Bony Skeleton of Nasal Cavity
1. Definition
- The nasal cavity is a large air-filled space inside the skull.
- It is divided into right and left halves by the nasal septum.
- Each cavity has a roof, floor, medial wall, and lateral wall.
Boundaries of the Nasal Cavity
A. Roof (arched, narrow)
- Anterior part → nasal bone, nasal spine of frontal bone
- Middle part → cribriform plate of ethmoid bone (has small foramina for olfactory nerves)
- Posterior part → body of sphenoid bone (with sphenoidal sinus above)
B. Floor (wider, flat)
- Formed by → palatine process of maxilla (anterior ¾) + horizontal plate of palatine bone (posterior ¼)
- Relation → forms the hard palate, separating nasal cavity from oral cavity.
C. Medial Wall (nasal septum)
- Formed by:
- Perpendicular plate of ethmoid bone (upper part)
- Vomer (posteroinferior part)
- Septal cartilage (anterior part, flexible)
- Small contributions → nasal crests of maxilla & palatine bones, nasal spine of frontal bone
MEDIAL WALL
D. Lateral Wall (irregular, most complex)
- Formed by several bones:
- 1. Maxilla (frontal process + body)
- 2. Lacrimal bone
- 3. Ethmoid bone (superior and middle conchae + part of labyrinth)
- 4. Inferior nasal concha (separate bone)
- 5. Perpendicular plate of palatine bone
- 6. Medial pterygoid plate of sphenoid
- Important structures on lateral wall:
- 3 bony projections → superior, middle, and inferior nasal conchae (turbinates)
- Spaces under conchae = meatuses (superior, middle, inferior) → openings of sinuses
- Sphenoethmoidal recess (above superior concha) → opening of sphenoid sinus
- Nasolacrimal duct opens into inferior meatus
3. Posterior Boundary
- Choanae (posterior nasal apertures) → open into nasopharynx
- Bounded by:
- Medial → vomer
- Lateral → medial pterygoid plate of sphenoid
- Superior → body of sphenoid
- Inferior → posterior border of hard palate
LATERAL WALL