The ethmoid bone ( Latin: Os ethmoidale or Os ethmoides ) is a bone of the brain skull . It lies at the end of the nasal cavity on the border with the cranial cavity in the depth and is therefore not visible when the skull is viewed from the outside.
The ethmoid bone consists of several bone plates ( laminae ). The vertical lamina perpendicularis lies in the median plane . Together with the ploughshare (vomer), this forms the rear part of the nasal septum ( septum nasi ). The wafer-thin orbital plate ( lamina orbitalis ) is the border to the orbit and is also called lamina papyracea in humans because of its delicacy .
In the other mammals , in addition to the median perpendicular lamina, a distinction is made between a roof plate ( lamina tectoria ) as the upper, an orbital plate ( lamina orbitalis ) as the lateral and the floor plate ( lamina basalis ) as the lower outer wall.
The sieve plate ( lamina cribrosa ) forms the end of the cranial cavity . It is a structure with many holes, which gave the bone its name. In the primates it is almost horizontal on the roof of the nasal cavity, in the other mammals it is perpendicular to the end of the nasal cavity. The nerve fibers of the 1st cranial nerve ( olfactory nerve ) run through the sieve plate to the brain and the ethmoidal nerve anterior and the ethmoidal artery anterior (from the ophthalmic artery ) to the nasal cavity. On the side of the skull cavity, the sieve plate is recessed on both sides. In this sieve pit ( ethmoid fossa ) lie the olfactory bulbs on both sides . Both sieve pits are separated by the cockscomb ( Crista galli ).
From the walls arise inside the so-called. Siebbeinmuscheln ( Ethmoturbinalia ). These are thin plates of bone that roll up in a spiral. In their entirety, they form the ethmoidal labyrinth ( Labyrinthus ethmoidalis ), the cavities that are delimited by it are called ethmoid cells ( Cellulae ethmoidales ). In humans, an additional ethmoid cell can appear in the floor of the eye socket and roof of the maxillary sinus, which is called Haller's cell . In animals, the larger, far inward-reaching Ethmoturbinalia are called Endoturbinalia , the smaller Ectoturbinalia . The ethmoturbinalia form the bony basis of the upper and middle turbinate ( concha nasalis superior (in animals dorsalis ) and media ).
In humans and great apes, the "simple" nose has only three turbinalia, of which the two upper ones arise from the ethmoid and form the bony basis for the upper and middle nasal concha ( concha nasalis superior and media ). The middle turbinate is of particular medical importance since, under their most sinuses , namely the maxillary sinus ( maxillary sinus ), the frontal sinus ( frontal sinus ) and the anterior ethmoidal cells ( sine ethmoidales anterior open) in the nose. Based on the bony structures in this area, in particular the uncinate process (hooked process), the nasal mucosa forms a funnel-shaped channel ( ethmoid infundibulum ) with a crescent-shaped opening ( semilunar hiatus ). Pathological changes in this area can be the cause of a chronic inflammation of the sinuses. In this case, an attempt is made to normalize the ventilation of the sinuses through surgical opening of the infundibulum with removal of the hook process ( infundibulotomy ).
- ↑ Federative Committee on Anatomical Terminology (FCAT) (1998). Terminologia Anatomica . Stuttgart: Thieme
- ^ Stieve, H. (1949). Nomina Anatomica. Compiled by the Nomenclature Commission elected in 1923, taking into account the proposals of the members of the Anatomical Society, the Anatomical Society of Great Britain and Ireland, and the American Association of Anatomists, and reviewed by resolution of the Anatomical Society at the Jena conference in 1935 finally accepted. (Fourth edition). Jena: Verlag Gustav Fischer.
- Franz-Viktor Salomon: Bony skeleton . In: Franz-Viktor Salomon et al. (Hrsg.): Anatomie für die Tiermedizin . 3. Edition. Enke, Stuttgart 2015, ISBN 978-3-8304-1288-5 , pp. 97-98 .