KS4 Biology. The Breathing System

1. KS4 Biology

The Breathing System
1 of 54
©©Boardworks
2004
Boardworks Ltd
Ltd 2003

2. Contents

The Breathing System
Basics of breathing
Cartilage and the trachea
Bronchi and the lungs
Inside an alveolus
Breathtaking features
Summary

3. What is breathing?

The body uses the respiratory system to get the oxygen
needed for respiration.
It is also used to get rid of one of the waste
products of respiration: the gas carbon dioxide.
Breathing in and breathing out are separate
processes in the body.
Breathing in is called inhalation. When you inhale, you breathe air, including oxygen,
into your lungs.
Breathing out is called exhalation. When you exhale, you breathe out the
contents of your lungs and get rid of the waste gas carbon dioxide.

4. Basics of breathing

Humans breathe to ensure that oxygen enters the body
and that carbon dioxide leaves the body.
The breathing system
Oxygen (O2)
Carbon Dioxide
(CO2)

5. Exercise, respiration and ventilation

Energy is used up by the active muscles
during exercise. The rate of respiration
must therefore increase to supply enough
energy to the muscles.
This means that more oxygen must be
breathed in and more carbon dioxide
breathed out.
During exercise, why does:
the heart rate increase
the rate and depth of breathing increase
the arteries supplying the muscles dilate?

6. Running and breathing rates

7. Carbon dioxide

The brain can detect the level of carbon dioxide in cells.
When the level of carbon dioxide increases during
exercise, the brain must coordinate ways to prevent the
levels reaching toxic levels.
One way the brain deals with a build up of
carbon dioxide during exercise is by increasing
the rate of breathing.
This increases the rate of gas exchange and the
removal of carbon dioxide from the lungs.

8. What if you forget to breathe?

Firstly the breathing system must inhale oxygen and secondly it must
exhale carbon dioxide.
It is designed to be able to perform both tasks using the same
organs.
One final important fact to remember is that breathing can be performed
without humans having to think about it.
Just imagine that as well as everything else you have to think about, you
would have to remember to tell your body to inhale, then exhale, then inhale,
exhale, inhale, … etc.
There would be no time for anything else.

9.

10. The pharynx

As the air passes through the nasal cavity, the air is
smelt, warmed, filtered and moistened slightly.
The air meets at the pharynx, a junction at back of the oral cavity.
The pharynx is a junction between two
tubes. The air must travel down only one of
these tubes. One is the windpipe (trachea)
and the other is the gullet (oesophagus).
trachea
gullet
As the name suggests, air must pass down through the windpipe
(trachea).

11. Contents

The Breathing System
Basics of breathing
Cartilage and the trachea
Bronchi and the lungs
Inside an alveolus
Breathtaking features
Summary

12. Cartilage in trachea

Diagram of trachea with cartilage rungs.
You can think of the trachea as a
tube lined with C-shaped supporting
rungs.
These rings are made
of a tough material
called cartilage. They
help to hold the tube
open.
You may be wondering why they are C-shaped and not full circles.

13. A clever design

Well, if a tube were lined with fixed circles of cartilage, it would
have a fixed diameter…
cartilage
Although this would stop the tube
from collapsing, this would also
mean that the tube would not be
able to expand.
When we breathe in, the trachea
must expand to allow more air in.
trachea

14. Expansion potential

Therefore, a C-shaped piece of cartilage can change shape.

15. The trachea

As well as being adapted on its outer surface, the trachea shows adaptations
on its inner lining.
If we look closely at the inner surface of the trachea…
trachea
ciliated epithelial cells

16. Ciliated epithelial cells

The cells that line the wall of the trachea show two special adaptations.
tiny hairs called cilia
produce a sticky liquid mucus
Ciliated epithelial cells
We say the cells show specialisation.
These specialised cells have a particular job to do.

17.

The presence of mucus and cilia on the lining of the trachea
ensures that the air we breathe is clean and free from disease.
microbes travelling
down the trachea
within inhaled air
ciliated cells
microbes become stuck
within the mucus
mucus being made by the ciliated cells

18. Elevator action

Once the microbes are stuck in the mucus, the cilia move the mucus
upwards using a wafting action. The mucus passes up to the top of the
trachea where it can either be swallowed or coughed out of the body.
coughed out
swallowed

19. Contents

The Breathing System
Basics of breathing
Cartilage and the trachea
Bronchi and the lungs
Inside an alveolus
Breathtaking features
Summary

20. Bronchi

Eventually the trachea branches,
dividing into two smaller tubes called
the left and right bronchi. The air
travels along this tubes into the
lungs.
(The singular of bronchi is a
bronchus.)
trachea
bronchi
Right
Don’t forget that in a picture of the human body, right
becomes left and left becomes right.
Check by holding up your right hand in a mirror. The
person staring back at you will be holding up their left
hand.
Left

21. Lungs and bronchi

Each Bronchus connects the trachea to a large air sac known as a
lung. Lungs are made of tiny air sacs called alveoli. where oxygen
comes into your body and you get rid of carbon dioxide from the flood.
You have two bronchi and therefore your body has two lungs, a left
and a right.
trachea
right bronchi
right lung
left bronchi
left lung

22.

