ganglion /ˈɡæŋɡliən/ - a mass of nerve cells
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Major functions of the human brain
i. The brain receives information carrying impulses from all the sense organs of the
body.
ii. It responds to the impulses by sending its own instructions through the motor
nerves to the effectors.
iii. The brain stores information so that behavior can be modified according to past
experience.
iv. The brain co-ordinates bodily activities so that the mechanism and chemical
reactions of the body work together efficiently.
v. The brain correlates the various stimuli from the various sense organs and
produces the most appropriate and intelligent response.
B. Spinal Cord
The spinal cord is a long, cylindrical structure that arises from the medulla oblongata of
the brain and passes through the neural canal of the vertebral column. The spinal cord is
protected inside the bony cage of the vertebral column. It is protected by the spinal meninges
and cerebrospinal fluid, which cushions the cord by acting as a shock absorber.
Each vertebra has an opening on its left and right side to let spinal nerves pass through. These
nerves extend into the body forming the peripheral nervous system. There are 31 pairs of
spinal nerves. Each spinal nerve consists of a dorsal root containing sensory neurons and a
ventral root containing motor neurons. The outer part of the spinal cord contains white matter
whereas the inner part contains gray matter. A group of nerves made of gray matter is found
near the spinal cord, which is known as ganglion. It communicates with the brain and spinal
cord.
Note: Any injury or shock to the spinal cord due to any disease or accident can cause
paralysis of the body below the point of injury.
Functions of spinal cord
i. The spinal cord connects a large part of the peripheral nervous system to the brain.
ii. It controls reflex actions.
15.8 Reflex Action
A spontaneous, mechanical and automatic response to a stimulus controlled by the spinal
cord without the involvement of the brain is called reflex action. Watering of mouth at the
sight of tasty food, immediate withdrawal of the hand after touching a hot object or pin prick,
blinking of the eyes in response to a foreign particle that has entered the eye, etc. are some
examples of reflex action. A reflex action is an automatic response to a stimulus. In a reflex
action, we are unaware that anything is going to happen to us.
spontaneous /spɒnˈteɪniəs/ - happening naturally, without being made to happen
BIOLOGY Oasis School Science - 10 269
Relay or internuncial neuron Synapse
(conducts impulses through Dorsal root of the
spinal nerve
the gray matter)
Ventral root of
Motor fibre (conducts Sensory fiber (conducts spinal nerve
impulses from the spinal impulses to the spinal cord) Spinal nerve
cord to the effector organ) Effector organ
Stimulated receptor
organ in the skin
Fig.15.6 Reflexaction and its path (reflex arc)
15.9 Reflex Arc
A reflex arc is the pathway followed by the sensory and motor nerves in a reflex action. The
major components of a reflex arc are as follows:
i. Sensory (receptor) organ: It perceives the stimulus.
ii. Sensory (afferent) nerve: It carries message from the receptor organ to the spinal cord.
iii. Internuncial or relay neurons of the spinal cord: These neurons transmit impulses
from afferent neurons to efferent neurons.
iv. Efferent (motor) nerve: It carries message from the spinal cord to the effector
organs.
A simple reflex arc consists of only one sensory neuron and one motor neuron. In this process,
stimulus is received by a sensory neuron which generates the impulse, and the neuron carries
the impulse towards the spinal cord along the dorsal root. Then the impulse arrives at the
nerve endings of the sensory neurons in the spinal cord, and the nerve endings release the
neurotransmitter. The impulse passes across the relay neuron to the motor neuron away from
the spinal cord along the ventral root, which carries the impulse out to an effector, such as a
muscle. Then the effector responds by contraction.
The sequence of events in a reflex arc can be summarized as follows:
Stimulus Receptors Sensory neuron
(Hot object) (Sensory cells)
Response Spinal cord
Effectors Motor neuron
(muscle)
enzyme /ˈenzaɪm/ - a substance produced by living beings which helps in chemical change, itself, however
remaining, unchanged
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Synapse
A synapse is the loose connection between the axon ending of one nerve cell and cell body
of the next cell. It can also be defined as the junction through which signals travel from one
neuron to another. [Please see fig.15.6] The major functions of a synapse are given below:
i. A synapse allows information to pass from one neuron to another.
ii. It allows the adjoining neuron to be excited.
iii. It amplifies a signal.
Ganglia
Ganglia are the groups of small nervous tissues located near the spinal cord. They are made
up of grey matter. They establish communication between the spinal cord and the brain.
15.10 Peripheral Nervous System
This nervous system consists of nervous tissues that communicate between the brain and
different parts of the body. The nervous tissues of the peripheral nervous system are of two
types. They are as follows:
1. Cranial nervous tissue: The nervous tissues that originate from the brain are called
cranial nervous tissues. Twelve pairs of cranial nerves originate from the brain. These
nerves communicate between the brain and different organs located in the head, such as
eyes, ears, nose, tongue, etc.
2. Spinal nervous tissue: The nervous tissues that originate from the spinal cord and
spread to various body parts are called spinal nervous tissues. Thirty one pairs of nerves
originate from the spinal cord. These nerves help to communicate between the brain,
spinal cord and different parts of the body.
15.11 Autonomic Nervous System
The nervous system that controls certain muscles and glands while sleeping or waking up
is called the autonomic nervous system. It is of two types: sympathetic nervous system and
parasympathetic nervous system.
The sympathetic nervous system increases the activities of the heart, stomach, lungs, intestine,
urinary bladder, etc.
