Editing Ethmoid bone

{{Short description|Bone of the facial skeleton}}
{{Use dmy dates|date=August 2021}}
{{Infobox bone
| Name          = Ethmoid bone
| Latin         = os ethmoidale
| Image         = Orbital_bones.png
| Caption       = Ethmoid inside the [[orbit (anatomy)|orbit]] (brown)
| Image2        = Rotation ethmoid.gif
| Caption2      = Animation of the ethmoid bone
| Origins       =
| Insertions    =
| Articulations =
}}

The '''ethmoid bone''' ({{IPAc-en|ˈ|ɛ|θ|m|ɔɪ|d}};<ref>''[[OED]]'' 2nd edition, 1989 as {{IPA|/ˈεθmɔɪd/}}.</ref><ref>[http://www.merriam-webster.com/dictionary/ethmoid Entry "ethmoid"] in ''[http://www.merriam-webster.com/ Merriam-Webster Online Dictionary]''.</ref> from {{langx|grc|ἡθμός|hēthmós|sieve}}) is an unpaired [[bone]] in the [[skull]] that separates the [[nasal cavity]] from the [[brain]]. It is located at the roof of the [[nose]], between the two [[orbit (anatomy)|orbit]]s. The cubical (cube-shaped) bone is lightweight due to a spongy construction. The ethmoid bone is one of the bones that make up the orbit of the eye.

==Structure==
The ethmoid bone is an anterior cranial bone located between the eyes.<ref name="Saladin">{{cite book |last=Saladin |first=Kenneth S. |title=Anatomy and Physiology: the Unity of Form and Function |publisher=McGraw Hill |edition=7th |location=New York |year=2015 |isbn=978-0-07-340371-7 }}</ref> It contributes to the medial wall of the orbit, the nasal cavity, and the nasal septum.<ref name="Saladin" /> The ethmoid has three parts: [[cribriform plate]], [[ethmoidal labyrinth]], and [[Perpendicular plate of ethmoid bone|perpendicular plate]]. The cribriform plate forms the roof of the nasal cavity and also contributes to formation of the [[anterior cranial fossa]],<ref>{{Cite web|url=https://www.anatomynext.com/ethmoid-bone|title=Ethmoid bone|website=www.anatomynext.com|language=en|access-date=2018-03-01|archive-date=3 September 2020|archive-url=https://web.archive.org/web/20200903013615/https://www.anatomynext.com/ethmoid-bone/|url-status=dead}}</ref> the ethmoidal labyrinth consists of a large mass on either side of the perpendicular plate, and the perpendicular plate forms the superior two-thirds of the nasal septum.<ref name="Saladin" /> Between the [[orbital lamina of ethmoid bone|orbital plate]] and the [[nasal concha]]e are the [[ethmoidal sinus]]es or ethmoidal air cells, which are a variable number of small cavities in the lateral mass of the ethmoid.<ref>{{cite book |title=Illustrated Anatomy of the Head and Neck |last1=Fehrenbach |last2=Herring |publisher=Elsevier |year=2012 |page=52 }}</ref><ref>{{cite book |title=Human Anatomy |last=Jacobs |publisher=Elsevier |year=2008 |page=210 }}</ref>

=== Articulations ===
The ethmoid [[Articulation (anatomy)|articulates]] with thirteen bones:

* two bones of the neurocranium—the [[frontal bone|frontal]], and the [[Sphenoid bone|sphenoid]] (at the [[Body of sphenoid bone|sphenoidal body]] and at the [[sphenoidal conchae]]).
* eleven bones of the viscerocranium—, two [[nasal bones]], two [[maxillae]], two [[lacrimals]], two [[palatine bone|palatines]], two [[inferior nasal concha]]e, and the [[vomer]].

===Development===
The ethmoid is [[ossified]] in the cartilage of the nasal capsule by three centers: one for the perpendicular plate, and one for each labyrinth.

The labyrinths are first developed, ossific granules making their appearance in the region of the [[lamina papyracea]] between the fourth and fifth months of [[fetus|fetal]] life, and extending into the [[Turbinate|conchæ]].

At birth, the bone consists of the two labyrinths, which are small and ill-developed. During the first year after birth, the perpendicular plate and [[crista galli]] begin to ossify from a single center, and are joined to the labyrinths about the beginning of the second year.

The [[cribriform plate]] is ossified partly from the perpendicular plate and partly from the labyrinths.

The development of the ethmoidal cells begins during fetal life.

