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Other Terms: Os lacrimale, Os lacrymal
It is extremely thin. When it is held up to a light source, the light easily penetrates the bone. The bone sits in the anterior part of the medial wall of the orbit. It has four margins and two surfaces. The margins are posterior, superior, anterior, and inferior. These margins form fine, butt-like sutures with neighboring bones. The surfaces are lateral or orbital and medial or nasal. The orbital surface is smooth and flat in its posterior half where it contributes to the medial wall of the orbit. Anteriorly this surface has a longitudinal groove that ends posteriorly in a longitudinal crest that is hook-shaped inferiorly. This groove supports the nasolacrimal duct. Covered with mucous membrane, the slightly rough, medial surface of the bone contributes to the nasal cavity.
This term has an interesting history. In Latin the term lacrima or lachryma means a tear. The Greek word for a tear is dakry or dakyron. Etymologists report that a copyist's error led to this change from Greek to Latin. They support this position by noting an older form of the Latin word spelled dacrimal. The bone's name derives from its housing of the tear duct.
The lacrimal bone articulates with four bones: the frontal, ethmoid, maxilla, and inferior nasal concha. Its posterior border forms a fine articular margin with the anterior edge of the ethmoid orbital plate. Inferiorly and anteriorly, the margins of the bone form fine articulations with the orbital plate and frontal process of the maxilla, respectively. The inferior border of the descending groove of the lacrimal bone articulates with the inferior nasal concha. Superiorly, the bone articulates with the frontal bone.
The lacrimal bone ossifies from a single center. This center appears during the twelfth prenatal week in the connective tissue superficial to the cartilage of the nasal capsule. It completely ossifies by birth. The bone thickens through early life. However, with aging the lacrimal can become thin and perforate.