The parasympathetic nervous system brings the activities of the heart, stomach, lungs, intes-
tine and urinary bladder to normal condition.
Sympathetic and parasympathetic nervous systems act in a reverse manner. For example, when
an accident occurs suddenly, the sympathetic nervous system increases the heart beat and
blood pressure whereas the parasympathic nervous system brings them to normal condition.
15.12 Endocrine System
The system formed by a group of endocrine glands is called the endocrine system. The
glands which do not have any duct and pour their secretion directly into the blood stream
are called endocrine glands. The endocrine system uses chemicals to communicate. These
chemicals are called hormones. The endocrine system plays an important role in controlling and
BIOLOGY Oasis School Science - 10 271
co-ordinating the functions of various organs and systems of the body by producing various
types of hormones.
Hormones
Hormones (Gk., hormones– to set in motion) are the chemical messengers (regulators) which
control, co-ordinate and integrate the functions of various organs of the body. Hormones are
synthesized and secreted by the endocrine glands. Hormones are released into the blood
stream and travel elsewhere in the body to the target organs, upon which they act.
The general properties of hormones are as follows:
i. Hormones act as chemical messengers to control and regulate metabolic activities,
growth and development of a body.
ii. Hormones are specific in function. They act only on target organs, tissues and
cells.
iii. Hormones are produced by the endocrine glands.
iv. Hormones are required in small amounts, and their effects are long lasting.
v. They are chemically proteins, steroids or amino acids.
Functions of hormones
i. Hormones stimulate and control various physiological and metabolic activities of
the body.
ii. They regulate growth and reproduction.
iii. They synthesize, store and utilize various substances like glucose.
iv. They conserve water and minerals in the body.
Reasonable Fact-1
Hormones are called chemical messengers, why?
Ans: Hormones are the chemicals carried to all parts of the body through blood
circulation to bring about the harmonious working of the body. So hormones are
called chemical messengers.
There are a large number of glands present in the human body. Among them, some are exocrine
(having ducts) and some are endocrine (ductless) glands. The exocrine gland produces
enzymes and secretes its product into a duct, e.g., salivary gland, gastric gland, etc. Similarly,
endocrine gland produces hormones and it secretes its product directly into the blood stream,
e.g. pituitary gland, thyroid gland, etc.
Differences between Exocrine and Endocrine Glands
S.N. Exocrine glands S.N. Endocrine glands
1. They have ducts. 1. They do not have ducts.
2. They secrete enzymes. 2. They secrete hormones.
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3. They discharge their secretions 3. They discharge their secretion directly
through the duct. into the blood stream.
4. They are located near the site of 4. They are present away from the site of
action. action.
Examples: Salivary gland, intestinal Examples: Thyroid gland, adrenal gland,
glands, etc. etc.
The endocrine glands present in the human body are given below:
i. Pituitary gland ii. Thyroid gland
iii. Parathyroid gland iv. Pancreas
v. Adrenal gland vi. Testes (only in males) and
vii. Ovaries (only in females)
Endocrine glands are located in the head, neck and trunk of the human body. The position of
various endocrine glands of the human body is shown in the given figure.
Pituitary gland
Thyroid gland
Parathyroid gland
Adrenal gland
Pancreas
Ovary (In female)
Testis (In male)
Fig.15.7 Various endocrine glands in the human body
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1. Pituitary gland
The pituitary gland is a small (about 1cm in diameter) oval gland of the size of a pea. It is
located just below the mid-brain and attached to the lower surface of the brain by a short
slender stalk called infundibulum.
The anterior lobe of the pituitary gland secretes six hormones. These hormones are
Growth hormone (GH), Thyroid stimulating hormone (TSH), Follicle stimulating
hormone (FSH), Trophic hormone (TH), Prolactin hormone (PRL) and Luteinizing
hormone (LH). Similarly, the posterior lobe of the pituitary gland secretes two hormones:
Oxytocin hormone and Vasopressin or Antidiuretic hormone (ADH).
Reasonable Fact-2
The pituitary gland is called the master gland, why?
Ans: The pituitary gland controls and stimulates many activities of the body, and the
secretion of other endocrine glands. So it is also called the master gland.
The following table shows the hormones secreted by the pituitary gland, functions of
these hormones and disorders:
Pituitary gland Hormones secreted Major functions
The anterior lobe of the pituitary 1. Growth hormone (GH) This hormone controls the overall
gland produces six hormones. or Somatotrophic hormone development or growth of muscles
(STH) and bones. It increases the rate of
protein synthesis.
Note: Hypoactivity (deficiency) of GH in childhood causes dwarfism whereas hyperactivity
(oversecretion) of GH causes gigantism. The oversecretion of GH in adults leads to overgrowth of the
jaw bone and bowing of the backbone. This condition is called acromegaly.
2. Thyroid stimulating This hormone stimulates the
hormone (TSH) growth and functioning of the
thyroid gland.
3. Follicle stimulating
hormone (FSH) In males, it stimulates
spermatogenesis, i.e. the formation
of sperms. In females, it stimulates
the development of follicle in the
ovaries to develop into mature
eggs. It also stimulates the ovaries
to produce oestrogen.
dwarfism /dwɔːfɪzəm/ - the medical condition of being a dwarf
gigantism /ˌdʒaɪˈɡæntɪzəm/ - a condition in which somebody grows to an unusually large size
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4. Trophic hormone (TH) This hormone regulates the
secretion of hormones the from
the endocrine glands like thyroid,
adrenal, testes/ovaries.
