Lacrimal bone
321727
195761478
2008-03-04T08:53:59Z
203.198.195.13
{{Infobox Bone |
Name = {{PAGENAME}} |
Latin = os lacrimale |
GraySubject = 39 |
GrayPage = 164 |
Image = Gray164.png |
Caption = Lacrimal bone visible near center. |
Image2 = Orbital bones.png| |
Caption2 = Orbital bones |
Articulations = |
MeshName = |
MeshNumber = |
DorlandsPre = |
DorlandsSuf = |
}}
The '''lacrimal bone''', the smallest and most fragile [[bone]] of the face, is situated at the front part of the medial wall of the [[Orbit (anatomy)|orbit]]. It has two surfaces and four borders.
== Surfaces ==
=== Lateral or orbital surface ===
The lateral or orbital surface is divided by a vertical ridge, the [[posterior lacrimal crest]], into two parts.
In ''front'' of this crest is a longitudinal groove, the [[lacrimal sulcus]] (''sulcus lacrimalis''), the inner margin of which unites with the frontal process of the [[maxilla]], and the lacrimal fossa is thus completed. The upper part of this [[fossa]] lodges the [[lacrimal sac]], the lower part, the [[nasolacrimal duct]].
The portion ''behind'' the crest is smooth, and forms part of the medial wall of the orbit.
The crest, with a part of the orbital surface immediately behind it, gives origin to the lacrimal part of the [[Orbicularis oculi]] and ends below in a small, hook-like projection, the [[lacrimal hamulus]], which articulates with the [[lacrimal tubercle of the maxilla]], and completes the upper orifice of the [[nasolacrimal canal]]; the hamulus sometimes exists as a separate piece, and is then called the [[lesser lacrimal bone]].
=== Medial or nasal surface ===
The medial or nasal surface presents a longitudinal furrow, corresponding to the crest on the lateral surface.
The area in front of this furrow forms part of the middle [[meatus]] of the nose; that behind it articulates with the [[ethmoid]], and completes some of the [[anterior ethmoidal cells]].
== Borders ==
Of the four borders:
* the ''anterior'' articulates with the frontal process of the maxilla;
* the ''posterior'' with the [[lamina papyracea]] of the ethmoid;
* the ''superior'' with the frontal bone.
* The ''inferior'' is divided by the lower edge of the posterior lacrimal crest into two parts:
** the posterior part articulates with the orbital plate of the maxilla;
** the anterior is prolonged downward as the descending process, which articulates with the lacrimal process of the [[inferior nasal concha]], and assists in forming the canal for the nasolacrimal duct.
== Ossification ==
The lacrimal is ossified from a single center, which appears about the twelfth week in the membrane covering the cartilaginous nasal capsule.
== Articulations ==
The lacrimal articulates with ''four'' bones: two of the cranium, the [[frontal bone|frontal]] and [[ethmoid bone|ethmoid]], and two of the face, the [[maxilla]] and the inferior nasal concha.
==Additional images==
<center>
<gallery>
Image:Gray163.png|Left lacrimal bone. Orbital surface. Enlarged
Image:Gray188.png|Side view of the skull.
Image:Gray190.png|The skull from the front.
Image:Gray192.png|Medial wall of left orbit.
Image:Gray196.png|Roof, floor, and lateral wall of left nasal cavity.
</gallery></center>
== See also ==
*[[Bone#Terminology|Bone terminology]]
*[[Terms for anatomical location]]
==External links==
* {{eMedicineDictionary|Lacrimal+bone}}
* {{UMichAtlas|eye_5}}
* {{UMichAtlas|rsa2p4}}
* {{RocheLexicon|34256.000-1}}
* [http://www.upstate.edu/cdb/grossanat/hnskullantlb.shtml Diagram at upstate.edu]
{{OrbitalBones}}
{{Facial bones}}
[[Category:Skeletal system]]
[[Category:Skull]]
[[ar:عظم دمعي]]
[[ca:Unguis]]
[[de:Tränenbein]]
[[es:Unguis]]
[[fr:Os lacrymal]]
[[ja:涙骨]]
[[lv:Asaru kauls]]
[[lt:ašarikaulis]]
[[pl:Kość łzowa]]
[[pt:Osso lacrimal]]
[[sk:Slzná kosť]]
[[sl:Solznica]]
[[uk:Слізна кістка]]
[[zh:淚骨]]