What is the Tear Bone
The tear bone is a small, delicate facial bone with a intricate structure and vital roles. The paired bone is about the size of the little fingernail, forming the front part of the eye socket’s inner wall. Its name comes from the Latin word ‘lacrima’, which means ‘tear’, as it supports the tear-producing system of the eye.
Where is the Tear Bone Located
Both tear bones are situated in the inner wall of the eye socket or orbit. They are not visible from the front of the skull as they are concealed behind the nasal bones.
Quick Facts
| Type | Flat bone |
| How many are there in the human body | 2 (1 in each eye socket) |
| Articulates with | 4 bones: frontal bone, ethmoid bone, inferior nasal concha, and maxilla |
Functions
The primary function of this bone is to provide structural support to the eye socket and tear-producing system, which consists of the tear gland that generates tears, and the nasolacrimal duct, which drains tears from the eye to the nose.
Anatomy
These rectangular bones have two surfaces and four borders.
Surfaces
Out of the two surfaces, the one facing the eye is known as the orbital or lateral surface, and the one facing the nose is called the inner or nasal surface.
1. Orbital surface
This surface includes a pronounced narrow vertical ridge called the rear tear crest, dividing the surface into front and rear sections. The front section houses the tear sac and tear duct, while the rear section forms a part of the rear wall of the eye socket.
The crest also has a longitudinally positioned groove called the tear sulcus at its front end. The inner edge of this sulcus forms the tear fossa by connecting with the frontal process of the maxilla. The upper part of this tear fossa houses the tear sac, while the lower part contains the nasolacrimal duct.
The smooth rear end of the rear tear crest forms the inner wall of the eye socket. The orbicularis oculi muscle, which aids in closing the eyelids, attaches here.
The rear tear crest ends in a small hooked shape called the tear hamulus that connects with the tear tubercle of the maxilla. It also creates a rounded orifice that houses the tear canal.
2. Nasal surface
This surface features a longitudinal groove or furrow along its length, which runs in the same direction as the rear tear crest. The front portion of the furrow forms a part of the central nasal meatus, while its rear portion articulates with the ethmoid bone.
Borders
The tear bone connects with other skull bones via these four borders.
1. The front border connects with the maxilla’s frontal process.
2. The rear border connects with the orbital lamina of the ethmoid bone.
3. The upper border connects with the frontal bone.
4. The lower border is divided into two parts by the lower edge of the rear tear crest. The part of the border placed behind the crest connects with the orbital plate of the maxilla, while the part located in front extends downward. This downward extension is called the descending process. It connects with the tear process of the inferior nasal concha and encloses the bony canal for the nasolacrimal duct.
Muscle Attachment
As mentioned, the orbicularis oculi muscle, which closes the eyelids and aids in tear drainage, inserts into this bone.
Articulations
It connects with four bones: the frontal bone, ethmoid bone, maxilla, and inferior nasal concha.
Ossification and Development
Around the 12th week of gestational period, a single ossification center appears within the cartilaginous membrane covering the cartilaginous nasal capsule. The tear bone develops from this single ossification center.
References
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- Tear bone – Kenhub.com
- Tear bone – Radiopaedia.org
- Tear Bone – Osmosis.org.
- Tear Bone Anatomy – Getbodysmart.com
- Tear Bone – Sciencedirect.com
