26.2 Paranasal Sinuses


Four paired sinuses

  • Maxillary
  • Ethmoidal
  • Frontal
  • Sphenoidal

The cavities are in the facial bones and communicate with the nasal cavity


  • Contribute to the  warming and humidifying of inspired air

  • Allow enlargement of the viscerocranium thus minimizing increase in bone mass
  • Determine position of eyes and nose

Frontal sinuses
  • Irregular cavity extending up into the diploe of the frontal bone.
  • The left and right separated by a thin bony septum separates the two.
  • May extend backwards into the roof of the orbits
  • Each drains via the infundibulum into the middle meatus

Ethmoidal air cells 
  • In the ethmoid bone
  • Three sets of air cells:
  1. anterior,
  2. middle and
  3. posterior ethmoidal air cells.
  • Anterior and middle opens in to middle meatus
  • Posterior opens in to superior meatus

Sphnoidal air sinus  
  • Lies within the body of the sphenoid bone
  • Divided into two halves by a bony septum
  • Each opens into superior meatus


Maxillary air sinus
  • Pyramidal cavity in the body of the maxilla,
  • Below the floor of the orbit.
  • Base is formed by the lateral wall of the nasal cavity
  • Apex lies in the zygomatic process of the maxilla.
  • The anterior and posterior walls are the corresponding walls of the maxilla.
  • The roots of maxillary teeth lie just beneath the floor. They may even penetrate the bony floor to lie beneath the mucosal lining of the sinus.
  • The opening near roof, so that in the anatomical position drainage is hindered by gravity.
  • It opens in the posterior part of the middle meatus.


Summary of relations






  • Orbit & Contents
  • Anterior cranial fossa
  • Frontal and Lacrimal bone
  • Pituitary gland


  • Alveola of maxilla
  • Orbit
  • Cribriform plate
  • Roof of nasopharynx


  • Nasal cavity
  • Septum separating from its fellow
  • Nasal cavity
  • Separated from fellow by septum


  • Zygoma
  • Greater wing of sphenoid
  • Orbit
  • Carvenous sinus and its contents


  • Cheek
  • Forehead eyebrow
  • Nasal bone
  • Orbit


  • Infratemporal pterygopalatine fossae
  • Lesser wing of sphenoid
  • Body of sphenoid bone
  • Posterior cranial fossa and pons

Condition at Birth

  • Present
  • Absent
  • Present
  • Present

Time of appearance

2nd year


Summary of neurovascular supply




Lymph nodes



  • Facial,
  • Maxillary,
  • Infraorbital
  • Greater palatine
  • Facial
  • Pterygoid
  • Sub-mandibular
  • Infraorbital
  • Superior alveolar


  • Supraorbital
  • Anterior Ethmoidal
  • Superior ophthalmic
  • Submandibular
  • Supraorbital


  • Supraorbital
  • Anterior ethmoidal
  • posterior ethmoidal
  • sphenopalatine
  • Superior ophthalmic
  • Submandibular
  • Retropharyngeal
  • Supraorbital
  • Anterior ethmoidal
  • Posterior superior nasal,
  • Orbital twigs from pteryngopalatine ganglion


  • Posterior ethmoidal
  • Superior ophthalmic
  • Carvenous sinus
  • Retropharyngeal
  • Posterior ethmoidal



Tabulate each sinus, blood supplies, innervation and lymphatic drainage


The Nasal Cavity and Paranasal Sinuses