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Patel D et al
IJARPB: 2013, 3(4),1-10
ISSN: 2277-6222
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Review Article
Received on 10/12/2013;
Revised on 20/12/2013;
Accepted 28/12/2013;
An Overview on Respiratory System
Dipal Patel*1, Komal Sharma1, C. S. Chauhan1Gunjan Jadon2
1Department of Pharmacology
2Department of Pharmaceutical Chemistry
1B.N. Institute of Pharmaceutical Science, Udaipur (Rajasthan), 313001
Shrinathji Institute of Pharmacy, Nathdwara (Raj.) 313301
E mail: [email protected]
Introduction
The respiratory system is the biological system of
any organisms that engages in gas exchange.
Even tree have respiratory systems, taking in
carbon dioxide and emitting oxygen during the
day, consuming carbon dioxide and producing
oxygen constantly. The respiratory works with the
circulatory system to deliver oxygen from the
lungs to the cells and remove the carbon dioxide
return it to the lungs to be exhaled. The
exchange of oxygen and carbon dioxide between
the airs: blood and body tissue is known as
respiration. Healthy lungs take in about 1 pint of
air about 12-15 times each minutes. All of the
blood in the body is passed through the lungs
every minute.
FUNCTION OF RESPIRATORY SYSTEM
 The functions of the nose is to begin the
process by which the air is warmed,
moistened and filtered.






The nose is the organ of sense. The
nerve endings that detect smell are
located in the roof of the nose.
Passage way for food and air- The
pharynx is an organ involved in both the
respiratory and digestive systems air
passes through.
The functions of the nose are to begin
the process by which the air, moistened
and filtered.
The nose is the organ of sense the nerve
endings that detect smell are located in
the roof of the nose.
Passage way for food and air- The
pharynx is an organ involved in both the
respiratory and digestive systems: air
passes through the nasal and oral
sections, and food through the oral and
laryngeal section.
Warming and humidifying- The air is
further warmed and moistened as it
passes through the pharynx.
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Taste- There are olfactory nerve endings
of the sense of taste in the epithelium of
the oral pharyngeal parts.
 Hearing- The auditory tube allows air to
enter the middle ear. Satisfactory hearing
depends on the presence of air at
atmospheric pressure on each side of
the tympanic membrane.
 Protection- The lymphatic tissue of the
pharyngeal and laryngeal tonsils
produces antibodies in response to
antigens, e.g. microbes. 1,3,4.5,9
ANATOMY OF RESPIRATORY SYSTEM
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The organs of the respiratory system are 