==Function==
===Role in magnetoception===
{{main|Magnetoception}}
Some [[bird]]s and other migratory animals have deposits of biological [[magnetite]] in their ethmoid bones which allow them to sense the direction of the Earth's [[magnetic field]]. Humans have a similar magnetite deposit (ferric iron), but it is believed to be [[vestigial structure|vestigial]].<ref>{{cite journal |first1=R. Robin |last1=Baker |first2=Janice G. |last2=Mather |first3=John H. |last3=Kennaugh |title=Magnetic bones in human sinuses |journal=[[Nature (journal)|Nature]] |volume=301 |issue=5895 |pages=78–80 |year=1983 |doi=10.1038/301078a0 |pmid=6823284 |bibcode=1983Natur.301...78R |s2cid=2385818 }}</ref>

==Clinical significance==

Fracture of the [[lamina papyracea]], the lateral plate of the ethmoid labyrinth bone, permits communication between the [[nasal cavity]] and the orbit on the same side of the body through the inferomedial orbital wall, resulting in [[orbital emphysema]].  Increased pressure within the nasal cavity, as seen during sneezing, for example, leads to temporary [[exophthalmos]].

The porous fragile nature of the ethmoid bone makes it particularly susceptible to fractures.  The ethmoid is usually fractured from an upward force to the nose. This could occur by hitting the dashboard in a car crash or landing on the ground after a fall.  The ethmoid fracture can produce bone fragments that penetrate the [[cribriform plate]].  This trauma can lead to a leak of [[cerebrospinal fluid]] into the nasal cavity.  These openings let opportunistic bacteria in the nasal cavity enter the sterile environment of the central nervous system (CNS).  The CNS is usually protected by the [[blood–brain barrier]], but holes in the cribriform plate let bacteria get through the barrier.  The blood–brain barrier makes it extremely difficult to treat such infections, because only certain drugs can cross into the CNS.

An ethmoid fracture can also sever the olfactory nerve.  This injury results in [[anosmia]] (loss of smell).  A reduction in the ability to taste is also a side effect because it is based so heavily on smell.  This injury is not fatal, but can be dangerous, as when a person fails to smell smoke, gas, or spoiled food.<ref name="Saladin" /> In fact, older people with anosmia were more than four times as likely to die in five years compared to those with a healthy sense of smell.<ref>{{cite journal |last1=Pinto |first1=Jayant |first2=Kristen |last2=Wroblewski |first3=David |last3=Kern |first4=Phillip |last4=Schumm |first5=Martha |last5=McClintock |title=Olfactory Dysfunction Predicts 5-Year Mortality in Older Adults |journal=[[PLOS One]]|volume=9 |issue=10 |pages=e107541 |doi=10.1371/journal.pone.0107541 |pmc=4182669 |pmid=25271633 |year=2014|bibcode=2014PLoSO...9j7541P |doi-access=free }}</ref>

{{expand section|date=December 2013}}

==Additional images==
<gallery>
 Image:Gray149.png|Ethmoid bone from above. 
 Image:Gray150.png|Perpendicular plate of ethmoid.
 Image:Gray151.png|Ethmoid bone (view from behind).
 Image:Gray152.png|Ethmoid bone from the right side.
 Image:Gray188.png|Side view of the skull.
 </gallery>

== See also ==
{{Anatomy-terms}}

== References ==
{{Gray's}}
{{Reflist}}

==Further reading==
*{{cite book |last=Saladin |first=Kenneth S. |title=Anatomy and Physiology: the Unity of Form and Function |publisher=McGraw Hill |edition=5th |location=New York |year=2010 |isbn=978-0-07-128341-0 }}
*{{cite book |last=Banks |first=Peter |title=Fractures of the facial skeleton |year=2000 |publisher=Wright |location=Oxford |isbn=0-7236-1034-7 |author2=Brown, Andrew E. }}

== External links ==
{{Commons category|Ethmoid bones}}
* http://www.theregister.com/2006/11/17/the_odd_body_nose_compass/
* {{cite web|url=http://www.tk.de/rochelexikon/pics/s34256.000-1.html|title=Anatomy diagram: 34256.000-1|work= Roche Lexicon – illustrated navigator|publisher= Elsevier|archive-url=https://web.archive.org/web/20121227145535/http://www.tk.de/rochelexikon/pics/s34256.000-1.html|archive-date=2012-12-27}}

{{OrbitalBones}}
{{Cranium}}
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[[Category:Bones of the head and neck]]
[[Category:Irregular bones]]
[[Category:Otorhinolaryngology]]