Ethmoid bone

Ethmoid bone: Anatomy & FunctionKey facts about the anatomy of the ethmoid bone
~ 3 min

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.

Ethmoidal bone (os ethmoidale)
Ethmoidal bone (os ethmoidale)

It has two plates:

  • cribriform plate (lamina cribrosa)

    Cribriform plate (lamina cribrosa)
    Cribriform plate (lamina cribrosa)
  • perpendicular plate (lamina perpendicularis)

Perpendicular plate (lamina perpendicularis)
Perpendicular plate (lamina perpendicularis)

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

Ethmoidal labyrinth (labyrinthus ethmoidalis)
Ethmoidal labyrinth (labyrinthus ethmoidalis)

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

Orbital plate (lamina orbitalis)
Orbital plate (lamina orbitalis)

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

Cribriform foramina (foramina cribrosa)
Cribriform foramina (foramina cribrosa)

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

Crista galli (crista galli)
Crista galli (crista galli)

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

Ala (ala cristae galli)
Ala (ala cristae galli)

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).

Ethmoidal cells (cellulae ethmoidales)
Ethmoidal cells (cellulae ethmoidales)

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)

Superior nasal concha (concha nasalis superior)
Superior nasal concha (concha nasalis superior)

and the middle nasal concha (concha nasalis media)

Middle nasal concha (concha nasalis media)
Middle nasal concha (concha nasalis media)

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

Supreme nasal concha (concha nasalis suprema)
Supreme nasal concha (concha nasalis suprema)

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

Superior nasal meatus (meatus nasi superior)
Superior nasal meatus (meatus nasi superior)

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

Middle nasal meatus (meatus nasi medius)
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.

Uncinate process (processus uncinatus)
Uncinate process (processus uncinatus)

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

Ethmoidal bulla (bulla ethmoidalis).
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.

Semilunar hiatus (hiatus semilunaris)
Semilunar hiatus (hiatus semilunaris)
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
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