Anatomy of Nasal Cavity

7/30/2019 Anatomy of Nasal Cavity

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Anatomy of Nasal Cavity & Paranasal Sinuses

Nasal Cavity:

The nares lead into the vestibule, the skin-lined part of the nasal cavity thatcontains the vibrissae (nasal hairs), the hair follicles, and the sebaceous glands.

The vestibule is limited above and behind by a curved ridge, the limen nasi. The union of the skin-lined nasal vestibule with the mucosa-lined chamber of the

nasal cavity has the shape of a triangularaperture.

The nasal valve constitutes the narrowest area of the normal nasal airway. Itssuperior and lateral limits are formed by the upper lateral cartilage; its medial wall

is the nasal septum.

The mucosa of the nasal cavity has a pseudostratified ciliated columnarepithelium .

It communicates with the adjoining paranasal sinus and with the nasopharynx viathe posterior choana.

ROOF (Olfactory Cleft):

Sloping anterior portion is formed by nasal bones and nasal spine of frontalbone.

Central segment (olfactory area) is formed by cribriform plate of the ethmoidbone.

Descending posterior part is formed by face of the sphenoid sinus.

FLOOR:


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Formed by the premaxilla, the maxilla (palatine plate), and the horizontal plateof the palatine bone in the posterior portion.

Bony floor is about 4.5 cm long and continues posteriorly into the soft palate.

MEDIAL WALL (Nasal Septum):

Cartilaginous segment:(Quadrilateral cartilage).

Superiorly, is connected to the the inter-nasal suture and to the upper lateralcartilages.

Inferiorly, it rests on the maxillary crest, its anterior extension the anterior nasalspine, and vomer.

Cranially, is related to the perpendicular plate of ethmoid bone. Caudally, cartilage is related to the medial crura of the lower lateral cartilages.

Bony segment:

Perpendicular plate of ethmoid bone:

Continuous superiorly with the cribriform plate. Continuous postero-inferiorly with vomer. The long anterior border of the vomer articulates

Vomer: Continuous antero-superiorly with the perpendicular plate, and septal cartilage. Continuous inferiorlywith bony floor.


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LATERAL NASAL WALL:

Bones forming the lateral wall:

Superior Turbinate:

Belongs to the ethmoid bone. Measures 1.5 cm in length. Attached laterally to the lamina papyracea of the ethmoid bone. It is usually pneumatized, forming part of the posterior ethmoidal cells. Supreme turbinate sometimes visible above the superior turbinate.


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Superior meatus:

Lies between the middle and superior turbinates and contains the ostia of theposterior ethmoidal cells.

Immediately behind the superior meatus is situated the sphenopalatine foramen.

Middle turbinate:

a portion of the ethmoid bone. 4 cm in length. Attachments: Anterior end inserts into the ascending process of the maxilla. Superior attachment (in the para-sagittal plane) to the lateral edge of cribriform

plate of ethmoid.

Lateral attachment:o Anteriorly: (in the coronal plane) into the lamina papyracea of the ethmoid

bone through the vertical part of basal (ground ) lamella.

o Posteriorly: (in the horizontal = axial plane) into perpendicular plate of thepalatine bone through the horizontal part of basal lamella.

o .


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Pneumatization of the middle turbinate (concha bullosa) is presentin one-third of the population.

Middle meatus:

Ostiomeatal complex describe a group of anatomical structuresbelonging to the nasal lateral wall that are contributing to the final

common drainage pathways of the anterior ethmoid, maxillary,

and frontal sinuses. It includes the middle meatus, the uncinate

process, the hiatus semilunaris, the ethmoid infundibulum, the

ethmoid bulla, the maxillary sinus ostia, and the frontal recess.

Uncinate Process:

Thin, sagittally oriented lamella, latin uncinatus,meaninghooked.

Attachment antero-superiorly: (variable)1. May attach to the roof of the ethmoid bone.2. May turn medially and fuse with the middle turbinate. Frontal

recess and, consequently, the frontal sinus open directly into

ethmoid infundibulum (Fronto-nasal communication Type II).

