Lacrimal bone

lacrimallacrimalslacrimal boneslachrymalcrestslacrimalacrimal canal
The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail.wikipedia
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Posterior lacrimal crest

posterior crest
The lateral or orbital surface is divided by a vertical ridge, the posterior lacrimal crest, into two parts.
The lateral or orbital surface of the lacrimal bone is divided by a vertical ridge, the posterior lacrimal crest, into two parts.

Facial skeleton

facial bonesfacial boneviscerocranium
The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail.
Lacrimal bones (2)

Fossa for lacrimal sac

lacrimal fossalacrimal sac fossa
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.
A smooth, more deeply concave depression on the lacrimal bone, which forms the medial wall of the orbital cavity, in which the lacrimal sac that drains into the nasolacrimal duct is located, is referred to as the lacrimal fossa (or fossa for the lacrimal sac).

Lacrimal sac

dacrocystographytear sacnasolacrimal sac
The upper part of this fossa lodges the lacrimal sac, the lower part, the nasolacrimal duct.
The lacrimal sac or lachrymal sac is the upper dilated end of the nasolacrimal duct, and is lodged in a deep groove formed by the lacrimal bone and frontal process of the maxilla.

Orbit (anatomy)

orbitorbitseye socket
It is situated at the front part of the medial wall of the orbit.
[[File:Orbital bones.png|275px|thumb|left|The seven bones that form the orbit:yellow = Frontal bonegreen = Lacrimal bonebrown = Ethmoid boneblue = Zygomatic bonepurple = Maxillary boneaqua = Palatine bonered = Sphenoid bone

Maxilla

upper jawmaxillaemaxillary bone
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 lacrimal articulates with four bones: two of the cranium, the frontal and ethmoid, and two of the face, the maxilla and the inferior nasal concha.
seven of the face: the nasal, zygomatic, lacrimal, inferior nasal concha, palatine, vomer, and the adjacent fused maxilla.

Lacrimal groove

lacrimal sulcuslacrimal
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.
On the nasal surface of the body of the maxilla, in front of the opening of the sinus is a deep groove, the lacrimal groove (or lacrimal sulcus), which is converted into the nasolacrimal canal, by the lacrimal bone and inferior nasal concha; this canal opens into the inferior meatus of the nose and transmits the nasolacrimal duct.

Nasolacrimal duct

tear ducttear ductsduct
The upper part of this fossa lodges the lacrimal sac, the lower part, the nasolacrimal duct.
The duct begins in the eye socket between the maxillary and lacrimal bones, from where it passes downwards and backwards.

Orbicularis oculi muscle

orbicularis oculiorbicularis musclemuscle of Riolan
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.
It arises from the posterior crest and adjacent part of the orbital surface of the lacrimal bone, and passing behind the lacrimal sac, divides into two slips, upper and lower, which are inserted into the superior and inferior tarsi medial to the puncta lacrimalia; occasionally it is very indistinct.

Nasolacrimal canal

nasal canallachrymal nasal canal
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.
It is formed by indentations in the inferior nasal conchae, maxilla and lacrimal bone.

Ethmoid sinus

ethmoidalethmoidal cellsethmoidal sinus
The area behind it articulates with the ethmoid, and completes some of the anterior ethmoidal cells.
The ethmoidal air cells are numerous thin-walled cavities situated in the ethmoidal labyrinth and completed by the frontal, maxilla, lacrimal, sphenoidal, and palatine bones.

Frontal bone

frontalfrontalsfrontal bones
The lacrimal articulates with four bones: two of the cranium, the frontal and ethmoid, and two of the face, the maxilla and the inferior nasal concha.
The nasal part is between the brow ridges, and ends in a serrated nasal notch that articulates with the nasal bones inferiorly, and with the lacrimal and maxilla bones laterally.

