1 2 Think about… 7.1 The human breathing system 7.2 Gas exchange in the air sacs 7.3 Transport of...

Think about…

7.1 The human breathing system

7.2 Gas exchange in the air sacs

7.3 Transport of respiratory gases

7.4 Ventilation

Recall ‘Think about…’

Summary concept map

The answer is…

…still a mystery.

Which parts ofour body are in action when we yawn

Where does the exchange of oxygen and carbon dioxide take place between our body and the atmosphere

In what formsare oxygen and carbon dioxide carried around our body

O2 CO2

gas exchange (氣體交換 )

• diffuses across cell membrane

In very small organisms:

In larger organisms:

• cannot diffuse across body surface

• breathing system (呼吸系統 )

• transport system (運送系統 )

In larger organisms:

- for gas exchange

- for carrying gases to body cells

What does the human breathing

system consist of?

Human breathing system

pharynx

larynxtracheabronchus

lungair sac

bronchiole

epiglottis

nostrilnasal cavity3D Model

diaphragm

intercostal muscle

inner pleural membrane

outer pleural membrane

pleural cavity

How does air flow into the lungs?

nasal cavity

pharynx

larynx

trachea

bronchus

bronchiole

air sac

1 Examine the breathing system of a dissected rat or a human torso model.

Examination of the mammalian breathing system

2 Identify the various structures.

1 Nostrils and nasal cavityi) Hairs

• filter larger dust particles

1 Nostrils and nasal cavityii) Mucus-secreting cells

mucustraps dust particles & moistens air

1 Nostrils and nasal cavityiii) Ciliated epithelial cells

sweep mucus with dust particles towards pharynx

1 Nostrils and nasal cavityiv) Capillaries

• blood warms up air

2 Pharynx and larynx7.1 The human breathing system

larynx oesophagus

trachea

pharynx

larynx

oesophagus

larynx oesophagus

1 Tongue pushes food towards pharynx

larynx oesophagus

2 Soft palate moves up, preventing food from entering nasal cavity

larynx oesophagus

3 Larynx rises and epiglottis covers entrance to trachea, preventing choking

2 Pharynx and larynx

larynx

• made up of cartilage

epiglottis

vocal cords (聲帶 )• can vibrate to

produce sound

trachea

bronchus

bronchioles

3 Trachea, bronchi and bronchioles

bronchus

bronchioles

trachea

C-shaped cartilage

ciliated epithelial cell

• prevents collapse

Trachea

Bronchi

Bronchiole

Ciliated epithelial cells

Trachea

Bronchi

Bronchiole

Mucus-secreting cells

Absent in smaller bronchioles

Trachea

Bronchi

Bronchiole

Capillaries

Trachea

Bronchi

Bronchiole

Cartilage

Absent

C-shaped

Circular

4 Air sacs

air sac

• large respiratory surface

capillary

5 Lungs

• in thoracic cavity (胸腔 )• composed of bronchioles and air sacs

5 Lungs• protected by rib cage (肋骨籃 )

cartilage

vertebral column (脊柱 )

sternum (胸骨 )

5 Lungs

intercostal musclesdiaphragm

• sheet of muscle

5 Lungs

right lung

ribintercostal muscle

outer pleural membraneinner pleural membrane

pleural cavity

5 Lungs

right lung

pleural cavity

• pleural cavity filled with pleural fluid (胸腺液 )

as lubricant (潤滑劑 )

1 Examine the pig lungs. Identify the larynx, epiglottis, trachea, bronchi, left and right lungs.

Examination of the pig lungs

2 The lungs have several lobes. Find out the number of lobes present in the left and the right lungs respectively.

3 Feel the hardness of the trachea and the lung tissue with a pair of forceps.

4 Use a water hose to fill the lungs with water through the trachea. Note the changes in the volume of the lungs.

5 Draw a labelled diagram of the lungs.

1a The human breathing system consists of the and structures that aid breathing.

respiratory tract

air sacs

bronchi

larynx

nasal cavity

bronchioles

pharynx

nostrils

trachea

1b Air flow along respiratory tract:

2a In the nostrils, filter larger dust particles.

2b In the lining of nasal cavity, trachea, bronchi and bronchioles, mucus-secreting cells secrete mucus to moisten the air. mucusmucus-secreting cells

2c In the lining of nasal cavity, trachea, bronchi and bronchioles,

mucus traps the dust particles and bacteria.

