LECTURE 11:
GAS
EXCHANGE
BIOLOGY
PREPARED BY:
DIVINE GRACE S. BATENGA, MSC,
LPT
LEARNING OUTCOMES
GAS EXCHANGE
2
MECHANISMS
OF GAS
EXCHANGE
Gas exchange occurs thin, moist
surfaces in respiratory organs
such as gills, tracheal systems,
and lungs.
G A S E X C H A N 3G E
Gas exchange in humans involves breathing, transport
of gases, and exchange with body cells.
• GASE EXCHANGE – the exchange of
O2 and CO2 between an organism and
its environment.
• Enable you to harvest energy from the
food molecules the digestive system
provides.
GAS EXCHANGE
4
1) BREATHING: as you inhale, a large,
moist internal surface is exposed to the
air entering the lungs.
2) TRANSPORT OF GASES BY THE
CIRCULATORY SYSTEM: the O2 that
diffused into the blood attaches to
hemoglobin in red blood cells.
3) EXCHANGE OF GASES WITH BODY
CELLS: your cells take O2 from the
blood and release O2 into the blood.
GAS EXCHANGE
5
Animals exchange O2 and CO2 across moist body
surfaces.
• RESPIRATORY SURFACE – the part
of an animal’s body where gas is
exchanged with the environment
• Made up of living cells, and like all cells, their
plasma membranes must be wet to function
properly.
• Respiratory surfaces are always moist.
GAS EXCHANGE
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Four types of respiratory organs, structures in which
gas exchange with the external environment occurs.
• Some animals use their entire
outer skin as a gas exchange
organ.
• There are no specialized gas
exchange surfaces.
• Oxygen diffuses into a dense
network of thin-walled
capillaries lying just beneath
the skin.
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Four types of respiratory organs, structures in which
gas exchange with the external environment occurs.
• Gills are extensions, or
outfoldings, of the body surface
specialized for gas exchange.
• The gills of clams and crayfish
are clustered in one body
location.
• A fish has a set of feather-like
gills on each side of its head.
GAS EXCHANGE
8
Four types of respiratory organs, structures in which
gas exchange with the external environment occurs.
• The tracheal system of insects is
an extensive system of
branching internal tubes with a
thin, moist epithelium forming
the respiratory surface at its tips.
GAS EXCHANGE
9
Four types of respiratory organs, structures in which
gas exchange with the external environment occurs.
• Most terrestrial vertebrates have
lungs which are internal sacs
lined with moist epithelium.
• Gases are carried between the
lungs and the body cells by the
circulatory system.
GAS EXCHANGE
10