Download Anatomy of the Respiratory System

Anatomy of the Respiratory System
The re spiratory s ystem or ( Latin =
classified into (Figure 1):
s ystema re spiratorium) functionality c an be
▪ Conducting zone
▪ Respiratory zone
In t he conducting zone, air moves in
continuous passages:
Nose
Pharynx
Larynx
Trachea
Bronchi
Bronchioles
In t he respiratory zone (lungs),
consists of thre e pa ssages which a re
responsible for inhaled ox ygen to be
passages include:
Figure 1. Respiratory system
exchanged for c arbon diox ide. The thre e
Respiratory bronchioles
Alveolar ducts
Alveoli
The respiratory system structures are divided into:
▪ Upper respiratory tract
▪ Lower respiratory tract
Upper respiratory tract is located in the
head a nd ne ck a nd c onsists of three re gions
(Figure 2):
Nose
Pharynx
Figure 2. Respiratory system
Larynx
Nose Region
The region of the no se c onsists of the
external nose and the nasal c avity. The a ir
travels from the nostrils to the back of the
nasal cavity where it e xits through the
posterior na res. The n asal mucosa c overing
the nasal cavity is made up of thre e la yers:
ciliated e pithelium, basement membr ane,
and lamina p ropria. The c iliated e pithelium
is the top portion of the na sal mucosa that
contains hair-like processes called the cilia
Figure 3. Ciliated cells
(Figure 3). The ciliated epithelium rests on
the basement membr ane. The lamina
propria (layer of connective tissue) lies below the basement membrane.
The na sal epithelium contains three diff erent type of c ells (Figure 4) . T he c iliated or
non-ciliated, goblet, and basal cells. The ciliated cells with their movement forward and
back create a flow of mucus (with any trapped material: bacteria, viruses, etc.) that ends
in the pharynx. W hen t he mucus arrives in
the pha rynx, the mucus is swallowed. This
movement of mucus (which is known a s
mucociliary clearance) is not random; rather,
it is pr ogrammed so that the mucus moves
along in a specific p attern (a ctive p rocess).
The goblet cells are specialized cells that are
responsible for c onstant secretion of the
mucus layer. While the secretion of mucus is
being seen in both the uppe r and low er
respiratory tr act, it is most pr onounced in
Figure 4. Nasal epithelium
the nasal cavity and paranasal sinuses. The
mucus has multiple functions that c an includ e ke eping the nasal passages moist,
trapping debris and infection material, and worm the incoming air.
The paranasal sinuses are air-filled pockets located within the bones of the face and
around the nasal cavity. Each sinus is name for the bone in which it is located:
Maxillary (one sinus located in each cheek)
Ethmoid (approximately 6-12 small sinuses per side, located between the eyes)
Frontal (one sinus per side, located in the forehead)
Sphenoid (one sinus per side, located behind the ethmoid sinuses, near the
middle of the skull)
Each of these pockets has an opening that connects to the nose. This opening is called
an ostium.
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The nose and sinuses are
closely related. The nasal
septum divides the nose
into two nasal cavities.
The side wall of the nose
(the lateral nasal wall) has
three important structures, which are known as
the superior, middle and
inferior turbinates. Each
turbinate is a rounded
projection that extends
the length of the nasal
cavity.
The
space
between each turbinate is
called a meatus, and each
meatus is named for the
meatus above it.
Figure 5. Nasal epithelium
The inferior turbinate, which is larger than the other turbinates, runs parallel to the floor
of the nose. The nasolacrimal duct drains tears into the inferior meatus. (This explains
why one develops nasal congestion when one cries.)
The middle turbinate is located above the inferior turbinate. The anterior (or front)
ethmoid cells open into the middle meatus. The term "frontal recess" refers "antechamber" just below the frontal sinus ostium. Therefore, the frontal sinus drains into the
middle meatus. The frontal recess contains a variable number of ethmoid cells.
The superior turbinate, which is the smallest turbinate, is above the middle turbinate.
The posterior (or back) ethmoid cells drain into the superior meatus. The space between
the superior turbinate, the septum and the sphenoid sinus front wall is known as the
sphenoethmoid recess. The sphenoid drains here.
Pharynx Region
There are three distinct parts in the pharynx region: nasopharynx, oropharynx, and
laryngopharynx. Through the nostrils (nasopharynx) air moves into the nasal cavity The
oropharynx opens into the oral cavity which encloses the lips, teeth, cheek, hard and
soft palates, tongue and tonsils. Extending from the tip of the epiglottis to the glottis and
the esophagus is the laryngopharynx and positioned in the anterior neck is the larynx.
The tonsils and adenoids are located in the pharynx. The middle ear communicates with
the nasopharynx thorough the Eustachian tubes.
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Larynx Region
The passageway between the pharynx and the
lower a irway structures is the lar ynx. It is a
short tube made up of supportive cartilage,
ligaments, muscle a nd mucosal lining. The
larynx mucosa forms the fa lse a nd tru e voc al
cords. The vocal cords and the space between
is c alled glottis. The glottis is re sponsible to
generate voice. The function of the supportive
cartilage (epiglottis) is to pr event food a nd
liquid c ontents from e ntering the lar ynx
during swallowing.. T he lar ynx c ontains
typical upper respiratory e pithelia, c onsisting
of ciliated cells that are responsible for mucus
transport a nd goblet cells where mucus
production occurs.
Lower respiratory tract (lung) is located
in the chest and makes up the (Figure 6):
Figure 6. Lower respiratory track
Trachea
Bronchial tree
Lungs
Trachea
Air passes from the larynx to the trachea. The
trachea (know n is the windpipe) is 10-12 c m
tube that runs through the lower ne ck a nd
chest and divi des int o the right and lef t
primary br onchi (bronchial tre e) The wa ll of
the trachea is made of hyaline cartilage which
enables the trachea to stay open so that air can
be conducted between the larynx and primary
bronchi. Note that the trachea mucosa contains
no smooth muscles (Figure 7).
Bronchial tree:
The br onchial tre e c onsists of a pr imary,
secondary (lob ar) a nd ter tiary b ronchi
(segmental bronchi). The tra chea spli ts into
the right a nd left bronchi a t the level of the
sternal angle. Th e se condary br onchi forms
Figure 7. Trachea epithelium
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when the primary bronchus enters
the lung; and conducts air directly to
one of the five lobes within the lung.
Tertiary bronchi derive from the
secondary bronchi and conduct air to
and from the bronchial segment.
There are eight bronchial segments
in the left lung and 10 in the right
lung. Note the smooth muscles (SM)
in the lamina propria that are
responsible for the respiratory
complications due to allergic Figure 8. Bronchial epithelium
reaction.
The
respiratory
complications include airway constriction
(narrowing bronchial lumen, Figure 9, also
see Figure 10), due to swelling of the smooth
muscles in the airway tract, bronchospasm
(constriction of bronchi), and angioedema
(swelling in the tissue – beneath the skin).
Angioedema of the upper respiratory
(pharynx, larynx and trachea) produces upper
airway obstruction, whereas bronchospasm
and mucosal edema produce lower
respiratory obstruction. Histamine tends to
cause constriction of the large airway tracts
and leukotrienes affect the smaller peripheral
airways.11 The airway obstruction can be just
as life threatening as a result of the laryngeal
edema and/or bronchial spasm. Death can
occur due to asphyxiation.
Figure 9. Bronchial lumen
Figure 10. Bronchial lumen
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