Allosaurus

Allosaurus fragilisA. fragilisallosaurid
In some theropods (e.g. Allosaurus, Ceratosaurus, Albertosaurus) the upper part of the lacrimal bone grew in such a manner as to form a horn on the top of the dinosaur's head, usually situated above, and anterior to the eye.
These horns were composed of extensions of the lacrimal bones, and varied in shape and size.

Inferior nasal concha

inferior conchainferior nasal conchaeinferior turbinate
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.
Of these, the anterior or lacrimal process is small and pointed and is situated at the junction of the anterior fourth with the posterior three-fourths of the bone: it articulates, by its apex, with the descending process of the lacrimal bone, and, by its margins, with the groove on the back of the frontal process of the maxilla, and thus assists in forming the canal for the nasolacrimal duct.

Ethmoid bone

ethmoidsupraethmoidinfundibulum
The area behind it articulates with the ethmoid, and completes some of the anterior ethmoidal cells. The lacrimal articulates with four bones: two of the cranium, the frontal and ethmoid, and two of the face, the maxilla and the inferior nasal concha.
eleven bones of the viscerocranium—, two nasal bones, two maxillae, two lacrimals, two palatines, two inferior nasal conchae, and the vomer.

Ceratosaurus

CeratosaursCeratosaurus nasicornisC. magnicornis
In some theropods (e.g. Allosaurus, Ceratosaurus, Albertosaurus) the upper part of the lacrimal bone grew in such a manner as to form a horn on the top of the dinosaur's head, usually situated above, and anterior to the eye.
The lacrimal bone formed not only the back margin of the antorbital fenestra, a large opening between eye and, but also part of its upper margin, unlike in members of the related Abelisauridae.

Dilophosaurus

DilophosaurDedilophosaurs
Rarely, the lacrimal bones fused with the nasal bones to form a pair of "nasolacrimal" crests, which are present in dinosaurs such as Dilophosaurus, Megapnosaurus and Sinosaurus.
The crests were formed significantly by the lacrimal bones and partially by the nasal bones.

Orbital lamina of ethmoid bone

lamina papyraceaorbital plateorbital plates
the posterior with the lamina papyracea of the ethmoid;
It articulates above with the orbital plate of the frontal bone, below with the maxilla and the orbital process of palatine bone, in front with the lacrimal, and behind with the sphenoid.

Coelophysis rhodesiensis

SyntarsusC. rhodesiensis Syntarsus
Rarely, the lacrimal bones fused with the nasal bones to form a pair of "nasolacrimal" crests, which are present in dinosaurs such as Dilophosaurus, Megapnosaurus and Sinosaurus.
According to Tykoski and Rowe (2004) Coelophysis rhodesiensis can be distinguished based on the following characteristics: it differs from Coelophysis bauri in the pit at the base of the nasal process of the premaxilla; it differs from C.? kayentakatae because the promaxillary fenestra is absent and the nasal crests are absent; the frontal bones on the skull are not separated by a midline anterior extension of the parietal bones; the anterior astragalar surface is flat; metacarpal I has a reduced distal medial condyle (noted by Ezcurra, 2006); the anterior margin of antorbital fossa is blunt and squared (noted by Carrano et al., 2012); the base of lacrimal vertical ramus width is less than 30% its height (noted by Carrano et al., 2012); the maxillary and dentary tooth rows end posteriorly at the anterior rim of the lacrimal bone (noted by Carrano et al., 2012)

Bone

bone tissuecancellous bonecortical bone
The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail.

Lacrimal hamulus

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.

Lacrimal tubercle

lacrimal tubercle of the maxilla
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.

Nasal meatus

middle meatussuperior meatusinferior meatus
The area in front of this furrow forms part of the middle meatus of the nose.

Nasal concha

turbinateturbinatesturbinate bone
The lacrimal articulates with four bones: two of the cranium, the frontal and ethmoid, and two of the face, the maxilla and the inferior nasal concha.

Sarcopterygii

lobe-finned fishsarcopterygiansarcopterygians
In early lobe-finned fishes and ancestral tetrapods, the lacrimal bone is a relatively large and robust bone, running from the orbit to the nostrils.