Ethmoid bone
An ethmoid bone is a very particular bone localized between eyeballs and making a significant part of the nasal cavity. By the way, it is the most fragile bone in our body – made almost entirely by thin bony lamellae. Usually, ethmoid isn't present in skulls available for learning in Anatomy departments. The reason behind it is that some students grab the skull by putting fingers in orbits and applying some pressure over ethmoid bone. One action like this is enough to impress 0.2–0.4 mm* thin lamina papyracea into the labyrinthus ethmoidalis and destroy it.
The list of terms:
Crista galliLabyrinthus ethmoidalis – Ethmoidal labyrinth
Lamina perpendicularis – Perpendicuar plate
The list of terms:
Crista galliLamina cribrosa – Cribriform plate
Lamina perpendicularis – Perpendicular plate
Labyrinthus ethmoidalis – Ethmoidal labyrinth
Note multiple ethmoid cells that open on top of an ethmoid labyrinth. The most ventral ethmoid cells communicate with the frontal sinus, and the dorsal ones are covered by the pars orbitalis ossis frontalis. Foramen ethmoidale anterius localized on orbit's medial wall connects orbit with the fossa cranii anterior via channel bordered by ethmoid bone (channel's floor) and the frontal bone (the channel's roof). This channel is known as canalis ethmoidalis anterior, is about 6 mm long, and contains clinically important a. ethmoidalis anterior*.
The list of terms:
Lamina perpendicularis – Perpendicular plateCrista galli
Ala cristae galli – Wings of crista galli
Cellulae ethmoidales – Ethmoidal air cells
Lamina cribrosa – Cribriform plate
Foramina cribrosa – Cribriform foramina
Foramen ethmoidale anterius – Anterior ethmoidal foramen
Foramen etnmoidale posterius – Posterior ethmoidal foramen
The list of terms:
Cellulae ethmoidales anteriores – Anterior ethmoid cellsCellulae ethmoidales mediae – Middle ethmoid cells
Cellulae ethmoidales posteriores – Posterior ethmoid cells
Bulla ethmoidalis – Bulla of ethmoid
Note the processus uncinatus – the tiny plate of a complex shape bending along to the bulla ethmoidalis and, in most cases, anteriorly attached to the lamina papyracea1. Processus uncinatus is believed to play an essential role in the prevention of the non-sterile inspired air from contacting the sinus surface and directing the sterile expired air toward the sinuses2.
The list of terms:
Crista galliAla cristae galli – Wings of crista galli
Lamina orbitalis (papyracea) – Orbital plate (paper-thin)
Lamina perpendicularis – Perpendicular plate
Bulla ethmoidalis
Processus uncinatus – Uncinate process
Infundibulum – Ethmoidal infundibulum
Concha nasalis media – Middle nasal concha
Concha nasalis superior – Superior nasal concha
Last update: 07/Nov/2020