23. Diagram of a lung

In reality, the lungs are different in shape.
Here is a more accurate diagram.
Right Lung
trachea
cartilage
right
bronchus
pleural
membrane
location of the heart
bronchiole

24. Branching bronchi

Each bronchus now starts branching to produce
smaller and smaller tubes.
bronchi
these smaller branches are
known as bronchioles
One bronchus gives rise to many bronchioles. The overall effect is similar to the
branching of a tree from a central trunk.
This branching of the bronchi occurs within both lungs.

25. The route that the oxygen gas takes

Oxygen will pass…
Down the trachea
Through each
bronchus
And through all the
bronchioles within
each lung
BUT WHAT
HAPPENS NEXT?
Always remember that the
CO2 is moving in the
opposite direction!

26. Problems with lung expansion

With air entering and leaving the lungs, they increase and decrease in size on a
regular basis.
When organs in the body increase in size, they will touch other organs because
of the lack of space.
This is a danger because living tissue is very delicate and when tissues rub
against each other, friction could be generated.

27. Danger of friction

Organ 1
Organ 2
FRICTION
This friction could damage the tissue and kill cells.
Therefore, a protective bag called the pleural membrane surrounds the
lungs, which are likely to rub against other organs during the breathing
process.

28. The pleural membrane

A fluid is found within this bag, surrounding the lungs.
This fluid lubricates the lining of the lungs and stops friction being
generated.
pleural membrane
lung
fluid

29. https://www.brainpop.co.uk/science/lifeprocesseshumans/respiratorysystem/

https://www.brainpop.co.uk/scienc
e/lifeprocesseshumans/respiratory
system/

30.

31. Contents

The Breathing System
Basics of breathing
Cartilage and the trachea
Bronchi and the lungs
Inside an alveolus
Breathtaking features
Summary

32. https://www.bbc.co.uk/schools/gcsebitesize/pe/appliedanatomy/1_anatomy_respiratorysys_rev3.shtml

https://www.bbc.co.uk/schools/gcs
ebitesize/pe/appliedanatomy/1_an
atomy_respiratorysys_rev3.shtml

33. The alveoli

34. Gas exchange

35. Inside an alveolus

Oxygen makes its way to special air sacs.
Actually, each air sac is found to
be a bundle of air sacs.
Together, they are known as an
alveolus.
The outside of the alveolus is
covered with tiny blood vessels.
We can look inside the alveolus to get some idea of why they
are shaped the way they are.

36. A cross-section of an alveolus

A cross-section of
an
oxygen
(O ) alveolus
gas
2
passes through here
epithelial lining
of the alveolus
This O2 is then
able to dissolve in
a small moist
lining.

37. Keeping the environment right

dissolve
moist lining
O2
O2
O2
O2
dissolve
This moist lining also stops the alveolus from drying and cracking. It
lubricates the insides of the air bag.

38. Label the alveolus

39. Diffusion at work

40.

41.

42. Inhalation and exhalation

43. The mechanism of ventilation

44. Respiration

45. Oxygen diffusion into red blood cells

After the oxygen dissolves it also diffuses.
O2
O2
O2
O2
D IFF USI ON
cell lining of
alveolus
cell lining of
capillary
blood
The oxygen molecules must diffuse through both the lining of the alveolus
and the lining of the blood capillary.
They are eventually picked up by red blood cells.

46. Blood leaving the lungs

The blood now carries this
oxygen to the cells of the body.
Right
Lung
Left
Lung
blood vessel
O2
O2
blood
body cells

47. Laws of diffusion

The movement of the oxygen
from the blood to the cells also
follows the law of diffusion.
blood coming
from the lungs
high
concentration
It is highly concentrated
within the blood.
Meanwhile the concentration
is low within the cell.
Therefore the oxygen passes
into the body cells.
low
concentration
body cell

48. Breathing system summary

Remember that the process of inhalation brings O2 into
the body whilst exhalation removes CO2.
So, how does our breathing system enable us to do this?
Well, inhaling and exhaling are brought about by certain changes in the
position of the components within our breathing system.
Let’s next look at the general structure of this system.
Remember, the breathing system is found in the upper region of the body.
This is known as the thorax.

49. Contents

The Breathing System
Basics of breathing
Cartilage and the trachea
Bronchi and the lungs
Inside an alveolus
Breathtaking features
Summary

50. Breathtaking features

The breathing system does not have a fixed shape.
trachea
ribs
rib muscles
right bronchus
diaphragm
Right Lung
Left Lung
It has the ability to move, whilst remaining enclosed within the protection of the
ribcage.