Nose
Pharynx
Larynx
Trachea
Two bronchi (one bronchus to each lung)
Bronchioles and smaller air passages
Two lungs and their coverings, the pleura
Muscles of breathing-the intercostals
muscles and the diaphragm
Figure A shows the location of the respiratory structures in the body. Figure B is an enlarged view of the
airways, alveoli (air sacs), and capillaries (tiny blood vessels). Figure C is a closeup view of gas exchange
between the capillaries and alveoli. CO2 is carbon dioxide, and O2 is oxygen.
Fig- 1 Anatomy of respiratory system
NOSE AND NASAL CAVITY
ciliated columnar epithelium, which
contains mucus-secreting goblet cell.
 Position and Structure
 Function
The nasal cavity is the main route of air
1. The functions of the nose is to
entry, and consists of a large irregular
begin the process by which the
cavity divided into two equal passages
air is warmed, moistened and
by a septum. The perpendicular plate of
filtered.
the ethmoid born and the vomer form the
2. The nose is the organ of sense.
posterior bony part of the septum.
The nerve endings that detect
Interiorly, it consists of hyaline cartilage.
smell are located in the roof of
The nose is lined with very vascular
the nose.
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PHARYNX
 Position and Sturcture
The pharynx is a tube 12 to 14cm long
that extend from the base of skull to the level of
the sixth cervical vertebra. It lies behind the nose,
mouth and larynx and it’s wider at its upper end.
The pharynx is divided into three parts:
nasopharynx, oropharynx and laryngopharynx.
The pharynx is composed of three layers of
tissue:
Mucous membrane lining, fibrous tissue and
smooth muscles.
1.
2.
3.
4.
5.
 Function
Passage way for food and air- The
pharynx is an organ involved in both
the respiratory and digestive
systems: air passes through the
nasal and oral sections, and food
through the oral and laryngeal
section.
Warming and humidifying- The air
is further warmed and moistened as
it passes through the pharynx.
Taste- There are olfactory nerve
endings of the sense of taste in the
epithelium of the oral pharyngeal
parts.
Hearing- The auditory tube allows
air to enter the middle ear.
Satisfactory hearing depends on the
presence of air at atmospheric
pressure on each side of the
tympanic membrane.
Protection- The lymphatic tissue of
the pharyngeal and laryngeal tonsils
produces antibodies in response to
antigens, e.g. microbes.
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6. Speech- The pharynx functions in
speech; by acting as a resonating
chamber for sound.
LARYNX
 Position And Structure
The larynx or voice box extends from the root
of the tongue and the hyoid bone to the trachea.
it lies in front of the laryngopharynx at level of the
third, fourth, fifth and sixth cervical vertebrae.
The larynx is composed of several irregularly
shaped cartilage attached to each other by
ligaments and membranes.
The main cartilages are1.
2.
3.
4.
1.
2.
3.
4.
5.
6.
Thyroid cartilage
Cricoids cartilage
Arytenoids cartilages
Epiglottis
 Function
Production of sound- Sound has the
properties of the pitch, volume and
resonance.
Pitch of the voice depends upon the
length and tightness of the cords.
Volume of the voice depends upon the
force with which the cords vibrate.
Resonance, or tone, dependent upon the
shape of the mouth, the position of the
tongue and the lips, the facial muscles
and the air in the Para nasal sinuses.
Speech- this occurs during the expiration
when the tongue, cheeks and lips
manipulate the sounds produced by the
vocal cords.
Protection of the lower respiratory
tract- During swallowing the larynx
moves upwards, occluding the opening
into it from the pharynx and hinged
epiglottis closes over the larynx.
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7. Passageway for air- This is between the
pharynx tracheas.
8. Humidifying, filtering and warmingThese processes continue as inspired air
travels through the larynx.
TRACHEA
 Position And Structre
The trachea is a continuation of the larynx
and extends downwards to about the level of the
fifth thoracic vertebra where it divides at the
carina into the right and left primary bronchi, one
bronchus going to each lung. It is approximately
10 to 11 cm long and lies mainly in the median
plane in front of the esophagus. The trachea is
composed of the three layers of tissue and held
open by between 16 and 20 incomplete rings of
hyaline cartilage lying one above the other. The
rings are incomplete posterior. Three layers of
tissue clothe cartilage of trachea.
1. The outer layer consist have the
fibrous and elastic tissue and
encloses the cartilages.
2. The middle layer consists of the
cartilages and bands of smooth
muscles that bound the trachea in a
helical arrangement.
3. The inner lining consists of ciliated
columnar epithelium, containing
mucus-secreting goblet cells.
 Functions
1. Support and potency- The
arrangement of cartilage and elastic
tissue
prevent
kinking
and
obstruction of the airway as the head
and the neck moves. The cartilages
prevent the collapse of trachea when
the internal pressure is less then
intrathoresic pressure.
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2. Mucociliary escalator- This is the
synchronous and regular beating of
the cilia of the Mucous membrane
lining that wafts mucus with adherent
particles upwards towards the larynx
where it is either swallowed or
coughed up.
3. Cough reflux- Nerve ending in the
larynx, Trachea and bronchi are
sensitive to irritation, which
generates nerve impulses conducted
by the vagus nerve to the respiratory
center in the brain steam.
4. Warming,
humidifying
and
filtering- These continue as in the
nose, although air is normally
saturated and body temperature
when it reaches the trachea. 1,5,8
LUNGS
 Position And Structure
In an elastic connective tissue matrix, each
lobe is made up of a large number of lobules.
Bronchi and Bronchioles
The two primary bronchi are formed
when the trachea divide, i.e. about the level of
the fifth thoracic vertebra. There are two lungs,
one lying on each side of the midline in the
thoracic cavity. They are cone-shaped and
medial surface. The apex is rounded and rises
into the root of the neck, about 25 cm above the
level of the middle third of the clavicle. It lies
close to the first rib and the blood vessel and
nerve in the root of neck. The base is concave
and semi lunar in shape, and lies on the thoracic
surface of the diaphragm. The costal surface
convex lies against the cortical cartilage, the ribs
and the intercostals muscles. The medial surface
is concave has a roughly shaped area the right
lung is divided into three distinct lobes: superior,
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middle and inferior. The left lung is smaller
because the heart occupies space left two of the
midline. It is divided into only two lobes: superior
and inferior.
PLEURA AND PLEURAL CAVITY
The pleura consist of serous membrane,
which contains a small amount of serous fluid.
The lung is invaginated into this sac so that it
forms two layers: one adheres to the lung and
other to the wall of the thoracic cavity. The
pleural cavity is only a potential space. The thin
film of serous fluid separates the two layers of
