Download 6.4 Respiration

Topic 6.4 Gas Exchange
6.4.1 distinguish between:
• Ventilation – breathing (air in and out of
lungs)
• Gas Exchange – diffusion of gases.
Occurs in 2 places:
• Cellular Respiration – What is it and where
does it take place?
Diffusion
• Protists, sponges, cnidarians, and
flatworms all obtain oxygen and get rid of
carbon dioxide via diffusion with the
aqueous environment in which they live.
• In all animals, the respiratory surface must
be moist and thin. In many it is highly
branched to provide greater surface area.
6.4.2 Need for ventilation system
• We are large so our surface area/volume
ratio is not favorable for the diffusion of
gases.
• Our exterior surface (skin) is not suited for
the exchange of gases. Respiratory
surfaces should be moist.
• A ventilation system ensures that the
transfer of gases is encouraged due to
concentration gradients.
6.4.4 Anatomy
Draw and label
• Nasal cavity – separated from mouth by
palate. Warms, filters, moistens air
• Pharynx – common passageway for
respiration and digestion
• Larynx – top of trachea, contains vocal
cords. Opening to larynx is glottis,
protected by epiglottis
• Trachea – C shaped rings of cartilage
support. Forks into 2 bronchi.
• Bronchi branch to form bronchioles
• Tips of bronchioles end in clusters of air
sacs called alveoli where gas exchange
occurs.
• Each lung has about 300 million alveoli
• Each alveoli cluster is surrounded by a
capillary bed.
3.4.3 Alveolar structure
• The small spherical shape of alveoli
provide a large surface area for gas
exchange
• Single cell thickness makes it easy for
gases to diffuse through alveoli wall
• Moisture allows for efficient diffusion
• Capillary bed ensures gases do not have
to diffuse far to reach circulatory system
Question
• Pneumonia (excess mucus) and smoking
(tar) create an extra lining inside of each of
the alveoli. Describe how and why this
could become life-threatening.
Ventilation
• Mammals – negative pressure breathing.
• Recall that there is an inverse relationship
between pressure and volume.
• Diaphragm and intercostal muscles
change the size of thoracic cavity which
changes air pressure in lung. Air always
flows from high pressure to low.
Inspiration
• Diaphragm contracts (moves down) and
intercostal muscles raise rib cage.
• Volume of thoracic cavity increases which
lowers air pressure in lungs (partial
vacuum)
• Air flows from high pressure (atmosphere)
to low pressure (lung) via your
mouth/nasal passages trachea
bronchi……
Expiration
• Diaphragm and intercostal muscles relax.
Diaphragm rises and rib cage collapses.
• Pressure in thoracic cavity increases. Air
flows from high pressure (lung) to low
pressure (atmosphere) and exits the way it
entered.