51. A mobile ribcage?

This means that the rib cage must also be able to change position.
Take your hands and place them flat on your chest just above
your hips on each side of your body. Now breathe in and out
very deeply. Whilst you do this, watch to see what happens to
your hands.
You should notice the following things…..

52. Take a breath

When you breathe in (inhale), your hands move up and outwards.
When you breathe out (exhale), your hands move down and inwards.

53. Inhaling: chest expansion

When we inhale, our lungs fill with air.
As they fill, they become enlarged.
The ribs must then move upwards and outwards to make
more room in the thorax.
The overall effect of this is that our chest expands.

54. The diaphragm

Your diaphragm is located beneath the lungs, which means that it separates the
thorax from the abdomen.
It is a sheet of muscle that
spans the width of the body.
Before we inhale, it is found in a dome shape.
As we inhale, it contracts and flattens.
The result of this change in shape is a
change in the volume of the thorax.
inhaling

55. Pressure regulation

As the volume of the thorax increases, the internal air pressure drops.
This means that the air pressure outside the lungs is greater than the air
pressure inside the lungs.
High
High air pressure outside
Low air pressure inside
Low
Diaphragm flattens
Thorax volume increases
Air pressure drops
Air diffuses into the lungs

56. Features of inhalation and exhalation

If these changes occur when we breathe in, the opposite must happen
when we breathe out.
These changes can be summarised in the table below...
Feature
Inhaling
Exhaling
diaphragm shape
flat
domed
ribs
up and out
down and in
diaphragm muscle
contracted
relaxed
rib muscle
contracted
relaxed
lungs
inflated
deflated

57. Click on the “Air Drawn In” buttons

58. Click on the “Passage of air” buttons

59. KS3 Biology

8B Respiration
59 of 54
©©Boardworks
2004
Boardworks Ltd
Ltd 2003

60. Contents

8B Respiration
Releasing energy
The circulation system
The breathing system
Anaerobic respiration
Summary activities

61. How is digested food used by the body?

The body needs a constant supply of energy which comes from digested food.
Glucose, from digested carbohydrates, is an important substance that contains
stored chemical energy.
When glucose reacts with oxygen, a lot of energy is released.
In the body’s cells, glucose and oxygen react to release
energy. Some of this is released as heat and the rest is used by the cells.
What is the release of energy from glucose called?

62. What is respiration?

Respiration is the process that the body uses to release energy from digested food
(glucose):
glucose
from the
digestive system
+
oxygen
from the
respiratory
system
carbon
dioxide
waste product
(exhaled)
+
water
(
+energy)
waste product
(exhaled)
This type of respiration is called aerobic respiration because energy is released in the
presence of oxygen.
How do the glucose and oxygen needed for aerobic respiration get to the all the
body’s cells?

63. Respiration

Respiration is the process that takes place in living cells which releases energy
from food molecules.
Glucose from food is used to fuel exercise.
Oxygen is required to ‘break down’ the glucose to
produce energy.
This energy is used to make muscles contract.
Waste products,
including carbon dioxide,
are produced as a result of
the chemical reactions. These
must be removed and excreted.
respiration
glucose
oxygen
energy

64. Aerobic respiration

There are two different types of respiration.
When you exercise at a steady, comfortable rate, the cardiovascular system is able to
supply the muscles with all the oxygen they need.
Under these conditions, aerobic respiration takes place.
glucose
+ oxygen
energy
+
carbon dioxide
+ water
Aerobic exercise can be maintained for long periods without the performer
getting breathless or suffering muscle cramps. Moderate activities like walking,
jogging, cycling and swimming use aerobic respiration.

65. Aerobic and anaerobic respiration

Aerobic respiration
When the body is able to supply the cells with the oxygen and
glucose that they need, it carries out aerobic respiration.
glucose
oxygen
carbon
dioxide
water
energy
Anaerobic respiration
When the body cannot supply the cells with the oxygen needed to
break down glucose, then it has to carry out anaerobic respiration.
Energy is released without oxygen:
glucose
lactic
acid
energy

66. Not enough oxygen!

glucose
lactic
acid
energy
When anaerobic respiration takes place, the lactic acid produced
soaks the muscle cells and prevents muscles from doing their job.
This causes fatigue and sometimes cramp.
After activity that has lead to anaerobic
respiration, the person involved pants and
breathes heavily.
This happens because they need lots of
oxygen to get rid of lactic acid that has built
up in their body.
lactic
acid
oxygen
carbon
dioxide
water

67. Oxygen debt

After anaerobic activity, oxygen is needed to
neutralize the lactic acid. This is called an oxygen
debt. It is repaid after exercise.
The oxygen reacts with the lactic acid to form CO2 and
water.
Rapid and deep breathing is needed for a short
period after high intensity exercise in order to repay
the debt.
This also helps to remove the carbon dioxide which
accumulates in the blood during intense exercise.