3. May insert laterally on the lamina papyracea (85% of cadavers),where the ethmoid infundibulum is closed superiorly by a blind

pouch named the recessus terminalis (cap of the egg). In this

situation, the ethmoid infundibulum and the frontal recess are

separated from each other, and so the frontal sinus drains into the

middle meatus medial to the infundibulum (Fronto-nasal

communication Type I).


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Type I Type II

Attaches postero-inferiorly to the perpendicular plate of thepalatine bone. The bony posterior end of the uncinate

process may be absent. This allows the mucosa of the

maxillary sinus to contact the mucosa of the lateral nasal

wall. This area is called the posterior fontanelle.

Inferiorly, it articulates with the ethmoid process of the inferiorturbinate. A dehiscence at this articulation with the inferiorn

turbinate is termed the anterior fontanelle, and it is located

anterior to the natural ostium of the maxillary sinus.

Perforation of these membranes (fontanellae) leads to openingsaccessory ostia of the maxillary sinus.

Free postero-superior edge, 2 cm in length, is hidden by middleturbinate.


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It may itself become pneumatized causing narrowing of theethmoid infundibulum. Its pneumatization can expand anteriorly

and superiorly as far as the lacrimal bone, thereby creating the

ethmo-lacrimal cells.

Uncinate process can occasionally be absent and be replaced by afibrous band, which is laterally pent.

Hiatus Semilunaris:

Two-dimensional space between the posterior edge of the uncinate process andthe anterior wall of the ethmoid bulla.

It is the doorway that leads to the ethmoid infundibulum.

Ethmoid Infundibulum:

Three-dimensional space bounded by the uncinate process medially, the ethmoidbulla posteriorly, and the lamina papyracea laterally.

Length of the ethmoid infundibulum may reach 4 cm, depending on the shape ofthe uncinate process.

The greatest width (free margin of the uncinate process to the lamina papyracea)is5 mm. It is wider antero-superiorly and narrower at its posterior end. It

may be atelectatic according to anatomical variations of other structures such as

paradoxical bending of the middle turbinate, a concha bullosa, or a hypoplastic

maxillary sinus.


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The lateral surface of the ethmoid infundibulum leads to ostium of the maxillarysinus. Its size is variable, with a diameter of1 to 4 mm, and it can be round or

elliptical or formed of two or three openings. An accessory maxillary opening is

often found posterior to the true ostium.

Depending on the anatomical configuration of the uncinate process, the superiorside of the infundibular space can communicate or not with the frontal recess.

Frontal Recess:

The funnel-shaped lower part of the hourglass-shaped space above the level ofthe ethmoid infundibulum that gives access to the frontal sinus.

Frontal sinus opens into the frontal recess through frontal ostium, a channel thatis 3 mm long, usually found in the most anterosuperior part of the frontal

recess.


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Agger nasi cells mark the anterior limit of the frontal recess. If there is markedpneumatization of these cells, the frontal recess may be reduced in volume and

limited to a small tubular lumen.

BOUNDARIES:

Medial: Superior attachment of the middle turbinate Lateral: Lamina papyracea Superior: Internal os of the frontal sinus Anterior: nasofrontal "beak" Inferior: ethmoid infundibulum or middle meatus Posterior: variable, depending on ethmoid bulla.

o If the ethmoid bulla and inserts into the roof of the ethmoid bone, it willform the posterior wall of the frontal sinus.

o Frontal recess to communicate with the space above the ethmoid bulla,termed the supra-bullar recess. If the bulla is well pneumatized and

extends far forward, the frontal recess will be narrowed.

Ethmoid Bulla:(Bulla Ethmoidalis)

A hollow bony protuberance situated in the lateral wall of the middle meatusbehind the uncinate process.

It is the most constant and largest of the anterior ethmoid air cells. There may be up tofour cells pneumatizing the bulla, with the most common one

being located supero-posteriorly.

It is pneumatized in 70% of all individuals, but, occasionally, the ethmoid bullamay not be pneumatized (Torus protuberance 30%).

