Transcript Document
The
Respiratory
System
Chapter 10
Organs of the Respiratory System
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Nose
Pharynx
Larynx
Trachea
Bronchi
Lungs
Accessory Structures
• Thorax
• Diaphragm
The Nose
The Nose (naso or rhino)
• Acts as entrance for air and exit for
carbon dioxide
• Lined with a ciliated epithelial
mucus membrane
• Filters dust and foreign material
• Warms & moistens entering air
• Has olfactory receptors
Nostrils (Nares)
• Paired openings that vary in
pliability and expandability to
accommodate an increased need
for oxygen.
• The horse has pliable and
expandable nostrils because mouth
breathing is not characteristic.
Pharynx (Throat)
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A musculomembranous saclike structure
Upper portion is attached to the base of the
skull and the lower portion with the esophagus
Connects with the nasal chambers, mouth,
larynx and eustachian tubes
The pharynx is divided into three parts:
• Nasopharynx – opens into the Eustachian tubes
• Oropharynx – opens into the mouth
• Laryngopharynx – opens into the larynx &
esophagus
The pharynx is used as
passageway for both air and
food. Depending on the species
it may also have a role in
vocalization.
Larynx (Voice Box)
• Located just below the pharynx
• Serves as a passage for air
• The epiglottis is a lid-like
structure that prevents food from
entering the airway during
swallowing
The larynx plays an important role in
creating sound. Air passes through the
glottis during expiration causing a
vibration, and producing a sound.
Trachea (Windpipe)
• A tube formed of smooth
muscle with numerous C
shaped rings of cartilage
embedded in the tissue
• These rings prevent collapse of
the structure.
The Bronchi
The end of the
trachea separates
into smaller
airways called
the primary
bronchi.
The Bronchi
• Lined with a ciliated mucous
membrane & C-shaped cartilage
rings, which become complete as the
bronchi enter the lungs
• They then divide into smaller
secondary branches, then
bronchioles, then alveolar ducts
The alveolar ducts terminate into
alveolar sacs:
Small, squamous epithelium
lined spaces that allow the lungs
to achieve the primary function
of oxygen and carbon dioxide
exchange.
As the bronchioles get smaller,
the cartilage rings begin to
disappear. There are no rings in
the alveolar ducts, sacs or
alveoli.
The Lungs
• The primary structures of the
respiratory system
• Occupy almost the entire
thoracic space
• Each contains millions of
alveoli and capillaries
Membranes in the Lungs
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Visceral pleura - Serous
membrane that encases the lungs
Parietal pleura – Lines the
thoracic cavity
These membranes reduce friction
during respiration.
The space between these
membranes is called the pleural
cavity or potential space.
Thorax (Chest Cavity)
Lined with a membrane similar to
the covering of the lungs, that
lubricates both surfaces during
respiration
The pleural membrane divides the
chest into 3 parts:
• Right pleural cavity
• Left pleural cavity
• Mediastinum
The mediastinum contains the heart, thymus,
esophagus, trachea, bronchi, nerves, arteries,
veins and lymphatic vessels.
The Diaphragm
• A dome-shaped musculomembranous
partition separating the thoracic and
abdominal cavity
• Attaches to the lumbar and
abdominal cavities at the lumbar
vertebra, lower ribs and sternum
Normal feline
chest
Diaphragmatic
Hernia
The diaphragm is the primary
muscle of respiration.
• Inspiration: Contracts, flattens
and lowers, increasing thoracic
capacity.
• Expiration: Relaxes and returns
to its normal position
Respiratory Process
The respiratory cycle is divided
into three parts:
• Inspiration
• Expiration
• Rest
Respiration
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Involves the
exchange of
oxygen and
carbon dioxide
wastes
Tissue does not
store oxygen and
takes in only the
oxygen it needs.
During exercise the oxygen requirement can more
than double. Flow of air in and out of the lungs
depends on changes in the thoracic cavity.
Inspiration and expiration are in accordance with
pressure differences between the atmosphere and
air in the lungs
Tidal volume (TV):
The amount of air inhaled during
ordinary respiration
Inspiratory reserve volume (IRV):
The amount of air that can be
forcibly inhaled beyond the normal
amount
Expiratory reserve volume (ERV):
The volume of air that can be
forcibly expelled beyond normal
expiration
Some air will always be trapped in
the alveoli no matter how forcibly
an animal exhales due to
intrathoracic pressure.
Residual Volume (RV):
Air remaining in the lungs after
forced expiration
Minimal volume:
Air remaining in the alveoli of a
collapsed lung
Vital capacity (VC):
The largest amount of air that can
be moved in and out of the lungs.
The sum of the total of inspiratory
and expiratory reserve volumes
plus tidal volume
There are several nerves from the
brain that pass down the chest
wall and diaphragm to control
respiration…
Vagus nerve:
Originates in the brain and sends
branches to the larynx, heart,
bronchi, esophagus, stomach, liver
and abdomen.
Phrenic nerve:
Originates in the cervical spine
and passes to the diaphragm
Thoracic nerve:
Originates in the thoracic spinal
cord, these are the nerves of the
muscles of the thorax
Next up…
The GI Tract