2d In the lining of nasal cavity, trachea, bronchi and bronchioles, blood in the warms the incoming air.

blood capillaries

Respiratory gases

OxygenCarbon dioxide

Where does gas exchange take place?

in the air sacs

Where does gas exchange take place?

blood flow

air sac

capillary

Uptake of oxygen by the blood

blood flowUptake of oxygen by the blood

1 O2 is inhaled.

2 O2 dissolves in water film.

3 O2 diffuses into red blood cells.

blood flowRemoval of carbon dioxide into the air sacs

1 CO2 diffuses out from capillary.

2 CO2 diffuses into air sacs.

3 CO2 is exhaled.

Animation

Adaptive features of air sacs7.2 Gas exchange in the air sacs

1 Large number of air sacs• provide large surface area for gas exchange

2 Thin wall of air sac• provides short

diffusion distance

air sac

one-cell thick epithelium

3 Water film lining inner surface• keeps inner surface

moist to dissolve gases

water film

4 Network of capillaries• Rapid transport of gases

• Maintain steep concentration gradient

air sac

capillary

red blood cell

1 Examine the slides or photomicrographs of the mammalian lungs.

Examination of the mammalian air sacs

2 Identify the air sacs.

air sac

capillary

3 Draw a labelled diagram of the air sacs.

Oxygen concentration in air sacs is higher than that in the capillaries.

1 How does gas exchange take place in the air sacs?

higher

Oxygen in incoming air dissolves in the lining the air sacs, and then across the walls of the air sacs and the capillaries into the blood.

diffuseswater film

Carbon dioxide concentration in capillaries is than that in air sacs.

higher

Carbon dioxide in blood diffuses across the walls of the capillaries and the air sacs into the air in the air sacs.

capillariesair sacs

provides a large surface area for gas exchange

2 Adaptive features of the air sacs:

Large number

large surface area

provides a for rapid diffusion of gases

Thin wall

short distance

allows gases to in the water film for diffusion

dissolve

Moist inner surface

allows rapid transport of gases to maintain a for diffusion gradient

Network of capillaries

steep concentration

A. Warm the incoming air.B. Moisten the incoming air.C. Trap dust in the inhaled air.D. Dissolve the gases in the inhaled air.

Quick check

The film of water on the surface of human air sacs serves to

Oxygen in blood is transported by…

83red blood cells

Oxygen in blood is transported by…

Oxygen is mainly transported by red blood cells

Adaptive features of red blood cells for carrying oxygen

fully packed with haemoglobin (血紅蛋白 )

oxygen carrier

biconcave disc shape (雙凹圓盤狀 ):

surface area cytoplasmic volume

short distance for diffusion

biconcave disc shape (雙凹圓盤狀 ):

without nucleus:

more room for haemoglobin

Transport of oxygenIn lungs

In body cells

air sac red blood cell

Hb + O2 → oxyhaemoglobin

In body cells

oxyhaemoglobin → Hb + O2

In body cells

Transport of carbon dioxideIn lungs

In body cells

CO2 + H2O → H+ + HCO3-

hydrogencarbonate ion

In body cells

H+ + HCO3- → H2O + CO2

In body cells

• increases surface area to volume ratio

1 Adaptive features of red blood cells for carrying oxygen:

shapeBiconcave disc

volumesurface area to

1 Adaptive features of red blood cells for carrying oxygen:

• shortens diffusion path for oxygen

shapeBiconcave disc

diffusion path

In air sacs, oxygen concentration is .

oxyhaemoglobin

haemoglobin

+ oxygen

carried by blood

2 Transport of oxygen:

haemoglobin

oxyhaemoglobin

lowIn body cells, oxygen concentration is .

+ oxygen

body cells

2 Transport of oxygen:

plasma

hydrogencarbonate ions (HCO3-)

carbon dioxide

3 Transport of carbon dioxide:

+ water

carried in

Carbon dioxide is produced by body cells.

watercarbon dioxide

3 Transport of carbon dioxide:

air sacs

hydrogencarbonate ions

When blood reaches the air sacs,

7.4 Ventilation

Ventilation (換氣 )

ExhalationInhalation

Breathing

involves

brought about by

7.4 Ventilation

InhalationAnimation

1a Intercostal muscles contract.Rib cage moves upwards and outwards.

7.4 Ventilation

Inhalation

1b Diaphragm muscles contract.Diaphragm flattens.

7.4 Ventilation

Inhalation

2 Volume of thoracic cavity increases, pressure decreases.

7.4 Ventilation

Inhalation

3b Air pressure in the lungs is lower than atmospheric pressure.

3a Lungs expand.

7.4 Ventilation

Inhalation

4 Air rushes into lungs.

7.4 Ventilation

Ventilation (換氣 )

ExhalationInhalation

Breathing

involves

brought about by

7.4 Ventilation

Exhalation

1a Intercostal muscles relax.Rib cage moves downwards and inwards.

7.4 Ventilation

Exhalation

1b Diaphragm muscles relax.Diaphragm returns to dome shape.