Laterally, the bulla is attached to the lamina papyracea.


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Superiorly, if the bulla does not reach the roof of the ethmoid bone, a supra-bullar recess is formed.

Posteriorly, if it not expand to the vertical portion of the basal lamella of themiddle turbinate, the formed space is named the lateral sinus. (recessus

terminalis)

A very large bulla may obliterate the space for the lateral sinus. On the contrary, asmall bulla allows communication between the suprabullar ethmoid infundibulum

and the sinus itself.

Agger Nasi:

A smooth bony swelling in the frontal process of the maxilla situated in front ofthe anterior insertion of the middle turbinate.

The lateral wall can extend to the lacrimal bone and/or the orbital wall. Anterolateral to the agger nasi and running parallel to it is the nasolacrimal duct. It drains into the anterior middle meatus and into the ethmoid infundibulum.

Frontal Cell:

Originates from the anterior ethmoid sinus above the agger nasi cell and mayobstruct the frontal recess or the frontal sinus itself.

Bent - Kuhn Classification:

Type I: Single frontal cell above agger nasi cell, but below frontal sinus. Type II:More than one cell in frontal recess above agger nasi cell, but below

frontal sinus.

Type III: Large single cell pneumatizing cephalad into frontal sinus. Type IV: Single isolated cell within the frontal sinus.


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Inferior Turbinate:

An independent anatomical structure composed of the inferior conchal bone,mucoperiosteum, a submucosal cavernous plexus, and respiratory mucous

membrane.

Attached to the conchal ridge of the medial process of the maxilla and thepalatine bone.

It articulates with the lacrimal bone by its lacrimal process and covers thelacrimal groove to form the bony canal for the nasolacrimal duct.

Inferior meatus lies inferolateral to the inferior urbinate. Nasolacrimal duct is the only structure that opens in this meatus. The duct opens

close to the angle between the two attachment limbs of the inferior turbinate,

between its anterior and middle thirds through a semi-valve (Hasner`s valve).

Maxillary Sinus:

A quadrilateral pyramidal-shaped cavity within the body of maxillary bone withits apex directed into the zygomatic process.

Average adult dimensions of the sinuses are 35 to 45 mm in height, 35 to 45 mmin length, and 25 to 35 mmin width. The mean volume is 15 cc.

Maxillary bone consists of:

1. body2. frontal process is articulated with the frontal bone and the nasal bone;3. zygomatic process is connected with the zygomatic bone;


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4. alveolar process is fused with the contralateral alveolar process, formingan alveolar arch containing the dentition;

5. palatine process is linked with the palatine bone to constitute the roof ofthe mouth.

Medial wall: (base of the pyramid) Can be divided into thirds; the superior third lies lateral to middle meatus, the

middle third lies lateral to inferior meatus, and the inferior third is the alveolar

process.

Natural ostium is located in the supero-posterior aspect of the medial sinuswall, it opens in the posterior third of the ethmoid infundibulum.

Ostium varies widely in size and shape, but the mean size is3 mm. There are one to three accessory ostia usually found within antero-inferior

fontanelle. They are located below and in front of natural ostium and sometimes

behind it.

Anterior wall:


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It extends from the pyriform aperture medially to the maxillo-zygomatic suturelaterally, and from the infraorbital rim superiorly to the alveolus inferiorly.

Anterior surface contains several elevations on its inferior area over the roots ofthe teeth. Above the elevations are slight depressions, including canine fossa, the

thinnest region of bone, which lies above the canine tooth. (Lateral and central

incisors are not part of the maxilla, and therefore the maxillary sinus does not

relate to their dental roots).

Above the canine fossa there is infraorbital foramen through which pass theinfraorbital vessels and nerve. It lies 5 mm below the inferior orbital ridge.

Lateral & Posterior walls:

Formed by the zygomatic bone and the greater wing of the sphenoid bone. They form the anterior boundary of the pterygo-palatine fossa.