the pleura, which allow them glide over each
other, preventing friction between them during
breathing. The epithelial cell of the membrane
secretes the serous fluid. If either layer of pleura
is punctured, the underlying lung collapses owing
to its inherent properties of elastic recoil.
The lungs are composed of the bronchi and
smaller air passages, alveoli, connective tissue,
blood vessel, lymph vessel and nerves, all
embedded.
The right bronchus- This is wider, shorter and
more vertical then the left bronchus and is
therefore more likely to become obstructed by an
inhaled foreign body. It is approximately 2.5 cm
long.
The left bronchus- This is about 5 cm long and
is narrower than the right. After entering the lung
at the hilum it divide into two branches, one to
each lobe. Each branch then subdivides into
progressively smaller tubes within into lung
substance. The bronchi are composed of the
same tissues as the trachea, and are the lined
with ciliated columnar epithelium. The bronchi
progressively subdivide into bronchioles, terminal
bronchioles, respiratory bronchioles, alveolar
ducts and finally alveoli.
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Function
1. Control of air entry
2. Warming and humidifying
3. Support and potency
4. Removal of particulate matter
5. Cough reflux
6. Defense against microbes
MUSCLES OF BREATHING
The main muscle used in normal quiet breathing
is the intercostals muscles and the diaphragm.
Intercostals muscles
There are 11 pairs of intercostals muscles that
occupy the spaces between the 12 pairs of ribs.
They are arranged in two layers, the external and
internal intercostals muscle. The external
intercostals muscle fibers: these extend
downwards and forwards from the lower border
of the rib above to the upper border of the rib
below. The internal intercostals muscle fiber:
these extend downwards and backwards from
the lower border of the rib above to the upper
border of the rib below, crossing the external
intercostals muscle fibers at the right angle. The
first rib is fixed. Therefore, when the intercostals
muscle contract they pull all the other ribs
towards the first rib. Because of the shape and
sizes of the ribs, they move outwards when
pulled upwards, enlarging the thoracic cavity.
The intercostals muscles are stimulated to
contract by the intercostals nerves. 1,6,10
DIAPHRAGM
The diaphragm is a dome shaped muscular
structure separating thoracic and abdominal
cavities. It forms the floor of the thoracic cavity
and the roof of the abdominal cavity. And consist
of a central tendon from which muscle fibers
radiate to be attached to the lower ribs and
sternum and to the vertebral column by two
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crura. When the muscle of the diaphragm is
relaxed, the central tendon is at the level of the
eighth thoracic Vertebra. When it contracts, its
muscle fiber shorten and the central tendon is
pulled downwards to the level of the ninth
thoracic vertebra, enlarging the thoracic cavity in
length. This decreases pressure in the thoracic
cavity and increases it in the abdominal and
pelvic cavity. The phrenic nerves supply the
diaphragm. The intercostals muscles and the
diaphragm contracts simultaneously, enlarging
the thoracic cavity in all directions, i.e. from back
to front, side to side and top to bottom.2
PHYSIOLOGY OF RESPIRATORY SYSTEM
EXCHANGE OF GASES
 External respiration
 Exchange of O2 & CO2 between external
environment & the cells of the body.
 Efficient because alveoli and capillaries
have very thin walls & are very abundant
(your lungs have about 300 million
alveoli with a total surface area of about
75 square meters).
 Internal respiration - intracellular use of
O2 to make ATP.
 Occurs by simple diffusion along partial
pressure gradients.
PARTIAL PRESSURE
 It’s the individual pressure exerted
independently by a particular gas within
a mixture of gasses. The air we breathe
is a mixture of gasses: primarily nitrogen,
oxygen, & carbon dioxide. So, the air you
blow into a balloon creates pressure that
causes the balloon to expand (& this
pressure is generated as all the
molecules of nitrogen, oxygen, & carbon
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dioxide move about & collide with the
walls of the balloon). However, the total
pressure generated by the air is due in
part to nitrogen, in part to oxygen, & in
part to carbon dioxide.
That part of the total pressure generated
by oxygen is the 'partial pressure' of
oxygen, while that generated by carbon
dioxide is the 'partial pressure' of carbon
dioxide. A gas's partial pressure,
therefore, is a measure of how much of
that gas is present (e.g., in the blood or
alveoli).
The partial pressure exerted by each gas
in a mixture equals the total pressure
times the fractional composition of the
gas in the mixture. So, given that total
atmospheric pressure (at sea level) is
about 760 mm Hg and, further, that air is
about 21% oxygen, then the partial
pressure of oxygen in the air is 0.21
times 760 mm Hg or 160 mm Hg.
Partial pressures of o2 and co2 in the body
(normal, resting conditions)
 Alveoli
 PO2 = 100 mm Hg
 PCO2 = 40 mm Hg
 Alveolar capillaries
 Entering the alveolar capillaries
 PO2 = 40 mm Hg (relatively low
because this blood has just
returned from the systemic
circulation & has lost much of its
oxygen)
 PCO2 = 45 mm Hg (relatively
high because the blood returning
from the systemic circulation has
picked up carbon dioxide)
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While in the alveolar capillaries, the diffusion of
gasses occurs: oxygen diffuses from the alveoli
into the blood & carbon dioxide from the blood
into the alveoli.
 Leaving the alveolar capillaries
 PO2 = 100 mm Hg
 PCO2 = 40 mm Hg
Blood leaving the alveolar capillaries returns to
the left atrium & is pumped by the left ventricle
into the systemic circulation. This blood travels
through arteries & arterioles and into the
systemic, or body, capillaries. As blood travels
through arteries & arterioles, no gas exchange
occurs.
 Entering the systemic capillaries
 PO2 = 100 mm
Hg
 PCO2 = 40 mm
Hg
 Body cells (resting conditions)
 PO2 = 40 mm
Hg
 PCO2 = 45 mm
Hg
Because of the differences in partial pressures of
oxygen & carbon dioxide in the systemic
capillaries & the body cells, oxygen diffuses from
the blood & into the cells, while carbon dioxide
diffuses from the cells into the blood.
 Leaving the systemic capillaries
 PO2 = 40 mm
Hg
 PCO2 = 45 mm
Hg
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Blood leaving the systemic capillaries returns to
the heart (right atrium) via venules & veins (and
no gas exchange occurs while blood is in venues
& veins). This blood is then pumped to the lungs
(and the alveolar capillaries) by the right
ventricle.
How are oxygen & carbon dioxide transported
in the blood?
Oxygen is carried in blood:
1 - Bound to hemoglobin (98.5% of all
oxygen in the blood)
2 - Dissolved in the plasma (1.5%)
Because almost all oxygen in the blood is
transported by hemoglobin, the relationship
between the concentration (partial pressure) of
oxygen and hemoglobin saturation (the % of
hemoglobin molecules carrying oxygen) is an
important one. 5