5. Prolactin hormone (PRL) This hormone stimulates the
development of the mammary
glands and milk production in
females.
6. Luteinizing hormone (LH) This hormone stimulates the
secretion of the male hormone,
i.e. testosterone in males whereas
it stimulates the secretion of
oestrogen and progesterone in
females.
The posterior lobe of the 1. Oxytocin hormone This hormone controls the vigorous
pituitary gland secretes two contraction of the uterine muscles
hormones. during childbirth. It also helps in
milk ejection from the mammary
glands (breasts) of a nursing
mother.
2. Vasopressin or Antidiuretic This hormone controls the
hormone (ADH) reabsorption of water in the
kidney tubules. It increases the
blood pressure by constricting the
arterioles.
Note: Hypoactivity of ADH causes diabetes insipidus in which the urine does not contain sugar. In
this disease, an individual feels thirsty due to the loss of water as the person urinates frequently.
2. Thyroid gland
The thyroid gland is located in the neck region in front of the trachea just below the
larynx. It has two lateral lobes, one on either side of the trachea. The two lobes are
connected by a narrow mass of tissue called isthmus.
The thyroid gland secretes two hormones, viz. Thyroxine and Calcitonin.
Cricoid cartilage
Thyroid gland
Parathyroid glands
Fig. 15.8 Thyroid and parathyroid glands
BIOLOGY Oasis School Science - 10 275
Functions of thyroxine
i. It stimulates the rate of cellular oxidation and metabolism.
ii. It regulates the growth and development of the body, ossification of the bones and
mental development.
iii. It regulates the activities of the nervous system.
Lack of iodine in the diet, or hyposecretion of thyroxin, causes simple goitres. In such a
condition the thyroid gland enlarges and becomes visible as a swelling in the neck. Similarly,
hyposecretion of thyroxin causes roughness or puffiness of the skin, falling of hairs, obesity,
stammering and physical and mental weakness. Hypersecretion of thyroxine causes mental
imbalance, bulging eyes, digestive disorders, loss of weight and excessive excitement.
Functions of calcitonin
i. This hormone regulates the level of calcium and phosphate in the blood.
ii. It facilitates calcium absorption and release by the bones.
3. Parathyroid gland
Two pairs of parathyroid glands are present on the dorsal side of the thyroid gland.
One pair of parathyroid glands is located on each lateral lobe of the thyroid gland. The
parathyroid gland is oval in shape. It secretes a hormone called parathormone (parathy-
roid hormone).
Functions of parathormone
i. This hormone controls the exchange of calcium between the blood and bones.
ii. This hormone increases the level of calcium in the blood.
Notes:
i. If parathyroid glands are removed from the body, wrinkles are seen on the
hands and face due to the lack of calcium in the blood.
ii. Undersecretion of the parathormone hormone causes painful jerk of the
voluntary muscles.
iii. Oversecretion of the parathormone hormone results in softening of the
bones that could be fractured easily. It may also cause parathyroid tumor and
kidney stone.
4. Adrenal gland
In the human body, two adrenal glands are located, one on the top of each kidney in
the form of a crown. It is a cream-colored gland. The adrenal gland secretes adrenalin
hormone at the time of emergency, which prepares the body to meet or cope with any
emergency situation for flight, fright or fight. So adrenalin is called an emergency
hormone, and the adrenal gland is called an emergency gland.
Function of adrenalin
Adrenalin hormone controls fear, anger, blood pressure, emotions, heart beat, respiration
and relaxation of the voluntary muscles.
stammer /ˈstæmə(r)/ - to speak with difficulty,repeating sounds or words,and often stopping before saying things correctly
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Reasonable Fact-3
Adrenalin is called an emergency hormone, why?
Ans: Adrenalin hormone is secreted by the adrenal gland at the time of emergency, which
prepares the body to face any emergency situation for flight, fright or fight. So adrenalin is
called an emergency hormone.
Reasonable Fact-4
Some adult women may develop facial hair. Give reason.
Ans: Some adult women may develop facial hair due to the overgrowth of the adrenal cortex.
When adrenal glands are removed from the body then:
i. Body will not be able to face emergency conditions (stress and strain).
ii. Secondary sexual characteristics will be poorly developed in males.
iii. Body will not be able to regulate carbohydrate, protein and fat metabolism.
iv. Kidneys will fail to retain sodium, etc.
Hyposecretion of adrenalin hormones results in weakness, low blood pressure, less
sugar content in blood, nausea, unconsciousness, etc.
Feminine characteristics like enlargement of the breasts develop in adult males when
the adrenal cortex increases. Similarly, masculine characteristics like a hoarse sound,
development of a beard, etc. develop in adult females when the adrenal cortex increases.
5. Pancreas
Thepancreasislocatedposteriortothestomachattachedtotheduodenumintheabdominal
region. It is pale gray in color and 12-15 cm in length. This gland has two parts, viz.
(i) exocrine part (having duct) and (ii) endocrine part (without duct). So, the pancreas is
also called a double gland or mixed gland.
The endocrine part of the pancreas produces three hormones. They are insulin, glucagon
and somatostatin.
Functions of insulin
i. Insulin regulates blood sugar level by regulating conversion of glucose into glycogen.
ii. It also stimulates deposition of extra glucose in the form of glycogen in the liver
and muscle.
The hyposecretion of insulin causes diabetes mellitus. In this disease, there is high
concentration of glucose in the blood and urine, and the person feels hungry, thirsty and
weak. It also results in increased volume of blood, loss of weight and delay in wound healing.
