By
Sergio Gonzalez
The main functions of the Respiratory System are:
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Providing an extensive area for gas exchange between air
and circulating blood.
To move the air from the exchanged surfaces of the lungs.
To protect respiratory surfaces from dehydration,
temperature changes, or other environmental variations and
to defend the respiratory system and other tissues from
invasion by pathogens.
To produce sounds involved in speaking, singing, and
nonverbal communications.
Providing olfactory sensations to the central nervous system
from the olfactory epithelium in the superior part of the
nasal cavity.
The Respiratory System is divided into two parts.
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The Upper Respiratory System:
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The Nose
Nasal Cavity
Para nasal Sinuses
Pharynx
The Lower Respiratory System
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Larynx (voice box)
Trachea (windpipe)
Bronchi
Bronchioles
Alveoli
The respiratory tract consist of the airways that
carry air to and from the exchange surfaces of
your lungs. It consist of two portions, the
conducting portion and the respiratory portion.
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Conducting Portion: beings at the entrance of the nasal
cavity extends through many passage ways such as the
pharynx (voice box) and the larynx.
Respiratory Portion: includes the delicate respiratory
bronchioles and the alveoli, the sites of gas exchange.
A series of filtration mechanism that work
together to prevent the contamination of air
containing debris or pathogens. There are two
main sources in the defense system.
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Sticky mucous: created from mucous glands which
bathe exposed surfaces.
Cilia: sweep the mucus and any trapped
debris/microorganisms toward the pharynx. They also
move a carpet of mucus toward the pharynx and clean
the respiratory surfaces.
This process is often described as mucous escalator.
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The nose is the primary passageway for air
entering the body (usually always enters
through the paired external nares) which then
opens into the nasal cavity. The nasal septum
divides the nasal cavity into two portions. The
superior portion of the nasal cavity include the
areas lined by the olfactory epithelium.
The inferior surface of the cribriform plate.
The superior portion of the nasal septum.
The superior nasal conchae.
The pharynx also known as the throat, is a
chamber shared by the digestive and respiratory
systems. It is the part that extends between the
internal nares and the entrances to the larynx and
esophagus. The pharynx is divided into 3 parts.
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Nasopharynx: the superior part of the pharynx and
connected to the posterior part of the nasal cavity.
Oropharynx: extends between the soft plate and the base of
the tongue close to where the hyoid bone is located.
Laryngopharynx: the inferior part of the pharynx. It is the
portion of the pharynx between the hyoid bone and the
entrance to the larynx and esophagus.
The larynx also known as the voice box, is a
cartilaginous structure that surrounds and protects the
glottis, a narrow opening where the air first has to pass
to get to the larynx. Three large, unpaired cartilages
form the larynx.
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Thyroid Cartilage: the largest laryngeal cartilage which forms
most of the anterior and lateral walls of the larynx (sits superior to
the cricoid cartilage).
Cricoid Cartilage: provides support in the absence of the thyroid
cartilage. It protects the glottis and the entrance to the trachea.
Epiglottis: shoehorn-shaped elastic cartilage that forms a lid over
the glottis. It plays an important role when the larynx is elevated
because it folds back over the glottis which prevents the entry of
liquids or solid food into the respiratory tract.
The larynx also is made up of other cartilages and
ligaments .
Hyaline Cartilages
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Arytenoid Cartilages and Corniculate Cartilages: responsible for
the opening and closing of the glottis and the production of
sound.
Cuneiform Cartilages: extend between the lateral surface of each
artyenoid cartilage and the epiglottis.
Ligaments
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Vestibular Ligaments and Vocal Ligaments: extend between the
thyroid cartilage and the arytenoid cartilages.
Folds
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Vestibular Folds: help prevent foreign objects to enter the glottis
and protect the more delicate vocal folds.
Vocal Folds: guard the entrance to the glottis (vocal cords).
Sound production is when the air passes
through the glottis vibrates the vocal cords and
then produces sound waves. The sound that
has been produced depends on the vocal cords
and their diameter, length, and tension.
Children are the ones that intend to have short
vocal cords, which means their voice is in a
high-pitch. Phonation is the name given to the
sound production at the larynx.
The trachea other known as the windpipe, is a
tough, flexible tube with a diameter of about
2.5 cm (1in.) and a length of about 11 cm. The
trachea begins in the anterior of vertebra C6
and ends at the level of vertebra T5, where it
branches to make the right and left primary
bronchi. It also contains 15-20 tracheal
cartilages.
The lungs are found in the right and left pleural
cavities. The tip of each lung points superiorly
meaning that each lung is a blunt cone. The base
of each lung also rests on the superior surface of
the diaphragm. The right lung has three lobes,
the superior, middle, and inferior which are
separated by the horizontal and oblique fissures.
In the other hand, we have the left lung which
unlike the right lung, it only has two lobes, the
superior and inferior being separated by the
oblique fissure. The lungs are different because
the right one is broader than the other.
