The document provides details on the anatomy and development of the paranasal sinuses. It discusses the ossification and development of the bones that form the sinuses, including the maxilla, ethmoid, frontal, and sphenoid bones. For each sinus, it describes the location, size, drainage pathways, blood supply, nerve innervation, and key relationships to surrounding structures. The maxillary sinus is the largest sinus and develops from the lateral nasal wall. The ethmoid sinuses develop within the ethmoid bone and include multiple air cells. The frontal and sphenoid sinuses have more variable development and anatomy.

1. ANATOMY OF
PARANASAL
SINUSES
1

2. MAXILLA:
*Mxilla develops during 6-7wks
from 5 ossification centres.
*These ossification centres gives
rise to
alveolar,palatine,zygomatic&
frontal processes of maxilla &
floor of the orbit.
*Ossification centre in the medial
floor of the pyriform apperture
forms the premaxilla.
*Premaxilla gives rise to upper
incisors & lower nasal spine.
2

3. ETHMOID:
•Ethmoid ossifies in the
cartilagenous nasal capsule from
3 centres.
•One centre for each labyrinth
&one for perp.plate of ethmoid.
•These centres appears during 45th IUL.
•Perp.plate &crista galli
developed from the same centre
during 1st yr of life & fuses with
labyrinth during 2nd yr.
3

4. FRONTAL:
Develops from 2 centres
during 8th wk.
Centres are present in
superciliary ridge.
At birth frontal bone –
2halves separated by frontal
or metopic suture.
Development complete by
2yrs.
4

5. SPHENOID:
 Develops from presphenoidal
&postsphenoidal portions.
These portions fuse during 8th IUM.
Central portion- body & lesser wings.
Lateral portion- greater wing &pterygoid
process.
These portions fuse during 1st yr of life.
Presphenoid portion: made of 6
ossif.centres.
Lies ant. To tuberculm sella.
Continous with the lesser wings of
sphenoid.
Postsphenoidportion: 8 ossif.c
Coposed of sella tursica &dorsum sella.
Gives rise to greater wings & pterygoid
process.
5

6. * Frontal,maxillary and
ethmoidal sinuses arise
from evagination of
lateral nasal wall of
nasal capsule.
* Sphenoid sinus arises
from a posterior
evagination of nasal
capsule.
6

7. * At 25-28wks IUG 3 medially
projections formed from lateral
wall of nose from this PNS are
developed.
* Anterior projection;agger nasi.
* Inferior projection (maxilloterbinal): inf.terbinate &
max.sinus.
* Superior
projection(ethmo_terbinal):
superior terbinate, middile.t, ant.
Ethmoidal cells &corresponding
drainage channels form.
* Middle meatus invaginates
laterally to form infundibulum
&UP.
* Infundibulum grows superiorly to
form frontal recess.
7

8. Frontal sinus:
*It develops during 4th foetal
month as an outpouching,
medial to most superior
aspect of uncinate process.
*It is very rudimentary at
birth, it developes in
childhood by upward
continuation of embryonic
infundibulum & frontal recess.
*Embryologically it can also
devlp from ant.ethmoidal air
cells.
8

9. Mxillary sinus:
•It develops from primitive
ethmoidal infundibulum in
to the mass of maxilla.
•It enlarges by absorbtion
and expantion.
•At 12yrs pneumatisation
reaches under lateral
orbital wall at insertion of
zygomatic process , inferior
to the nasal floor.
9

10. * Ethmoid sinus:
* Develops fromlateral wall of
th
nasal capsule at 9 to10th wk.
* 6-7 folds appear,these folds
are separated by grooves.
* Folds are fuse to form 3-4
crests with anteriorly ramus
ascendus and posteriorly
ramus descendus.
* From the main fold middle,
superior ,supreme terbinates
form.
* From inferior fold inferior
terbinate form so called
maxillo-turbinal.
10

11. Sphenoid sinus:
It is a evagination from
sphenoethmoid recess at 3rd
month of gestation.
At 7thyr reaches floor of
sella.
Pneumatisation progress
rate 0.25mm/yr frm 4yr of
age.
In some cases internal
carotid artery and optic.n
may lie naked with in the
sinus cavity.
11

12. Paranasal sinuses:INTRODUCTION
These are air filled cavities in relation to nasal cavities.
*Classified in 2 groups anterior & posterior.
Four on each side:
(labyri
(labyrinth )
12
They are lined with a mucous membrane continuous with that of the
corresponding nasal fossa through their ostia.

