Very good revision tool

1. TOPIC 11-GAS EXCHANGE IN
HUMANS

2. THE RELATIONSHIP BETWEEN BREATHING, GAS
EXCHANGE AND RESPIRATION

3. 11.1 GAS EXCHANGE SURFACES
OBJECTIVES: 23/1/2024
1. To define gas exchange surfaces and give
examples.
2. To list the features of gas exchange surfaces.
QN: WHAT ARE GAS EXCHANGE SURFACES?
• THESE ARE SURFACES (MEMBRANES) THAT
ALLOW GASES TO MOVE IN AND OUT OF BLOOD
OF AN ORGANISM.
EXAMPLES:

4. •ALVEOLI
•GILL FILAMENTS
•CELL MEMBRANE
•MOIST SKIN
•CELL WALLS/CELL MEMBRANES OF
RESPECTIVE CELLS.

5. ACTIVITY: NAME THE GAS EXCHANGE SURFACES
ORGANISM GAS EXCHANGE SURFACE
HUMAN
FISH
BACTERIA/AMOEBA
EARTHWORM/FROGS
PLANTS

6. PROPERTIES OF GAS EXCHANGE
SURFACES
ALL GAS EXCHNAGE SURFACES HAVE:
1. Large surface area, for quick diffusion
2. Thin surface, to reduce distance for
diffusion to occur quickly.
3. Good blood supply (vascularized), for quick
transportation and maintenance of a
concentration gradient.
4. Good ventilation with air/water, to
maintain a concentration gradient
5. Moist surfaces- to dissolve the diffusing
gases.

7. 11.2 STRUCTURE OF THE HUMAN RESPIRATORY
SYSTEM:
OBJCTIVES: 19/1/24
1. To identify and name parts of the human respiratory system limited to the
 lungs, alveoli, associated capillaries.
 diaphragm,
 ribs,
 intercostal muscles,
 larynx, trachea,
 bronchi, bronchioles,
 Nose.
2. To state the functions of each part as well as the cartilage in the trachea.
ACTIVITY: 2
1. Identify the parts of the human respiratory system on a diagram and
describe their structure and functions.

8. MAIN PARTS OF THE HUMAN RESPIRATORY
SYSTEM.

9. •ACTIVITY 1:
1. Name and identify the parts shown below:

10. VENTILATION
OBJECTIVES:
1. TO Define ventilation
2. To explain the role of the ribs, the
intercostal muscles and the diaphragm in
ventilation.
Activity:
1. Define ventilation
2. Explain the role of ribs, intercostal
muscles and the diaphragm in ventilation
of the lungs.

11. The role of ribs, the internal and external intercostal muscles
and the diaphragm is to produce volume and pressure
changes in the thorax leading to ventilation of the lung

14. GAS EXCHANGE:
•Gas exchange takes place by diffusion in the
alveoli within the lungs.
•Oxygen diffuses from air sacs in the lungs to
red blood cells and combines with
hemoglobin to form oxyhemoglobin.
•Carbon dioxide diffuses out of blood to the
air sacs and expelled from the lungs together
with water vapor.
•As a result the composition of inhaled and
exhaled air is different.

15. THE AIR SACS/ALVEOLI

16. Gas exchange

17. BLOOD CAIPLLARIES AND ALVEOLI

18. How are alveoli adapted for gas
exchange?

19. COMPOSITION OF INSPIRED AND EXPIRED
AIR:
OBJECTIVES:
1. To explain the differences in
composition between inspired and
expired air.
2. To describe an experiment to
investigate the differences in
composition between inspired and
expired air, using limewater as a test

20. INHALED AND EXHALED AIR
•Inhaled air contains:
•more oxygen used to create energy
•less carbon dioxide than exhaled
air.
•Exhaled air contains:
•more carbon dioxide produced as a
waste product of energy production
•less oxygen as it has been used in
respiration

21. COMPOSITION OF INSPIRED AND EXPIRED AIR:
• The composition of inspired air, normal expired air is shown in
the Table:

22. EXPERIMENT PROVING THAT EXHALED AIR CONTAINS
MORE CARBON DIOXIDE THAN INHALED AIR.
• (A, B and C refer to the tubes unless specified)
• Close end of B. Breathe in. Air from atmosphere enters through A, passes through
limewater and enters your mouth (cannot enter through B because closed).
• Open end of B and close end of A. Breathe out.
• State and explain the observations

23. •RESULTS:
•Exhaled air passes through limewater in test
tube B and exits through B.
•Limewater in test tube B (which contained
the air you exhaled) turns milky much faster
than in test tube A (which contained the air
you inhaled).
•Conclusion:
•Air exhaled has more carbon dioxide than the
air inhaled.

