This document provides an overview of the anatomy of the paranasal sinuses. It describes the four main paranasal sinuses - maxillary, frontal, ethmoid, and sphenoid sinuses. For each sinus, it details their location, drainage pathways, surrounding structures, timing of development, and other key anatomical features. The maxillary sinus is the largest sinus, located within the cheekbones. The ethmoid sinus is a complex bony labyrinth near the skull. The sphenoid sinus is positioned at the base of the skull. The frontal sinus is situated within the frontal bones and has significant anatomical variability between individuals.

1. Anatomy of paranasal sinus
Dr. shubham
17/05/17

2. introduction
 Para nasal sinuses are air filled sacs found in the skull bone
 These sacs surround the nasal cavity
 They include frontal, maxillary, ethmoidal and sphenoid sinuses
 Ethmoidal sinuses can be divided into anterior, middle and posterior groups

4. Sinuses
Each sinuses have
orifices that open into
the meatus, covered
by turbinates

7. EPITHELIUM
They are lined by mucosa similar to that of the nasal cavity – pseudo stratified ciliated columnar
epithelium
Epithelium contains – Mucinous & serous glands
Mucoperiosteum

8. Physiology

9. Sinuses Status at
Birth
First
Radiological
evidence
Reaches
Adult size
by
Maxillary sinus Present at
birth
4-5 months after
birth
15 years
Ethmoid sinus Present at
birth
1 year 12 years
Sphenoid sinus Not Present 4 years 15 years –
adult age
Frontal Sinus Not Present 6 years Size
increases
until teens

10. FRONTAL SINUS
 Situated between the outer & inner table of frontal bone
 Funnel shaped
 Two sinuses on either side
 Asymmetrical
 Intervening bony septum which may be thin or deficiency

11. Frontal Sinus
 Not present at birth
 First radiological evidence is at 6 years
 Reaches adult size after puberty
 This sinus shows the maximum variation
 It is shaped more or less shaped like L
 Posterior wall – Related to the anterior cranial fossa
 Floor – Is formed by the upper part of orbit
 Drains into the anterior part of middle meatus via the frontonasal duct
 The natural frontal sinus ostium is usually located in the posteromedial floor of the sinus (most dependent
part).
 The ethmoidal infundibulum can act as a channel for carrying the secretions (and infection) from the
frontal sinus to anterior ethmoid cells and the maxillary sinus or vice versa.

12. Ct image showing frontal sinus

13. 1. Also known as Antrum of Highmore
2. This is the largest of all paranasal sinuses
3. Lie just under the cheek area
4. Pyramidal in shape
5.Present at birth as a rudimentary sinus
6.First radiological evidence is at 4-5 months after birth
7.Reaches adult size by 15 years
8. On average, it has capacityof 14.75 ml (14-15)
Maxillary Sinus

14. Maxillary Sinus - boundaries
• Facial surface of maxilla and cheek
Ant wall
• Infra temporal & pterygopalatine fossa
Post wall
• lateral wall of the nasal cavity (Middle & inferior
meatuses (this wall is thin & membranous)
Med wall
• Floor of orbits
Roof
• Alveolar part of maxilla(maxillary alveolus)
Floor

15. Maxillary Sinus –ct image

16. Maxillary Sinus - (Antrum of Highmore )
 DRAINAGE – OSTIUM
Seen high up in the medial wall
Does not open directly into the nasal cavity, but opens into post. part of
ethmoidal infundibulum, via hiatus semilunaris into middle meatus.
The infundibulum is the air passage that connects the maxillary sinus
ostium to the middle meatus.
Unfavourable for natural sinus drinage
Accessory ostium – 30 % cases

17. Ma

18. The ostiomeatal unit
• Drains the frontal, anterior ethmoidal and maxillary sinuses.
• The OMU is sited in the area of the superomedial maxillary
sinus and middle meatus and includes the maxillary sinus
ostium, ethmoid infundibulum, hiatus semilunaris, and frontal
Recess.

19.  Occupies the body of sphenoid
 Right & left, seperated by a thin strip of
bony septum (like frontal sinus)
 This sinus is located in the skull base at the
junction of anterior and middle cranial fossa.
 Drains into the superior meatus.
 Relations of the sinus are very important, esp
during the surgical approach of pituitary gland.

20. Sphenoid sinus
 Relations –
 Anterior part –
 Roof – olfactory tract, optic chiasma &
frontal lobe
 Lateral – optic nerve, internal carotid artery
& maxillary nerve
 Posterior part
 Roof – Pituitary gland in sella turcica
 Lateral – Cavernous sinus,ICA & Cranial
nerves III, IV, VI & all divisions of V

21. Sphenoid sinus

22. Ethmoidal sinus
 Situated close to the anterior skull base
 It is composed of complex bony labyrinth with thin walls
 There may be 6 – 10 ethmoid cells present in adults
 Ethmoidal sinus anatomically have been divided into anterior, middle
and posterior groups according to their drainage pattern.
 The size of Ethmoidal air cells increases from above downwards and
from before backwards.
 Present at birth
 Reaches adult size by 12 years
 First radiological evidence seen at 1 year

23. DRAINAGE:
 Anterior - a recess of hiatus semilunaris
 Middle meatus via ehmoid bulla
 Posterior- sup.meatus & spenethmoidal recess.

24.  Roof – formed by the anterior cranial fossa
 Lateral wall - orbit
 Medial wall – nasal cavity
 Thin paper like bony part of the ethmoid separating the air cells from the orbit, called lamina papyracea,
can be easily destroyed leading to spread of ethmoidal infections into the orbit
 Optic nerve forms a close relationship with the posterior ethmoidal cells & is at risk during ethmoidal
surgery

28. THANKYOU