13. Anterior group:
I.Frontal sinus.
II.Anterior ethmoidal cells.
III.Maxillary sinus.
Posterior group:
I.Posterior ethmoidal sinuses.
II.Sphenoid sinus.
13

14. Maxillary sinus:
*It is the largest of the sinuses,
with an average capacity of
about 10-20 ml in the adult.
* Is pyramidal in shape and
occupies the body of the
maxilla.
* The base lies medially,
the apex is in the zygomatic
portion of the maxilla.
* Medial wall is the wall
between the sinus and the
nasal fossa.
*
Dimensions :
height)3.3cm(
width)2-3cm(
ant.post)3-4cm(
14

15. * Floor :is formed by the alveolar
process and hard palate:
Œ- In children the floor lies
at, or above, the level of
the floor of the nasal
fossa.
Œ- In adults it lies about
1.25cm below the floor of
the fossa.
1,25cm
Œ- The roots of several teeth
may project into, or even
perforate, the floor.
15

16. The ostia of maxillary
sinus:
*Main ostium is situated
high up between the
medial wall and roof of
the cavity.
It opens into the
hiatus semilunaris.
*Accessory ostia are
sometimes present,
behind the main one.
Both main and accessory
ostia are surrounded by
a wide area of mucous
membrane unsupported
by bone.
16

17. Relations of maxillary sinus:
1*Orbit: is separated from
the antrum by the thin
roof of the sinus which
contains the infraorbital
nerve.
2*Teeth: may produce
elevations in the floor of
the sinus and the number
of related teeth depends
on the size of the antrum.
The second premolar and
first molar are usually
related.
17

18. 3* Middle meatus of nose:
is related to the upper
part of the antrum.
4* Inferior meatus of nose:
is separated from the middle
part of its medial wall by bone,
which is usually thick in front
and below,but thinner above and
behind.
18

19. 5* maxillary
artery :
is related to the posterior
wall, where it occupies the
pterygopalatine fossa.
It may be approached
through the antrum for
ligature.
6* Maxillary
division of
the Vth cranial nerve:
also traverses the pterygopalatine fossa.
19

20. 7* Nasolacrimal
duct:
passes downwards,
medial to the antrum,
to open into the inferior
meatus.
maxillary sinus
20

21. ARTERIAL:
oBy facial artery branch of ECA.
oBy infra orbital & greater palatine
arteries branch of max. art which is
branch of ECA.
Infraorbital
artery
VENOUS:
oTo anterior facial vein& pterygoid
plexus.
superior dental
arteries
21

22. o
Maxillary division of trigeminal.n gives sensory
supply via.
o
o
Infraorbital.n ,sup.alveolar.n , greater palatine.n.
o
Also supply-pulps of canine, incisors teeth,
ant.inf.quadrant of lat.wall of nose,floor of nose,ant.
Part of nasal septum.
o
o
o
o
Middle sup. Alveolar.n-
o
o
o
Adjacent mucosa,molar teeth.
Ant superior alveolar.n- ant. Wall of antrum passing
through canalis sinosus.
Lateral wall of sinus, upper pre molar teeth.
Posterior.sup.alveolar.n
Through pterygo palatine fossa supply posterior
sinus wall.
Greater palatine.n – posterio medial wall of sinus.
Perforating branches of infra orbital.n –roof of sinus.
22

23. Ethmoid means sieve
like
Ethmoid is trapezoid box
narrow/taller anteriorly
wide posteriorly.
Multiple air containing
cells situated
in ethmoidal labyrinth(318)
23

24. Anterior group-(drains –middle
meatus)
Middle group(drains-middle
meatus)
Posterior group(drainssuperior meatus)
Haller cell..ant ethmoidal cells seen
anteriorly & below the orbit
Onadi cells… posterior ethmoidal
cells seen just in front of sphenoid
24

25. Type I: depth of olfactory fossa 1-3mm
(26.3%)
Type II: 4-7mm(73.3%).
TypeIII:8-16MM(0.5%).
25

26. Anterior ethmoidal
artery(ophthalmic artery)
Post. Ethmoidal artery
Sphenoidal
artery(maxillary artery)
Anterior ethmoid
artery
Venous drainage
Nasal veins
Ant. Ethmoidal vein
Post. Ethmoidal vein
26
posterior ethmoidal
artery

27. Ethmoidal aircells
recieves innervation
from anterior &posterior
ethmoidal.n & orbital
branches of
pterygopalatine
ganglion.
Postganglionic
parasympathetic fibres
for mucous secreton
from facial .n
27

