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Breathing and Gas Exchange
Breathing and Respiration
Respiration is the oxidation of glucose
Breathing is the exchange of gasses in the lungs
Ventilation
Not Really The Respiratory System
Proper term should be the
Gas Exchange System
Composition of Air
Inhaled
Oxygen – 21%, Carbon dioxide – 0.04%, Nitrogen – 79%
Exhaled
Oxygen – 17%, Carbon dioxide – 4%, Nitrogen – 79%
Composition of Air
Exhaled is also saturated with 6% water vapour
Basic Structure
Larynx
Trachea
Bronchus
Bronchioles
Alveolus
Pleural membrane
Pleural fluid
Diaphragm
Basic Structure
The are found in the thorax of the body
You may be wondering why they are C-shaped and not full circles.
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.
Diagram of trachea with cartilage rungs
Organ 2 Organ 1
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.
Danger of friction
pleural membrane
lung
fluid
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.
The Lungs
Regulate breathing
A route for water loss and heat elimination
Removal of CO2
Maintains acid-base balance
Enables speech, singing, etc.
Serves as defense mechanism
Affect chemical signals
Breathing
When you breathe in (inhale), your hands move up and outwards.
When you breathe out (exhale), your hands move down and inwards.
Take a breath
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.
Inhaling: chest expansion
Breathing
Air moves into and out of the lungs by changing volume
Volume is increased by the contraction of the diaphragm and the intercostal muscles
Intercostal Muscles
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.
inhaling
The diaphragm
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.
Low
High
Diaphragm flattens
Air pressure drops
Thorax volume increases
High air pressure outside
Low air pressure inside
Air diffuses into the lungs
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.
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
Features of inhalation and exhalation
Click on the “Air Drawn In” buttons
Click on the “Passage of air” buttons
Control of Respiration
Chemoreceptors in the carotid arteries monitor pH of the blood
Control of Respiration
When CO2 production increases blood pH decreases.
Chemoreceptors sends a message to the diaphragm and intercostal muscles to increase breathing rate
Air Breathed
Tidal air – quiet breathing, ½ litre
Vital capacity – forced breathing, 3.5 litre
Residual air – can’t expelled, 1.5 litre
The lungs
Keeping Airways Clean
Cilia hairs
Mucus
ciliated cells
mucus being made by the ciliated cells
microbes travelling
down the trachea
within inhaled air
microbes become stuck
within the mucus
The presence of mucus and cilia on the lining of the trachea
ensures that the air we breathe is clean and free from disease.
.
swallowed
coughed out
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
Actually, each air sac is found to
be a bundle of air sacs.
Together, they are known as an
alveolus.
We can look inside the alveolus to get some idea of why they
are shaped the way they are.
The outside of the alveolus is
covered with tiny blood vessels.
Oxygen makes its way to special air sacs.
Inside an alveolus
Alveoli (air sacs)
provide large surface area for gas exchange
one lung equivalent to a tennis court of surface area using alveoli
Features of Alveoli for efficient
gas exchange
large surface area to absorb oxygen.
moist surface to allow oxygen to dissolve.
thin lining to allow easy diffusion of gases.
dense network of blood capillaries for easy gas exchange.
oxygen (O2) gas
passes through here
This O2 is then
able to dissolve in
a small moist
lining.
epithelial lining
of the alveolus
A cross-section of an alveolus
O2 O2
O2
O2
dissolve
dissolve
moist lining
This moist lining also stops the alveolus from drying and cracking. It
lubricates the insides of the air bag.
Keeping the environment right
Diffusion at work
After the oxygen dissolves it also diffuses.
O2 O2 O2 O2 cell lining of
alveolus
cell lining of
capillary
blood
D I F F U S I O N
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.
Oxygen diffusion into red blood cells
Features of capillaries for
efficient gas exchange
dense network to carry CO2 and O2
Large surface area to transport gases
Lining is one cell thick so gases can pass through quickly and easily.
Carbon Dioxide
CO2 is transported as dissolved bicarbonate ions (HCO3) in the plasma
This formation occurs in the red blood cells.
Hemoglobin (Hb)
Four protein fractions
O2 binds to the iron heme group
Hemoglobin (Hb)
Binding increased by many different conditions:
Increase in pH
Decrease in Temperature
Increase in CO2
High altitude
Diffusion into Tissue
Why Do You Breath Faster When You Exercise?
Lung Diseases
Pollution
Cystic fibrosis
Bronchitis
Enemia
Lung Diseases
Smoking
Emphysema
Lung cancer
Carbon monoxide