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Anatomy and Physiology of The
Nose & Paranasal Sinuses
Dr. Abdullah Alkhalil
MRCS-ENT(UK), DOHNS(London)
Higher specialty(JUST),
Jordanian Board.
1
Introduction
• The nose is the part of the respiratory tract
superior to the hard palate and contains the
peripheral organ of smell. It includes the
external nose and nasal cavity, which is
divided into right and left cavities by the nasal
septum.
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External Nose
• The external nose is the visible portion that
projects from the face. Noses vary
considerably in size and shape. The dorsum of
the nose extends from the root of the nose to
the apex (tip) of the nose. The inferior surface
of the nose is pierced by two piriform
openings, the nares , which are bound
laterally by the alae (wings) of the nose.
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External Nose
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External Nose
• The superior bony part of the nose,
including its root, is covered by thin skin.
The skin over the cartilaginous part of the
nose is covered with thicker skin, which
contains many sebaceous glands. The skin
extends into the vestibule of the nose ,
where it has a variable number of stiff
hairs (vibrissae).The junction of the skin
and mucous membrane is beyond the hairbearing area.
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Skeleton of the External Nose
• The supporting skeleton of the nose is
composed of bone and hyaline cartilage. The
bony part of the nose consists of the nasal
bones, frontal processes of the maxillae, the
nasal part of the frontal bone and its nasal
spine, and the bony parts of the nasal septum.
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Skeleton of the External Nose
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Skeleton of the External Nose
• The cartilaginous part of the nose consists of
five main cartilages: two lateral cartilages, two
alar cartilages, and one septal cartilage. The
U-shaped alar cartilages are free and movable;
they dilate or constrict the nares when the
muscles acting on the nose contract.
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Skeleton of the External Nose
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External Nose Blood Supply
1). External carotid a.
- facial a. :
angular br., alar br.,
septal br., external nasal br.
2). Internal carotid a.
- ophthalmic a. :
dorsal nasal br.
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Nasal Septum
• The nasal septum divides the chamber of the
nose into two nasal cavities and has a bony
part and a soft mobile cartilaginous part. The
main components of the nasal septum are the
perpendicular plate of the ethmoid, the
vomer, and the septal cartilage.
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Nasal Septum
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Nasal Septum
• The thin perpendicular plate of the ethmoid
bone, forming the superior part of the nasal
septum, descends from the cribriform plate
and is continued superior to this plate as the
crista galli. The vomer, a thin flat bone, forms
the posteroinferior part of the nasal septum,
with some contribution from the nasal crests
of the maxillary and palatine bones.
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NASAL CAVITIES
• The term nasal cavity, divided into right and
left halves by the nasal septum, refers to
either the entire cavity or one of its halves,
depending on the context. The nasal cavity is
entered anteriorly through the nares. It opens
posteriorly into the nasopharynx through the
choanae. Mucosa lines the nasal cavity, except
for the nasal vestibule, which is lined with
skin.
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NASAL CAVITIES
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NASAL CAVITIES
• The nasal mucosa is firmly bound to the
periosteum and perichondrium of the
supporting bones and cartilages of the nose.
The mucosa is continuous with the lining of all
the chambers with which the nasal cavities
communicate: the nasopharynx posteriorly,
the paranasal sinuses superiorly and laterally,
and the lacrimal sac and conjunctiva
superiorly.
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NASAL CAVITIES
• The inferior two thirds of the nasal
mucosa is the respiratory area and
the superior one third is the olfactory
area. Air passing over the respiratory
area is warmed and moistened before
it passes through the rest of the
upper respiratory tract to the lungs.
The olfactory area contains the
peripheral organ of smell; sniffing
draws air to the area.
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Boundaries of the Nasal Cavity
The nasal cavity has a roof, floor, medial and lateral
walls.
• The roof of the nasal cavity is curved and narrow,
except at its posterior end; it is divided into three
parts (frontonasal, ethmoidal, and sphenoidal)
named from the bones forming each part.
• The floor of the nasal cavity is wider than the roof
and is formed by the palatine processes of the
maxilla and the horizontal plates of the palatine
bone.
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Boundaries of the Nasal Cavity
• The medial wall of the nasal cavity is formed
by the nasal septum.
