Download The Nasal Cavity

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Human Anatomy
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The Nasal Cavity
The nasal cavity consists of right and left halves that are
separated by a nasal septum. The cavity opens, anteriorly, on
the front of the skull through the anterior nasal aperture; and,
posteriorly, on the base of the skull just above the posterior
edge of the bony palate, through the right and left posterior
nasal apertures.
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Boundaries of the nasal cavity:
≡ The lateral wall is formed by meeting of several bones. The
bones taking part in forming it are (a) the medial surface of
the maxilla, (b) the palatine bone; (c) the lacrimal bone; (d)
the inferior nasal concha; and (e) the ethmoid bone.
≡ The floor of the nasal cavity is formed anteriorly by the
palatine process of the maxilla, and posteriorly by the
horizontal plate of the palatine bone.
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≡ The roof of the nasal cavity is formed by several bones. From
front to back these are parts of the nasal bone, the frontal
bone, the cribriform plate of the ethmoid and the anterior
surface of the body of the sphenoid bone.
≡ The medial wall or nasal septum is formed in its upper part by
the perpendicular plate of the ethmoid bone, and its lower
part by the vomer. Anteriorly, there is a gap in the septum
that is filled in by cartilage.
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Lateral wall of the
nasal5 cavity
medial wall
of the nasal
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cavity
Nasal Conchae
Projecting out of the lateral walls of the nasal cavity are curved shelves of
bone. They are called conchae (or turbinates). The are three conchae –
inferior, middle and superior.
They project into the nasal cavity, creating four pathways for the air to flow.
These pathways are called meatuses:
-Inferior meatus: Lies between the inferior concha and floor of the nasal
cavity.
-Middle meatus: Lies between the inferior and middle concha.
-Superior meatus: Lies between the middle and superior concha.
-Spheno-ethmoidal recess: Lies superiorly and posteriorly to the superior
concha.
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Paranasal Sinuses
Paired air spaces in certain bones of the skull are called
paranasal sinuses. These sinuses are named according to the
bones in which they are found; thus, there are the maxillary,
frontal, sphenoidal, and ethmoidal sinuses. Each sinus
communicates via drainage ducts within the nasal cavity on its
own side.
### Paranasal sinuses may help to
• warm and moisten the inspired air.
• These sinuses are responsible for some sound resonance.
• The most important function is to decrease the weight of the
skull while providing structural strength.
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A. FRONTAL SINUSES
The right and left frontal sinuses are between the outer and
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. The right and left
sinuses each drain 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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B. 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 anterior ethmoidal cells drain into the middle meatus
through the ethmoidal infundibulum.
• The middle ethmoidal cells open directly into the middle
meatus on or above the bulla ethmoidalis.
• 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
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(CN V1).
C. SPHENOIDAL SINUSES
The sphenoidal sinuses are located in the body
of the sphenoid, but they may extend into the
wings of sphenoid. They are unevenly divided
and separated by a bony septum. This sinus
opens above the superior concha within
sphenoethmoidal recess.
***The mucous membrane receives sensory
innervation by the posterior ethmoidal nerve
(branch of the ophthalmic nerve).
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D. MAXILLARY SINUSES
The maxillary sinuses are the largest of the
paranasal sinuses. They occupy the bodies of
the maxillae. Each maxillary sinus drains by
one or more openings into the middle meatus
of the nasal cavity by way of the semilunar
hiatus.
***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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Other Apertures in the Nasal Cavity
In addition to the anterior and posterior nasal apertures,
and the openings of the paranasal sinuses, we see the
following openings in the nasal cavity.
a. The nasolacrimal canal opens into the inferior meatus.
The upper end of this canal is seen in the orbit.
b. The sphenopalatine foramen opens behind the superior
meatus, just above the posterior end of the middle
concha
c. The nasal cavity communicates with the anterior cranial
fossa through numerous apertures in the cribriform
plate of the ethmoid bone.
d. In the anterior part of the floor of the nasal cavity there
is a funnel shaped opening that leads into the incisive
canals that open on the lower surface of the palate.
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Innervation of the nose:
☻ General sensation:
1. maxillary nerve, by way of the
• nasopalatine nerve to the nasal septum.
• posterior superior lateral nasal and inferior lateral
nasal branches of the greater palatine nerve to the
lateral wall.
2. ophthalmic nerve by way of the anterior and posterior
ethmoidal nerves, branches of the nasociliary nerve.
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3. 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 of the nose are supplied by the
nasal branches of the infra-orbital nerve (CN V2).
☻ Special sensation
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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