Pterygopalatine fossa:

Entrance into the pterygopalatine fossa is gained through the pterygo-maxillaryfissure, which transmits the internal maxillary vessels. This fissure is situated on

the medial wall of the infra-temporal fossa and is represented by the space

between the pterygoid process of the sphenoid bone and posterior surface of the

maxilla.

Fossa is pyramidal in shape (inverted cone), it apex pointing inferiorly to thepalatine canal.

It is formed by three bones: the maxilla, the palatine bone, and the pterygoidprocess of the sphenoid bone.

It communicates with:


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1. Middle cranial fossa through foramen rotundum, which transmits themaxillary division of the trigeminal nerve (V2).

2. Orbit via the inferior orbital fissure containing the infraorbital artery (acontinuation of the maxillary artery), and zygomatic branch of V2.

3. Nasal cavity by the sphenopalatine foramen, which carries thesphenopalatine artery and sphenopalatine nerve of V2.

Extending posteriorly from this fossa is the pterygoid (vidian) canal, which iscrossed by the nerve of the pterygoid canal (vidian nerve) formed ofdeep

petrosal nerve and the greater petrosal nervethe former carrying sympathetic

fibres and the latterparasympathetic fibres of the autonomic nervous system to

lacrimal gland and mucosal glands of the nose, palate, and pharynx.

1. . Vidian nerve then passes through foramen lacerum, together with;artery of the ptyregoid canal, terminal branch of ascending pharyngeal

artery, emmissary veins.

2. Inferiorly, the fossa ends in the pterygo-palatine canal, which conductsthe Greater palatine vessels (of internal maxillary A) and Palatine

nerve (of sphenopalatine ganglion), which emerge from the greater

palatine foramen.

It contains: Pterygo-palatine ganglion,

Located high in the fossa. Postsynaptic parasympathetic fibers leave this ganglion and distribute with

branches of the maxillary division of the trigeminal nerve (V2).

These fibers are secretomotor in function and provide parasympatheticinnervation to the lacrimal gland and the mucosal glands of the nose, palate, and

pharynx.
http://en.wikipedia.org/wiki/Deep_petrosal_nervehttp://en.wikipedia.org/wiki/Deep_petrosal_nervehttp://en.wikipedia.org/wiki/Deep_petrosal_nervehttp://en.wikipedia.org/wiki/Greater_petrosal_nervehttp://en.wikipedia.org/wiki/Greater_petrosal_nervehttp://en.wikipedia.org/wiki/Parasympathetichttp://en.wikipedia.org/wiki/Autonomic_nervous_systemhttp://en.wikipedia.org/wiki/Autonomic_nervous_systemhttp://en.wikipedia.org/wiki/Parasympathetichttp://en.wikipedia.org/wiki/Greater_petrosal_nervehttp://en.wikipedia.org/wiki/Deep_petrosal_nervehttp://en.wikipedia.org/wiki/Deep_petrosal_nerve


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Acts as aperipheral

regulatory center for

the innervation of

the vessels of the

nasal mucosa.

Stimulation of this

ganglion may produce

redness, swelling,

increased secretions

from the nasal

mucosa. Thus

ganglion block were

applied in cases with severe mucosal reactivity.


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Superior wall (Roof):

Represents the majority of the floor of the orbit, which also includes the orbitalprocess of the palatine bone posteromedially and the zygomatic bone

anterolaterally.

This wall is very thin, Extending postero-laterally to the infraorbital fissure (between maxilla and greater

wing of sphenoid bone).

Infra-orbital canal is a groove in the roof of the maxillary sinus containing theinfraorbital vessels and nerve. Near its midpoint this canal gives off a small canal

for dental vessels and nerve.

Inferior wall (floor):

Formed by the alveolar process of maxilla. Each maxilla contains 5 deciduous or8 permanent teeth.

The projecting roots are usually separated from the maxillary sinus by bone ofvariable thickness, but sometimes by mucosa alone. Periapical or periodontal

inflammation of upper premolars and molars may therefore spread to the sinus,

and endodontic treatment or extraction of these teeth may penetrate into the sinus.

