Thursday, March 22, 2012

Anatomy and functions of maxillary sinuses

Anatomy and functions of maxillary sinuses

The largest paranasal sinuses, maxillary sinuses, occupy the maxilla bone. The maxillary sinuses, referred to as the antrum of Highmore, are easily accessible as compared to the other sinuses. The maxillary sinus plays an important role in our body: reduces the weight of the cranium, performs functions of a resonant bone, controls the inhaled air temperature and pneumatizes. The size of right and left maxillary sinuses varies substantially and affects the sinus wall thickness. If the sinus is abnormally big, the walls will be ultra thin. Abnormally small sinus may have thick osseous lamellae. The thick facial walls may also reduce the size of the sinus.

The maxillary sinus cavity resembles to a pyramid. The sinus base contributes to the nose’s lateral wall. The apex of the sinus reaches to the maxilla’s zygomatic process. The maxilla bone’s orbital plate forms the sinus roof that features blood vessels and infraorbital nerve. The flat roof has slight slope in anterior and lateral part. The middle part of the roof forms the maxilloethmoidal sinus wall.
The alveolar process forms the sinus floor, which is situated below the nose floor level. The curved sinus floor may have conical projections representing the teeth root apices. There are occasional incidences of missing bone that lies between the teeth and the sinus. Some times this bone is extremely thin. A bony septum may divide the floor.
The anterior wall of the sinus, associated with the face, features infraorbital nerve’s branches. The opposite wall relates to the infratemporal fossa. The maxillary nerve branches occupy this posterior wall. The wall bulges near the fossa. Both walls contain blood vessels. The convex medial wall consists of maxilla, palatine bone’s vertical plate, the inferior concha and ethmoid’s uncinate process.  The lateral wall is associated with cheek and zygoma.
The maxillary sinus cavity is usually interrupted with septa and bony ridges, dividing the sinus into two areas.  The superior area of the sinus base has an opening that links the sinus and the nose. The opening (s) in the hiatus semilunaris drains into the nose’s middle meatus.
The posterior, middle and anterior superior alveolar nerves and the infraorbital nerve supplies to the mucous membrane. The posterior and anterior superior alveolar branches of the maxillary and infraorbital arteries respectively supply blood to the sinus. The veins draining through the ostium join the nose’s venuous plexuses. The lymphatic vessels move through the ostium and open into the submandibular nodes.
Although paranasal sinuses have many recesses, the recess frequency is quite less in the maxillary sinuses. The sinuses feature alveolar, zygomatic, nasal and infraorbital recesses. Mucoperiosteum lines the maxillary antrum containing air.

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