Anatomy Of Paranasal Sinuses
Nafisa parveen
Jawaharlal nehru medical college
Aligarh muslim university
India
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Paranasal sinus
 Air-filled pockets within the cranium which communicate
with the nasal cavity and lined with the same type of ciliated
mucous membrane.
 Late 19th century Emil Zukerkandl published 1st detailed
anatomic and pathologic description of paranasal sinus.
 ‘Father of modern sinus anatomy’ .
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Paranasal sinus
 Divided in two groups-
 Anterior group
Frontal
Maxillary
Anterior ethmoid
 Posterior group
posterior ethmoid
sphenoid
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Development of PNS
 All except sphenoid sinus develop as outpouchings from the
mucous membrane of lateral wall of nose.
 Sphenoid sinus arises within the nasal capsule of the
embryonic nose.
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Maxillary sinus
 Antrum of highmore
 These paired sinuses lie under the cheek.
 Largest and most constant pns.
 First sinus to develop.
 These structures are usually fluid-filled at birth.
 Appears slit like in fetal life.
 Adult maxillary sinus is pyramidal in shape.
 Volume of maxillary sinus approximately 15ml.
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Maxillary sinus
 It has biphasic growth.
 The 1st phase of growth occur during the 1st 3yrs of life.
 The 2nd phase occur btw 7-18yrs .
 During the later phase pneumatization spreads more
inferiorly as the permanent teeth take their place.
 Pneumatization can be so extensive as to expose tooth roots
with only a thin layer of soft tissue covering them.
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Maxillary sinus
Base(medial wall)
 The base of the pyramid corresponds to the lateral nasal
wall.
 This wall has its convexity facing the sinus.
 The central portion of the base is very thin, in some areas
could even be membranous.
 The natural ostium of this sinus is present in this wall.
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Natural ostium
 Located at the superior aspect of the medial wall of the maxillary
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sinus.
Intranasally ,natural ostium is in anterior fontanelle.
The posterior edge of the ostia is continuous with the lamina
papyracea.
Size averages 2.4mm but can vary from 1 to 17mm.
The ostium is much smaller than actual bony defect,as mucosa fills
this area.
88% of maxillary ostium are hidden behind the uncinate process.
Cannot visualised endoscopically.
Seen after uncinectomy.
Opens in the post part of ethmoidal infundibulum into the middle
meatus.
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Accessory ostia
 Usually found in the posterior fontanelle.
 Circular in shape.
 Easily seen unlike the natural ostia.
 They are nonfunctional ostia.
 Serve to drain the sinus only if the natural ostium is blocked
and intrasinus pressure moves material out of the ostium.
 Incidence varies from 15%-45%,an average of 25%
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Maxillary sinus
Anterior wall
 Wall corresponds to the facial surface of the superior maxilla.
 Over canine fossa it is only 2mm in thickness.
 Through this fossa maxillary antrum is entered during
caldwell luc surgery.
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Boundaries of canine fossa
 Inferiorly-bounded by the alveolar ridge.
 Laterally-bounded by the canine eminence which is caused by
the canine tooth.
 Superiorly –infra orbital foramen which located at the
midsuperior portion with the infra orbital nerve running
over the roof of the sinus and exiting through the
foramen.this nerve can be dehiscent in 14%
 Medially- pyriform aperture
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Maxillary sinus
Posterior wall
 Also known as temporal surface.
 It is very thick.
 Formed by the body of the superior portion of the maxilla.
 Behind this wall is the pterygomaxillary fossa with the
internal maxillary artery, sphenopalatine ganglion and the
vidian canal, the greater palatine nerve and the foramen
rotundum.
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Maxillary sinus
Roof
 Formed by thin orbital wall.
 Which is traversed by the infra orbital foramen containing
the infra orbital vessels and nerves.
 This wall is very fragile.
 Any disease process involving the maxilla is likely to affect
the orbit through this wall.
 This wall is further thinned out where the infra orbital canal
is present.
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Maxillary sinus
Floor
 Formed by the alveolar process of the maxilla and the hard palate.
 The roots of the 1st and 2nd molar reach upto the floor of the
maxillary sinus.
 From birth to age 9yrs the floor of the sinus is above the level of
nasal cavity.
 At 9yrs the floor lies at the same level as that of the nasal cavity.
 In adult it lies 5-10mm below the nasal cavity.
 Dental infections involving the 1st and 2nd molars may involve the
maxillary sinus.
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Arterial supply
Branches of the internal maxillary artery i.e.
 Infraorbital artery
 Lateral branches of the sphenopalatine
 Greater palatine artery
 Alveolar artery
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Venous supply
 Venous drainage runs anteriorly into the facial vein.
 Posteriorly into the maxillary vein and jugular and dural
sinus system.
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Nerve supply
Innervated by branches of V2.