Ethmoid Sinus:

Group of small cavities within the ethmoid bone, 3.3 cm 3. 2 cm 3 1. cm in sizeand contains 3 to 15 cells.

5 parts of the ethmoid bone:


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Bilateral labyrinths (containing air cells). Crista galli. Cribriform plate. Perpendicular plate.

Cribriform plate:

Perforated by olfactory nerve fibers, dura, and ethmoid vessels and nerves. Lies at a lower level than the roof of the ajdacent ethmoid labyrinth. Slope downward as it passes posteriorly. Divided into 3 parts:1. Horizontal medial portion, thick, contains 20 or more foramina for the

olfactory fibers.

2. Lateral lamellae; that arises from the horizontal segment at an angle to join theorbital plate of the frontal bone. It is usually thin. The angle at which it rises

determines the height of the olfactory groove. A more horizontal lateral

cribriform plate produces a shallow olfactory groove. Ethmoidal Arteries then

enterolfactory fosssa through an openings in lateral lamella of cribriform plate

(this points are considered the areas ofleast resistance because the lateral lamella

is only one-tenthas strong as the roof of the ethmoid)

3. The junction of the horizontal and lateral parts, which is the attachment pointof the middle turbinate and superior turbinate to the ethmoid roof.

Keros Classification of the Depth of Olfactory Fossa:


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o Roof of the ethmoid labyrinth (Fovea ethmoidalis):

o formed by the strong bony plate of the frontal bone.o Anterior part of the fovea ethmoidalislies more superiorly than the

posterior one becausethe floor of the anterior cranial fossa descends 15

degrees as it passes posteriorly.

o The junction of this structure with the lateral lamella ofthe cribriformplate defines the fronto-cribriform suture.This suture is situated in the

medial wall of theethmoid labyrinth above the level of the olfactory

groove.

Lateral surface of the ethmoid labyrinth (Lamina papyracea): Thin, flat, smooth, rectangular bony plate. Articulates with;

1. Lacrimal bone anteriorly,2. Maxilla inferiorly3. Lesser wing of the sphenoid bone posteriorly.4.

Frontal bone superiorly, toform the fronto-ethmoidsuture, along this suture lie:

a. Anterior ethmoid foramen:


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o Crossed by the anteriorethmoid artery, a terminal branch of theophthalmicartery.

o Located 25 mm posterior to the anteriorrim of the lacrimal fossa.o Anterior ethmoidartery and the accompanying nerve course medially

between the superior oblique and medial rectus muscles and exit the orbit

through the anterior ethmoidforamen. They enter the anteriorethmoid

canal which passes in an anterior and medial directionwithin the roof of

the ethmoid labyrinth, cross the ethmoid cells. The anterior ethmoid canal

may be absent, and the artery and the nerve are then exposedto the

ethmoid air cells.

o Artery then enterolfactory fosssa through an opening in lateral lamellaof cribriform plate (this point is considered the area ofleast resistance

because the lateral lamella is only one-tenthas strong as the roof of the

ethmoid) to the olfactory fossa.

b. Posterior ethmoid foramen:

Located 7 mm anterior to the anterior rim of the optic canal.

This foramen is the begining of the posterior ethmoid canal, which coursesalmost directly medial to its foramen. The smaller posterior ethmoid artery runs

through the canal in the medial orbital wall to supply the posterior ethmoid cells..

Classification of the ethmoid cell groups:

A. Anterior ethmoid cells: (Anterior to ground lamella) comprise three cellular systems:

1. Bullar system:


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between the basal lamella of the bullaanteriorly and the basal lamella of the

middle turbinate posteriorly.

consists ofone to fourintrabullar cells +suprabullar cells.

all drain into the bullar groove.2. Uncinate system:

lies laterally to uncinate process, and its posterior limit is bulla. drain into the ethmoid infundibulum, above and behind maxillary ostium.

1. Superior cell (Frontal cell = Boyers cell): may project superiorly andcontributes to the formation of the frontal sinus (Bent-Kuhnclassification).