The hypersecretion of insulin causes insulin shock. In this condition, the sugar level in
the blood is reduced, the person becomes unconscious (frequently) and the brain may
enter into a coma.
Functions of glucagon
i. This hormone increases the sugar level in the blood.
ii. It stimulates the liver to convert glycogen into glucose.
gonad /ˈɡəʊnæd/ - a male sex organ that produces sperms or a female sex organ that produces eggs
BIOLOGY Oasis School Science - 10 277
Function of somatostatin
This hormone controls the secretion of insulin and glucagon.
Reasonable Fact-5
The pancreas is called a mixed gland, why?
Ans: The pancreas has an endocrine part to produce hormones and an exocrine part
to produce enzymes. So the pancreas is called a mixed gland.
6. Testes
Testes, i.e., male gonads are the oval organs situated in a small muscular pouch called the
scrotum outside the abdominal cavity of a man. Leydig cells, or interstitial cells, present
in the testes produce a male hormone called 'Testosterone'.
Functions of testosterone
This hormone controls the development of secondary sexual characteristics in males like
the enlargement of the penis and scrotum, growth of facial and pubic hair, enlargement
of the larynx, deeper voice, etc.
7. Ovaries
Ovaries, i.e., female gonads are the oval organs located in the lower abdominal cavity
of a woman near the kidneys.
Ovaries produce two female sex hormones–Oestrogen and Progesterone.
Function of oestrogen
This hormone controls the development of the female sex organs and female features
like feminine voice, soft skin and breasts (mammary glands), hair pattern, etc.
Functions of progesterone
i. This hormone plays an important role in ovulation, i.e., release of ovum from the ovary.
ii. This hormone also helps in the maintenance of pregnancy.
Reasonable Fact-6
Endocrine glands are very important even if they are small in size. Give two reasons.
Ans: Endocrine glands are very important even, if they are small in size because:
(i) Undersecretion or oversecretion of hormones produced by these glands directly affects the
growth and development of the body.
(ii) Any disturbance in the function of these glands results in dwarfism, gigantism, obesity,
sterility, etc.
Activity 2
• Take a white cardboard paper and draw a figure showing various endocrine glands
present in the human body.
• Put suitable colors in various glands and also write down the hormones produced
by these glands.
278 Oasis School Science - 10 BIOLOGY
SUMMARY
• The nervous system is a network of organs and tissues that controls and co-ordinates
all the activities of the body with the help of nerves.
• A nerve is a long, slender, thread-like structure which arises from the brain and the
spinal cord.
• Neuron or a nerve cell is a highly specialized cell which acts as the structural and
functional unit of the nervous system.
• An impulse is a wave of electrical disturbances that sweeps over the nerve cells,
e.g., impulse of touch, impulse of cold, etc.
• The human brain is a highly developed organ which acts as the highest co-
ordinating center in the body. It is a hollow organ and located inside the skull,
which remains protected by a bony box called the cranium.
• The spinal cord is a long cylindrical structure that arises from the medulla oblongata
and passes through the neural canal of the vertebral column.
• A spontaneous, mechanical and automatic response to a stimulus controlled by the
spinal cord without the involvement of the brain is called reflex action.
• The reflex arc is the pathway followed by the sensory and motor nerves in a reflex
action.
• The system formed by a group of endocrine glands is called the endocrine system.
• Stimulus is the change in the environment or environmental factors to which the
organisms respond and react.
• The response shown by organisms towards or away from a stimulus is called
reaction. It may be positive or negative.
• The nervous system that controls certain muscles and glands while sleeping or
waking up is called the autonomic nervous system.
• The system formed by a group of endocrine glands is called the endocrine system.
The glands which do not have any duct and pour their secretion directly into the
blood stream are called endocrine glands.
• Hormones (Gk., hormones– to set in motion) are the chemical messengers
(regulators) which control, co-ordinate and integrate the functions of various
organs of the body.
• The exocrine gland produces enzymes and secretes its product into a duct,
e.g., salivary gland, gastric gland, etc. Similarly, the endocrine gland produces
hormones, and it secretes its product directly into the blood stream, e.g., pituitary
gland, thyroid gland, etc.
• The adrenal gland secretes adrenalin hormone at the time of emergency, which
prepares the body to meet or cope with any emergency situation for flight, fright or
fight. So adrenalin is called an emergency hormone, and the adrenal gland is called
an emergency gland.
• Adrenalin hormone controls fear, anger, blood pressure, emotions, heart beat,
respiration and relaxation of the voluntary muscles.
BIOLOGY Oasis School Science - 10 279
Exercise
Group-A
1. What is stimulus and reaction?
2. What is nervous system?
3. Write any two functions of nervous system.
4. Write any two functions of human brain.
5. What is cerebrospinal fluid? Write down its main function.
6. Write down two functions of cerebrum.
7. What is spinal cord? Where is it located?
8. Write down the major functions of spinal cord.
9. How many pairs of nerves are originated from the spinal cord?
10. What is a neuron?
11. What is sensory nerve?
12. Write down the function of motor nerve.
13. What is reflex action? Give an example.
14. What is endocrine system?
15. How many types of glands are there? Name them.
16. Define exocrine gland with any two examples.
17. What are endocrine glands?
18. Name any two endocrine glands found in our body.
19. What is a hormone?
20. Where is pituitary gland located?
21. Write the name and function of the fluid found in brain?
22. Write any two functions of cerebrospinal fluid.
23. Write any two functions of medulla oblongata.
24. How many numbers of spinal nerves are present in human body?
25. Write the name of hormone and gland that controls blood sugar.
26. Which hormone balances calcium in bone?
27. Name the hormone secreted by male gonads. Mention one important function of this
hormone.
