Anatomy of paranasal sinuses

1. ANATOMY OF
PARANASAL SINUSES

2. PARANASAL SINUSES
• Air containing cavities in certain bones of skull.
• They surround the nasal cavity
• Paired , 4 on each side .
• Clinically divided into 2groups:
• Anterior group: maxillary,frontal,anterior ethmoidal
• Posterior group: posterior ethmoidal sinuses,sphenoid
sinus .

4. MAXILLARY SINUS (ANTRUM OF HIGHMORE)
• Largest of all PARANASAL sinuses .
• Pyramidal in shape with base towards lateral wall of nose
and apex directed laterally into zygomatic process of
maxilla .
• Average capacity in adults : 15ml
• Height : 33mm, depth: 35mm, width: 25 mm

5. RELATIONS
• Anterior wall : facial surface of maxilla and is related to the soft tissues of cheek .
• Posterior wall: rel to infratemporal and pterygopalatine fossae
• Medial wall: rel to middle and inferior meatuses.
• Floor: formed by alveolar and palatine processes of the maxilla ,situated 1cm
below the Level of floor of nose and rel to roots of second premolar and first
molar teeth.
• Roof: formed by floor of the orbit .traversed by infraorbital nerve and vessels .

6. APPLIED ANATOMY
• Roof of maxillary sinus is weakened by the presence of infraorbital canal and
foramen
• Dental infections involiving 1st and 2nd molar may involve maxillary sinus because
the bone is thin in this area.
• Maxillary sinus shows biphasic growth ; Ist growth phase during 1st 3 years of life
;next phase between 7 and 18 years

7. FRONTAL SINUS
• Upward extensions of the anterior ethmoidal sinuses that occupies the frontal
bone.
• Shows variation in shape
• Capacity in adults: 7 cc
• Has 3 walls and a partition in between the two sinuses.

8. RELATIONS
• Anterior wall : formed by the outer table of the frontal bone and rel to skin over
the forehead
• Posterior wall: formed by a thin compact bond separating the frontal lobe of
brain from the sinuses And rel to meninges and frontal lobe of brain
• Inferior wall (floor): thinnest, rel to the orbit and its contents

9. ETHMOIDAL SINUS ( LABYRINTHS)
• Thin walled air cavities in the lateral masses of ethmoid bone .
• Occupy the space between upper third of lateral nasal wall and the medial wall of
orbit .
• 3 to 18 in nos
Clinically divided by the basal lamina into
Anterior ethmoid group : opens into middle meatus
Posterior ethmoid group: opens into superior meatus and into supreme meatus(if
present)

10. RELATIONS
• Roof: formed by medial extension of the orbital plate of the frontal bone, show
depression on undersurface:- fovea ethmoidalis
• Lateral wall : formed by a thin plate of bone :- lamina papyracea

11. ANTERIOR GROUP
• Important ethmoid cells in the anterior group include:
• Agger nasi cells
• Ethmoid bulla
• Supraorbital cells
• Frontoethmoid cells
• Haller cells

12. POSTERIOR GROUP
• Lies posterior to basal lamina of middle concha.
• 1-7 in nos
• Open into superior meatus or supreme meatus
• Imp cell group: sphenoethmoid cell or onodi cell
• Optic nerve and sometimes the carotid artery are related to it laterally and are in
danger during endoscopic surgery .

13. APPLIED ANATOMY
• Large agger nasi air cells can impede Frontal sinus discharge due to its close
proximity to the front sinus drainage pathway
• Enlargement of Haller cells may block drainage of the maxillary sinus.
• Inflammation of onodi cells may cause blindness .

14. SPHENOID SINUS
• Occupies the body of sphenoid .
• Capacity of each sinus :7cc
• 2 sinuses separated by a thin plate of bone partition .
• Opening of sinuses situated in the upper part of the anterior wall .
• Drains into superior meatus through the sphenoethmoidal recess.

15. RELATIONS
• Floor : rel to vidian nerve (nerve of pterygoid canal).
• Lateral wall : rel to optic nerve and carotid artery
• Roof :
• Anterior part: olfactory tract,optic chiasma, frontal
lobe
• Posterior part: pituitary gland , cavernous sinus .
• Posterior wall : rel to basilar artery , brainstem

16. MUCOUS MEMBRANE OF PARANASAL SINUSES
• Lined by mucous membrane which is continuous with that of nasal cavity through
the ostia of sinuses.
• Thinner and less vascular compared to that of nasal cavity.
• Histologically: ciliated columnar epithelium with goblet cells.
• Cilia more marked near ostia of sinuses and help in drainage of mucous into nasal
cavity .

17. LYMPHATIC DRAINAGE OF PARANASAL SINUSES
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 retropharynheal and/or jugulodigastric nodes.

18. DEVELOPMENT OF PARANASAL SINUSES
• Develop as outpouchches from the mucous membrane of lateral wall of nose.
• At birth ,only the maxillary and ethmoidal sinuses are present .
• Growth of sinuses continues during childhood and early adult life .
• Radiological identification
• Maxillary : at 4-5 months
• Ethmoids: at 1 year ,frontals : at 6 years, sphenoids : at 4 years

19. FUNCTIONS OF PARANASAL SINUSES
• Air conditioning of the inspired air.
• Provide resonance to voice.
• Thermal insulators
• Lighten skull bones
• Provide extended surface for olfaction.
• Provide local immunologic defence against microbes.
• Act as buffers against trauma and protect brain from injury

20. THANKYOU