The posterior lacrimal crest is a vertical bony ridge on the orbital surface of the

lacrimal bone The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail. It is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders. Several bony landmarks of ...

. It divides the bone into two parts. It gives origin to the lacrimal part of the

orbicularis oculi muscle The orbicularis oculi is a muscle in the face that closes the eyelids. It arises from the nasal part of the frontal bone, from the frontal process of the maxilla in front of the lacrimal groove, and from the anterior surface and borders of a short ...

Structure

The posterior lacrimal crest is a vertical bony ridge on the orbital (lateral) surface of the

. It divides the lacrimal bone into two parts. It is quite thin and fragile in most people. The

lacrimal groove 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 ...

is in front of this crest. The inner margin of it unites with the frontal process of the

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. T ...

to complete the fossa for the lacrimal sac. The portion of the lacrimal bone behind the posterior lacrimal crest is smooth, and forms part of the medial wall of the

orbit In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...

. The lacrimal crest ends below in the

lacrimal hamulus The lacrimal hamulus is a small, hook-like bony projection of the lacrimal bone. It is a continuation of the posterior lacrimal crest. It articulates with the lacrimal tubercle of the maxilla, and completes the upper orifice of the lacrimal cana ...

(a small hook-like projection), which articulates with the lacrimal tubercle of the

Relations

The posterior lacrimal crest is just behind the

lacrimal sac 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. It connects the lacrimal canaliculi, which drain tears from the ...

, and its upper part lodges the lacrimal sac. The lower part lodges the

nasolacrimal duct The nasolacrimal duct (also called the tear duct) carries tears from the lacrimal sac of the eye into the nasal cavity. The duct begins in the eye socket between the maxillary and lacrimal bones, from where it passes downwards and backwards. T ...

. Horner's muscle, part of the

orbicularis oris muscle In human anatomy, the orbicularis oris muscle is a complex of muscles in the lips that encircles the mouth. It is a sphincter, or circular muscle, but it is actually composed of four independent quadrants that interlace and give only an appearance ...

, inserts between 2 mm and 4 mm from the posterior lacrimal crest. Together with the thicker and more prominent anterior lacrimal crest, it forms the fossa for the lacrimal sac.

Variation

In most people, the posterior lacrimal crest is fairly prominent. However, in around 20% of people, it is fairly shallow. In contrast, the anterior lacrimal crest is almost always very prominent.

Function

The posterior lacrimal crest gives origin to the lacrimal part of the

. It also helps to protect the

Clinical significance

The posterior lacrimal crest may be vulnerable to

avulsion fractures An avulsion fracture is a bone fracture which occurs when a fragment of bone tears away from the main mass of bone as a result of physical trauma. This can occur at the ligament by the application of forces external to the body (such as a fall ...

. It is generally quite thin and fragile. 25% of such avulsion fractures are related to a Le Fort III skull fracture.

Additional images

File:Slide4gre.JPG, Cranium. Posterior lacrimal crest. Lacrimal bone.

References

{{Authority control Bones of the head and neck