Transcript Lung Structure PowerPoint slides Unit 1 VCE Biology

VCE Unit 1 Biology
Respiration
Lung structure and function
The respiratory system
Structure of the respiratory system?
1. Air enters the
nose/mouth
2. Air travels in the
trachea
3. Air reaches major
bronchi
4. Air then gets fed
through a number
of smaller tubes
called bronchioles
5. Air eventually
reaches the alveoli
Functions of the upper airway
•
•
•
•
Nose, larynx and
trachea
Warms and
humidifies inspired
air
Traps & eliminates
foreign particles –
involved in coughing
Not involved in gas
exchange
Functions of the lower airway
•
From the bronchi to
lungs
•
Secrete mucus to
catch foreign
material
•
Cilia (hair-like
structure on top of
cell) can beat to
push mucus back up
airways where it can
be coughed out
The alveoli are the site of gas exchange
•
There are approximately 8 million alveoli in our
lungs
•
The look a bit like a bunch of grapes
•
If you spread out each of these alveoli, they would
take up an entire tennis court!
Alveoli are surrounded by capillaries
Why do you think this is the
case?
Alveoli are surrounded by capillaries
Answer:
• Capillaries ensure that the breathed “air” is brought into
close proximity to the “pulmonary” blood.
• This allows thorough gas exchange between the air and
the blood
Thin tissue separates blood from alveoli
• Alveolar and capillary walls are thin, permitting
rapid diffusion of gases.
• Each RBC is only in lung capillary for 1 second
(RBC)
Answer the following in your workbooks
• Where does gas exchange occur?
• What structures does air pass through to get to the site of
gas exchange?
• What would happen if there was a thick gap between the
alveoli and the capillaries?
• Name a disease where the gap between the alveoli and
capillary is increased.
• What respiratory structure is affected in bronchitis and
asthma?
Questions to be finished for homework and handed in next
class
Respiratory muscles allow us to inspire
• There are two phases in respiration
(breathing): inspiration and expiration
• Inspiration (breathing in) allows gas to
enter the lung
• Expiration (breathing out) allows gas to
exit the lung
The process of inspiration
• Inspiration relies on the diaphragm and the rib
muscles
• The diaphragm is a very thin muscle that
separates the chest cavity from the abdomen
• During inspiration, the diaphragm and rib muscles
contract. This increases the size of the chest
cavity.
• The increase in chest cavity size decreases
pressure inside the chest.
• As a result, the lungs are expanded and air is
sucked in (just like a vacuum!)
The process of expiration
• Expiration occurs when the muscles relax
• The lungs undergo a process called recoil which
allows them to return to their original size
• Recoil of the lungs occurs because the lungs are
very elastic – just like an elastic band!
Question: what
happens to an elastic
band after you
stretch it?
Muscles of Respiration
Inspiration
• Inspiratory muscles
act to  chest
volume
• Diaphragm - major
inspiratory muscle
• Rib muscles – help
the diaphragm to
increase chest volume
Expiration
• The muscles relax
• The lungs recoil
because they are
elastic
Lung expansion relies on intrapleural pressure.
• How does increasing and
decreasing thoracic volume
alter lung volume?
• The lungs are only attached
at the hilus!
• Lung expansion following
increased thoracic volumes
is dependent on intrapleural
pressures
Lung only attached at hilus
What is intrapleural space?
• Each lung is attached to and
surrounded by a thin membrane
called a visceral pleural sac
Visceral pleura
• The inside of the rib cage is also
covered in a thin membrane
called the parietal pleura
• These two membranes are
separated by the a thin layer of
liquid known as the intrapleural
space
• Imagine effects of drop of water
between two glass sheets - easy to
slide; hard to pull apart
Parietal pleura
Intrapleural space
(-5cmH2O)
Why is intrapleural space important?
• The pressure within the intrapleural
space is negative (like a vacuum). This
holds the lungs open even though they
want to collapse like an elastic band
• When the chest expands during
inspiration, the intraplueral pressure
becomes even more negative and
sucks the lung to the chest wall
• This results in the lungs expanding
during inspiration
Visceral pleura
Parietal pleura
Intrapleural space
Loss of intrapleural pressure
Sheep diaphragm
Loss of intrapleural
pressure…
Using a model to understand breathing
• Using the instructions provided on the handout, make
your own model of a chest cavity, diaphragm and lungs
• This will help you understand the processes of inspiration,
expiration and intrapleural pressure
• Complete the questions on the handout (for homework if
necessary)
What is in the air we breathe?
• Atmospheric air contains mostly nitrogen
gas and oxygen
• Nitrogen makes up approximately 80% of air
but is “inert”
• Oxygen makes up approximately 21% of air
• Not much carbon dioxide is in atmospheric
air – it only makes up a tiny percentage
(0.0004%!)
• Small amounts of water vapour and other
gases are also present
What do our cells need?
• The cells in our body need oxygen to
survive
• They use this oxygen in a process called
metabolism to create energy
• A by-product of metabolism is the
generation of carbon dioxide
• Carbon dioxide can be toxic if it builds up in
the body
• Therefore, the lungs need to supply oxygen
for our cells but remove carbon dioxide
How do the lungs do this?
• Via a process called “gas exchange”
• Gas exchange does not occur on a 1:1
basis (ie 1 molecule of oxygen is not
exchanged for every molecule of carbon
dioxide)
• Rather the entry of oxygen into the blood
and the removal of carbon dioxide occurs
according to differences in concentrations
between the alveoli and blood
• That is, it occurs via diffusion, down a
concentration gradient
What happens then?
• Once oxygen diffuses across the alveoli, it
enters the blood. Which components of
blood carries oxygen?
• Gases dissolve within the blood. They do
not exist as bubbles. (eg The bends in
diving – what happens when bubbles of gas
form in the body?)
• The oxygenated blood travels to the heart
and then around the body to the
tissues/cells.
Blood goes to tissues and then returns
to the lung
• The oxygen diffuses down its concentration
gradient to enter the tissues
• Carbon dioxide concentrations are high in
the cells. What do you think happens to the
carbon dioxide here?
• Blood returning to the lung is deoxygenated.
What does this mean?
• What happens to this blood at the lungs?
• What happens to the blood then? Think
back to your circulation lessons!
Diffusion of gases at the alveoli
Gas exchange re-enactment
• Come and collect 3 balloons each
• There are 3 different colours and different
numbers of each colour
• Which gas do you think each colour represents
(nitrogen, oxygen, carbon dioxide – think about
relative percentages)
• If you have brown eyes, you are going to
represent gas in the atmosphere are in the lungs
• If you have don’t have brown eyes, you need to
stand behindn the tables – you are gas molecules
in the blood stream