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The Respiratory System


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KS4 Physical

Education


Le

arn

ing

ob

jecti

ves


Learning objectives

The structures of the respiratory system and their

functions

The mechanisms of breathing

How gases are exchanged during breathing

The composition of inhaled and exhaled air

The different measurements of lung capacity and

breathing

The effects of exercise on the respiratory system

What is meant by aerobic and anaerobic respiration

The oxygen debt.

What we will learn in this presentation:


The respiratory system


The nasal passages and lungs

Air is drawn into the body via the nose or mouth.

There are advantages to breathing through your nose:

Air then travels through the larynx, trachea (windpipe),

bronchi (one bronchus to each lung) and bronchioles to

the alveoli, where oxygen passes into the bloodstream.

the air is warmed so that it is closer to

body temperature

tiny hairs and mucus in the nose filter

the air, preventing larger dust and

pollen particles reaching the alveoli

mucus moistens the air, making it

easier for the alveoli to absorb.


When you breathe in:

intercostal muscles between

the ribs contract, pulling the

chest walls up and out

the diaphragm muscle

below the lungs contracts and

flattens, increasing the size of

the chest

the lungs increase in size,

so the pressure inside them

falls. This causes air to rush in

through the nose or mouth.

Mechanisms of breathing – inspiration

Diaphragm

contracts and

moves down

Intercostal

muscles pull ribs

up and out


Mechanisms of breathing – inspiration


Mechanisms of breathing – expiration

When you breathe out:

Intercostal muscles between

the ribs relax so that the chest

walls move in and down.

The diaphragm muscle below

the lungs relaxes and bulges up,

reducing the size of the chest.

The lungs decrease in size, so

the pressure inside increases

and air is pushed up the trachea

and out through the nose or

mouth.Diaphragm

relaxes and

bulges up

Ribs move in

and down


Mechanisms of breathing – expiration


Gas exchange at the alveoli

The alveoli are bunches

of tiny air sacks inside

the lungs.

Each individual sack is

called an alveolus.

When you breathe in,

they fill with air.

The alveoli are covered in tiny capillaries (blood vessels).

Gases can pass through the thin walls of each alveolus and

capillary, and into the blood stream.

Gases can also pass from the blood stream, into the alveolus.


Gas exchange at the alveoli


Composition of inhaled and exhaled air

GasAmount in

inhaled air

Amount in

exhaled air

Oxygen

Carbon dioxide

Nitrogen

Water vapour

17%

3%

79%

Large amount

21%

Very small amount

79%

Small amount

Why does mouth-to-mouth resuscitation work?

What are the main differences between

inhaled and exhaled air?


Measuring breathing

Tidal volume is the amount you breathe

in and out in one normal breath.

Residual volume is the amount of air left in your lungs

after you have breathed out as hard as you can.

Minute volume is the volume of air

you breathe in one minute.

Respiratory rate is how many

breaths you take per minute.

Vital capacity is the maximum volume of air you can

breathe out after breathing in as much as you can.


Measuring breathing


Calculating minute volume

Question

If you breathe 14 times in one minute (respiratory rate)

and you breathe 0.5 litres in each breath, what is your

minute volume?

Answer:

Minute volume = 14 × 0.5 litres

= 7.0 litres

Remember:

You can calculate a person’s minute volume by multiplying

the volume of air they breathe in one breath, by their

respiratory (breathing) rate.

Minute volume is the volume of air

you breathe in one minute.


Breathing during exercise

During exercise the muscle cells

use up more oxygen and

produce increased amounts of

carbon dioxide.

Your lungs and heart have to

work harder to supply the extra

oxygen and remove the carbon

dioxide.

Your breathing rate increases and

you breathe more deeply.

Heart rate also increases in order

to transport the oxygenated blood

to the muscles.


Breathing during exercise

Muscle cell respiration increases – more

oxygen is used up and levels of CO2 rise.

The brain detects increasing levels of CO2 – a

signal is sent to the lungs to increase breathing.

Breathing rate and the volume of air in

each breath increase. This means that

more gaseous exchange takes place.

The brain also tells the heart to beat

faster so that more blood is pumped

to the lungs for gaseous exchange.

More oxygenated blood gets to the

muscles and more CO2 is removed.


Breathing changes during exercise

During rest During exercise

Respiratory rate 14 breaths/ minute 32 breaths/ minute

Volume per

breath0.4 litres 2.4 litres

Minute volume ? ?

Look at these statistics for a 16 year-old athlete:

Calculate the athlete’s minute volumes

during rest and exercise.

Rest minute volume = 5.6 litres

Exercise minute volume = 76.8 litres


The effects of exercise on lung structures

The respiratory muscles (the

diaphragm and intercostals) get

stronger, so they can make the

chest cavity larger.

This larger chest cavity means

more air can be inspired, therefore

increasing your vital capacity.

More capillaries form around the alveoli,

so more gaseous exchange can take place.

In the long-term, regular exercise strengthens

the respiratory system.

Gas exchange can now take place more

quickly meaning exercise can be maintained

at a higher intensity for longer.


Respiration

Glucose from food is used to fuel exercise.

Respiration is the process that takes place in living

cells which releases energy from food molecules.

Waste products,

including carbon dioxide,

are produced as a result of

the chemical reactions. These

must be removed and excreted.

glucoseoxygen

energy

respiration

Oxygen is required to ‘break down’

the glucose to produce energy.

This energy is used to make

muscles contract.


Aerobic respiration

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.

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 energycarbon

dioxide+ + water


Aerobic respiration


Anaerobic respiration

When you exercise at a high intensity, the cardiovascular

system cannot supply enough oxygen to the muscles.

Under these conditions, anaerobic respiration takes place.

With no oxygen available, glucose is burned to produce

energy and lactic acid.

Lactic acid is a mild poison. As it builds up, it causes muscle

pain and eventually cramp.

Short, intense activities like sprinting, weightlifting, jumping

and throwing use anaerobic respiration.

glucose energy + lactic acid


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.


Anaerobic exercise


Exam-style questions

1. Describe the passage of oxygen from the nasal passages

to the bloodstream.

2. David goes jogging once a week for 45 minutes.

David tries to increase his pace. He finds that he is forced

to stop running and breathe hard for several minutes.

a) List two differences between the air that David

inhales and the air that he exhales while jogging.

b) What two substances are used by David’s body

cells to produce energy? What are the products of

this reaction?

c) Explain why David had to stop.

d) How did breathing hard help him to recover?


Can you remember all these keywords?

Larynx

Trachea

Bronchus / Bronchi

Bronchioles

Alveoli

Diaphragm

Intercostal muscles

Oxygen uptake

Tidal volume

Respiratory rate

Minute volume

Vital capacity

Residual volume

Aerobic respiration

Anaerobic respiration

Oxygen debt

Lactic acid

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