7.4 Ventilation

Exhalation

2 Volume of thoracic cavity decreases, pressure increases.

7.4 Ventilation

Exhalation

3b Air pressure in the lungs is higher than atmospheric pressure.

3a Lungs recoil.

7.4 Ventilation

Exhalation air

4 Air is forced out of the lungs.

7.4 Ventilation

air pressure in thoracic cavity

atmospheric pressure

exhalation inhalation exhalation inhalation

respiration = breathing = ventilation

7.4 Ventilation

Respiration :

The chemical process of releasing energy from food.

7.4 Ventilation

Breathing :

The mechanical process of moving air into and out of the breathing system.

7.4 Ventilation

Ventilation :

The movement of air over the respiratory surface to faciliate gas exchange.

7.4 Ventilation

What is the difference in composition between

inhaled and exhaled air?

1 Collect two jars of inhaled air (atmospheric air) and two jars of exhaled air as shown.

Comparison of the composition of inhaled air and exhaled air

7.4 Ventilation

7.42 Lower a burning candle quickly into one jar

of inhaled air. Close the jar and record how long the candle can burn. Repeat with one jar of exhaled air.

7.4 Ventilation

3 Add 10 cm3 of red hydrogencarbonate indicator into one jar of inhaled air. Close the jar and shake. Note any colour change. Repeat with one jar of exhaled air.

7.4 Ventilation

Results and discussion

The results show that exhaled air contains less oxygen but more carbon dioxide than inhaled air.

Oxygen7.4 Ventilation

Inhaled air

Exhaled air

Why different / the same?

Used by body cells for respiration

Carbon dioxide7.4 Ventilation

Inhaled air

Exhaled air

Produced by body cells during respiration

Nitrogen7.4 Ventilation

Inhaled air

Exhaled air

Not used or produced by body cells

Water vapour7.4 Ventilation

Inhaled air

Exhaled air

Variable

Saturated

Moistened by mucus and water film

Other gases7.4 Ventilation

Inhaled air

Exhaled air

Temperature7.4 Ventilation

Inhaled air

Exhaled air

Cooler

Warmer

Warmed by blood

• Inhaled air consists mainly of oxygen.

7.4 Ventilation

• Exhaled air consists mainly of carbon dioxide.

Both inhaled and exhaled air consists mainly of nitrogen (about 78%).

7.4 Ventilation

There is more carbon dioxide than oxygen in exhaled air.

O2 7.4 Ventilation

Exhaled air contains a higher proportion of carbon dioxide when compared with that in inhaled air, its absolute amount (in terms of %) is still lower than that of oxygen.

7.4 Ventilation

1 Ventilation involves and ex . It is brought about by the movements of the and the .

inhalation

diaphragm

exhalationrib cage

7.4 Ventilation

Inhalation Exhalation

Diaphragm muscles

Diaphragm

Contract Relax

Flattened Dome shape

7.4 Ventilation

Intercostal muscles

Rib cage

Contract Relax

Moves upwards & outwards

Moves downwards & inwards

7.4 Ventilation

Volume of thoracic cavity

Increases Decreases

Inflated Deflated

7.4 Ventilation

Air pressure in lungs

Lower than atmospheric

pressure

Higher than atmospheric

pressure

Direction of air flow

Into the lungs

Out of the lungs

2 Exhaled air contains more / less O2 than inhaled air.

Its CO2 content is higher / lower than that in inhaled air.

Exhaled / Inhaled air is saturated with water vapour.

7.4 Ventilation

Which parts of our body are in actionwhen we yawn?1

Our mouth opens and we breathe in deeply. The abdominal muscles are stretched, the rib cage raises and the diaphragm is pushed down.

Where does the exchange of oxygenand carbon dioxide take place between our body and the atmosphere?

The exchange of oxygen and carbon dioxide takes place in the air sacs.

In what forms are oxygen and carbondioxide carried around our body?3

Oxygen is transported mainly in form of oxyhaemoglobin in red blood cells. Carbon dioxide is transported mainly in form of hydrogencarbonate ions dissolved in plasma.

Gas exchange

respiratory surface (air sacs)

human breathing system

are parts of

takes place at

Gas exchange

ventilation

breathing

brought about by

facilitated by

involvesbreathing

inhalation exhalation

contraction of intercostal &

diaphragm muscles

relaxation of intercostal & diaphragm muscles

brought about by

Gas exchange

respiratory gasesinclude

involves diffusion of

oxygen carbon dioxide

haemoglobin in red blood cells

hydrogencarbonate ions in plasma

transported by transported mainly as

1 2 Think about… 7.1 The human breathing system 7.2 Gas exchange in the air sacs 7.3 Transport of...

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