28. Frontal sinus:
*Should be regarded as an
upward extension of an
anterior ethmoidal cell.
*It occupies a very variable
extent of the frontal bone
and may be partly loculated.
*Its average capacity is about
5-10ML in the adult.
* The right and left sinuses
are often asymmetrical.
* Dimensions…height(28-32mm)
width(24-26mm)
depth(18-20mm)
28

29. *They are separated by a thin
bony septum, which may be
deficient in part.
* The sinus may invade the
orbital plate of the frontal
bone and occasionally it
extends to the optic foramen.
29

30. Relations of frontal sinuses:
Anterior cranial fossa:
separated from the sinus by
the compact bone of its
posterior wall.
Orbit: lies below the floor of
the sinus. This is also compact
bone which may rarely be
deficient.
Skin and periosteum of forehead:
cover the anterior wall, which is
of diploic bone and is related
To supratrochlear and
supraorbital
nerves.
30

31. *Type1…single frontal recess
cell above the agger nasi cell,
but below the frontal sinus
*Type11…A tire of more than
one cell in frontal recess above
the agger nasi cell, but below
the frontal sinus
*Type111…large single cell
pneumatizing cephaloid into
frontal sinus
*Type1V…single isolated cell
within the frontal sinus
31

32. The frontonasal duct:
*It passes through the anterior
part of the ethmoidal labyrinth.
* Its length and curvature vary
considerably.
* Its lower end (ostium) usually
opens in to the infundibulum,
less often independently above
this level.
32

33. * Drainage into frontal recess
anterior to the
infundibulum(55%)
* Drainage above but not into the
infundibulum(30%)
* Drainage into
infundibulum(15%)
* Drainage above the bulla(1%)
33

34. Blood supply of frontal sinus
*Supraorbital artery
*Supratrochlear artery
Venous drainage
*Small vein that unites the Supraorbital and
Superior ophthalmic veins.
Nerve supply
*Supraorbital nerve(ophthalmic nerve)
*Supratrochlear nerve(ophthalmic nerve)
Lymphatic drainage
*Submandibular nodes
34

35. Sphenoidal sinus:
*Lies behind the upper part
of the nasal fossa.
* It occupies the body, and
some­times the wings and
pterygoid processes, of the
sphenoid bone.
* The average capacity is
about 7 ml in the adult.
* The right and left sinuses
are rarely symmetrical.
* They are separated by a
septum which may be
deficient in part and is
often oblique.
* Dimensions … (L..4­44mm)
W(25­34mm)h(5­33)
35

36. 1.
conchal…(3%)
2.
Presellar(11%)
36

37. 37

38. The ostium of sphenoid sinus:
*situated in the upper part of
the anterior wall of the sinus.
*It communicates with the
superior meatus indirectly
through the sphenoethmoidal
recess.
38

39. Relations:
*Cavernous sinus lies laterally containing the:
IIIrd,
IVth,
Vth (ophthalmic
and maxillary­
divisions) and
VIth cranial nerves,
internal carotid artery
optic nerve
39

40. *Above the sinus there are:
Pituitary gland,
optic chiasm,
frontal lobe of brain
olfactory tract
The pituitary gland may be approached surgically through the sinus.
40

41. *Posterior ethmoidal
artery(roof of sinus)
*Sphenopalatine
artery(floor of sinus)
Nerve supply
*Trigeminal (I/II div)
Lymphatics
*Retropharyngeal nodes
to upper deep cervical
nodes.
41

42. 42

43. 43

44. * Lined by mucus membrane
* Ciliated columnar epithelium
* goblet cells secretes mucus
* Cilia are more marked near
ostia.
44

45. *Plain sinus
radiography
*Computed
tomography
*Magnetic
resonance imaging
45

46. * Radiographic positions to study the paranasal
sinuses are standardised around three positions:
* 1. Two anatomical - namely coronal and sagittal
* 2. One radiographic - termed as radiographic base
line..
* The various radiographic positions used to study
paranasal sinuses are:
1. Occipito-mental view (Water's view)
2. Occipital-frontal view (Caldwell view)
3. Submento-vertical position (Hirtz position/jug
handle)
4. Lateral view
5. Oblique view 39 Degrees oblique (Rhese
position)
46

47. Fronta.s
orbit
ethmoids
ns
Infra orbital
margin
Max.sinus
47

48. Frontal.s
Ethmoid air.c
orbit
Sphenoid.b
ns
Hard palate
Max.s
Inferior.t
48
mandible

49. 49

50. 50

51. 51

52. 52

53. MAXILLARY.S
53

54. 54

55. 55

56. 56

57. 57

58. 58