2. Anterior cell (agger nasi cell): is not a constant finding, but when wellpneumatized it produces a smooth bony swelling on the lateral nasal wall

in front of the anterior insertion of the middle turbinate.

3. Posterior cell: lies in front of the bulla.4. Inferior cell (Hallers cells = infra-orbital): expand into roof of the

maxillary sinus (orbital floor). (15% of cases).

1. Meatal system: Two cells (ant & post), located medially to uncinate process, both may grow

upward into the frontal sinus.

B. Posterior ethmoid cells:

1. Central cells: bounded by the basal lamella of the middle turbinate andthe basal lamella of the superior turbinate posteriorly.

2. Supreme cells: located behind the basal lamella of the superior turbinate.3. Spheno-ethmoid (Onodi) cell:12%


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Large posterior ethmoid cell that invades the superior aspect of the sphenoidsinus, sometimes mistaken for the sphenoid cells itself, but there are sphenoid

sinus cells below it.

May extend postero-laterally to embrace or even surround the optic nerve. The internal carotid artery may also project on its lateral wall. May migrate to the body of the sphenoid and even reach the anterior wall of the

sella turcica.

Present in12% of individuals.


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Frontal Sinus:

Pyramid-shaped cavity extending between the anterior and posterior tables of theascending portion of the frontal bone. The apex of the pyramid is superior, and the

base lies inferiorly.

The two frontal sinuses separated completely by a bony septum, which is locatedapproximately in the midline. Bilateral asymmetry is a frequent anatomical

finding, and the inter-sinus septum may be deviated as a result.

Each sinus is further divided into incomplete chambers by a bony intra-sinusseptation.

Average frontal sinus measures 3 cm in height, 2.5 cm in width, and 2 cm indepth.

Mean volume of10 cc. Walls:

Anterior wall: forms the forehead and is the thickest of all sinus walls, measuringup to 10 mm.

Posterior wall: is a plate of thin, compact bone (12 mm) whose upper part isvertical. It gradually curves downward and posteriorly until it is almost

horizontal. It is also the anterior wall of the anterior cranial fossa, it is attached to

its dura.

Medial wall: inter-sinus septum. Inferior wall: formed by orbital roofs on the lateral side and the frontal recess

cells on the medial side.

Frontal sinus ostium:

located antero-medially on the floor.


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has an hourglass shape composed of three distinct segments: The top part of thehourglass is the frontal infundibulum, which is the inferior portion ofthe frontal

sinus cavity, the frontal ostium. The third segment is the frontal recess.

Depends on insertion of uncinate process, fronto-nasal pathway is classified intoType I, II, III.

Sphenoid Sinus:

o Sphenoid bone:

o Largest single bone in the skull base.o Contributes to the floor of the middle cranial fossa, together with petrous

and squamous parts of the temporal bone.

o Composed of: body (containing the sinus), lesser wings, greater wings,pterygoid plates, and upper part of clivus.

o Lesser wing:o Forms the posterior lip of the anterior cranial fossa, part of the orbital wall

that includes the optic canal and the anterior clinoid processes.

o Connected to the frontal bone along the posterior border of the anteriorcranial fossa and to the cribriform plate of the ethmoid bone in the

midline.

o Greater wing:

o Form part of the floor of the middle cranial fossa.


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o More anteriorly, forms the posterior wall of the orbit, including theinferior lip of the superior orbital fissure.

o Posteriorly, it creates the lateral side of the carotid canal.o At its junction with the body medially, lie foramen ovale posteriorly

((accessory meningeal artery and the mandibular division of the trigeminal

nerve), and foramen rotundum anteriorly ((maxillary branch of

trigeminal nerve).

o Projecting off its inferior and most posterior portion the spine of thesphenoid bone, an important landmark for identification offoramen

spinosum ((middle meningeal vessels and the recurrent meningeal branch

of the mandibular division of the trigeminal nerve)).

o Medial and lateral pterygoid plates:

o Extend inferiorly from the body of the sphenoid and are attached to theposterior wall of the maxillary sinus.

o Medial pterygoid plate forms the lateral wall of the nasopharynx superiorto the Eustachian tube.

o Between the base of medial pterygoid plate and vertical segment of thepalatine bone lies spheno-palatine foramen, located 10mm above the

posterior end of the middle turbinate and in front of the choanae

((sphenopalatine artery and the posterosuperior nasal branches of the

maxillary nerve)).

o Clivus: The inferior projection of the body of the sphenoid which forms

the posterior wall of the nasopharynx and part of the anterior wall

of the foramen magnum.


