Maxillary Sinus Lining Composition
The maxillary sinus is lined by the Schneiderian membrane, which consists of an overlaid periosteum with a thin layer of pseudostratified ciliated columnar epithelium 1.
Detailed Histologic Structure
The Schneiderian membrane represents the mucous membrane covering the inner part of the maxillary cavity and has a characteristic multilayered composition:
Epithelial Layer
- Pseudostratified ciliated columnar epithelium forms the superficial layer
- Contains ciliated cells that are essential for mucociliary clearance
- Includes goblet cells interspersed throughout for mucus production
- The epithelium is relatively thin and delicate compared to nasal mucosa 2
Deeper Layers
- Periosteal layer lies beneath the epithelium, directly adherent to the underlying bone
- The majority of fibers and cells in the deeper layers run horizontally, oriented parallel to the underlying bone wall 3
- Overall membrane thickness averages approximately 0.40 ± 0.12 mm in healthy specimens 3
Clinical Significance
The membrane's structural characteristics have direct surgical implications. The horizontal fiber orientation means there are relatively few perpendicular attachments to the maxillary lateral wall 3. This anatomical feature explains why the membrane can be elevated during sinus augmentation procedures, but also why it is vulnerable to perforation during surgical manipulation.
Membrane Thickness Variations
- In healthy sinuses, the membrane is typically not visible on imaging and measures less than 2 mm 1
- Thickening beyond 2-5 mm suggests altered sinus physiology or pathology 1
- Thickening of a healthy membrane occurs at the periosteal layer and may enhance its strength, whereas thickening of a diseased membrane creates a weaker, gelatinous texture 1
Important Caveats
The membrane differs from nasal mucosa in several key ways that affect its clinical behavior 2:
- Relatively diminished number of cilia
- Lower resistance to infection
- More delicate structure with easier penetration by microorganisms
- Diminished activity of seromucous glands
These characteristics explain why the maxillary sinus is particularly vulnerable to odontogenic infections and why membrane perforations during surgical procedures are common (occurring in 19.5-23.5% of sinus elevation procedures) 1.