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GRYFFINDORS

BISCUIT

PRESENTATION

CHAPTER 7 :RESPIRATION

7.2 : The Respiratory Structures and BreathingMechanisms in Humans and Animals

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RESPIRATORY STRUCTURES

Breathing is the exchange of gases between an organism and the environmentand it takes place through specializedstructure called the respiratory structure.

The respiratory structures in humans and animals are shown in table below.

The respiratory structures of most organisms have the following three basic

characteristics :a.) Moist respiratory structures to facilitate the diffusion of oxygen and carbon

dioxide.

b.) Thin respiratory wall that is one cell thick to allow gaseous exchange to take

place at faster rate.

c.) A high total surface area to volume ratio helps to increase gaseous exchange.

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THE RESPIRATORY STRUCTURES AND

BREATHING MECHANISMS IN

ORGANISMS

PROTOZOA :

The respiratory surface of a unicellular organism is its entire

plasma membrane.

The unicellur organisms have high total surface area per

volume ratio.

Hence,simple diffusion alone is sufficient to transport gases

into,around and out of their bodies.

Their aquatic habitats ensure that the plasma membrane is

constantly moist so that respiratory gases can easily dissolve and diffuseacross the respiratory surface.

The thin plasma membrane allows the rapid diffusion of gases.

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THE RESPIRATORY STRUCTURES AND

BREATHING MECHANISMS IN

ORGANISMS

INSECTS :

The respiratory system insects is known

as tracheal system.

The tracheal system consists of a

network of air tubes called trachea.

Air enters the trachea through tiny

openings called spiracles.

The trachea are lined with rings of chitin

which prevent them from collapsing. The trachea branch into fined tubes called tracheoles.

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THE STRUCTURAL ADAPTION OF TRACHIOLES FOR GASEOUS

EXCHANGE.

The tracheoles branch throughout the body of an insect and penetiate into

the body tissue.

>> This means that oxygen can be channeled

directly through the cells

The large number of tracheoles.

>> Provides a large surface area for the

diffusion of respiratory gases.

The tips of the tracheoles have thin permeable

walls and contain water in which the respiratory

gases can be dissolve and diffuse rapidly into the body cells.

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THE BREATHING MECHANISM OF INSECTS.

Insects inhale and exhale through the

rhythimic relaxation and contraction of

their abdominal muscles.

When an insect inhale,the abdominal relax

and the spiracles open.

Air pressure inside the trachea decreases

and air is drawn in.

When the insect exhales,the abdominal muscles contract.

The increase air pressure forces air out through the spiracles.

The tracheal system with its network of small tubes allows oxygen to be

absorb directly from rhe atmosphere into the body cells.

There is no blood circulatory system in insects.

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THE RESPIRATORY STRUCTURES AND

BREATHING MECHANISMS N

ORGANISMS

FISH :

Gills are speacialised respiratory structures fo gaseous exchange in water.

Each gill has two rows of thin filament arranged in v-shape.

These filaments consist of numerous thin-walled lamellae.

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THE STRUCTURAL ADAPTION OF GASEOUS EXCHANGE.

There are large number of filaments and lamellae.

>> To provide a large surface area for efficient gaseous exchange in fish.

The membrane of gill is thin.

>> To allow the rapid absorption of respiratory gases into the blood

capillaries.

The filaments are supplied with network of blood capillaries.

>> For an efficient absorption and transport of respiratory gases.

The gill filaments are constantly surrounded by water.>> To enable respiratory gases to dissolve in them.

The efficiency of the gaseous exchange is further enhanced by water.

>> To maximize the oxygen transfer because as water flows over the gills in

one

direction,the deoxygenated blood flows in the opposite direction throughthe

blood capillaries in the lamellae.

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THE BREATHING MECHANISM OF FISH.

When the mouth opens,the floor of the buccal cavity lowers.

At the same time,the opercular cavity enlarges and the operculum closed.

Hence,water with dissolved oxygen is drawn into mouth.

When the mouth closes,the floor of the buccal cavity rises.

Water flows through the lamellae and gaseous exchange between theblood capillaries and water takes place.

At the same time,the opercular cavity becomes smaller. The pressure in thebuccal cavity is higher than the pressure outside.