24. BREATHING RATE AND EXERCISE:
Objectives:
• Explain the link between physical activity, rate and
depth of breathing.
• Investigate and describe the effects of physical activity on rate
and depth of breathing.
ACTIVITY 1:
1. WHAT IS THE EFFECT OF EXERCISE ON BREATHING RATE?
2. HOW IS THIS EFFECT BROUGHT ABOUT?
3. WHY IS this CHANGE NECESSARY.

25. •The increased rate and depth of breathing
during exercise allows more oxygen to dissolve
in the blood and supply the active muscles.
•The extra carbon dioxide that the muscles put
into the blood is detected by the brain, which
instructs the intercostal muscles and diaphragm
muscles to contract and relax more rapidly,
increasing the breathing rate.
•Carbon dioxide will be removed by the faster,
deeper breathing.

26. INVESTIGATING AND MEASURING RATE AND
DEPTH OF BREATHING:
Activity:
1. Describe an investigation to measure rate of
breathing
2. Describe the use of an equipment to
measure the depth of breathing.

27. • To investigate the effects of exercise on breathing,
record the rate of breathing for a few minutes when the
person is at rest.
• After they do some exercise, record their rate of
breathing every minute until it returns to the normal
resting value.
• Repeat step 1and 2 several times to find the mean for
more reliable results.
• The rate of breathing can be measured by counting the
number of breaths in one minute.
• The depth of breathing can be measured using a
spirometer (a device that measures the volume of air
inhaled and exhaled in one breath-tidal volume.).

28. PROTECTING THE GAS EXCHANGE SYSTEM
Objective:
Explain the role of goblet cells, mucus and ciliated cells in protecting the gas
exchange system from pathogens and particles.
Pathogens are present in the air we breathe in and are potentially dangerous if
not actively removed. There are two types of cells that provide mechanisms to
help achieve this.
1. Goblet cells are found in the epithelial lining of the trachea, bronchi and some
bronchioles of the respiratory tract. Their role is to secrete mucus. The mucus forms a
thin film over the internal lining. This sticky liquid traps pathogens and small particles,
preventing them from entering the alveoli where they could cause infection or
physical damage.
2. Ciliated cells are also present in the epithelial lining of the respiratory tract. They are
in a continually flicking motion to move the mucus, secreted by the goblet cells,
upwards and away from the lungs.
3. When the mucus reaches the top of the trachea, it passes down the gullet during
normal swallowing, taking the trapped particles with it and thus removing it from the
system.

29. REVIEW ACTIVITY 1
• Fig. 1.1 shows photomicrographs of lung tissue at the same
magnification. One shows healthy lung tissue and the other shows lung
tissue from a person with COPD. Line AB shows the diameter of one
healthy alveolus. Line CD shows the diameter of an area of lung where
the alveoli have been destroyed.

30. (a) Describe three visible ways that the lungs of the healthy person differ from
the person with COPD in Fig. 1.1. (3)
(b) Some students decided to investigate the concentration of carbon dioxide in
expired air compared to that in inspired air.
They used the apparatus shown in Fig. 1.2 by breathing into the tube labelled T.

31. (i) Suggest one possible hazard in this investigation. [1]
(ii) State one other substance which could be used instead of limewater to
determine the concentration of carbon dioxide. [1]
(iii) When the students used the apparatus shown in Fig. 1.2, inspired air
passed through the limewater in test-tube A and expired air passed through
the limewater in test-tube B.
The students timed how long it took for the limewater in test-tubes A and B to
go cloudy.
Their results are shown in Table 1.1.

32. The concentration of carbon dioxide in inspired air is 0.04%. Calculate, using
the results in Table 1.1, the concentration of carbon dioxide in expired air.
Show your working. [3]
(c) A student wanted to investigate the hypothesis:
‘Expired air contains more carbon dioxide immediately after exercise than
before exercise.’
Plan an investigation using the apparatus shown in Fig. 1.2 to test this
hypothesis. [6]