HEMOGLOBIN SATURATION
Extent to which the hemoglobin in blood is
combined with O2 depends on PO2 of the blood.
The relationship between oxygen levels and
hemoglobin saturation is indicated by the
oxygen-hemoglobin dissociation (saturation)
curve (in the graph above). You can see that at
high partial pressures of O2 (above about 40 mm
Hg), hemoglobin saturation remains rather high
(typically about 75 - 80%). This rather flat section
of the oxygen-hemoglobin dissociation curve is
called the 'plateau.' Recall that 40 mm Hg is the
typical partial pressure of oxygen in the cells of
the body. Examination of the oxygen-hemoglobin
dissociation curve reveals that, under resting
conditions, only about 20 - 25% of hemoglobin
molecules give up oxygen in the systemic
capillaries. This is significant (in other words, the
'plateau' is significant) because it means that you
have a substantial reserve of oxygen. In other
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words, if you become more active, & your cells
Factors that affect the Oxygen-Hemoglobin
need more oxygen, the blood (hemoglobin
Dissociation Curve
molecules) has lots of oxygen to provide. When
The oxygen-hemoglobin dissociation curve
you do become more active, partial pressures of
'shifts' under certain conditions. These factors
oxygen in your (active) cells may drop well below
can cause such a shift:
40 mm Hg. A look at the oxygen-hemoglobin
 Lower pH
dissociation curve reveals that as oxygen levels
 Increased temperature
decline, hemoglobin saturation also declines  More 2,3-diphosphoglycerate
and declines precipitously. This means that the
 Increased levels of CO2
blood (hemoglobin) 'unloads' lots of oxygen to
active cells - cells that, of course, need more
oxygen.7,8
CLASSIFICATION OF DRUG
Medications for Lower Respiratory Conditions
Table- 4 Medications for Lower Respiratory Conditions
Bronchoconstriction Mediators
Cytokines, Chemokines
Bronchodialation Mediators
Prostaglandin’s
Leukotrienes
Histamine
Nor epinephrine
(SNS-beta)
Asthma
Methylxanthines
(Theophylline,
aminophylline,
choline theophyllinate)
Anticholinergics
(Ipratropium, tiotropium, oxitropium)
Beta2-agonists
 Non-selective
(epinephrine)
 Relatively
selective
(albuterol,
metaproteronol)
Medications for Upper Respiratory Conditions
Table- 5 Medications for Upper Respiratory Conditions 11
Decongestants
Antihistamines
1. Pseudo- ephedrine
(Sudafed)
2.
Phenylpropanolamine (Contac)
Sedating
1.diphen-hydramine
(Benadryl)
2.chlor-pheniramine
(Chlor-Trimeton)
Low sedating
1.cetrizine (Zyrtec)
Non sedating
2.fexofenadine (Allegra)
Intra
nasal
steroids
&
cromolyn