 Greater palatine nerve
 Infraorbital nerve
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Ethmoid sinus
 Situated in the anterior skull base.
 Made up of complex bony labyrinth of thin walled cells.
 A few ethmoid cells may be present at birth.
 At birth it is filled with fluid.
 In adult 3-14 ethmoid cells may be present.
 During primary pneumatization ethmoids develop from
dimple like depression on nasal mucosa, deepen and become
air cells.
 The common infections affecting the pediatric age group
occur in this sinuses.
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Ethmoid sinus
 Well-delineated.
 Ant cells form 1st, followed by the posterior cells.
 The cells grow gradually and are adult size by age 12.
 They are not seen on radiographs until age one.
 Ant and post combined volume is 15ml.
 Pyramidal in shape
 Divided into multiple cells by thin septa.
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Lateral wall
 Formed by the orbital plate of the ethmoid,known as the
lamina papyracea.
 this wall could be dehiscent(normal variant)
 Infections involving the ethmoid air cells may spread to the
orbit through this wall.
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Roof
 Formed by the frontal bone anteriorly
 Posteriorly by the sphenoid and orbital process of palatine bone.
 The roof slopes both posteriorly(angle of 15 degrees) and medially.
 Ant 2/3 of the roof is thick and strong and composed of the frontal
bone and the foveolae ethmoidalis.
 The post 1/3 is higher laterally and slopes down medially to the
cribiform plate.
 The difference btw the lat and medial roof is variable,but can be as
much as 15-17mm..
 The post aspect of the ethmoid cells borders on the sphenoid sinus.
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Ethmoid cells
 The ant cells drain into the infundibulum of the middle
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meatus.
Post cells drain into the superior meatus.
The anatomy of the ethmoidal cells are highly variable.
A cell above the orbit is called a supraorbital cell. found in
15% of pt.
Invasion of an ethmoid cell into the floor of the frontal sinus
is called a frontal bulla.
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Concha bullosa
 Sometimes the middle turbinate may contain an air cell known as
concha bullosa.
 An enlarged concha bullosa may impede drainage from the
middle meatus.
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Agger nasi air cells
 Anterior most anterior ethmoid air cells.
 1st prominent anatomical landmark encountered in FESS.
 Located antero-superior to insertion of middle turbinate.
 Endoscopically seen as a ridge ,prominence on lateral wall.
 Boundaries
Anteriorly—frontal process of maxilla
Posteriorly-- ethmoidal infundibulum
Superiorly—frontal recess and frontal sinus
Infero-medially—uncinate process
Laterally—nasal and lacrimal bone
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Agger nasi air cells
 Since these cells lie in close proximity to the frontal recess
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area, they could impede ventilation and drainage of the
frontal sinus.
Commonly involved in the pathogenesis of the formation of
frontal mucocele.
At 1st the frontal sinus enlarges in size by expansion of its
bony walls.
At a later stage bone erosion can occur.
Commonly the post table of the frontal sinus is eroded.
Ant.table also can be eroded in rare cases.
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Haller cells
 Ethmoidal air cells belonging to the anterior ethmoidal
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group.
Also known as the infra orbital cells.
best studied on ant and post coronal ct images.
Adhere to roof of maxillary sinus forming the lat wall of
infundibulum.
Incidence 10-40%
Enlargement of these cells can impede the maxillary sinus
drainage.
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Onodi cells
 Post group of ethmoidal air cells.
 Supero-lateral to the sphenoid sinus.
 Incidence 9-12%
 Optic nerve and medial rectus muscle lie in close relation
with the lateral wall of this cells. making them at risk during
fess surgeries.
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Vascular supply
 The sphenopalatine artery as well as the ophthalmic artery
which branches into the anterior and posterior ethmoid
arteries supply the sinus.
 Venous drainage follows arterial supply.
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Nerve supply
 Both V1 and V2 innervate this region.
 V1 supplies the more superior aspect .
 V2 supplies the inferior regions.
 Parasympathetic innervation is via the vidian nerve.
 Sympathetic innervation is via the cervical sympathetic
ganglion.
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Frontal sinus
 Formed by the upward movement of the anterior most ethmoid
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cells.
Pyramidal in shape.
The volume of the sinus is approximately 6-7ml.
Rudimentary at birth.
True growth begins at age five and continues into the late teens.
Among the paranasal sinuses this sinus shows the maximum
variations.
Sinuses are unique in each and every individual
Asymmetry btw the two sinuses.
It may be absent in 5% of cases.
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Frontal sinus
 Both the anterior and posterior walls of this sinus are
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composed of diploe bone.
The post wall separates the frontal sinus from the anterior
cranial fossa, is much thinner.
Floor is formed by the upper part of the orbits.
Both frontal sinuses have their ostia at the most dependant
portion of the cavity(posteriomedially)
So these sinuses are rarely involved with infectious disease.
