2. 6.4.1
Ventilation- The flow of air within the lungs that
rotates Oxygen (O2) and Carbon Dioxide (CO2) in
and out of the lungs. Also allows for Oxygen and
Carbon Dioxide to diffuse in and out of the alveolus.
Gas Exchange- The changing of Oxygen and
Carbon Dioxide within the capillaries of the lungs.
Cell Respiration- The feeding of Oxygen and the
taking away of Carbon Dioxide to and from the cells
which allows for the cells to produce energy to carry
out their functions.
3. 6.4.2- WHY WE NEED A VENTILATION SYSTEM
A Ventilation system is needed when an organism
is very wide.
An aerobic single-celled organism like an amoeba
survives because oxygen can enter the cell from all
sides.
In humans, only the outer layer of skin is exposed
to oxygen.
The respiratory system and the circulatory system give
oxygen to the rest of the cells not exposed to oxygen.
4. 6.4.3- FEATURES OF ALVEOLI
Feature Function
Spherical Shape Large surface area for diffusion
of gases
Flattened, Single Cell Thickness Gases only have to diffuse
through one layer of cells
Moist Inner Lining of Alveolus Allows for efficient diffusion
Nearby Capillary Bed Shorter distance for gases to
diffuse into capillaries
6. 6.4.5- MECHANISM OF VENTILATION
Inhalation
The external intercostal muscles contract. This moves
the ribcage up and out.
The diaphragm contracts. As it does so it moves down
and becomes relatively flat.
Both of these muscle contractions result in an increase
in the volume of the thorax which in turn results in a
drop in pressure inside the thorax.
Pressure eventually drops below atmospheric pressure.
Air then flow into the lungs from outside the body,
through the mouth or nose, trachea, bronchi and
bronchioles.
Air continues to enter the lungs until the pressure inside
the lungs rises to the atmospheric pressure.
7. 6.4.5- MECHANISM OF VENTILATION
Exhalation
The internal intercostal muscles contract. This moves the
ribcage down and in.
The abdominal muscles contract. This pushes the diaphragm
up, back into a dome shape.
Both of these muscle contractions result in a decrease in the
volume of the thorax.
As a result of the decrease in volume, the pressure inside the
thorax increases.
Eventually the pressure rises above atmospheric pressure.
Air then flows out of the lungs to outside of the body through
the nose or mouth.
Air continues to flow out of the lungs until the pressure in the
lungs has fallen back to atmospheric pressure
