Lacrimal bone

The lacrimal bones are the smallest and most fragile bones in the skull, positioned at the front of the medial walls of the eye sockets. Each lacrimal bone is comprised of two surfaces (medial and lateral) and four borders (anterior, posterior, superior, and inferior).

The lateral, or orbital, surface of the lacrimal bone forms part of orbital cavity’s medial wall. This surface is distinguished by a vertical posterior lacrimal crest, which forms the posterior raised edge of the lacrimal groove or fossa.

Anteriorly, the lacrimal bone meets the frontal process of the maxilla, characterized by a noticeable anterior lacrimal crest. These posterior and anterior lacrimal crests, from both the lacrimal and maxillary bones respectively, define the rear and front boundaries of the lacrimal groove. This groove or fossa is crucial because it contains the lacrimal sac, an essential part of the tear drainage system.

Behind the posterior lacrimal crest, the lacrimal bone’s orbital surface provides an attachment point for the lacrimal part of the orbicularis oculi muscle. This crest and the orbital surface behind it, extends to form a small hook-like projection called the lacrimal hamulus, which semi-circles to be part of the posterior bony edge of the opening of the nasolacrimal canal. The anterior semi-circle is formed by maxilla’ frontal process, completing the bony edge of the nasolacrimal canal’s opening.

Anterior to the posterior lacrimal crest, the medial wall of the lacrimal groove prolongs downward to become the descending process of the lacrimal bone. This connects anteriorly with the frontal process of maxilla and at the bottom with the lacrimal process of the inferior nasal concha, together forming the floor of the nasolacrimal canal.

In a fully connected skull, the lacrimal bone links with several other bones: Posteriorly, it touches with the orbital plate of ethmoid labyrinth, enclosing the ethmoid air cells; Anteriorly, it articulates with the frontal process of the maxilla, superiorly with the orbital plates of frontal bone, and inferiorly with the orbital surface of the maxilla.