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Take in oxygen
Get rid of carbon dioxide
Helps with smelling
Filters air that is inhaled
Produces sounds
Rids the body of some water and heat in
exhaled air
The organs of the respiratory system include the
nose, pharynx, larynx, trachea, bronchi,
bronchioles, alveoli and lungs.
Nose:
• The 2 external openings are called external
nares.
• The internal portion of the nose has 2 openings
that connect to the throat called internal nares
• The nose is divided into right and left internal
parts by the septum.
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Coarse hairs in the nose filter out large dust
particles
Nasal conchae- 3 shelves that extend out of
the wall of the nasal cavity to increase
surface area for warming, moistening and
filtering.
Mucous membranes line the nasal cavity
and secrete mucus that moistens the air and
traps dust particles.
Above the conchae is the olfactory
epithelium which detects smells.
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Pharynx is also called the throat- A tube that starts
at the internal nares and extends part way down
the neck.
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A passageway for air and food and provides a
resonating chamber for speech sounds.
Larynx is the voice box. It is a short passageway
that connects the pharynx with the trachea.
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Thyroid cartilage (Adam’s apple) forms the anterior
wall of the larynx
Epiglottis is elastic cartilage that is the most superior
part of the larynx. It prevents food and drink from
entering the larynx.
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The mucous membrane of the larynx forms 2 pairs
of folds: false vocal cords and true vocal cords.
True vocal cords produce sound. They are elastic
ligaments that are stretched between pieces of
cartilage. They are also attached to muscles that
pull the ligaments tightly when contracted. This
moves the true vocal cords out into the air
passageway. Air pushed against the cords causes
them to vibrate and produce sound waves.
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Males have thicker vocal cords due to male sex
hormones. These vibrate more slowly and produce a
deeper pitch.
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Windpipe- Air passageway anterior to the
esophagus
Extends from the larynx to the 5th thoracic
vertebra
Wall is lined with mucous membrane
Cilia also line the wall-move mucus up the
trachea
Supported by cartilage- 16 to 20 C-shaped rings
of hyaline cartilage stacked on top of another.
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Heimlich maneuver may be used to expel
an aspirated object.
If not successful, a tracheostomy may be
performed- incision in the trachea below
the cartilage and a tube is inserted.
Intubation is another method when a
tube is inserted into the mouth or nose
and passed down through the larynx and
trachea.
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Bronchi are branches of the trachea that each
feed a lung.
The right bronchus is more vertical, shorter
and wider than the left. As a result, foreign
objects are more likely to enter and lodge in the
right bronchus than in the left.
Bronchi contain C-rings of cartilage and are
lined with cilia.
Bronchi branch into smaller bronchioles, which
do not contain cartilage rings but are lined with
more smooth muscle for support.
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Asthma is chronic airway inflammation due to
hypersensitivity to a variety of stimuli. These
triggers include allergens, emotional upset,
exercise, breathing cold air and cigarette
smoke.
Triggers cause the walls of the bronchi and
bronchioles to spasm, the mucous membranes
to swell, increased mucus secretion or damage
to the lining of an airway.
Asthma symptoms include difficulty breathing,
coughing, wheezing, chest tightness, fatigue
and anxiety.
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Lungs are covered directly with visceral pleura
and the lung cavity is lined with parietal pleura.
Pleurisy- inflammation of the pleural membranes
which causes friction during breathing which is
quite painful.
The narrow top of each lung is the apex. The
broad bottom is the base. The area on the medial
side through which bronchi enter is called the
hilus.
The right lung has 3 lobes and the left lung has 2
lobes. The left lung has a concavity where the
heart lies- called the cardiac notch.
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The airways dead-end with thin air sacs called
alveoli.
Associated with alveoli walls are alveolar
macrophages which remove fine dust particles
and other debris.
Capillaries surround the alveoli and allow for
gases to be exchanged between the respiratory
tissue and the blood.
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Normal quiet breathing is called eupnea.
A cessation in breathing is called apnea.