The higer water pressure forces the opperculum to apen and water to flowout through the opperculum.

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THE RESPIRATORY STRUSTURES AND

BREATHING MECHANISMS IN

ORGANISMS

AMPHIBIANS :

The gaseous exchange occurs in the skin and in

the lungs.

THE STRUCTURAL ADAPTIONS OF THE SKIN FOR

GASEOUS EXCHANGE.

The skin is thin,moist and permeable.

>> To enable a rapid and efficient exchange

of gases between the skin and the air.

Beneath the skin is a network of blood

capillaries.

>> To absorp and transport respiratory gases to and from all the body cells.

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THE STRUCTURAL ADAPTION OF LUNGS FOR GASEOUS EXCHANGE.

The lungs of a frog consist of a pair of thin-walled

sacs for rapid diffusion of respiratory gases.

There are numerous inner partitions in the lungs.

>> To increase surface area to facilitate gaseous

exchange.

The membranes of the lungs are thin.

>> For rapid diffusion of gases

The membranes of the lungs are moist.

>> To allow respiratory gases to dissolve and diffuse into the blood

capillaries.

The lungs are supplied with a rich network of blood capilllaries.

>> To transport the respiratory gases to the body cells.

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THE BREATHING MECHANISM OF FROGS.

The bucco-pharyngeal floor lowers and the glottis closes.

As a result,fresh air is drawn into the bucco-pharyngeal cavity.

When the glottis open,the nostrills close and the bucco-pharyngeal floor

rises. The higher air pressure forces air into the lungs.

The lungs expand when air pushed in.

When the lung muscles contract,air is expelled from the lungs.

The air escapes from the nostrill.

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THE RESPIRATORY STRUCTURES AND

BREATHING MECHANISMS IN HUMANS

LUNGS :

Located in the thoracic cavity.

Protected by ribcage.

INTERCOSTAL MUSCLE :

Found between the ribcage.EPIGLOTTIS :

A flap that closes the air passage mometarily

during swallowing to prevent food and water

from entering the trachea.

TRACHEA : Supported by C-shaped cartilage rings which keep the trachea open.

The trachea will collapsed during inhalation without the cartilage due to theatmospheric pressure outside is higher than the pressure inside the trachea.

Ephitelial cells are lned with the cilia to sweep the dust together with the foreignparticles towards the back of the mouth to be swallowed or coughed out.

Goblet cells will secrete mucus to trap dust and microorganisms present in theair.

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BRONCHI :

The two tubes divided from the lower end of

trachea.

BRONCHIOLES :

Each bronchus subdivides repeatedly to form

smaller tubes called the bronchioles which end

in small air sacs called the alveoli.

ALVEOLI :

Alveoli are thin-walled air sacs where gaseous exchange occurs.

DIAPHRAGM :

A dome-shaped sheet of muscle.

Play important roles in the breathing mechanism in human.

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ADAPTATION OF ALVEOLI FOR GASEOUS EXCHANGE.

There are large number of alveoli.

>> To provide a large surface area for efficient

gaseous exchange.

The inner surface of each alveolus is moist.>> To enable oxygen and carbon dioxide to dissolve

in it and diffusion to take place.

The outer surface of each alveolus is covered by a

network of blood capillaries.

>> To provide a large surface area to volume ratio for the rapid diffusion

and

transport of respiratory gases.

The wall of an alveolus in only one-cell thick.

>> To allow the diffusion of respiratory gases across the membranes totake place

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THE HUMAN BREATHING MECHANISM.

INHALATION :

The external intercostal muscles contract while the

internal intercostal muscles relax.

This will cause the ribcage to move upwards and

outwards.

At the same time,diaphragm muscles contract and

become flatten.

These two actions cause the volume of thoracic cavity

to increase and the pressure of the thoracic cavity to

decrease.

Higher atmospheric pressure on the outside forces the

air into the lungs.

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EXHALATION :

The external intercostal muscles relax while the intercostal

muscles contract.

This action causes the ribcage to move downwards and

inwards.

At the same time,the diaphragm muscles relax and curve

inwards.

These two actions cause the volume of the thoracic cavity

to decrease and the pressure ofcthe thoracic cavity to

increase.

Lower atmospheric pressure inside the lungs forces the air out of the lungs.

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