The right and left primary bronchi are given rise
by the trachea branches, which are separated by
a ridge called carina. The right bronchus supply
the right lung while the left bronchus supplies
the left lung. The difference between the two
bronchi is that the right is larger in diameter and
it also descends towards the lung in a steeper
angle than the left, meaning that most of the
foreign objects that enter are found by the right
bronchus, not the left.
The primary bronchi and its branches are what form
the bronchial tree. The left and right bronchi are called
extrapulmonary bronchi because they are located
outside the lungs. Intrapulmonary bronchi are braches
that are formed when the primary bronchi enter the
lungs. Primary bronchi are divided into smaller
bronchi.
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Secondary Bronchi: (lobar bronchi) each lung contains one
secondary bronchus that goes to each lobe meaning the right
lung has three secondary bronchi and the left lung has two.
Tertiary Bronchi: (segmental bronchi) formed by secondary
bronchi. It supplies air to a specific region of the lung other
know as a single bronchopulmonary segment.
The walls of the all these bronchi contain less amounts of
cartilage.
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The bronchioles are given rise by each tertiary
bronchus branches. These several bronchioles
branch further into the finest conducting
branches which are called the terminal
bronchioles.
Bronchodilation: the enlargement of the airway
diameter.
Bronchodistruction: the reduction in the
diameter of the airway.
The pulmonary lobules are created by the
finest partitions, the interlobular septa. Each of
the pulmonary lobules is supplied by branches
of the pulmonary arteries, veins, and
respiratory passageways. The thinnest and
most delicate branches of the bronchial tree are
called respiratory bronchioles which are
formed by the terminal bronchioles.
The alveoli are connected
with the respiratory
bronchioles to form
regions called alveolar
ducts. Alveolar sacs is
the place where alveolar ducts end, which are
connected to some alveoli (individually). Each
lung contains over 15,000 alveoli which is the
reason why they have that spongy appearance.
The alveolar epithelium has mainly created of
simple squamous epithelium.
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Alveolar Macrophages: they patrol the alveolar epithelium
surface.
Septal Cells: scattered among the squamous cells.
Surfactant: has several roles such as:
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Forms a superficial coating over a thin layer of water.
Reduces surface tension in the liquid coating the alveolar surface.
Gas exchange occurs across the respiratory
membrane which consist of three parts:
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Squamous epithelial cells lining the alveolus.
Endothelial cells lining an adjacent capillary.
Fused basement membranes that lie between the alveolar
and endothelial cells.
Two pleural cavities are separated by the mediastinum;
each lung also uses a single pleural cavity which is
lined up by a serous membrane called the pleura,
which consist of two layers.
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Parietal Pleura: covers the inner surface of the thoracic wall
and extends over the diaphragm and mediastinum.
Visceral Pleura: covers the outer surface of the lungs also
extending but into the fissures between the lobes.
Both of these pleura secrete a small amount of
pleura fluid, which gives a moist slippery coating
that provides lubrication which plays an important
role because it reduces friction between the
parietal and visceral surfaces as we breathe.
The word respiration refers two the two processes
external respiration and internal respiration.
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External Respiration: includes all the processes involved in
the exchange of oxygen and carbon dioxide between the
body’s external environment as well as the interstitial fluids.
This respirations mains purpose is to meet the respiratory
demands of cells and also is involved in three integrated
steps which are:
Pulmonary ventilation (other known as breathing)
 Gas diffusion
 The transport of oxygen and carbon dioxide.
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Internal Respiration: the absorption of oxygen and the
release of carbon dioxide.
The cycle it takes to breathe, meaning the cycle of
inhalation and exhalation. The tidal volume is the amount
of air a person moves in and out of the lungs during one
respiratory cycle. At the beginning of this cycle, the
intrapulmonary and atmospheric pressures are equal and
no air movement is occurring. Once the intrapleural
pressure begins to fall, that when inhalation starts. In the
other hand, when exhalation begins, the intrapleural and
intrapulmonary pressures rise very quickly which forces
the air out of the lungs. Once exhalation is over, air
movement again ceases when the pressure difference
between intrapulmonary and atmospheric pressures are
eliminated. The amount of air moved into the lungs
during inhalation is the same as the one moved out of the
lungs during exhalation.
There are many muscles used in the respiratory cycle,
but the ones used in inhalation are different from those
used in exhalation.
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Muscles used in inhalation are:
Diaphragmatic Contraction: responsible for roughly 75% of the air
movement in normal breathing when in rest.
 External Intercostal: assist in inhalation by elevating the ribs.
Contributes roughly 25% to the volume of air in lungs.
 Accessory: include the sternocleidomastoid, serratus anterior,
pectoralis minor, and scalene muscles which assist the external
intercostal muscles in elevating ribs.
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Muscles used in exhalation are:
Internal intercostal & transversus thoracis: depress the ribs and reduce
the width and depth of thoracic cavity.
 Abdominal: includes the external and internal abdominal oblique,
transversus abdominis, and rectus abdominis muscles which by
compressing the abdomen and forcing the diaphragm upward assist
the internal intercostal muscles in exhalation
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Quiet Breathing: (eupnea) the inhalation involves muscular
contraction but exhalation is a passive process. Most of the
time, inhalation involves the contraction of the diaphragm
and the external intercostal muscles.
