c) Maxillary Sinus

The maxillary sinus is the largest of the paranasal sinuses.

The maxillary sinus has been the subject of several exam questions in the past


Location and Boundaries

The maxillary sinuses are located within the maxillary bones, lateral to the nasal cavity and inferior to the orbit. They communicate via a small meatus on their medial wall with the nasal cavity.


Anteriorly with the oral vestibule, soft tissues of the face and upper lip.
Laterally with the cheeks.
Posteriorly with the pterygopalatine fossa.
Medially with the nasal cavity
Superiorly with the ethmoid air cells and orbit
Inferiorly with the mucosa of the hard palate, the alveolar process of the maxilla, the teeth and the oral cavity.

Macroscopic structure

Like the other sinuses, lined with a pale pink mucosa.
The maxillary sinus has a pyramidal shape, with its base directed medially against the nasal cavity and the apex pointing posterolaterally. The floor is the made up of the alveolar and palatine processes of the maxilla, and lies just above the roots of the teeth. The posterior wall contains grooves for the posterior superior alveolar and vessels; the anterior wall contains similar grooves for the anterior superior alveolar neurovasculature. The roof contains the infraorbital nerve and vessels as they leave the orbit and pass anteriorly to the surface of the maxilla.

Microscopic Structure

Modified respiratory epithelium.

Physiological Variations

The sinuses are small at birth and enlarge in late childhood/puberty.

Neurovascular Supply

Arterial Supply

The maxillary sinus is unique in that it is not supplied by the anterior or posterior ethmoidal arteries. Instead, it receives supply from the superior alveolar arteries (anterior, middle and posterior) as well as the infraorbital and greater palatine arteries.

Venous drainage

Veins drain posteriorly into the pterygopalatine venous plexus or laterally into the facial vein.


Lymph originating in the maxillary sinus drains inferiorly to submandibular nodes.


The maxillary sinus receives general sensory supply from branches of the maxillary nerve (V2), including the superior alveolar nerves and the infraorbital nerve.

Spread of cancer

Local Invasion

Maxillary tumours may cause significant symptoms through local invasion. Invasion superiorly can lead to palsy of the infraorbital nerve (V2) and proptosis of the eyeball. Invasion through the floor of the mouth can lead to loss of teeth and a fistula between the sinus and the oral cavity. Medial invasion leads to obstruction of the sinus with pain and infection.

Lymphatic spread

Lymph generally spreads to submandibular nodes.

Neurological spread

There are numerous branches of the maxillary nerve in close proximity to the sinus, including the infraorbital and superior alveolar nerves. If perineural invasion is present, tumour may accompany these nerves posteriorly to the trigeminal ganglion.