Lacrimal Bone
Os Lacrimale
location_on Medial wall of the orbit, posterior to the frontal process of the maxilla
The lacrimal bone is the smallest and most fragile bone of the face, roughly the size and shape of a fingernail. It forms part of the medial wall of the orbit and contributes to the nasolacrimal canal, which drains tears from the eye into the nasal cavity. Despite its small size, it plays a crucial role in the lacrimal drainage system.
Key Anatomical Features
- Posterior lacrimal crest is a vertical ridge dividing the lateral surface
- Lacrimal groove anterior to the crest forms part of the fossa for the lacrimal sac
- Lacrimal hamulus curves over the nasolacrimal canal entrance
- Orbital surface is smooth and forms part of the medial orbital wall
- Nasal surface articulates with the middle nasal concha of the ethmoid
Muscle Attachments
| Muscle | Attachment | Action |
|---|---|---|
| Orbicularis oculi (lacrimal part) | Posterior lacrimal crest | Compresses the lacrimal sac to assist tear drainage |
| Lacrimal part of orbicularis oculi (Horner's muscle) | Posterior lacrimal crest | Pumps tears into the nasolacrimal duct during blinking |
| Medial palpebral ligament | Anterior lacrimal crest (of maxilla, adjacent) | Anchors the medial eyelid |
| No other direct muscular attachments | Due to small size | Primarily structural function in the lacrimal apparatus |
Joints and Articulations
| Joint | Type | Connects to |
|---|---|---|
| Lacrimomaxillary suture | Fibrous suture | Maxilla |
| Lacrimoethmoidal suture | Fibrous suture | Ethmoid bone |
| Frontolacrymal suture | Fibrous suture | Frontal bone |
Common Pathologies
Dacryocystitis
Infection of the lacrimal sac located in the fossa formed by the lacrimal bone and maxilla. Presents as a painful swelling at the medial canthus with purulent discharge.
Nasolacrimal duct obstruction
Blockage of the tear drainage pathway at the lacrimal bone region, common in newborns (congenital) and elderly. Causes excessive tearing (epiphora).
Lacrimal bone fracture
Usually occurs as part of naso-orbito-ethmoidal fractures rather than in isolation. Can disrupt the lacrimal drainage system.
Clinical Relevance
The lacrimal bone is a key landmark in dacryocystorhinostomy (DCR) surgery, where a new pathway is created between the lacrimal sac and nasal cavity to treat chronic nasolacrimal duct obstruction. The posterior lacrimal crest is the surgical boundary between the lacrimal bone and the lacrimal sac. Congenital nasolacrimal duct obstruction affects about 6% of newborns.
Development and Ossification
The lacrimal bone ossifies intramembranously from a single center appearing around the 12th fetal week. It is one of the last facial bones to ossify and is fully formed by birth.
Did You Know?
- The lacrimal bone is the smallest bone of the face, measuring roughly 12mm by 7mm
- The word lacrimal comes from the Latin lacrima meaning tear
- Despite being one of the smallest bones, the lacrimal bone is a critical component of the tear drainage system
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