Labored breathing is called dyspnea.
At rest, a healthy adult takes 12 breaths a
minute.
The volume of one breath is called tidal
volume.
Minute ventilation is the total volume of air
inhaled and exhaled each minute.
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MV=12 breaths/min X 500 mL/breath
= 6 liters/min
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The 4 basic events of respiration are: ventilation,
external respiration, internal respiration, and
transport of respiratory gases.
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Ventilation- The passive process by which air
flows into and out of the lungs. This occurs due to
differences in air pressure between the thoracic
cavity and the atmosphere.
- Inhalation- Air rushing in- occurs when the
atmospheric air pressure is greater than the
thoracic cavity air pressure.
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What causes the thoracic air pressure to decrease?
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Thoracic air pressure decreases and inhalation
occurs due to:
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Contraction of the diaphragm (flattening)
Contraction of muscles that cause the ribs and
sternum to elevate anteriorly.
Expansion of the lungs due to the parietal and
visceral pleura being pulled outward.
Exhalation- Air rushing out- occurs when the
thoracic cavity air pressure is greater than the
atmospheric air pressure. This pressure
difference is due to:
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Elastic recoil of the chest wall and lungs
Relaxation of the diaphragm
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External Respiration is the exchange of O2 and CO2
between the air in the alveoli and the blood in the
capillaries around the alveoli.
Internal Respiration is the exchange of gases
between the blood in the capillaries and the cells of
the body.
What causes these gases to be exchanged?
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Diffusion- movement of molecules from where there is
more of them to where there is less of them.
O2 moves from the alveoli (higher concentration) to the
capillaries (lower concentration)
CO2 moves from the capillaries (higher concentration) to
the alveoli (lower concentration)
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Oxygen does not dissolve well in water.
Therefore, only 1.5% of oxygen dissolves in
plasma. Most of it is carried by hemoglobin of
erythrocytes.
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About 7% of carbon dioxide dissolves in
plasma. About 23% binds with hemoglobin.
About 70% of carbon dioxide is transported in
the bloodstream(plasma) as bicarbonate ionsHCO3-
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CO is an odorless and colorless gas produced
when there is incomplete burning of natural
gas or any carbon containing fuel.
Why is it dangerous when inhaled?
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At rest, 200 ml of oxygen are used by the
body’s cells each minute. Of course, this
need is increased during exercise.
There are groups of neurons in the brain
stem which adjust respiratory effort to meet
metabolic demand. These neurons are
called the respiratory center.
The 3 parts to the brain stem include the
midbrain, pons and medulla oblongata.
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There are 3 areas to the respiratory center:
1. Medullary rhythmicity areaLocated in the medulla oblongata- This
controls the basic rhythm of respiration.
During quiet breathing, inhalation lasts 2
seconds and exhalation lasts 3 seconds.
2. Pneumotaxic areaLocated in the upper pons- This turns off
inspiration before the lungs become too full and
pressurized.
3. Apneustic areaLocated in the lower pons- This sends
stimulatory impulses to increase and activate
inhalation. This can be overidden by the
pneumotaxic area.
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Temperature- Increased temp = increased
respiration. A sudden cold stimulus causes
apnea- temporary cessation of breathing.
Pain- Sudden pain causes brief apnea and
prolonged pain increases respiratory rate.
Stretching the anal sphincter muscle- Increases
respiratory rate. This is sometimes done to
newborns.
Blood pressure- A rise in blood pressure
decreases respiration rate and vice versa.
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As we age, the following changes occur to the
respiratory system:
• Tissues become less elastic which results in a
decrease of lung capacity.
• There is a decrease in oxygen levels in the
blood.
• There is a decrease in the activity of alveolar
macrophages
• There is diminished ciliary action of the
respiratory tract
Because of these, elderly people are more
susceptible to pneumonia, bronchitis, and
emphysema.
1. Apneustic center
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13. Thyroid cartilage
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15. Olfactory epithelium
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19. Larynx
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