CHAPTER 10
Respiration in
Humans
Chapter
10
Respiration in Humans
10.1 Why Do Living Things Respire?
10.2 Studying Respiration
10.3 Gas Exchange in Humans
10.4 Breathing Mechanisms in Humans
10.5 Effects of Tobacco Smoke on Human Health
10.1
Why Do Living Things Respire?
Learning Outcomes
After this section, you should be able to:
• understand that living things respire to release the
energy locked up in food molecules;
• define aerobic respiration and anaerobic
respiration;
• state the equation, in words and in symbols, for
aerobic respiration and anaerobic respiration in
humans; and
• describe the effect of lactic acid in muscles during
exercise.
10.1
Why Do Living Things Respire?
Why respire?
• Living organisms respire because they need energy
to sustain life.
• Energy that is needed for organisms to move, grow,
excrete and reproduce, is obtained through the
consumption of food.
• To use the energy available in food, living things
need to break down the food molecules through a
process called ____________________.
• The oxidation of food molecules to produce energy
is called ____________________.
10.1
Why Do Living Things Respire?
What is aerobic respiration?
• It is the breakdown of food molecules in the
____________________.
• It results in the production of __________________
and it gives off ____________________ and
_______________ as waste products.
• The chemical equation for aerobic respiration:
C6H12O6
glucose
+6
O2
oxygen
6
CO2
carbon
dioxide
+6
H 2O
water
+
energy
Why Do Living Things Respire?
10.1
What is anaerobic respiration?
• It is the breakdown of food molecules in the
____________________.
• It releases __________________ than aerobic
respiration.
• The chemical equation for anaerobic respiration in
humans:
C6H12O6
glucose
2
C 3 H 6 O3
lactic acid
+
energy
(energy produced
is less than in
aerobic respiration)
10.1
Why Do Living Things Respire?
What happens during exercise and why?
• Muscles ___________________ to enable movement.
• Respiratory rate and heart rate increase to enable more
oxygen to reach the muscles.
• If the increased oxygen intake is not able to meet the
oxygen demand, an __________________ results and
___________ takes place to provide the energy required.
• Anaerobic respiration results in the accumulation of
____________________ in the muscle cells.
• Lactic acid accumulation can cause _______________
and muscular pains.
Chapter
10
Respiration in Humans
10.1 Why Do Living Things Respire?
10.2 Studying Respiration
10.3 Gas Exchange in Humans
10.4 Breathing Mechanisms in Humans
10.5 Effects of Tobacco Smoke on Human Health
10.2
Studying Respiration
Learning Outcomes
After this section, you should be able to:
• describe simple experiments that show what the
products of respiration are.
10.2
Studying Respiration
Carbon dioxide is a product of respiration
• The potassium hydroxide in flask A removes carbon
dioxide from the air entering flask B.
• The limewater in flask B should not turn chalky.
• The air entering flask C does not contain carbon dioxide.
Hence, any carbon dioxide detected in flask D would be
due to respiration by the snails.
A
B
potassium
limewater
hydroxide solution
C
D
snails
limewater
10.2
Studying Respiration
Carbon dioxide is a product of respiration
• The glucose solution that is used was
first boiled and cooled to remove the
dissolved oxygen from the solution.
• Due to the limited oxygen available to
the yeast, the yeast undergoes
anaerobic respiration.
• If carbon dioxide is released during the
anaerobic respiration of yeast, the
limewater will turn chalky.
glucose and yeast
suspension
limewater
10.2
Studying Respiration
Heat is a product of respiration
• The vacuum flask prevents heat from
escaping and entering the area where
the seeds are germinating.
vacuum
flask
• The cotton wool plug allows gaseous
exchange between the seeds and the
environment.
• The antiseptic solution prevents the
growth of microorganisms like bacteria.
• If heat is produced during respiration,
the thermometer would register a
temperature higher than the surrounding
temperature.
pea seeds
in antiseptic
solution
cotton wool
plug
thermometer
Chapter
10
Respiration in Humans
10.1 Why Do Living Things Respire?
10.2 Studying Respiration
10.3 Gas Exchange in Humans
10.4 Breathing Mechanisms in Humans
10.5 Effects of Tobacco Smoke on Human Health
10.3
Gas Exchange in Humans
Learning Outcomes
After this section, you should be able to:
• identify the parts in the human gaseous exchange
system;
• describe the role of the alveoli in gaseous
exchange; and
• describe the removal of carbon dioxide from the
lungs.