28. What is the function of motor nerve?
29. Name the hormone secreted by pancreas. Mention one important function of this
hormone.
280 Oasis School Science - 10 BIOLOGY
Group-B
1. Write any two differences between sensory neuron and motor neuron.
2. Write any two differences between axon and dendrites.
3. Write any two differences between cerebrum and cerebellum.
4. Write any two differences between exorine gland and endocrine gland.
5. Brain is considered as the centre of all sense, why?
6. Pituitary gland is called master gland, why?
7. Hormones are called chemical messengers, why?
8. Adrenal gland is called an emergency gland, why?
9. Pancreas is called a mixed gland, why?
10. ‘Endrocrine glands are very important even they are small in size’. Give any two reasons
to justify this statement.
Group-C
1. Draw a neat diagram showing the structure of human brain.
2. Write any three functions of nervous system.
3. Write any three functions of cerebrum.
4. Write any three functions of medulla oblongata.
5. Write any three characteristics of endocrine glands.
6. Name the hormones produced by pituitary gland and mention the major functions of
each hormone.
7. Write name of the hormone secreted by thyroid gland and its one function. What
symptom is seen due to over secretion of that hormone?
8. Write down one function of each thyroxin and insulin hormone. Also, give the name of
glands that produce thyroxin and insulin.
Group-D
1. Write one function of each of parts A, B, C and D shown in the diagram of human brain.
A
B
C
D
E
F
2. Name the parts A, B, C and D shown in the given diagram of neuron.
Also, write down the function of A and D.
BIOLOGY Oasis School Science - 10 281
3. Name the glands (A to F) shown in the given diagram. Also, name a hormone produced
by each of them.
A
B
C
D
E
F
4. Write down the position of the following glands in our body. Name the hormones
produced by them. Also, write down the functions of each hormone.
a) Thyroid gland
b) Parathyroid gland
5. Write down the position of the following glands in our body. Name the hormones
produced by them. Also, write down the functions of each hormone.
a) Pancreas
b) Adrenal gland
6. Write down the position of the following glands in our body. Name the hormones
produced by them. Also, write down the functions of each hormone.
a) Testes
b) Ovary
282 Oasis School Science - 10 BIOLOGY
UNIT 16 Estimated teaching periods
Theory 5
Practical 1
BLOOD CIRCULATORY
SYSTEM IN HUMAN BODY Karl Landsteiner
(1868-1943 AD)
Objectives
After completing the study of this unit, students will be able to:
• describe the structure (composition) and functions of blood.
• describe the circulation of blood in the human body with figures.
• give general introduction to blood pressure, blood sugar and uric acid.
16.1 Introduction
In the human body, a rapid supply of oxygen, nutrients, hormones, etc. to various tissues and
disposal of waste products is an essential requirement. So, the human body has a specialized
system called the blood circulatory system. It is an organ system in the human body
responsible for transporting various materials inside the body with the help of blood. The
blood circulatory system in human body consists of three main parts: (i) Blood (circulatory
medium) (ii) System of blood vessels (arteries, veins and capillaries) and (iii) Heart (pumping
organ).
The circulatory system supplies food and oxygen to the cells of the body for survival. It
carries away carbon dioxide and other metabolic wastes from the cells. This system transports
various substances to - and - fro between different tissues of the body. It also helps to maintain
a balanced chemical composition in the body. This system is also responsible for maintaining
constant body temperature. In addition to the blood circulatory system, for the transport of
blood in human beings, there is another system called the lymphatic system.
In the blood circulatory system, the heart acts as a pumping organ. The arteries, veins and
capillaries act as tubes through which blood flows and the blood itself acts as a circulatory
medium.
16.2 Main Functions of Circulatory System
1. It transports oxygen, digested food materials and hormones to various parts of the body.
2. It transports waste materials produced in various tissues/organs for their elimination
from the body.
3. It regulates the body temperature, water and mineral content of the body.
viscous /ˈvɪskəs/ - thick and sticky; not flowing freely
erythrocyte /ɪˈrɪθrəsaɪt/ - RBC or red blood cell
BIOLOGY Oasis School Science - 10 283
16.3 Blood
Blood is a red-colored viscous and complex tissue fluid made up of plasma (55%) and
blood corpuscles (45%). The human body contains about 4.8 to 5.8 liters of blood. The blood
constitutes about 1/30 of the body's weight. The composition of human blood is given below:
Blood
Plasma Blood corpuscles
55% 45%
Red blood corpuscles White blood corpuscles Blood platelets
(RBC or erythrocytes) (WBC or leucocytes) (Thrombocytes)
Properties of blood
1. Blood is a red, viscous and complex fluid connective tissue.
2. It is salty in taste and slightly alkaline in nature with a pH range of 7.3 to 7.5.
3. The specific gravity of blood is 1.05 to 1.06.
Composition of Blood
Blood contains three types of cellular elements: (i) Red blood corpuscles, (ii) White blood
corpuscles and (iii) Platelets that move about in a clear yellowish fluid called plasma. The
plasma occupies about 55% and cellular elements (blood corpuscles) occupy about 45% of the
blood by volume.
Plasma
Red blood cell Fact File - 1
White blood cell
Platelet • Blood constitutes about 1/30
of the body weight.