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Walls of sphenoid sinus:

Superior wall (Roof):Planum sphenoidale: in direct contact, from front toback, with the olfactory nerves, optic chiasm, and sella turcica. It lies in

continuity with the roof of the ethmoid sinus, and this provides a useful landmark

for surgical dissection.

Lateral wall:

Composed of two areas: orbital area in front and cranial area behind.


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Related structures: optic nerve (postero-superiorly), internal carotid artery(postero-inferiorly), with carotido-optic recess in-between, and, more postero-

inferiorly, cavernous sinus and its contents (ICA, CN III, IV, VI, V2 of CN V).

In addition, bulging ofmaxillary nerve(V2) may be seen on the lateral wall of

the sinus.

Normally, a thin layer of bone covers these structures. However, optic nerve maybe dehiscent (6% of patients).

Internal carotid artery ascends from the carotid canal and courses vertically tocross posterior and lateral to the optic nerve. In approximately 25% of patients,

there is dehiscence of bone over the artery.

Posterior wall:

Forms the floor of the sella turcica, which can be divided into three parts: anolive-shaped swelling called the tuberculum sellae, a saddle-like depression

(hypophysial fossa), and posteriorly the dorsum sellae.

Sella turcica producing a pulge into the sinus, and containing the pituitary gland.

Anterior wall:


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Faces the upper region of the nasal cavity, and is connected to the perpendicularplate of the ethmoid and vomer in the midline through the rostrum, and to the

lateral masses of the ethmoid bone on each side. Between these attachments

remains a free vertical surface (face of sphenoid).

Can be displaced by well-developed Onodi cells. In this situation, the optic nerveis surrounded by the Onodi cells.

Spheno-ethmoid recess is located within this wall, above the choana and betweenthe superior or supreme turbinates and the septum.

Inferior wall (Floor):

Forms dome of choanae and the nasopharynx. Junction of the anterior and inferior walls makes an obtuse, rounded angle called

the choanal arch.

Vidian canal may bulge on the floor of the sphenoid sinus.

Size (Pneumatization):

Average adult sphenoid sinus measures H 25 mm W 20 mm D 15 mm. Depending on degree of pneumatization, sphenoid sinus can be described as

conchal (fetal),presellar (juvenile), or sellar (adult).

When the pneumatization of the sphenoid sinus is well developed, thesurrounding vessels and nerves are in contact with the lateral wall of the sinus.

o Inter-sinus septum:

o May be deviated, causing asymmetry.o Minor incomplete septations of the sphenoid sinus are common.


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o Removal of any sphenoid septations should be undertaken with great care,as the septations and the intersinus septum are sometimes attached on the

bony canal of optic nerve and/ internal carotid artery.

o Ostium:

o Located in the spheno-ethmoid recess, medial to the superior orsupreme turbinates and close to the nasal septum.

o 1 cm above choana, and 5 mm lateral to the nasal septum.o Shape varies widely. It may be elliptical, oval, or round.o 2 to 3 mm in diameter.o There may be two or more ostia on one side.

Vasculature, Lymphtics, and Innervation of Nasal Cavity &

PNSs:

Arterial supply:

1. Ophthalmic artery:


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Gives off the anterior and then the posterior ethmoid arteries along the medialwall of orbit.

Anterior ethmoid artery supplies much of the blood flow to the nasal septumand anterior portion of the lateral nasal wall.

Posterior ethmoid artery supplies the posterior portion of the nasal septum andparts of the middle and superior turbinates.