• The lateral walls of the nasal cavity are
irregular owing to three bony plates, the nasal
turbinates, which project inferiorly.
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Features of the Nasal Cavity
• The three scroll-like, pitted turbinate bones,
on each side of the nose divide the nasal
lumen into meatus. The space between the
inferior turbinate and floor of the nose is the
inferior meatus, the space between the
inferior and middle turbinates is the middle
meatus, and the space above the middle
turbinate is the superior meatus. Occasionally,
there is a supreme turbinate.
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Features of the Nasal Cavity
• The middle and superior turbinates are
extensions of the ethmoid bones, whereas the
inferior turbinate is a separate bone attached
by its superior border to the lateral nasal wall.
At the anterior ends of the middle and inferior
turbinates, a low cuboidal or squamous cell
epithelium is found.
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Features of the Nasal Cavity
• The epithelial stroma of the middle
turbinate contains many glands. The
large, tortuous, valveless,
anastomosing veins, called
sinusoids, are found mainly in the
middle and inferior turbinates. By
the degree of fluid contained in the
sinusoids, they can influence the
size of the nasal airway and, in
effect, are capacitance structures.
They respond to neural,
mechanical, thermal, physiologic,
and chemical stimuli.
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Features of the Nasal Cavity
• Superior Meatus The superior meatus (also
called the ethmoid fissure) is a slit-like space
above the middle turbinate and is situated
between the nasal septum and the ethmoid
bone. The posterior ethmoid cells open into
the central portion of this meatus. Above and
posterior to the superior turbinate is the
sphenoid recess, into which the sphenoid
sinus opens.
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Features of the Nasal Cavity
• Middle Meatus This meatus lies between the
middle and inferior turbinates. It contains the
orifices of the frontal and maxillary sinuses and
also the anterior ethmoid cells. Hidden by the
anterior half of the overhanging middle turbinate
is a deep crescentic groove, the infundibulum.
The crescent-shaped opening is called the hiatus
semilunaris. The inferior medial wall of the
infundibulum forms a shelf-like ledge known as
the uncinate process and above the ledge a
hemispheric prominence termed the ethmoid
bulla.
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Features of the Nasal Cavity
• The frontal, maxillary, and anterior ethmoid
sinuses open into the infundibulum. Some
ethmoid cells may open above the ethmoid
bulla, and the frontonasal duct may have a
separate opening.
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Features of the Nasal Cavity
• Inferior Meatus The inferior meatus lies below
the inferior turbinate. On its lateral surface, 3
to 5 cm beyond the naris, is found the orifice
of the duct from the lacrimal gland. The floor
of the meatus is congruent with the roof of
the mouth.
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Vascular Supply
• The arterial supply of the medial and lateral walls of
the nasal cavity is from five sources:
1. Anterior ethmoidal artery (from the ophthalmic
artery).
2. Posterior ethmoidal artery (from the ophthalmic
artery).
3. Sphenopalatine artery (from the maxillary artery).
4. Greater palatine artery (from the maxillary artery).
5. Septal branch of the superior labial artery (from the
facial artery).
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Vascular Supply
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Vascular Supply
• The first three arteries divide into lateral and
medial (septal) branches. The greater palatine
artery reaches the septum via the incisive
canal through the anterior hard palate. The
anterior part of the nasal septum is the site
(Kiesselbach area) of an anastomotic arterial
plexus involving all five arteries supplying the
septum.
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Vascular Supply
• A rich submucosal venous plexus deep to the
nasal mucosa drains into the sphenopalatine,
facial, and ophthalmic veins. This venous
plexus is an important part of the body's
thermoregulatory system, exchanging heat
and warming air before it enters the lungs.
Venous blood from the external nose drains
mostly into the facial vein via the angular and
lateral nasal veins.
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Nerve Supply
• the nasal mucosa can be divided into
posteroinferior and anterosuperior. The nerve
supply of the posteroinferior portion of the
nasal mucosa is chiefly from the maxillary
nerve, by way of the nasopalatine nerve to the
nasal septum, and posterior superior lateral
nasal and inferior lateral nasal branches of the
greater palatine nerve to the lateral wall.