Fig.16.1 Blood film under a compound microscope
• Blood is alkaline in nature
but salty in taste.
anaemia /əˈniːmiə/ - a medical condition having too few RBCs in the blood
leucocyte /ˈluːkəsaɪt/ - WBC or white blood cell
284 Oasis School Science - 10 BIOLOGY
Plasma
Plasma is a transparent clear yellowish liquid. It forms about 55% of the blood volume.
Plasma contains about 90% water, 8% proteins (albumin, globulin and fibrinogen) and
2% other dissolved substances like minerals, carbohydrates, salts, antibodies, hormones,
respiratory gases and waste products. Plasma transports all these dissolved substances
from one part of the body to another. Red blood cells, white blood cells and platelets are
immersed in the plasma.
Functions of Plasma
1. Plasma transports digested food to different parts of the body.
2. It transports waste materials like carbon dioxide, urea, etc. to their respective sites
for excretion.
3. It regulates the body temperature, amount of water and other chemicals in the
body.
4. It transports hormones secreted by the endocrine glands to various parts of the
body.
5. Fibrinogen present in plasma plays an important role in blood clotting.
Red blood cells or Erythrocytes Fig.16.2 Red blood cells
Erythrocytes (RBCs) are red colored (erythros-
red), biconcave and enucleated (without nucleus)
disc-like structures present in the plasma. They
are thick and rounded at the peripheral region
and flat in the center. Erythrocytes are very small
in size (about 7 µ in diameter). An erythrocyte
is bound by an elastic and a semi-permeable
plasma membrane. Red blood cells appear red
due to the presence of haemoglobin, i.e. iron-
containing pigment.
Fact File - 2
The number of RBCs is about 30% more in persons living in the Himalayan region than
those living in the Terai region.
Red blood cells are produced in the bone marrow of bones such as ribs, vertebrae and skull
bones. The average life span of red blood cells is about 120 days. They are destroyed in the
liver. The number of RBCs ranges from 5 – 5.5 million per cubic millimeter in an adult man
and 4.5 – 5 million per cubic millimeter in an adult woman.
Note: In infants, the count of RBCs is 6–7 million / mm3 whereas in a foetus it is 7.8 million
/ mm3. In the first ten days of the post natal life, a large number of RBCs are destroyed. This
is one of the causes of jaundice in a new born.
BIOLOGY Oasis School Science - 10 285
Functions of Erythrocytes (RBCs)
1. Erythrocytes transport oxygen from the lungs to the tissues and carbon dioxide
from the tissues to the lungs.
2. Erythrocytes maintain the viscosity of blood and ion-balance.
Haemoglobin
Haemoglobin is a red-colored respiratory pigment. It is made up of an iron-containing pigment
called haemin (4%) and a protein called globin (96%). The iron content of haemoglobin is
about 0.34%, and about 3 g of iron is present as haemoglobin in the total blood of an adult.
Haemoglobin combines with oxygen and forms oxyhaemoglobin. Similarly, it combines with
carbon dioxide and forms carboxyhaemoglobin.
Functions
1. Haemoglobin plays an important role in oxygen and carbon dioxide transport.
2. It helps to balance the acid-base balance of the blood.
Anaemia
When there is a long-term decrease in the number of RBCs or in the amount of haemoglobin
or in both, the condition is called anaemia. It is mainly caused due to malnutrition. The major
symptoms of anaemia are as follows:
i. Loss in weight
ii. Loss in appetite
iii. Slow and retarded growth
iv. Pale and dull-colored skin
Reasonable Fact-1
A person suffering from anaemia feels tired after walking for a short period, why?
Ans: A person suffering from anaemia has deficiency of red blood cells, or haemoglobin
in his/her blood. So, adequate amount of oxygen cannot be supplied to the body to
release energy. As a result, a person suffering from anaemia feels tired after walking for
a short period.
White blood cells or Leucocytes
White blood corpuscles (WBCs), or leucocytes, are larger (8 – 15 µ in diameter) and irregular
cells having a nucleus. They are capable of amoeboid movement. Leucocytes are of two types:
granulocytes (having granules in their cytoplasm and lobed nucleus) and agranulocytes
(without granules in their cytoplasm and unilobed nucleus). Neutrophils, eosinophils and
basophils are granulocytes whereas monocytes and lymphocytes are agranulocytes.
malignant /məˈlɪɡnənt/ - that cannot be controlled and is likely to cause death
leukaemia /luːˈkiːmiə/ - a serious disease in which too manyWBCs are produced, causing weakness and death
286 Oasis School Science - 10 BIOLOGY
Neutrophil Eosinophil Basophil
Monocyte
Lymphocyte
Fig. 16.3 Various types of leucocytes (WBCs)
Leucocytes (WBCs) are produced by the stem cells in the red bone marrow and lymph nodes.
The average total number of WBCs is 4000 - 11000 per cubic millimeter. They live for a few
hours to a few days. They are destroyed in the liver, spleen and at the site of infection.
Functions of WBCs
1. WBCs help in destroying solid substances like bacteria by engulfing them, and
hence they defend the body from various diseases.
2. They fight against germs (microbes) and destroy the damaged cells by phagocytosis.
3. They also help in the formation of antibodies, which neutralize or kill the germs
that enter the body.
Leukaemia and Leucopenia
Leukaemia is a malignant disease of one or more variety of leucocytes, the number of which
are greatly increased. It is caused due to enormous increase in the WBCs at the cost of RBCs.
This condition is also called blood cancer.
Leucopenia is a condition in which there is a decrease in the WBC count below 4000 per mm3.