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Diaphragmatic breathing: (deep breathing) the air is drawn into the
lungs as the diaphragm contracts, and exhalation occurs calmly when
the diaphragm relaxes.
Costal breathing: (shallow breathing) inhalation occurs when
contractions of the external and intercostal muscles elevate the ribs
and enlarge the thoracic cavity. In the other hand, exhalation occurs
calmly as well when these muscles relax.
Forced Breathing: (hyperpnea) involves active inspiratory and
expiratory movements. This type of breathing calls on the
accessory muscles to assist with inhalation, and exhalation
invloves contraction of the internal intercostal muscles.
Gas exchange is when pulmonary ventilation ensures that
your alveoli are supplied with oxygen and to remove the
carbon dioxide that arrives from your bloodstream. The
process of the gas exchange occurs between the blood and
alveolar air across the respiratory membrane. There are
five main reasons why gas exchange at the respiratory
membrane is efficient and those are:
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The differences in parietal pressure across the respiratory
membrane are substantial.
The distances involved in the gas exchange are small.
The gases are lipid-soluble.
The total surface area is larger.
Blood flow and airflow are coordinated.
The respiratory centers have an indirect effect
because of the activity of the cerebral cortex.
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Conscious thought processes tied to strong emotions
such as rage/fear, which affects the respiratory rate by
stimulating centers in the hypothalamus.
The respiration through activation of the sympathetic
or parasympathetic division of the autonomic nervous
system can be affected by emotional states. One way it
can affect it is by increasing the respiration rate
(sympathetic) or the opposite (parasympathetic).
An automatic increase in the respiratory rate can be
triggered by an anticipation of strenuous excercise.
The respiration process of a baby and an adult is
not the same in several important ways.
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Pulmonary arterial resistance is high since the pulmonary
vessels are collapsed before delivery.
The lungs and conducting passageways contain only a bit of
small amount of fluid and no air because the rib cage is
compressed.
The lungs are compressed further meaning the blood
oxygen levels fall and carbon dioxide levels climb rapidly
(the placental connection is lost).
A newborn takes a really long breath through strong
contractions of the diaphragmatic and external intercostal
muscles
Elderly individuals tend to reduce the efficiency of
their respiratory system. These are three examples:
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The deterioration of the tissues throughout the body
reduce the compliance of the lungs which lowers the
vital capacity.
Arthritic changes in the rib articulations restrict
movements of the chest as well as by decreasing
flexibility at the costal cartilages.
The fact of smoking affects the breathing of the body by
lowering the rate. If a person that smokes and one that
doesn’t were to be compared, the decrease in respiratory
performance is inevitable.
The Respiratory system works with all the other
systems such as the:
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Integumentary System: protects upper portions of the respiratory
system by having the hairs guard entry to external nares.
Skeletal System: the movement of the ribs are important in
breathing and the axial skeleton surrounds and most importantly
protects the lungs.
Muscular System: the respiratory muscles fill and empty the
lungs; other muscles have the role of controlling the entrance to
the respiratory tract.
Nervous System: monitors the respiratory volume and blood gas
levels as well as controlling the pace and depth of respiration.
Endocrine System: epinephrine and norepinephrine stimulate
respiratory activity and dilate respiratory passageways.
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Cardiovascular System: Red blood cells transport oxygen
and carbon dioxide between the lungs and peripheral
tissues.
Lymphatic System: the tonsils protect against infection at
the entrance of the respiratory tract. When infection occurs,
lymphatic vessels monitor lymph drainage from lungs and
mobilize specific defenses.
Digestive System: to provide substrates, vitamins, water,
and ions that are necessary to all cells of the respiratory
system.
Urinary System: eliminates all the waste generated by the
respiratory system and also maintains normal fluid and ion
balance in the food.
Reproductive System: during sexual arousal, the respiratory
system changes in its rate and depth.
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Pathogenesis: Organisms gain entry to the
respiratory tract by inhalation of droplets and
invade the mucosa. Epithelial destruction may
ensue, along with redness, edema, hemorrhage
and sometimes an exudate.
Microbiologic Diagnosis: Common colds can
usually be recognized clinically. Bacterial and
viral cultures of throat swab specimens are
used for pharyngitise epiglottitis and
laryngotracheitis. Blood cultures are also
obtained in cases of epiglottitis.
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Why do we yawn?
A yawn is caused when you are sleepy or drowsy. The lungs
do not take enough oxygen from the air which causes a shortage
of oxygen in our bodies. That’s when the brain senses this
shortage of oxygen and sends a message that causes you to take a
deep long breath.
Why do we sneeze?
Sneezing is when the body needs to take an irritant from the
sensitive mucous membranes of the nose. It is like a cough in the
upper breathing passages. Things such as pollen and dust cause
these irritant mucous membranes.
Most North Americans die of lung cancer.
People breathe about 50,400 times a day, about 35 times a minute.
It depends on how long a person can go without breathing, but
usually a person can only go around 4-5 minutes without
breathing for the brain to start dying.