What Is the Lacrimal Bone?

The lacrimal bone is one of 22 bones of the skull and is, in fact, the tiniest of these bones. Situated within the orbit or eye socket, it is a flat, quadrilateral bone found on the side of the socket nearest the nose. Its borders make contact with four other bones of the skull: the ethmoid and frontal bones of the cranium, and the maxilla and inferior nasal concha bones of the face. On the surface of the lacrimal bone that faces outward from the nose lie two structures important to eye function. These are the lacrimal sac, which collects excess tears that have been removed from the eye by the lacrimal canaliculi, and the nasolacrimal ducts, which transmit the tears from the lacrimal sac to the nasal fossa, the cavity immediately behind the nose.

Of the skull bones, eight can be considered a part of the cranium, or the rounded part of the skull that houses the brain, while the remaining 14 are found in the face. These bones shape and give support to the jaw, upper lip, cheeks, nose, and eye socket. The large cavity that is the orbit is formed by several adjacent bones, among them the lacrimal bone. Also intersecting to form this socket are the sphenoid, ethmoid, maxilla, zygomatic, frontal, and palatine bones.

The lacrimal bone corresponds with the inside corner of the eye, along the side of the bridge of the nose. To the front of this bone is the maxilla, a bone of the cheek felt immediately below the eye socket. The long anterior or front border of the lacrimal bone articulates with a surface on the maxilla known as the frontal process.

Along the edge of the bone that is deepest in the eye socket is the ethmoid bone of the cranium. The narrow top edge of the lacrimal bone aligns with the frontal bone, the large skull bone that forms the forehead. Below, the similarly narrow bottom border meets the inferior nasal concha, a curly projection of bone named for its resemblance to a seashell that is found inside of the nasal cavity behind the nose.

This four-sided bone, long from top to bottom and narrow from side to side, functions as a structural support for the tear gland, which consists of the lacrimal canaliculi, the lacrimal sac, and the nasolacrimal ducts. The canaliculi are situated just lateral to the lacrimal bone and convey the tears away from the eyeball into the lacrimal sac, a structure just superficial to the top of the lacrimal bone. Situated at the top end of the nasolacrimal ducts, the lacrimal sac acts as a basin inside of which the tears collect before emptying into the nasolacrimal ducts, which follow the length of the lacrimal bone downward and in turn deposit the tears in the nasal cavity.