Transcript The Respiratory System

The Respiratory System
General Functions of the System
• Ventilation (breathing) – the entrance and exit of
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air into and out of the lungs
External respiration – the exchange of gases
(carbon dioxide and oxygen) between the air
and blood
Internal respiration – the exchange of gases
between the blood and tissue fluid
Transport – of gases to and from the lungs and
the tissues
Anatomy and the flow of air:
• The Nose / Nasal passages begin to cleanse the air with
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course hairs inside the nostrils and continue to do so
with cilia and mucus in the nasal cavities.
Air warmed by the blood vessels lying close to the
surface of the lining of the airways.
Air is moistened by the mucus epithelium that lines most
of the air passages.
Conversely, as air leaves the body it deposits its moisture
along the way. This can cause the nose to drip and is
what is responsible for you being able to see your
breathe on a cold day.
Nose and Nasal Cavity
• 2 Nostrils
• 2 Nasal cavities separated by a septum
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composed of bone and cartilage.
Conchae are bony ridges that project out
laterally trapping air and increasing surface area
for moistening and warming.
Lacrimal glands (tear) drain into the nasal cavity
which is why your nose runs when you cry.
Nasal cavity is separated from the oral cavity by
the hard and soft palate.
Pharynx
• Broken into three parts: nasopharynx,
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oropharynx, and laryngopharynx.
The tonsils form a protective ring around the
pharynx – this is lymphatic tissue that protects
against the invasion of inhaled pathogens.
It is the junction of air and food passage. The
esophagus remains closed by the epiglottis
unless a person is swallowing.
Larynx
• A cartilaginous structure
• Contains the Adam’s Apple
• Called the voice box because it contains the
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vocal cords.
The vocal cords are mucosal folds supported by
elastic ligaments, and the opening between
them is the glottis.
When air is expelled past the vocal cords
through the glottis the cords vibrate producing
sound. The greater the tension on the cords
and the narrower the glottis, the higher the
pitch.
Trachea
• Tube with c-rings of cartilage. The open part of
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the c is facing the esophagus – why do you think
this is?
Lined with pseudostratified ciliated columnar
epithelium. Cilia beat upward moving the
particles out of the system. Goblet cells produce
mucus to trap debris.
Smoking destroys the cilia causing soot from
smoking to get caught in the lungs.
Bronchial Tree
• Contains the same histology as the trachea.
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Divides trachea into right and left primary
bronchi.
Branches into a large number of secondary
bronchi that eventually lead to bronchioles –
rings of cartilage are no longer present.
During an asthma attack, the smooth muscle of
the bronchioles contracts, causing constriction
and wheezing.
Each bronchiole leads to an elongated space
enclosed by a bunch of air pockets called alveoli.
Lungs
• Paired, cone-shaped structures.
• The right lung has 3 lobes and the left, 2.
The lobes are divided further into lobules
which each have a bronchiole serving
many alveolar sacs.
• Diaphragm sits inferiorly to the lungs.
• Each lung is enclosed by a pleural sac
(serous membrane).
Alveoli
• Composed of simple squamous epithelium and is
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surrounded by capillaries which are also
composed of simple squamous. What major
function does the structure of simple squamous
allow?
Alveoli are covered in surfactant, a lipoprotein
that allows them not to collapse under the
pressure of water surface tension.
Breathing Mechanism
• Air into the lungs is called inspiration or
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inhalation. Air leaving the lungs is expiration or
exhalation.
When we are relaxed only a small amount of air
moves into and out of the lungs with each
breath = tidal volume (about 500ml).
Deep breathing = vital capacity (max in and max
out).
About 70% never reaches the alveoli, it fills the
rest of the air passages (dead air space).
Ventilation
• Things to recall: location of intercostals,
location of diaphragm, lungs adhere to
thoracic wall because of the pleura, a
continuous column of air extends from the
pharynx to the alveoli.
Inspiration
• Diaphragm contracts and lowers. Internal
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intercostals contract and lift the rib cage up and
out – this increases the volume of the thoracic
cavity.
Air pressure in the alveoli decreases due to the
above and causes a partial vacuum.
Difference in alveolar compared to atmospheric
pressure allows the lungs to fill.
Expiration
• Passive phase – diaphragm and
intercostals relax.
• The volume of the thoracic cavity
decreases to less than the atmospheric
pressure allowing the air to leave the
alveolar sacs.
Cough Reflex – dislodge foreign
material from the lower respiratory
passages.
• Initiated when the sensory receptors detect substances
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and initiate action potentials that pass along the vagus
nerves to the medulla oblongata.
2.5L of air is inspired  the epiglottis closes  the
vestibular folds close tightly to trap the air in the lungs
 the abdominal muscles contract to force the
abdominal contents up against the diaphragm  the
muscles of expiration contract forcefully.
As a result the pressure in the lungs increases to 100
mm Hg then the vestibular folds and epiglottis open
suddenly and air rushes at a high velocity carrying the
particles with it.
Sneeze Reflex – dislodges foreign
material from the upper respiratory
passages.
• Similar to cough reflex.
• Source of irritation is in the trigeminal
nerves in the nasal cavity.
• The uvula and the soft palate are
depressed so that air is directed primarily
through the nasal passages.
Respiration and Health - URI
• Many times caused by Streptococcus pyogenes.
• Sinusitis – caused when nasal congestion blocks the
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openings between the nasal cavity and the cranial
sinuses.
Otitis Media – bacterial infection in the middle ear –
spreads from nasal congestion through the eustachian
tubes from the nasopharynx to the middle ear.
Tonsillitis – occurs when the (lymphatic) tissues in the
pharynx become inflammed.
Laryngitis – infection of the larynx – usually accompanies
upper respiratory infection – if it doesn’t it could mean
there is cancer in the throat.
Respiration and Health - LRI
• Bronchitis – infection of the primary and
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secondary bronchi causes inflammation, mucus
production, and usually results in coughing.
Pneumonia – viral or bacterial infection of the
lungs in which the bronchi and alveoli fill with a
thick fluid.
Tuberculosis – caused by the bacteria Tubercle
bacillus – the bacteria invade the lungs and
cause the cells to isolate themselves by building
a capsule.
Respiration and Health – other
respiratory disorders.
• Restrictive Pulmonary Disorders – vital capacity is
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reduced due to loss of elasticity (results from a build up
in fibrous connective tissue) this is usually a result of
inhaling asbestos or fiberglass.
Obstructive Pulmonary Disorders – air does not flow
freely in the airways – includes things like chronic
bronchitis (airways inflamed and full of mucus – cilia
lost), emphysema (alveoli are distended and the area
available for gas exchange is reduced), and asthma
(disease of the bronchi and bronchioles – exposure to
irritants causes spasms in the smooth muscle of the
bronchi).
Lung Cancer
• Occurs in progressive steps:
• 1st – thickening and callusing of the cells lining the
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primary bronchi.
2nd – cells with atypical nuclei appear in the callused
lining.
3rd – a tumor made of these cells may occur in one area
4th – some of these cells break loose and penetrate other
tissues a process called metastasis.
Tumors may continue to grow eventually blocking off the
bronchi completely and causing the lung to collapse.
Aging and the Respiratory System
• Maximum breathing capacities decline and as a
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result fatigue increases.
Weakened intercostal muscles and increased
inelasticity of the rib cage reduce the volume
that the thoracic cavity can hold.
Changes in the lungs and capillaries result in
less efficient gas exchange.
Risk of contracting respiratory disease increases
as the cells of the passages age and lose cilia.