1. Internal maxillary artery: Greater palatine artery, descending palatine artery which leaves the

ptyregopalatine fossa via palatine canal, divides into Greater, and Lesser palatine


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branches. The later enters nasal cavity via incisive canal and foramen to irrigate

the anterior floor.

Spheno-palatine artery, which enters through the sphenopalatine foramen at theposterior end of the middle turbinate. Almost immediately after exiting the

foramen, the sphenopalatine artery gives off the posterior nasal artery. This

artery supplies branches to the superior turbinate before passing above the

posterior bony choana on the anterior face of the sphenoid sinus to the posterior

aspect of the septum. This vessel may be cut if the natural ostium of the sphenoid

sinus is enlarged inferiorly and can result in an impressive arterial bleeder during

surgery.

Posterior pharyngeal artery, anastmoses with sphenopalatine artery is theregion under the posterior end of the inferior turbinate, forming another

potentially vascular area on the lateral nasal termed Woodruff's area.

4. Facial artery:

Gives offsuperior labial artery that supplies blood to the columella, nasalvestibule, and anterior lateral nasal wall.


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All of these vessels form a plexiform network in the mucosa and contribute to theKiesselbachs plexus on the anterior septum (Lytles area), the most common

site of epistaxis.

Venous drainage:

1. Anterior and posterior ethmoid veins through the ophthalmic vein.2. Spheno-palatine vein to the pterygoid plexus of veins.

o These veins usually do not have valves, thus; infection may be propagatedthroughout the entire septum, affecting the dural venous sinuses

(especially cavernous sinus).

Sensory innervation:

o Supplied by ophthalmic (V1) and maxillary (V2) branches of trigeminalnerve.

o Ophthalmic nerve (V1):

o Gives off the nasociliary nerve and its terminal branches, anterior andposterior ethmoid nerves.

o Supply anterior part of the nasal septum and lateral wall of the nose.

o Maxillary nerve (V2): Gives off;

o Naso-palatine N: Innervates posterior and inferior part of septum andlateral wall.


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o Antero-superior alveolar N: Innervates anterior-inferior portions ofseptum and lateral nasal wall with floorof the nasal cavities.

o Infra-orbital N:Innervates nasalvestibule,

columella, nasal tip, and alar regions.


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Sympathetic innervation:


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Relays in the superior cervical sympathetic ganglion. Postganglionic sympathetic fibers course through the carotid

plexus and follow the internal and external carotid arteries to their

final destination on small arterioles in the mucosa, where they

provoke vasoconstriction

Parasympathetic innervation:

Arises from the superior and inferiorsalivatory nuclei, join the facial nerve. Some fibers branch off facial nerve at geniculate ganglion into greater

superficial petrosal nerve, ending at pterygo-palatine ganglion.

Postganglionic fibers follow spheno-palatine nerve through the sphenopalatineforamen into the posterior area of the nose to innervate the nose and the sinuses.

These fibers terminate on blood vessels and mucous glands within the mucosa. Stimulation leads to mucosal congestion due to dilatation of the blood vessels and

increased production of mucous.

Olfactory Innervation: see olfaction.

Lymphatic drainage:

Anterior part of the nasal cavities follows the vascular channels and joins those ofthe external nose to reach the submandibular nodes.

Posteriorly, it drains into the retropharyngeal lymph nodes OR passes directlyto the deep cervical lymph chain.

In addition, there are connections along the olfactory nerves draining into thesubdural and subarachnoid spaces.

Variations of Sinonasal Anatomy


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1. Septal deviation and spurs2. Concha bullosa3. Paradoxically curved middle turbinate4. Hypertrophic inferior turbinate5. Pneumatization of inferior turbinate6. Pneumatization of superior turbinate or vomer7. Choanal atresia8. Prominent ethmoid bulla9. Torus protuberence10.Pneumatization of uncinate process11.Hook-shaped/inverted/duplicated uncinate process12.Hypoplasia of maxillary sinus13.Hellar cell14.Onodi cell

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Anatomy of Nasal Cavity