Anatomy of the nose and paranasal sinuses

** The Nose **

Dr.Hussein
L.1 Anatomy of the nose and paranasal sinuses

External nose: external nose is pyramidal in shape consists of:

1) Anterior nares: opens dO\Vl1\vards and separated by collumella.
2) Bony constituents: consists of nasal processes of frontal bone
, nasal bones, asccnding process of the maxilla.
3) Cartilaginous portion: consists of upper and lower lateral
cartilages, alar cartilage, and quadrilateral cartilage of nasal septum. The
skin is thin over the upper part of the nose, thicker over the lower
cartilaginous part.
Vestibule: lined with skin and contains sebaceous glands and hairs (vibrissae).
Nasal fossae: the right and the left nasal fossae (cavities) arc separated by
the nasal septum and include those parts which are lined with mucous membrane
and communicate with:
1) The paranasal sinuses: through their ostia.
2) The nasopharynx; through the posterior choanae.


Boundaries:
Floor:
1) Palatine process of the maxilla in the anterior 3/4.
2) Horizontal process of the palatine bones in the posterior 1/4.
Roof:
1) Nasal process of the frontal bone anteriorly
2) Cribriform plate of the ethmoid.
3) Body of the sphenoid bone posteriorly.
Medial wall: Nasal septum consists of:
a) Perpendicular plate of ethmoid above and behind.
b) Vomer bone below and behind.
c) Quadrilateral cartilage.
Lateral wall:
a) Medial wall of the maxilla.
b) Lateral mass of ethmoids and lacrimal bone .and have the following features:
The three turbinates: superior, middle (40 mm long 14.5 mm height ant. &7mm
posteriorly), and inferior turbinate is the largest (60mm long).
Three meati: lies below and lateral to the corresponding turbinates.
Sphenoethmoidal recess: lies above the superior turbinates and receive the
ostium of the sphenoid sinus. Superior meatus: contains the ostia of the
posterior ethmoidal sinuses. Middle meatus receives the ostia of the maxillary
sinuses, anterior ethmoidal sinuses, and the frontal sinuses. Bulla ethmoidalis:
is a smooth rounded mass formed by the anterior ethmoidal cells. Hiatus
semilunaris: lies below and in front of the bulla, bounded below by the uncinate
process of the ethmoid. Inferior meatus: receives the nasal opening of the
nasolacrimal duct.



The medial nasal wall

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The lateral nasal wall

Paranasal sinuses

They are air spaces within the bones of the skull: Maxillary sinuses, ethmoidal
sinuses (labyrinth), frontal sinuses, sphenoidal air sinuses, lined by the
mucous membrane.
Maxillary sinus (antrum):
Is pyramidal in shape and occupies the body of the maxilla, the base lies
medially, the apex in the zygomatic portion of the maxilla, it is the largest of
the sinuses, the main ostium is situated high up between the medial wall and the
roof of the cavity, it opens into the hiatus semilunaris , accessory ostium are
sometimes present behind the main one ,the average capacity of the sinus is
about 15 ml in the adults.
The orbit is separated from the antrum by thin plate of bone which contains the
infraorbital nerve.
Teeth: the second premolar and the first molar are usually related to the floor.

Middle meatus: is related to the upper portion of the antrum.

The internal maxillary artery is related to the posterior wall.
Nasolacrimal duct passes downwards medial to the antrum to open into the
inferior meatus.


Ethmoidal sinuses (labyrinth)
Consist of a number (approximately 7 - 15) of thin walled cavities within the
lateral masses of the ethmoid bones; there arc two groups of cells:
1) Anterior: usually small and numerous opens into the middle meatus.
2) Posterior: usually large and few opens into the superior meatus, the ethmoid
is separated from the orbit by thin plate of bone named lamina papyracea;
lacrimal sac is related laterally to the anterior cells.
Optic nerve may be very close to the post group.
Frontal sinus:
Its average capacity is about 7 ml in the adults, the right and the left sinuses
are often asymmetrical and separated by thin bony septum, and the frontonasal
duct passes through anterior part of the ethmoidal labyrinth and opens into the
middle meatus.
Sphenoidal sinuses:
Lies behind the upper part of the nasal fossae, it occupies the body of the
sphenoid bone, the average capacity is about 7 ml in the adults the right and
the left are a symmetrical separated by a septum, the pneumatization is very
variable, the ostium situated in the upper part of the anterior wal1 or the
sinus and opens into the sphenoethmoidal recess.
Relations:
Cavernous sinus containing 3rd, 4th, 5th, (ophthalmic and maxillary divisions)
and the 6th cranial nerves with the internal carotid artery and optic nerve lies
laterally or within the lateral wall of the sphenoid sinus.
Pituitary glands, optic chiasma, olfactory tracts, frontal lobe of the brain lie
above the sinus.
Vessels and nerves from the sphenopalatine foramen lies in front the sphenoid
face as they pass to the septum, basilar artery, brain stem related to its post
wall (basisphenoid).