Anti-tussive
Expectorant
Central Acting
1. codeine
2. dextro-methorphan
Local
1.Benzonatate
1.Guaifenesin
2.Bromhexine
3.Dornasealfa
4.Amonium-chloride
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DISEASES & TREATMENT
Common respiratory diseases treated by
respiratory care physicians and other specialists
include

Asthma - constriction of hypersensitive
airways.

Chronic Obstructive Pulmonary Disease
(COPD) - lung disease causing shortness of
breath Chronic Bronchitis - inflammation and
permanent scarring of the bronchial tube.

Emphysema - damage to air sacs walls
causing loss of elasticity.

Pleurisy - inflammation of the pleural
membrane lining lungs and the chest cavity.

Lung Cancer - malignant tumors that develop
in lung tissue.

Acute Bronchitis-inflammation
bronchial tubes.

Influenza - serious infection cause by the
influenza virus.

Pneumonia - infection of the lungs caused by
a virus or bacteria.

Sinusitis - inflammation of the sinus cavities.

Common Cold - infection caused by a virus.
of
the
However, respiratory disease may involve
more than lung disease, and can include a
malfunction of the brain stem controlling the
breathing mechanism, or disease and
malfunction of the diaphragm and
surrounding muscles.
CONCLUSION
Respiratory system is the essential body part of
living beings. Disturbance of it or its organ in
respect of anatomy, physiology can cause severe
disease or may be death. Care in normal
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condition as well as disease state is necessary.
Now day the various medication objects are
available which protect it from any malfunctioning
or disease condition. It included the various drug
systems, devises and many more.
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