Transcript Gas Exchange and Breathing

Gas Exchange and
Breathing
Characteristics of a Gas Exchange Surface
Structure and Functioning of the Gas
Exchange System
The Need for Gas Exchange and Ventilation
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In humans O2 is used in cell respiration (in cytoplasm
and mitochondria) and CO2 is released
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Gas exchange happens in the alveoli of human lungs:
O2 diffuses from the air into the alveoli to blood
capillaries, CO2 diffuses in opposite direction
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A ventilation system maintains a high conc. Of O2 in
the alveoli
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Ventilation in humans is produced by changes in
pressure in the chest cavity. Changes in pressure are
carried out by the action of two sets of muscles in the
breathing apparatus: diaphragm and the intercostal
muscles
How are alveoli adapted to gas
exchange?
Adaptations of the alveoli to gas exchange
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Alveoli are small (~100 um in diameter) but the lungs contain
hundreds of millions of alveoli (huge overall surface area for
gas exchange)
Walls of the alveoli and capillaries consist of a single layer
The capillaries surrounding the alveoli contain high CO2 and
low O2 concentration
Cells in the alveolus secrete a fluid which helps keep the walls
moist facilitating gas diffusion
The walls of the alveoli produce a natural detergent that
prevents the walls from sticking together. Certain alveolar cells
synthesize a mixture of lipoproteins called surfactant (secreted
into alveolar air spaces continuously, reduces surface tension
thus decreasing tendency of alveoli to collapse
Ventilation of the Lungs
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Air is inhaled into the lungs
through trachea, bronchi
and bronchioles
Air is exhaled via the same
route
What are the structures
involved in gas
exchange???
Gas Exchange Structures
Structure
Description
Function
Nostrils/Nasal
cavity
Internally supported by bone
and cartilage. w/numerous
internal hairs
Larynx
Top of trachea.. Composed of Houses vocal cords
muscles, cartilage and elastic Prevents foreign objects
tissue
from entering trachea
Glottis/epiglottis
Entrance to the nasal
cavity; warms-up air;
remove particles from air
Pharynx
Cavity line-up by
mucous epithelium
Passageway of food.
Aids in producing sounds
Trachea
Cartilage (25 c-shaped).
Flexible, cylindrical. 2.5 cm
dia. 12.5 cm length. In front
of esophagus. Line-up with
ciliated mucus
Passageway of air.
Continues to remove
particle of air
Structures of the Gas Exchange
System (cont…)
Bronchi
(bronchus)
Branched cartilaginous
tube. Lined-up by
mucous epithelium
Conducts air form
trachea to
bronchioles
Bronchiolus
Branched cartilaginous
tube. Lined-up by
mucous epithelium
Conducts air from
bronchioles to alveoli
Diaphragm
Muscle tissue.
Dome-shaped
Inhalation and
Exhalation
Lungs
Contain alveoli, blood
Gas exchange
vessels, lymphatic
(diffusion of gases)
vessels and nerves of the
lower resp. tract
Ventilation of the Lungs
INHALING
The external intercostal muscles
contract, raising the ribs and
elevating sternum
The diaphragm contracts becoming
flatter and moving downwards
The muscle movements increase the
volume of the thorax. Lungs
expand, partial lung pressure
decreases
The pressure inside the thorax
therefore drops below
atmospheric pressure
Air flows into the lungs from outside
the body until the pressure inside
the lungs rises to atmospheric
pressure
EXHALING
The internal intercostal muscles relax
following inhalation. Abdominal
organs spring back to original
shape, moving the ribcage down
and in
The diaphragm pushes up into a
dome shape
The muscle movement decrease the
volume of the thorax. Lungs
contract, partial lung pressure
increases
Therefore pressure inside the thorax
rises above atmospheric pressure
Air flows out from lungs to outside of
the body. Lung pressure falls
below atmospheric pressure
Self-planned laboratory
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How does exercise affect the functioning of
the heart and lungs
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Exercise increases cardiac output
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Cardiac output = stroke volume X heartrate
Stroke volume = volume of blood ejected by the
ventricles in one beat