Mucous membrane of the nose and paranasal sinuses
1) Respiratory epithelium: this pinkish epithelium lines the lower 2/3 of the
nasal septum, lateral wall of the nose below the superior turbinate and the
floor of the nasal fossae and it is ciliated columnar epithelium with goblet
cells, thick mucus between ciliated cells and thin fluid comes from compound
acinar secreting glands, both mucus spread over the epithelium and propelled by
the cilia.
2) Olfactory epithelium: also called Schneiderian membrane lines the upper
1/3of the nasal septum, the roof the nose, the lateral wall above the superior
turbinate, the olfactory epithelium is non ciliated columnar epithelial cells,
and yellowish in color and contains the serous glands of Bowmann.

Blood supply of the nose and paranasal sinuses

I. External nose:
A. arterial supply:
1) Internal carotid artery (minor contribution): via nasal branches of the
anterior ophthalmic and anterior ethmoidal arteries.
2) External carotid artery (primary supply): superior labial, lateral nasal,
angular arteries.
B. venous drainage: is important because the nose lies in the danger triangle
of the face.
1) Anterior facial vein: drains through the common
facial vein to the internal jugular vein; also communicates through infraorbital
vein and pterygoid venous plexus to the cavernous sinus.
2) Angular vein: communicates via ophthalmic veins to
the cavernous sinus, anterior facial vein.
C. lymphatic drainage: follow anterior facial vein to the submandibular
nodes.


II. Nasal cavity and paranasal sinuses:
A. arterial supply:
1) Branches of the external carotid artery:
a. Sphenopalatine artery via the sphenopalatine foramen which is a branch of
the maxillary artery is the major supply of the nasal cavity /septum plus
adjacent sinuses.
b. Descending palatine artery posterior inferior nasal cavity.
c. Greater palatine artery via incisive foramen from the oral cavity, which
is, branch of the maxillary artery.
d .Superior labial artery which is branch of the facial artery, it sends
branches to the tip of the septum and forms anastomosis with a branch of the
sphenopalatine artery and the greater palatine artery, forms plexus of arteries
named Kiesselbach's plexus in little's area.
e. Infraorbital and superior dental artery: supplies maxillary antrum.
2) Branches of the internal carotid artery:
a. Anterior and posterior ethmoidal arteries which are branches of the
ophthalmic artery supplies the roof of the nose, ant part of the septum ,and the
lateral wall of the nose ,including ethmoidal and the frontal sinuses.
b. Supraorbital and supratrochlear arteries to the frontal sinuses.

B. Venous drainage:
The veins form cavernous plexus beneath the mucous membrane.
1) Supraorbital, supratrochlear, and ethmoidal veins: drain via ophthalmic vein
to the cavernous sinus.
2) Sphenoidal, alveolar, and palatine veins: drain via maxillary vein to the
posterior facial vein but communicate with cavernous sinus via the pterygoid
venous plexus.
C. Lymphatic drainage:
anterior 1/3 of the nose drains to the submandibular nodes. Posterior 2/3
plus sinuses drains to the retropharyngeal nodes (of Rouviere) and superior deep
cervical nodes.
Autonomic nerve supply:
Sympathetic stimulation cause tonic vasoconstriction, while parasympathetic
stimulation causes vasodilatation.
Nerve supply of the nose:
1) Branches of the 5th cranial nerve: anterior ethmoidal nerve which is branch
of the ophthalmic division supplies the anterior part of the septum and the
lateral wall.
2) Branches of the sphenopalatine ganglion: greater palatine, short and long
sphenopalatine nerves.
3) Olfactory nerves: the sense of smell is supplied by the 1st cranial nerve
through the olfactory area located at the upper part of the nasal cavity (1
square cm).


Functions of the nose:
1) Purification by vibrissae, cilia, sneezing, mucus.
2) Warming of the inspired air.
3) Moistening of the inspired air.
4) Olfaction: the breath is held if noxious smells are detected.

Disturbances of smell:

1) Anosmia: complete loss of smell, it must be bilateral before it is
noticeable.
2) Hyposmia: it is partial loss of smell either because of the nasal
obstruction, polyps, turbinate hypertrophy, septal deviation, common cold,
allergic rhinitis, .etc.
3) Cacosmia: perception of a bad smell due to intrinsic causes like maxillary
sinusitis of dental origin, F.B. in the nose, foetid pus.
4) Parosmia: a perversion of the sensation of smell or a subjective sensation of
non existent smells.

Functions of the paranasal sinuses:

Are uncertain, but there are several theories:
1) Result of facial development.
2) Air conditioning.
3) Lightening of the skull.
4) Resonance of voice.