It is caused due to the fall in neutrophil cells.
Reasonable Fact-2
White blood cells are called soldiers of the body. Why?
Ans: White blood cells protect the body from the attack of disease causing germs
(pathogens) and other harmful foreign materials. Therefore, white blood cells are called
soldiers of the body.
Fact File - 3
WBCs are the largest blood corpuscles whereas platelets are the smallest.
coronary /ˈkɒrənri/ - connected with the heart, particularly the arteries that take blood to the heart
BIOLOGY Oasis School Science - 10 287
Thrombocytes or Platelets
Thrombocytes are colourless, oval or round, non-nucleated cytoplasmic fragments formed
from giant cells of the bone marrow. They are found floating in the plasma. The number of
platelets varies from 2.5 lakh to 4.5 lakh per cubic millimeter. The average diameter of platelets
is about 2.5 µ. They live for about 5 to 10 days and are destroyed in the spleen.
Function of thrombocytes
Thrombocytes play an important role in the coagulation or clotting of blood. They release
a chemical called thromboplastin, which initiates the process of clotting the blood.
Fact File - 4
Blood does not clot when inside the blood vessels due to the presence of a strong, natural
anticoagulant called heparin or antiprothrombin produced in the liver. But when platelets
come in contact with the environment, they burst and liberate thromboplastin, which helps
in the formation of an enzyme prothrombinase. This enzyme inactivates heparin and it
converts inactive prothrombin into its active form, thrombin. Therefore, blood clots only
when it escapes the blood vessels but does not clot inside the blood vessels.
Activity -1
To study the blood film under a compound microscope
• Clean a finger tip of your friend with a spirit swab.
• Prick the fingertip with a sterilized lancet. Don’t use that lancet to prick another
finger tip as it may transmit dangerous diseases.
H•a emaPonuopttahhedirlriosalpidoef blood on a one end of a slide, spread it throughout the slide by using
and allow it to dry.
It•is a gePnuettaicfdewisedarsoepins owfhLiecihshthmeabnl’ososdtalionsoens iittsaanbdilidtyrytoitcfloort,alefeawdinmgintoutselos.w and persistent
bdli•esee dasineW.g.aIsthisthaesselxid-leinwkietdh dreicsteisllseivdewdaitseerasaendfooubnsderivnemitaulensd.eTrhaecfoemmpaoleusnadremciacrrorisecrospoef. this
• Draw a neat and labeled figure and prepare a short report.
Clotting of blood
The blood, when exposed to air, changes into a jelly-like mass as a result of a series of changes.
This process of solidification of blood is called clotting or coagulation of blood. The clotting
time of blood is normally 4 to 10 minutes.
Table: Various types of blood cells, their number and life span
Name of blood cells No. in 1mm3 volume of Life span
blood
1. Erythrocytes or RBCs 4.5 – 5.5 million 120 days
2. Leucocytes or WBCs 4000 – 11000 Few hours to few days
a. Granulocytes 1–4 days
288 Oasis School Science - 10 BIOLOGY
i. Eosinophils 60 – 300 8 – 12 days
ii. Neutrophils 4000 – 5000 6 hours to a few days
iii. Basophils 35 – 100 Few hours to few days
b. Agranulocytes Few months
i. Lymphocytes 1500 – 2000 Few hours to years
ii. Monocytes 200 – 700 Few months
3. Thrombocytes or Platelets 250000 to 400000 5 – 10 days
16.4 Functions of Blood
i. Transport of respiratory gases: Blood transports oxygen from the lungs to the tissues
and carbon dioxide from the tissues to the lungs.
ii. Transport of nutrients: The digested food materials are absorbed by blood at the site of
absorption (intestine) and transported to various parts of the body.
iii. Transport of waste products: The metabolic waste materials produced in the body are
transported by blood to the organs meant for their removal from the body.
iv. Transport of body secretions: Blood transports chemical secretions like hormones from
the site of their secretion to the targeted organ.
v. Regulation of body temperature: Blood helps to regulate the body temperature.
vi. Defense against infection: WBCs present in blood help to prevent the body against
infection.
vii. Prevention of blood loss: Prothrombin and fibrinogen proteins present in platelets and
plasma help in blood clotting at the site of injury. This prevents the loss of blood.
viii. Water balance: Blood maintains water balance in the body to a constant level.
16.5 Heart: Location, Shape and Size
The human heart lies near the middle of the thoracic cavity, between the two lungs. Two-third
of the heart is located in the left side of the thorax whereas one-third is located in the right side.
The heart is a hollow, conical organ made up of cardiac muscles. It is about the size of a fist of
the owner. It measures about 12 cm in length and 9 cm in breadth. The average weight of the
heart is about 300 grams in adults.
16.6 External Morphology
The human heart contains four complete chambers. It is divided into two halves (right half
and left half) by septa. Each half consists of two chambers: the upper, small-sized atrium or
pulmonary /ˈpʌlmənəri/ - connected with the lungs
vena cava /ˌviːnəˈkeɪvə/ - either of the two veins that carry deoxygenated blood to the heart
BIOLOGY Oasis School Science - 10 289
auricle and the lower, large-sized ventricle. The human heart remains enclosed in a double
layered membranous sac called pericardium. The space between two pericardial layers is
filled with a slippery fluid known as pericardial fluid. This fluid enables the heart to contract
smoothly, keeps tissues of the heart moist for proper beating and also protects the heart from
mechanical injury.