10.3
Gas Exchange in Humans
Why the need for a respiratory system?
• Humans are large organisms that are made up of
millions of cells.
• We have a _______________________________,
unlike unicellular microorganisms.
• Therefore, we need a special system of organs for
gaseous exchange between the environment and
the cells in our bodies.
• This mechanism of exchange is called external
respiration and it involves a process called
_________________________.
10.3
Gas Exchange in Humans
Human gas exchange system
nasal passage
pharynx
larynx
The fringe of hair and the
mucous layer on the walls
of the _______________
trap dust and foreign
particles.
As the air passes through
the air passages, it is
warmed and moistened.
Gas Exchange in Humans
10.3
Human gas exchange system
nasal passage
pharynx
larynx
The _________________
is supported by C-shaped
rings of cartilage that
ensure that the trachea is
always open.
_________
_________
C-shaped
ring of
cartilage
Transverse section of a trachea
10.3
Gas Exchange in Humans
On the inner walls of the
trachea and bronchi are:
• ____________, and
• ___________________
_
Gland cells _____________
that trap dust particles and
bacteria in the air that is
channelled to the lungs.
Ciliated cells have __________
that sweep the trapped
particles and bacteria up the
bronchi and trachea, into the
___________________.
gland cell
mucus
produced
by gland
cell
cilia
ciliated cell
Gas Exchange in Humans
10.3
Human gas exchange system
nasal passage
pharynx
larynx
trachea
The lungs lie in the pleural
cavity.
Within the lungs, the bronchial
tubes divide repeatedly to form
__________________.
Bronchioles end in cluster of
_______________ called
____________________.
bronchus
_____________
__________
cluster of _________
UR
L
10.3
Gas Exchange in Humans
The alveoli
The alveoli are the ______
_____________________.
The numerous alveoli in the lungs increase
the surface area for gaseous exchange.
10.3
Gas Exchange in Humans
The alveoli
blood vessel
blood vessel
from heart
to heart
The alveoli are well-supplied
with _________________ to
enable the efficient exchange of
gases.
air in and out
The alveolar surface is coated
with a ___________________.
This allows gases to dissolve in
it.
capillary
wall
alveolar
wall
capillary
thin film
network
of water
The wall of each alveolus is only
_____________________. It is
supplied by _______________
that are also only one cell thick.
Gas Exchange in Humans
10.3
Gas exchange in the alveolus
inhaled oxygen
carbon dioxide
to be exhaled
oxygenated blood
(transported to the
heart and enters the
systemic circulation)
alveolus
deoxygenated
blood (carbon
dioxide rich)
CO2
O2
capillary
UR
L
Gas Exchange in Humans
10.3
How oxygen is transported
Haemoglobin
Oxygen molecules bind to ________________
(Hb) in red blood cells to form
__________________________.
+ O2
- O2
Oxyhaemoglobin
O2
High O2 concentration
Hb
haemoglobin
+
4 O2
oxygen
Low O2 concentration
O2
Hb
O2
O2
oxyhaemoglobin
10.3
Gas Exchange in Humans
How carbon dioxide is transported
Carbon dioxide molecules from respiring cells
enter the red blood cells in the blood stream.
There, the carbon dioxide molecules react with
water to form ____________________.
This reaction is catalysed by an enzyme found in the red blood cells
– ____________________.
The carbonic acid is then converted into ______________________
which will diffuse out of the red blood cells and into the blood
plasma.
Most of the carbon dioxide is transported as hydrogen carbonate
ions in the _________________________.
Chapter
10
Respiration in Humans
10.1 Why Do Living Things Respire?
10.2 Studying Respiration
10.3 Gas Exchange in Humans
10.4 Breathing Mechanisms in Humans
10.5 Effects of Tobacco Smoke on Human Health
10.4
Breathing Mechanisms in Humans
Learning Outcomes
After this section, you should be able to:
• describe the role of the cilia, diaphragm, ribs and
intercostal muscles in breathing.
