QS Study

The maxillary sinus lies in the body of the maxilla and is the largest of all paranasal sinuses. It is the largest of the paranasal sinuses.

Shape: It is pyramidal in shape, the base is directed medially towards the lateral wall of the nose and the apex directed laterally in the zygomatic process of the maxilla. The two maxillary sinuses are located below the cheeks, above the teeth and on the sides of the nose.

Opening: It opens into the middle meatus of the nose in the lower part of the hiatus semilunaris. The opening is nearer to the roof than the floor.

Size: The size of the sinus is variable average measurements are: 3.5 cm x 2.5 cm x 3.5 cm.


The roof is formed by the floor of the orbit. The floor is formed by the alveolar process of the maxilla. It is marked by roots of the upper molar and premolar teeth. They reduce skull weight, produce mucus, and affect the tone quality of a person’s voice.

Maxillary Sinus 1

Fig: Maxillary Sinus


It is the first paranasal sinus to develop. It is usually present at birth and it develops until around the age of 14 years.

Blood supply

The sinus is supplied by the facial, infraorbital and greater palatine arteries. Veins drain into the facial vein and the pterygoid plexus of veins.

  • Arterial supply: Small arteries from the facial, maxillary, infraorbital and greater palatine arteries pierce the bony walls of the maxillary sinus.
  • Venous drainage: Venous drainage anteriorly is via the sphenopalatine vein and posteriorly via the pterygoid venous plexus and the facial vein.

Nerve supply: The sinus in supplied by the infraorbital and anterior, middle and posterior superior alveolar nerves.

Lymphatic drainage: To the submandibular nodes.

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