The atria (auricles) are demarcated externally from the ventricles by an irregular groove called
coronary sulcus. The atria form the upper smaller part of the heart whereas the ventricles
form the lower larger part. Two ventricles are demarcated externally from one another by an
oblique groove called interventricular sulcus which contains coronary blood vessels. Various
blood vessels entering and leaving the heart can be seen externally.
Superior vena cava Aorta
Pulmonary artery
Pulmonary veins Pulmonary veins
Right auricle Left auricle
Right ventricle
Left ventricle
Inferior vena cava
Pericardium
Fig.16.4 External structure of human heart
16.7 Internal Morphology
The longitudinal cross-section of the human heart shows two upper chambers called auricles,
two lower chambers called ventricles, great blood vessels entering and leaving the heart,
various apertures and valves.
The atria (right atrium and left atrium) are thin-walled chambers which are separated from
each other by a muscular wall called inter-auricular septum. The ventricles are thick-walled
chambers which are separated by a thick muscular wall called inter-ventricular septum. The
thickness of the walls in different chambers reflects their functions. The auricles are thinly
muscled as they pump blood to only short distances to the ventricles. The wall of the right
ventricle is more muscular than that of the auricles because it has to pump blood to a much
farther distance to the lungs. Similarly, the left ventricle has the thickest wall as it has to force
the blood all the way round the body.
valve /vælv/ - a structure in the heart or in a vein that lets blood flow in one direction only
superficial /ˌsuːpəˈfɪʃl/ - of or on the surface of something
290 Oasis School Science - 10 BIOLOGY
Superior vena cava Aorta
Pulmonary artery
Pulmonary artery
Pulmonary veins
Right auricle Left auricle
Pulmonary veins Pulmonary valve
Tricuspid valve Aortic valve
Bicuspid/mitral valve
Right ventricle Left ventricle
Inferior vena cava
Septum
Cardiac muscle
Fig.16.5 Internal structure of human heart
Various blood vessels enter and leave the heart. Three blood vessels are connected to the
right atrium. The superior vena cava brings deoxygenated blood from the upper region, i.e.
head, neck and upper limbs of the body whereas the inferior vena cava brings deoxygenated
blood from the lower region of the body. Similarly, coronary sinus brings deoxygenated blood
from the heart's wall. The left auricle is connected to two pairs of pulmonary veins, one pair
from each lung. Pulmonary veins bring oxygenated blood from the lungs to the left auricle.
Pulmonary aorta arises from the right ventricle and it transports deoxygenated blood to the
lungs for purification. Similarly, systemic aorta arises from the left ventricle and transports
oxygenated blood to various parts of the body except the lungs.
Four different types of valves are present in the human heart which regulate the flow of
blood within the heart and its passage. Two valves separate the auricles from the ventricles.
They are known as auriculoventricular valves. The tricuspid valve having three concentric
flaps is present between the right auricle and right ventricle whereas the bicuspid or mitral
valve is present between the left auricle and left ventricle. It has two concentric flaps.
Auriculoventricular valves allow the flow of blood from the auricles to ventricles and prevent
the back flow. Similarly, the aortic semilunar valve is present at the base of the aorta and the
pulmonary semilunar valve is present at the base of the pulmonary artery. Each semilunar
valve contains three flaps, shaped like a half moon.
Activity -2
To study the external and internal morphology of the mammalian heart
• Visit a butcher’s shop and buy a heart of a goat.
• Keep the heart in a dissecting tray, observe its external morphology and draw a neat
and labeled figure.
• Cut open the heart longitudinally and observe the internal parts carefully.
• Draw a neat and labeled figure showing the internal structure of the heart.
BIOLOGY Oasis School Science - 10 291
Reasonable Fact-3
The wall of the left ventricle is thicker than that of the right ventricle, why?
Ans: The left ventricle pumps out a large amount of blood to different parts of the body through the
aorta. For this, a great force is required, which is provided by its thick walls but the right ventricle
supplies blood only towards the lungs, which requires less force. Therefore, the wall of the left
ventricle is thicker than that of the right ventricle.
Reasonable Fact-4
The wall of the right ventricle is thicker than that of the right auricle, why?
Ans: The right ventricle pumps blood into the pulmonary artery forcibly whereas the
right auricle does not pump blood into the arteries. Hence, the wall of the right ventricle
is thicker than that of the right auricle.
Reasonable Fact-5
The right auricle is larger than the left auricle.
Ans: In the right auricle, impure blood of the whole body is poured through the superior
venacava and inferior vena cava whereas pure blood is poured into the left auricle from
the lungs through the pulmonary veins. Since a larger volume of blood is collected in the
right auricle than that of the left auricle, the right auricle is larger than the left auricle.
16.8 Blood Vessels
Blood vessels are the tubes or pipes through which blood flows. They form a system of channels
for blood circulation. There are three types of blood vessels, viz. arteries, veins and capillaries.
i) Arteries
Arteries are thick-walled blood vessels that carry blood away from the heart to
different parts of the body. All arteries carry oxygenated blood except the pulmonary artery,
which carries deoxygenated blood from the heart to the lungs.
Tunica interna
Tunica media
Tunica externa
Fig.16.6 Detailed structure of an artery
An artery has a narrow lumen whereas the wall is thick and elastic. The wall of the artery
is made up of three layers – the innermost tunica interna made up of thin and smooth
cells, the middle tunica media made up of the muscle and the outermost tunica externa
made up of elastic tissue. The branches of arteries are called arterioles.
292 Oasis School Science - 10 BIOLOGY
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Science and Environment 10
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