The paranasal sinuses are air-filled spaces in the skull bones surrounding the nose. There are four main paranasal sinuses: the frontal sinuses, ethmoidal sinuses, maxillary sinus, and sphenoid sinus. The paranasal sinuses lighten the skull, increase voice resonance, and act as cushions protecting the brain, eyes, and pituitary gland. The sinuses develop after birth and increase in size with the eruption of permanent teeth.

1. Paranasal sinuses
By :
Student at faculty of dentistry
Ahram Canadian university

2. • What are paranasal sinuses?
They are air filled spaces in the skull bones surrounding
the nose.
They are lined with mucous membrane which is
continous with the nose and they open in the lateral
wall of the nasal cavity by special foramina.

3. What are the functions of paranasal
sinuses ?
• Decrease the weight of the skull.
• Increase resonance of voice.
• They act as air insulator cusions for the
brain, eye and pituitary gland
• The paranasal air sinuses are abscent at
birth except the maxillary sinus.
• They show marked growth at the time of
eruption of permanent teeth.

4. Paranasal sinuses
• The paranasal sinuses are:
• 1) frontal sinuses.
• 2) ethmoidal sinuses.
• 3) maxillary sinus
• 4) sphenoid sinus.

6. • They are 2 asymmetrical sinuses present in the
squamous part of frontal bone above and behind
supercilliary arches .
• The are separated by a bony septum which is usually
deviated to one side .
• Each sinus opens into front nasal duct (ethmoidal
infandibulum ) which opens at the anterior end of
hiatus semilunaris in the middle meatus of the nose .

7. • They are inter communicating spaces lying inside
ethmoidal labyrinth between the orbit and the upper
part of the nasal cavity.
• They vary in number from 3-18 air cells arranged into 3
groups :
• 1) anterior ethmoidal sinus or cells opens in the
ethmidal infandibulum in the middle meatus of the
nose.
• 2) middle ethmoidal sinuses or cells produces bulla
ethmoidalis on which it opens .
• 3) posterior ethmoidal sinus opens in the superior
meatus .

8. • They are the largest air sinuses and the only present in
birth.
• Pyramidal in shape and occupies the whole body of the
maxilla .

9. apex : Laterally directed towards the
zygoma
Base: directed
medially towards the
nasal cavity
roof
floor

10. • Relations :
• Apex : directed towards zygomatic bone.
• Base : directed medially towards the nasal cavity.
• Roof : it’s the roof of the orbit containing infraorbital groove and
canal and infraorbital nerves and vessels.
It separates the sinus from contents of the orbit
Floor : formed by alveolar process of the maxilla .
It lies 1cm below the floor of the nose.
Its lower part lies opposite to the second premolar and first molar
teeth so, the extraction of these teeth may damage and perforate the
floor leading to oraantral fistula.

12. • Anterior wall : subcutaneous , containing infraorbital and anterior
superior alveolar nerve and vessels .
• Posterior wall : separates the sinus from temporal and
pterygopalatine fossae pierced by posterior superior alveolar nerve
and vessels .

13. • Openings of maxillary sinus :
• large rounded opening 2 cm in diameter present in the upper part of
the base of the the sinus.
It opens in the middle meatus of the nose at the posterior end of the
hiatus semilunaris below the bulla ethmoidalis.
• Acessory small openings are usually present behind the main
opening .
• N.B: the higher position of the opening of the sinus makes the
drainage of pus or blood very hard.

14. Opening of maxillary sinus at the middle meatus

15. • Nerves and vessels related to maxillary sinuses:
• 1) anterior superior alveolar: from infraorbital nerves and vessels
they ascend in the anterior wall supplying it.
• 2) Middle superior alveolar : from infraorbital nerves and vessels.
They descend in the lateral wall of the sinus supplying it .
• 3)Posterior superior alveolar : from the maxillary nerve and vessels
They descend and supply the posterior wall of the sinus .
4) infraorbital nerve and vessels : they pass in the infraorbital groove
and canal through the roof of the sinus .
5) greater palatine nerve and vessels : they descend behind the sinus
supplying its posterior wall .

18. It occupies the body of the sphenoid and lies behind the upper part of
the nasal cavity .
The 2 sphenoid sinuses are separated by a bony septum which lies in
the midline and maybe deviated to one side at most of cases .
Relations :
Superiorly : pituitary gland and optic chiasma .
Posteriorly: pons and basilar artery.
Anteriorly: the opening of the sinus lies in the upper part of its anterior
wall and it opens in the sphenoethmoidal recess .
Laterally : on both sides there are cavernous sinuses with internal
carotid arteries and abducent nerves .

19. Sphenoid sinuses