Let us examine the structure of the ethmoid bone (os ethmoidale). This bone is involved in the formation of the nasal cavity and the orbit.

It has two plates:

• cribriform plate (lamina cribrosa)

  

• perpendicular plate (lamina perpendicularis)

On each side of the cribriform plate is the ethmoidal labyrinth (labyrinthus ethmoidalis).

On the lateral side, the labyrinth is covered by the orbital plate (lamina orbitalis).

The cribriform plate has numerous cribriform foramina (foramina cribrosa), through which the olfactory nerves (components of the olfactory nerve) pass.

The crista galli (crista galli) lies above the cribriform plate.

On each side, the crista galli has an ala (ala cristae galli). These alae limit the foramen caecum.

The perpendicular plate is oriented sagittally and is part of the nasal septum.

The labyrinth essentially consists of numerous ethmoidal cells (cellulae ethmoidales). All these cells together make up the pneumatized cavities of the cranium (along with the sinuses).

Depending on the location, we distinguish between:

• anterior ethmoidal cells (cellulae ethmoidales anteriores), which are connected to the middle nasal meatus

• middle ethmoidal cells (cellulae ethmoidales mediae), which are connected to the superior nasal meatus

• posterior ethmoidal cells (cellulae ethmoidales posteriores), which are connected to the superior nasal meatus

At the bottom, the bone changes and adjusts to the form of so-called nasal conchae.

These are the superior nasal concha (concha nasalis superior)

and the middle nasal concha (concha nasalis media)

Occasionally, we can also distinguish the supreme nasal concha (concha nasalis suprema). This is an individual anatomical peculiarity

Between the superior nasal concha and the middle nasal concha lies the superior nasal meatus (meatus nasi superior).

And below the middle nasal concha lies the middle nasal meatus (meatus nasi medius).

The middle nasal concha has an uncinate process (processus uncinatus). It is connected to the ethmoidal process of the inferior nasal concha.

Behind the uncinate process lies the largest cell of the labyrinth, which is called the ethmoidal bulla (bulla ethmoidalis).

Between these formations is the ethmoidal infundibulum (infundibulum ethmoidale), through which the frontal sinus connects to the middle nasal meatus.

There is also the semilunar hiatus (hiatus semilunaris) under the ethmoidal bulla, through which the maxillary sinus connects to the middle nasal meatus.

Dictionary

Ethmoid Bone

ethmoid bone

os ethmoidale

cribriform plate

lamina cribrosa

perpendicular plate

lamina perpendicularis

ethmoidal labyrinth

labyrinthus ethmoidalis

orbital plate

lamina orbitalis

cribriform foramina

foramina cribrosa

crista galli

crista galli

ala of crista galli

ala cristae galli

ethmoidal cells

cellulae ethmoidales

anterior ethmoidal cells

cellulae ethmoidales anteriores

middle ethmoidal cells

cellulae ethmoidales mediae

posterior ethmoidal cells

cellulae ethmoidales posteriores

superior nasal concha

concha nasalis superior

middle nasal concha

concha nasalis media

supreme nasal concha

concha nasalis suprema

superior nasal meatus

meatus nasi superior

middle nasal meatus

meatus nasi medius

uncinate process

processus uncinatus

ethmoidal bulla

bulla ethmoidalis

ethmoidal infundibulum

infundibulum ethmoidale

semilunar hiatus

hiatus semilunaris