B. Respiration System - Part 2

8/13/2019 B. Respiration System - Part 2

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RESPIRATION SYSTEM

IN HUMANGASEOUS EXCHANGERESPIRATORY SYSTEM


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HUMAN RESPIRATION SYSTEMA. Respiration organs.

B. Breathing mechanism.

C. Internal respiration.


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GASEOUS EXCHANGE IN HUMAN

GASEOUS EXCHANGE OCCURS IN THE RESPIRATORY SYSTEM

The most important are the two lungs. Each lung is filled

with many tiny air spaces called air sacs or alveoli. It is here

that the oxygen diffuses into the blood. Because they are so

full of spaces, lungs feel very light and spongy to touch. The

lungs are supplied with air through the windpipe or trachea.

A. Respiration organs.B. Breathing mechanism.

C. Internal respiration.


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AIR IS TAKEN DOWN INTO THE LUNGS

Air can enter the body through either the nose or mouth. The noseand the mouth are separated by the palate, so you can breathe

through your nose even when you are eating.

Is is better to breathe through your nose, because the structure of the

nose allows the air to become warm, moist, and filtered before it getsto the lungs. Inside the nose are some thin bones called turbinal

bones which are covered with a thin layer of cells. Some of these cells

make a liquid containing water and mucus which evaporates into the

air in the nose and moistens it.

1. The NOSE and MOUTH

Other cells have very tiny hair-like projections called cilia. The cilia

are always moving, and bacteria or particles of dust get trapped in

them and in the mucus. Cilia are found all along the trachea and

bronchi, too. They waft the mucus, containing bacteria & dust, up to

the back of the throat, so that it doesnt not block up the lungs.


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The air then passes into the windpipe or trachea. At the top of the

trachea, is a piece of cartilage called epiglottis. This closes thetrachea and stops food going down the trachea when you swallow.

This is a reflex action, which happens automatically when a bolus

of food touches the soft palate.

2. The TRACHEA

The air then passes into the windpipe or trachea. At the top of thetrachea, is a piece of cartilage called epiglottis. This closes the

trachea and stops food going down the trachea when you swallow.

This is a reflex action, which happens automatically when a bolus

of food touches the soft palate.

Just below the epiglottis is the voice box or larynx. This contains

the vocal cords. The vocal cords can be tightened by muscles so

that they make sounds when air passes over them. The trachea

has rings of cartilage around it, which keep it open.


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The trachea goes down through the neck and into the thorax. The

thorax is the upper part of your body from the neck down to thebottom of the ribs and diaphragm. In the thorax, the trachea

divides into two. The two branches are called the right and the left

bronchi. One bronchusgoes to each lung and then branches out

into many smaller tubes called bronchioles.

3. The BRONCHI

At the end of each

bronchiole are tiny air

sacs or alveoli. This iswhere gaseous

exchange takes place.

4. The ALVEOLI


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ALVEOLAR WALLS FROM THE RESPIRATORY SURFACE

The walls of the alveoli are respiratory surface. Tiny blood vessels,

called capillaries, are closely wrapped around the outside of thealveoli. Oxygen diffuses across the walls of the alveoli into the blood.

Carbon dioxide diffuses the other way.

The walls of the alveoli have several features which make them an

efficient gaseous exchange surface.

They are very Thin

Alveolar walls are only one cell thick. The

capillary walls also only one cell thick. Anoxygen molecule only has to diffuse across

this small thickness to get into the blood.


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They have an excellent transport system

Blood is constantly pumped to the lung along the pulmonary artery.

This branches into thousands of capillaries, which take blood to allparts of the lungs. Carbon dioxide in the blood can diffuse out into

the air spaces in the alveoli, and oxygen can diffuse into the blood.

The blood is then taken back to the heart in the pulmonary vein,

ready to be pumped to the rest of the body.

They have a large surface area

In fact, the surface area is

enormous! The total

surface area of all the

alveoli in your lungs is over

100 m2.

They have a good supply of O2

Your breathing movements

keep your lung well

supplied with Oxygen.


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THE RIBS & DIAPHRAGM MOVE DURING BREATHING

To make air move in and out of the lungs, you must keep changing

the volume of your thorax. First, you make it large so that air is

sucked in. then, you make it smaller again so that air is squeezed

out. This is called breathing or ventilation.

There are 2 sets of muscles which help you to breathe. One set is

in between the ribs. This set is called intercostal muscles made upof the external and internal intercostal muscles. The other set is in

the diaphragm. The diaphragm is a large sheet of muscle and

elastic tissue which stretches across your body, underneath the

lung and hearth.


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BREATHING IN IS CALLED INSPIRATION

When breathing in, the muscles of the diaphragm contract. This

pulls the diaphragm downwards, which increases the volume in the

thorax. At the same time, the external intercostal muscles contact.

This pulls the ribs the ribs cage upwards and outwards. Together,

these movements increase the volume of the thorax.

As the volume of the thorax increases, the pressure inside it fallsbelow atmospheric pressure. Extra space has been made and

something must come in to fill it up. Air therefore rushes in along

the trachea and bronchi into the lungs.


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BREATHING OUT IS CALLED EXPIRATION

When breathing out, the muscles of the diaphragm relax. The

diaphragm springs back up onto its domed space because it is

made of elastic tissue. This decreases the volume in the thorax.

The external intercostal muscles also relax. The rib cage drops

down again into its normal position. This also decreases the

volume of the thorax.As the volume of the thorax decreases, the pressure inside it

increases. Air is squeezed out through the trachea into the nose

and mouth, and on out of the body.


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INTERNAL INTERCOSTAL MUSCLES CAN FORCE AIR OUT

Usually, you breathe out by relaxing the external intercostal

muscles and the muscles of the diaphragm. Sometimes, you

breathe out more forcefullywhen coughing, for example. Then

the internal intercostal muscles contract strongly, making the rib

cage drop down even further. The muscles of the abdomen walls

also contract, helping to squeeze extra air out of the thorax.


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EXERCISE CAN CREATE AN OXYGEN DEBT

All the cells in your body need oxygen for respiration

and all of this oxygen is supplied by the lungs. The

oxygen is carried by the blood to every part of the body.

Sometimes, cells may need a lot of oxygen

very quickly. Imagine, you are running in a

race. The muscles in your legs are using up a

lot of energy. To produce this energy, the

mitochondriain the muscles will be combining

oxygen with glucoseas fast as they can, to

provide the energy for the muscles.


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How can that extra energybe found?

It doesnt release very much energy, but a little extra might make all

the difference.

Glucose lactic acid + energy

Extra energy can be produced by anaerobic respiration. Some

glucose is broken down without combining it with oxygen:

A lot of oxygen is needed to workas hard as this.

You breathe deeper and faster to get more oxygen

into your blood. Your heart beats faster to get the

oxygen to the leg muscles as quickly as possible.

Eventually a limit is reached. The heart and lungs

cannot supply oxygen to the muscles any faster.

But more energy is still needed for the race.


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When you stop running, you will have quite a lot of lactic acid in

your muscles and your blood. This lactic acid must be broken

down by combining it with oxygen. So, even though you do notneed the energy anymore, you go on breathing hard. You are taking

in extra oxygen to break down the lactic acid.

While your are running, you built up an oxygen debt. You

borrowedsome extra energy without payingfor it with oxygen.Now, as the lactic acid is combined with oxygen, you are paying off

the debt. Not until all the lactic acid has been used up, does your

breathing rate and rate of heart beat return to normal?

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B. Respiration System - Part 2