68.

• https://www.brainpop.co.uk/uk/science/lifeproce
ssescells/cellularrespiration/

69. Aerobic respiration

70. Contents

The Breathing System
Basics of breathing
Cartilage and the trachea
Bronchi and the lungs
Inside an alveolus
Breathtaking features
Summary

71. Glossary

aerobic –
alveoli –
The type of respiration that occurs with oxygen.
Tiny air sacs in the lungs where gas exchange takes place.
anaerobic –
The type of respiration that occurs without oxygen.
exhalation –
The process of breathing out.
A type of sugar that the body releases energy from
during respiration.
glucose –
inhalation –
The process of breathing in.
The process that the body uses to release energy from
digested food.
respiration –

72. Breathing in or out?

73. Multiple choice section

74. Multiple-choice quiz

75. Homework

• Work in pairs
• Make a poster about respiration, do not use to
much words
• Use internet for interesting ideas, use picture
or draw by yourself to make your poster as
nice as you can.

76.

So far, we have considered both the structure of the breathing
system and how it is adapted for breathing in and out.
BUT...
We have not talked about why the body needs to breathe.
If you remember, we know that we breathe constantly throughout life.
Also, we know that if we stopped breathing we would eventually die.
So, breathing in Oxygen (O2) must be linked to something that
we need constantly and without it our bodies would die.
The answer is ENERGY making

77.

The energy making process depends on the breathing
system and the digestive system.
Imagine a fire...
This will produce energy in the form of heat but only if it is supplied
with 2 main ingredients.
FUEL
OXYGEN

78.

Well, the bodies energy making reaction needs similar things to
the energy making process of fire.
Like the fire, the body needs Oxygen and a Fuel.
The Oxygen is
supplied by the
breathing system
+
2
And the fuel (in the form of
digested food) comes
courtesy of the digestive
system

79.

If we now think back over the journey of oxygen and digested food through the human
body, we will realise that they both end up in the same place.
Food
Oxygen
Breathing
system
These
substances
eventually
arrive at the
body cells
Digestive
system
BLOOD

80.

Therefore, the raw materials for the energy making process eventually arrive
at the body cells.
This energy making process is known as...
RESPIRATION
Each living cells is supplied with food and oxygen in order to generate
energy
capillary
E.g.
Blood
Oxygen
muscle cell
+
Food

81.

No chemical reaction is 100% efficient.
Therefore, as well as producing the useful energy,
respiration also produces waste products.
These waste
products must be
removed from the
body
If the process of breathing in is used to
obtain the O2 for respiration, it would
make sense for the body to use the
process of breathing out to remove
these waste products of this reaction.
This is exactly what happens!!

82.

If we study the composition of the air that is breathed out,
we will identify the waste products of respiration.
Two tests help us identify these waste products.
Before you start
exhaling, the lime
water is a clear
liquid
Test One
Blow gently through a
straw into a test tube
filled with lime water.
straw
lime water
After a short while,
the lime water
becomes cloudy.

83.

If a gas is bubbles through lime water and the liquid becomes cloudy, the
gas is identified as….
Carbon Dioxide (CO2)
This is the first of our waste
respiration.
products of
Test Two
On a freezing cold
day, watch what
happens when you
breathe out.
The air you breathe out is
visible because the mystery
waste product condenses
back into a liquid.

84.

This waste product is water vapour and so our final waste product of the
process of respiration is...
Water
Using this information, we can now write out the full equation for
respiration
FOOD
(GLUCOSE)
from
digestive
system
+
OXYGEN
CARBON
DIOXIDE
from
breathing
system
waste
product
exhaled
+
WATER
waste
product
exhaled
+
ENERGY
USEFUL!

85.

85 of 54
©©Boardworks
2004
Boardworks Ltd
Ltd 2003

86. How is digested food used by the body?

The body needs a constant supply of energy which comes from digested food.
Glucose, from digested carbohydrates, is an important substance that contains
stored chemical energy.
When glucose reacts with oxygen, a lot of energy is released.
In the body’s cells, glucose and oxygen react to release
energy. Some of this is released as heat and the rest is used by the cells.
What is the release of energy from glucose called?

87. What is respiration?

Respiration is the process that the body uses to release energy from digested food
(glucose):
glucose
from the
digestive system
+
oxygen
from the
respiratory
system
carbon
dioxide
waste product
(exhaled)
+
water
(
+energy)
waste product
(exhaled)
This type of respiration is called aerobic respiration because energy is released in the
presence of oxygen.
How do the glucose and oxygen needed for aerobic respiration get to the all the
body’s cells?