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Nerve Supply
• The nerve supply of the anterosuperior
portion is from the ophthalmic nerve (CN V1)
by way of the anterior and posterior
ethmoidal nerves, branches of the nasociliary
nerve. Most of the external nose (dorsum and
apex) is also supplied by CN V1 (via the
infratrochlear nerve and the external nasal
branch of the anterior ethmoidal nerve), but
the alae are supplied by the nasal branches of
the infraorbital nerve (CN V2).
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Nerve Supply
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Nerve Supply
• The olfactory nerves, concerned with smell,
arise from cells in the olfactory epithelium in
the superior part of the lateral and septal
walls of the nasal cavity. The central processes
of these cells (forming the olfactory nerve)
pass through the cribriform plate and end in
the olfactory bulb, the rostral expansion of the
olfactory tract.
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Paranasal Sinuses
• The paranasal sinuses are air-filled
extensions of the respiratory part of
the nasal cavity into the following
cranial bones: frontal, ethmoid,
sphenoid, and maxilla. They are
named according to the bones in
which they are located. The sinuses
continue to invade the surrounding
bone, and marked extensions are
common in the crania of older
individuals.
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Frontal Sinuses
• The frontal sinuses are between the outer and
the inner tables of the frontal bone, posterior to
the superciliary arches and the root of the nose.
Frontal sinuses are usually detectable in children
by 7 years of age. Each sinus drains through a
frontonasal duct into the ethmoidal
infundibulum, which opens into the semilunar
hiatus of the middle nasal meatus. The frontal
sinuses are innervated by branches of the
supraorbital nerves (CN V1).
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Ethmoidal Cells
• The ethmoidal cells (sinuses) are small invaginations of
the mucous membrane of the middle and superior
nasal meatus into the ethmoid bone between the nasal
cavity and the orbit. The ethmoidal cells usually are not
visible in plain radiographs before 2 years of age but
are recognizable in CT scans. The anterior ethmoidal
cells drain directly or indirectly into the middle nasal
meatus through the ethmoidal infundibulum. The
posterior ethmoidal cells open directly into the
superior meatus. The ethmoidal cells are supplied by
the anterior and posterior ethmoidal branches of the
nasociliary nerves (CN V1).
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Sphenoidal Sinuses
• The sphenoidal sinuses are located in the body of
the sphenoid and may extend into the wings of
this bone. They are unevenly divided and
separated by a bony septum. Because of this
extensive pneumatization (formation of air cells
or sinuses), the body of the sphenoid is fragile.
Only thin plates of bone separate the sinuses
from several important structures: the optic
nerves and optic chiasm, the pituitary gland, the
internal carotid arteries, and the cavernous
sinuses.
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Sphenoidal Sinuses
• The sphenoidal sinuses are derived from a
posterior ethmoidal cell that begins to invade
the sphenoid at approximately 2 years of age.
In some people, several posterior ethmoidal
cells invade the sphenoid, giving rise to
multiple sphenoidal sinuses that open
separately into the sphenoethmoidal recess.
The posterior ethmoidal arteries and posterior
ethmoidal nerve supply the sphenoidal
sinuses .
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Maxillary Sinuses
The maxillary sinuses are the largest of the paranasal sinuses.
They occupy the bodies of the maxillae and communicate
with the middle nasal meatus :
• The apex of the maxillary sinus extends toward and often
into the zygomatic bone.
• The base of the maxillary sinus forms the inferior part of
the lateral wall of the nasal cavity.
• The roof of the maxillary sinus is formed by the floor of the
orbit.
• The floor of the maxillary sinus is formed by the alveolar
part of the maxilla. The roots of the maxillary teeth,
particularly the first two molars, often produce conical
elevations in the floor of the sinus.
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Maxillary Sinuses
• Each maxillary sinus drains by one or more openings,
the maxillary ostium (ostia), into the middle nasal
meatus of the nasal cavity by way of the semilunar
hiatus.
• The arterial supply of the maxillary sinus is mainly from
superior alveolar branches of the maxillary artery;
however, branches of the descending and greater
palatine arteries supply the floor of the sinus.
Innervation of the maxillary sinus is from the anterior,
middle, and posterior superior alveolar nerves, which
are branches of the maxillary nerve.
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Physiology of the nasal cavity
• The nasal cavity functions to allow air to enter
the respiratory system upon respiration.
