How is maxillary sinus developed? Briefly describe the applied anatomy of adult masallary sinus with illustrations.

  • The maxillary sinus is the first sinus to appear (7-10 weeks) as a shallow groove expanding from the primitive ethmoidal infundibulum into the mass of the maxilla.
  • Abortion and expansion result in a small cavity at birth which measures 7x4x4 mm.
  • It continues to grow during childhood at an estimated rate of annually 2 mm vertically and 3 mm anteroposteriorly. This process slows down around seven years of life followed by a 2nd growth phase thereafter.
  • At 12 th year of life, pneumatization may reach laterally just under the lateral orbital wall at the insertion of the zygomatic process, inferiorly to the level of the nasal floor and after the dentition below the nasal floor.
  • After dentition the sinus only gradually enlarges reaching its final size at 17-18 years of life.

Maxillary sinus (Antrum of high more)

  • It is largest of paranasal sinuses and occupies the body of maxilla.
  • B/L maxillary sinuses are relatively symmetrical and only rarely absent.
  • It is pyramidal in shape with base towards lateral wall of the nose and apex directed laterally into the zygomatic process.
  • On an average, maxillary sinus has a capacity of 15 ml in an adult.

Roof: Formed by orbital floor: superiorly related to infraorbital artery and nerve +orbit, Infraorbital canal may be dehiscent exposing the new or it may lie submucosally.

Floor: Formed by alveolar and palatine process of the maxilla and is situated 1cm below the level of floor of nose: Inferiorly related to upper dentition (2nd pm and 3 m) and hard palate.

Posterior wall is related to pterygopalatine fossa and infratemporal fossa.

Anterior is formed by facial surface of maxilla and is related to cheek with skin ,fat and facial musculature.

  • Natural maxillary ostium is in the posterior part of the ethmoidal infundibulium which opens into the middle meatus (located in the medial wall of the ethmoidal infundibulum, at the transition of its middle to posterior third)
    • During the enlargement of the middle metal antrostomy , if excessive enlargement is done there is a chance of damaging the sphenopalatine artery which enters through the sphnopalatine which lies just inferior to the horizontals attachment of the middle turbinate.
    • Accessory ostia may be present in the posterior fontanelle> anterior fontanelle in 25% of cases.
    • The natural otium is usually avoid, lies in an oblique plane and appears tunnel like during endoscopy. It may however be pinpoint/round or multiple.
  • Partial or complete septations may occur within the maxillary sinus.
  • A Heller cell may compromise the infundibulum and the drainage of the maxillary sinus through it normal ostium.
  • An extensive pneumatized maxillary sinus may encroach upon the alveolar process of the maxilla or into the zygomatic process of the maxilla.
  • An extensive pneumatized maxillary sinus may encroach upon the alveolar process of the maxilla or into the zygomatic process of the maxilla.
  • The medial wall of the maxillary sinus may be bowed literally to produce the maxillary sinus.

Maxillary ostium:

  1. The normal maxillary sinus ostium lies deep in the infundubulum very close to the attachment of the uncinate process to the lateral wall. If the entire width of the unconate process is not removed the normal ostium can be missed ostium sequence and recriculation of mucus
  2. The presence of accessory ostia also leads to reciculation of mucus. The mucus is transported out of sinus through an accessory ostium. This recirculation of mucus can be prevented by joining the normal ostium with the accessory ostium so as to get one large opening.
  3. The normal ostium should be widened in an anteroinferior direction at the expenses of the anterior fontanelle to prevent injury to nasolacrimal dut, which lies 5 mm anterior to it.
  4. The lamina papyracea and the orbit lie just above the maxillary ostium. Hence if for some reason the normal ostium cannot be located, it is safest to probe for the maxillary. Thus ostium just above the inferior turbinate. The probe should be directed in an anterior direction and prevent accidental entry into the orbit.
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