Lacrimal Bone Definition

The lacrimal bone, also known as the os lacrimale, has channels for the lacrimal apparatus (tear generation) as well as an area for muscle connection. These two pairs of bones surround the face and the skull’s maxilla, ethmoid, and frontal bones. The lacrimal bone is a tiny and fragile bone.

Where is the Lacrimal Bone?

The location of the lacrimal bone requires knowledge of the neighbouring bones; nonetheless, its function as a component of the lacrimal or tear-production process implies that it is located around the inside corner of the eye. Both os lacrymal are virtually totally concealed beneath the nasal bone in a frontal view of the skull.

When the nasal bone is removed, the anterior (superior) surface of every tiny bone can be seen in its whole.

The anterior crest of the labelled lacrimal bone connects into the maxillary frontal process, and the apex of the bone fits into the frontal bone of the forehead. The bone fits snuggly into the eye socket.

Lacrimal Bone Anatomy

When we examine its diminutive proportions on the human face – around 1.5 centimetres in height and less than 1 centimetre in width – lacrimal bone architecture is quite intricate.

If you’re not sure whether to call them facial or cranial lacrimal bones, go with the former. The frontal bone is where the skull finishes in the face.

Both bones have two surfaces: the lateral (orbital) surface and also the medial (nasal) surface. The grooves, ridges, and furrows on these surfaces offer the lacrimal bones a secondary role. The frontal, ethmoid, and maxilla bones, as well as the nasal concha, have articulations with the two bones.

Lateral Surface of the Lacrimal Bone

The lacrimal bone’s lateral surface is divided into four sections:

• The crest of the posterior lacrimal gland
• Sulcus of the lacrimal gland
• Hamulus of the lacrimal gland

The lateral surface is divided into two pieces by the posterior lacrimal crest. The side surfaces of this bone are referred to as the lateral surfaces. The posterior lacrimal crest is a small, vertically elevated ridge that forms a groove around the eye (the lacrimal sulcus). It’s where the orbicularis oculi muscle, which shuts the eyelids, attaches.

The soft tissues that comprise the lacrimal sac and nasolacrimal duct are housed in the lacrimal sulcus. This groove, designated fossa for lacrimal sac, may be seen in the photograph. The crest terminates in the lacrimal hamulus, a tiny hooked form that provides a spherical aperture that houses the lacrimal canal.

The anterior lacrimal crest, which is often referred to as a portion of the lacrimal bone, is also regarded to be a component of the maxilla’s frontal process. This is where the two bony surfaces meet.

Medial Surface of the Lacrimal Bone

The posterior aspect of the lacrimal bone includes the medial surface that confronts the body’s midline. It contains a lengthy groove (furrow) which continues similarly as the rear lacrimal crest throughout its whole.

The medial surface provides a bony surface for the middle meatus that supports the anterior portion of the middle concha.

Lacrimal Bone Borders

The lacrimal bone contains four articulations that connect it to other craniofacial bones. The frontal, ethmoid, inferior nasal concha, and maxilla all have these articulations. Because the lacrimal bones are among the tiniest in the body—they are among the tiniest bones in the face—they can only interact with larger bones at certain locations.

Every bone generates the indentation on the roof of the eye socket, which is bounded between the frontal process of the maxilla and the orbital plate of the frontal bone.

The ethmoid bone’s eye socket-facing surface is likewise bordered by the lacrimal bones. In the illustration of the orbital bones below, these bones are shaded in pink tones.

There is also a line between the inferior nasal concha’s lacrimal process and the inferior nasal concha’s lacrimal process.

These lines aid in determining the placement of the lacrimal bone.

Lacrimal Bone Function

There are three roles for the lacrimal bone. The primary purpose is to create articulation sites between the maxilla, ethmoid, and inferior nasal concha. Because these bones move through articulations as opposed to fixed sutures, they have a relatively limited range of motion and hence perform a protective function.

The orbicularis oculi muscles connect to the lacrimal bone through the orbicularis oculi muscular attachment point. This circular muscle not only shuts the eyelids, but it also aids tear drainage by pushing tears into the nasolacrimal duct as it contracts.

Finally, soft tissue ducts, such as the nasolacrimal duct, which carries tears from the lacrimal pouch towards the inferior meatus of the nasal canal and explains how tears flow down our nose while we cry, may run beside this bone due to its structure. Because the nasolacrimal (or nasolacrimal) duct is so small, it may get obstructed.

Lacrimal Bone Fracture

Greater facial injuries, especially to the eye socket, nose, and forehead, may result in lacrimal bone fractures. Fractures of this exceedingly delicate bone as a consequence of blunt upper face trauma are not uncommon. When compared to other facial bones, the lacrimal and ethmoid bones are regarded as having the strength of an eggshell. Osteoporosis can impair an extremely susceptible structure, and there is a relationship between lacrimal bone density and total bone density.

The frontal lobe of the brain and the nasal airway are quite near to the lacrimal bones. Fractures in this area may block the airway and injure the frontal lobe of the brain. In Le Fort III, mid-face fractures, lacrimal bone fractures, as well as complex mid-face fractures of the bones which encircle the nose and eyes, are prevalent.

When healing such fractures, maxillofacial surgeons must restore the normal contour of the face. Surgery is avoided when the bones shatter but do not move. When the fractures have produced positional alterations, surgical treatment will be required. The small plates are rarely used to restore the fragile lacrimal bone and are instead wire-attached to the surrounding bones. The tendon of the orbicularis oculi is locked into place using screw holes and sutures where it detaches from the posterior lacrimal crest. During type III fractures, the more extreme naso-orbito-ethmoid (NOE) fracture type, main bone transplants are frequently required to restore damaged or broken bone.

To prevent permanent obstruction of the nasolacrimal duct, all lacerations to the tear ducts must be properly repaired.

The ducts may be reached by the inside of the nasal canal or the corner of the eye in situations of obstructions caused by congenital abnormalities. The surgery that opens the duct is known as a dacryocystorhinostomy; a stent is occasionally used to keep the duct open.

References

Ducker L, Rivera RY. Anatomy, Head and Neck, Eye Lacrimal Duct. [Updated 2019 Feb 7]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2020 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK531487/

Pogrel MA, Kahnberg KE, Andersson L. (Ed.) (2014). Essentials of Oral and Maxillofacial Surgery. Hoboken (NJ), Wiley Blackwell. Hoboken.