Structures within the cavity regulate the flow
of air and particles it contains. The olfactory
region of the nasal cavity regulates the sense
of smell.
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The turbinates
• The conchae (turbinate bones) of the nasal
mucosa expand the total surface area of the
mucosa and create turbulence in air entering
the respiratory passage. This causes air to
swirl as it moves through the nasal cavity and
increases contact between infiltrating air and
the nasal mucosa, allowing particles in the air
to be trapped before entering other parts of
the respiratory system (e.g. the lungs).
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Olfactory system
• The olfactory system functions to process sensory
information related to smell.
Bowman’s glands
Bowman’s glands secrete the majority of the
mucus which overlies the nerves of the olfactory
system. They also secrete the pigment which gives
this mucus its yellow colour. Mucus secreted by
these glands dissolves odours as they enter the nose,
enabling them to interact with the olfactory receptors.
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Surrounding structures
Paranasal sinuses
The paranasal sinuses function to resonate speech
and produce mucus which enters the nasal passage.
Other functions of the sinuses are not well
understood.
Nasolacrimal ducts
The nasolacrimal ducts drain tears from the lacrimal
(tear) ducts of the eyes, to the nasal mucosa.
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Physiology of the nasal mucosa
• The nasal mucosa plays an important role in
mediating immune responses to allergens and
infectious particles which enter the nose. It helps
prevent allergens and infections from invading
the nasal cavity and spreading to other body
structures, for example the lungs. The mucus
secreted by and which lines the mucosa provides
a physical barrier against invasion by pathogens.
It is sticky and traps pathogens when they enter
the nasal cavity.
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Physiology of the nasal mucosa
• However, in some individuals abnormal
responses of the nasal mucosa occur and
immune responses are mounted against allergens
which the body does not usually recognize as
pathogenic and thus does not usually mount an
immune response to. In these individuals the
mucosa, which usually functions to protect the
body from invading microorganisms, is also
thought to play a role in the pathological allergic
response referred to as a type 1 hypersensitivity
reaction.
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Physiology of the nasal mucosa
• Mucus glands
Glands in the nasal mucosa produce a sticky
mucus which moistens air and traps bacteria
as they enter the respiratory passage.
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Physiology of the nasal mucosa
• Cilia
Cilia or small hairs which project from the epithelium
and line the nasal mucosa create motions which drain
mucus from the nasal passage to the throat from
where it is swallowed and digested by stomach juices.
The activity level of cilia is dependent on temperature
and in cold temperatures cilia become less active.
Mucus may accumulate in and drip from the nostrils
(runny nose) in these conditions. Infectious particles
and allergens also impair cilia activity and can lead to
symptoms such as a congested or runny nose.
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Physiology of the nasal mucosa
• Underlying blood vessels
The thin walled veins on which the nasal mucosa
rests function to warm air entering the
respiratory passage. Due to the high
concentration of blood vessels in the nasal cavity,
changes in these blood vessels contribute to
nasal congestion. For example, constriction of
these blood vessels decreases airway resistance,
making it easier for air to enter the respiratory
system. The nasal nerves also regulate the
congestion response.
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Physiology of the nasal mucosa
• Nerves
Innervation of the nasal mucosa is regulated by
the trigeminal and maxillary nerves which also
provide sensations to other areas of the face. The
trigeminal nerve regulates sensations including
touch, pressure and temperature in the nose,
while sympathetic and parasympathetic
innervation (innervation which controls
involuntary movements like constriction and
dilation of the blood vessels) occurs via the
maxillary nerve.
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Physiology of the nasal mucosa
• The different types of nerves found in the nasal
cavity and mucosa have various functions. For
example, constriction of blood vessels which feed
the nasal cavity is regulated in part by the
sympathetic nervous system, while the
parasympathetic nervous system plays a role in
regulating secretions of mucus from nasal glands.
Other nerves in the nasal cavity influence the
dilation of blood vessels, nasal secretions,
inflammation and interactions between nerves
and the mast cells which mediate allergic
responses.
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Physiology of the nasal mucosa
• Venous-like spaces
Venous-like spaces found throughout the
nasal mucosa swell and become congested in
response to allergens and infection.
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