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Frontal recess
 Space btw the frontal sinus and the hiatus semilunaris into
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which the frontal sinus drains.
Bounded
Anteriorly-agger nasi cell
Superiorly-frontal sinus
Medially- middle turbinate
Laterally- lamina papyracea
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Vascular supply
 Ophthalmic artery via the supra orbital and supra trochlear
arteries.
 Venous drainage is via superior ophthamic veins to the
cavernous sinus and via small venulae in the posterior wall
which drain to the dural sinuses.
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Nerve supply
 Innervated by branches of V1.
 Supraorbital and supratrochlear branches.
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Sphenoid sinus
 It is located in the skull base at the junction of the anterior
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and middle cranial fossa.
Bilateral and asymmetry very common.
Adult volume of the sinus is 7.5ml.
Extensive variation in pneumatisation.
Pneumatisation can extend as far as the clivus, the sphenoid
wings and the foramen magmum.
The walls of the sphenoid vary in thickness with the
anterosuperior wall and roof being the thinnest(.1 to
1.5mm)
The other wall are thicker.
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Pneumatisation
 The position of the sinus depend on the extent of
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pneumatisation.
3 types of pneumatisation seen
Conchal(fetal)—2%
Presellar(juvenile)—10-24%
Sellar(adult)—86%
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Pneumatisation
 These sinuses arise from within the nasal capsule of the
embryonic nose.
 They remain undeveloped until age three.
 By age seven the pneumatisation has reached the sell turcica.
 By age 18 the sinuses have reached full size.
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Sphenoid sinus ostia
 Drains into the sphenoethmoidal recess.
 The ostium is located 1-1.5cm above the posterior end of choana.
 A 30degree angle drawn from the ant nasal floor approximates
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the location of the ostium on the posteriosuperior nasal wall.
It is close to the midline at the junction of the upper 1/3 and the
lower 2/3 of the anterior sinus wall.
medial to the supreme/superior turbinate,and only few mm from
the cribiform plate.
The ostium is very small.5-4mm .
Has a much larger bony dehiscence which is narrowed by a
membranous septum.
Below the ostia is the mesh of blood vessels forming the
‘woodruff’s plexus’
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Spheno-ethmoidal recess
 Recess is a space behind and above the most superior
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turbinate.
The ant wall of the sphenoid sinus forms the posterior
aspect.
The nasal septum and cribiform plate form the medial and
superior aspects .
The anterolateral extent is determined by the most superior
turbinate.
The space opens into the nasal cavity inferiorly.
The posterior ethmoid cells and sphenoid sinus empty into
this region.
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Related structure
 Pituitary gland lies above the sphenoid sinus.
 Optic nerve and internal carotid arteries traverse its lateral
wall.
 The nerve of pterygoid canal lie in thefloor of the sinus.
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Vascular supply
 Posterior ethmoid artery supplies the roof of the sphenoid
sinus.
 Rest of the sinus is supplied by the sphenopalatine artery.
 Venous drainage is via maxillary veins to the jugular and
pterygoid plexus system.
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Nerve supply
 Supplied by branches from both V1 and V2.
 The nasociliary nerve (V1) supplies the roof.
 The branches of the sphenopalatine nerve(V2)supply the
floor.
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Lymphatic drainage of pns
 The lymphatics of maxillary,ethmoid,frontal and sphenoid
sinuses form a capillary network in their lining mucosa and
collect with lymphatics of nasal cavity.
 Then they drain into lateral retropharyngeal and /or
jugulodigastric nodes.
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Microscopic anatomy
 Sinuses are lined with pseudostratified ciliated columnar
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epithelium which is continuity with the mucosa of the nasal
cavities.
The epithelium of the sinuses is thinner than that of the nose.
There are four basic cell types.
Ciliated columnar epithelial cells
Nonciliated columnar cells
Basal cells
Goblet cells
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Ciliated columnar epithelium
 The ciliated cells have 50-200 cilia per cell.
 Usual structure of 9+2 microtubules with dynein arms.
 These cells beat at 700-800 times a minute.
 Moving mucus at a rate of 9mm/minute
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Non ciliated columnar cells
 Characterized by microvilli which cover the apical aspect of
the cell
 Serve to increase surface area
 Likely to facilitate humidification and warming of inspired
air.
 There is an increased concentration upto 50% at the sinus
ostium.
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Goblet cells
 Basal cell’s function is unknown.
 Goblet cells produce glycoproteins which are responsible for
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the viscosity and elasticity of mucus.
They are innervated by the parasympathetic and sympathetic
nervous system.
The parasympathetic stimulation induces thicker mucous .
Sympathetic stimulation leading to more watery mucous
secretion.
Goblet cells are less in sinuses than nasal mucosa.
Maxillary sinus has the highest density of goblet cells.
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Microscopic anatomy
 The epithelial layer is supported by a thin basement
membrane, lamina propria and periosteum.
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Thank you
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