Wednesday, February 25, 2015
Anatomy of the maxillary sinuses
The maxillary sinuses are the first of the sinuses to begin in fetal development. While the maxillary sinus is pea sized and fluid filled at birth, it undergoes two rapid growth spurts. The first is between birth and age three years and the second is between age seven and 18. The sinus becomes adult size by adolescence.
The drainage pathway or ostium of the maxillary sinus is located in the upper and front part of the middle wall of the maxillary sinus. Through this ostium the maxillary sinus communicates with the nose. Specifically, mucus drains from the maxillary sinus into the infundibulum in the middle meatus and out into the nose.
If the main drainage pathway becomes closed by inflammation or infection, accessory or secondary openings can be formed. These are essentially holes in the thin bone making up the middle wall of the sinus that are caused when pressure buildup pushes through. If your doctor finds an accessory opening on examination of the inside of your nose, that may be "evidence" that you have had previous problems with sinus blockage.
The maxillary sinus is beneath the eye, so the roof of the maxillary sinus is also the floor of the orbit. The floor of the maxillary sinus is formed by the maxillary bone; specifically, a part called the "alveolar process." It is important to know that the roots of the first and second molar teeth and the second bicuspid teeth often project through the floor of the maxillary sinus, where they are covered only by the thin mucus membrane within the sinus. Infection around these tooth roots may cause inflammation of the sinus mucous membranes and sinus pain. At times, removal of these teeth can cause a fistula (opening between the mouth and sinus) which can lead to repeated sinus infections.
The anterior or front wall of the maxillary sinus separates the sinus from the cheek skin, while the posterior or back wall separates the sinus from a space filled with blood vessels and nerves. The upper part of this space is called the infratemporal fossa, and the lower part is called the pterygomaxillary space.
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