10.4
Breathing Mechanisms in Humans
nasal passage
pharynx
larynx
trachea
bronchus
The ______ support the chest
wall.
Two sets of muscles can be found
between the ribs:
• ____________________, and
• ____________________.
________
bronchiole
lung
cluster of alveoli
10.4
Breathing Mechanisms in Humans
Intercostal muscles
Vertebral
column
Sternum
Rib
Intercostal
muscles
Left lung inside
the rib cage
The intercostal muscles
move the rib cage up and
down during breathing.
10.4
Breathing Mechanisms in Humans
The ______________
is a dome-shaped
sheet of muscle and
elastic tissue that
contracts and relaxes
to change the volume
of the ____________.
nasal passage
pharynx
larynx
trachea
rib
bronchus
bronchiole
lung
cluster of alveoli
____________
UR
L
10.4
Breathing Mechanisms in Humans
Inspiration
air is sucked in
2
spinal
column
External intercostal muscles
contract and internal intercostal
muscles relax  rib cage is raised
__________________ and
__________________
3
Thoracic volume ___________,
so air is drawn into the lungs
1
Diaphragm __________
and flattens down.
10.4
Breathing Mechanisms in Humans
air is expelled out
Expiration
2
spinal
column
External intercostal muscles
relax and internal intercostal
muscles contract  rib cage
moves _________________
and ____________________
3
Thoracic volume __________,
lungs are compressed and air
is forced out of the lungs
1
Diaphragm ____________
and arches upwards.
10.4
Breathing Mechanisms in Humans
Model showing the movement of the ribs
during breathing
Just like how the handle
of a pail is moved
upwards
External
intercostal
muscles contract,
raising the ribs
upwards
Internal intercostal
muscles relax,
allowing the ribcage
to move outwards
Position during
inspiration
Position during
expiration
10.4
Breathing Mechanisms in Humans
What is the stimulus for breathing?
Which curve, A, B or C, represents what happens when pure
oxygen is supplied for breathing?
Number of breaths per minute
high
low
Answer:
A
90% O2 + 10% CO2
B
21% O2 + 0.03% CO2
C
100% O2
Time
Carbon dioxide is the stimulus for breathing.
Chapter
10
Respiration in Humans
10.1 Why Do Living Things Respire?
10.2 Studying Respiration
10.3 Gas Exchange in Humans
10.4 Breathing Mechanisms in Humans
10.5 Effects of Tobacco Smoke on Human
Health
10.5
Effects of Tobacco Smoke
on Human Health
Learning Outcomes
After this section, you should be able to:
• describe the effects of the major toxic components
of tobacco smoke on human health.
10.5
Effects of Tobacco Smoke
on Human Health
Nicotine
•
•
•
addictive
makes blood clot more
easily
increases the risk of
heart diseases
Carbon monoxide
•
•
•
decreases the ability of red
blood cells to transport oxygen
increases the rate at which fats
are deposited on the inner
arterial walls
increases the risk of
artherosclerosis
Irritants
(e.g. formaldehyde, hydrogen
cyanide)
•
•
paralyse the cilia lining in air
passages
increase the risk of chronic
bronchitis and emphysema
Tar
•
•
•
carcinogenic
paralyses the cilia lining
in air passages
reduces the efficiency of
gaseous exchange
10.5
Effects of Tobacco Smoke
on Human Health
Chronic bronchitis
In chronic bronchitis,
• the epithelium lining the airways is
inflamed,
• there is excessive mucus
secretion, and
• the cilia lining the airways are
paralysed.
Symptoms:
• Breathing difficulties due to
blocked airways
• Persistent cough (body’s
response to clear the blocked
airways)
over secretion
of mucus
cilia paralysed and
unable to remove
mucus
10.5
Effects of Tobacco Smoke
on Human Health
Emphysema
In emphysema,
• the partition walls of alveoli
break down due to violent
coughs. (This reduces the
surface area available for
gaseous exchange.)
• The lungs lose their elasticity
and become inflated with air.
Symptoms
• Breathing difficulties
• Wheezing
partition
walls
between
alveoli
healthy
lungs
damaged
partition
walls
diseased
lungs
Chapter
10
Respiration in Humans
Chapter
10
Respiration in Humans
The URLs are valid as at 15 October 2012.