Lacrimal bone- Function, Border, Where is the Lacrimal Bone?

Lacrimal Bone 

The lacrimal bone or os lacrimal is a paired flat craniofacial bone that provides a surface for the union of parts of the lacrimal apparatus (which produces tears) and muscles.

Both paired bones form the border with the maxillary, ethmoid, and frontal bones of the face and skull. The lacrimal bone is very small and quite fragile.

Where is the Lacrimal Bone?

The location of the lacrimal bone requires a little knowledge of the surrounding bones; However, its function as part of the lacrimal or tear-producing system tells us that it is closer to the inner corner of the eye. With a frontal view of the skull, both tear ducts are almost completely hidden behind the nasal bone.

When the nasal bone is removed, the front (top) surface of each small bone can be seen in its entirety.

Each lacrimal bone has two surfaces (lateral and medial) and four edges (anterior, posterior, superior, and inferior).

The lateral (orbital) surface of the lacrimal bone is divided by a vertical posterior lacrimal ridge. In front of the lacrimal crest, there is a vertical sulcus – the lacrimal sulcus.

The lacrimal groove is a groove for the nasolacrimal duct, located in the anterior part of the lateral surface of the lacrimal bone and in the frontal process of the maxilla. The lacrimal sulcus of the lacrimal bone fuses anteriorly with the posterior border of the frontal process of the maxilla, which contains the lacrimal sac. The medial wall of the sulcus has a descending extension that contributes to the formation of the nasolacrimal canal.

The medial (nasal) surface of the lacrimal bone has a longitudinal ridge corresponding to the lacrimal crest on the lateral surface. The anterior region of the medial surface of the lacrimal bone forms part of the middle nasal meatus.

The anterior border of the lacrimal bone joins the frontal process of the maxilla.

The posterior border of the lacrimal bone joins the orbital plate of the ethmoid bone.

The upper border of the lacrimal bone is attached to the frontal bone.

The lower border of the lacrimal bone joins the orbital surface of the maxilla, while its anterior part elongates downward and articulates with the lacrimal process of the inferior nasal concha, contributing to the formation of the canal for the nasolacrimal duct.

The photo above shows the labeled lacrimal bone, in which the anterior ridge fits into the frontal process of the jawbone and with the frontal bone of the upper forehead. This photo of the skull on the left shows the right-hand bone fitting snugly into the eye socket.

Lacrimal bone anatomy

The anatomy of the lacrimal bone is relatively complicated if we consider its small size on the human face: about a centimeter and a half in height and less than a centimeter in width.’

If you are wondering whether to label them as facial or cranial tear bones, they are the bones of the face. On the face, the skull ends at the frontal bone.

Both bones have two surfaces: the lateral (orbital) surface and the medial (nasal) surface. These surfaces have grooves, ridges, and grooves that give the tear bones an additional function. The two bones also have joints with the frontal, ethmoid, and maxillary bones and the nasal shell.

The lateral surface of the lacrimal bone

The lateral surface of the lacrimal bone consists of four anatomical parts:

  1. Posterior lacrimal crest
  2. tear groove
  3. tear Humulus

The posterior lacrimal crest divides the lateral surface into two segments. The lateral surface refers to the lateral surfaces of this bone. The posterior lacrimal crest is a narrow, vertically raised surface that forms a sulcus (lacrimal sulcus) near the eye. It is a point of attachment for the orbicularis oculi muscle that closes the eyelids.

The lacrimal sulcus provides space for the soft tissues of the lacrimal sac and the nasolacrimal duct. You can see this groove in the picture, which is labeled the lacrimal sac fossa. The ridge ends in a small sloping shape called the lacrimal hamulus that forms a round hole that contains the lacrimal canal.

The anterior lacrimal crest, mentioned in some articles as part of the lacrimal bone, is also considered part of the frontal process of the maxilla. This is where the two bone surfaces meet.

Medial surface of the lacrimal bone

The medial surface of the lacrimal bone is the part that faces the midline of the body, the posterior surface. It has a long groove along its length that runs in the same direction as the posterior lacrimal crest.

The medial surface provides a bony surface for the medial meatus of the nose that helps support the front of the median shell (see image below).

Edges of the lacrimal bone

The lacrimal bone has four boundaries with other craniofacial bones called joints. These joints are found in the frontal, ethmoid, lower nasal concha, and maxilla. Since the tear bones are some of the smallest bones in the body, and the smallest facial bones, they articulate with the largest bones only at specific points.

Each bone borders the frontal process of the maxilla (see image) and the orbital plate of the frontal bone that forms the blank region of the eye socket at the top of the eye socket.

The lacrimal bones also line up with the surface of the ethmoid bone that faces the eye socket. These bones are pink in the image below of the orbital bones.

There is also a boundary between the lacrimal process of the lower nasal concha.

These edges help us to indicate the location of the lacrimal bone.

Lacrimal bone function

The lacrimal bone has three functions. The first is to provide points of articulation between the maxilla, the ethmoid, and parts of the lower nasal concha. Joints, rather than stable sutures, mean that these bones have a much smaller range of motion when they move and therefore play a protective role.

The second function of the lacrimal bone is to provide a point of attachment for the orbicularis oculi muscle. This circular muscle closes the eyelids, but it also helps with the drainage of tears; when contracting, the tears are pushed into the nasolacrimal duct.

Finally, the shape of this bone means that soft tissue ducts can run along with it, the nasolacrimal duct that carries tears from the lacrimal sac to the lower meatus of the nasal passages, which is why the nose sheds tears when we cry. The nasolacrimal duct (or nasolacrimal duct) is very narrow and can become blocked.

lacrimal bone fracture

Lacrimal bone fractures are part of more facial trauma, particularly to the eye socket, nose, and forehead. An extremely fragile bone, a fracture resulting from blunt upper facial trauma is not unexpected. In particular, the lacrimal and ethmoid bones are described as having an eggshell-like strength compared to other bones in the face. This already fragile structure can be affected by osteoporosis); There is a relationship between tear bone thickness and general bone density throughout the body.

The tear bones are very close to the nasal airways and the frontal lobe of the brain. Fractures in this area can lead to airway obstruction and damage to the frontal lobe of the brain. Le Fort III fractures of the midface usually present with fractures of the lacrimal bone, along with complex fractures of the midface of the bones around the nose and eyes.

Maxillofacial surgeons need to restore the natural appearance of the face when treating these types of fractures. When the bones break but do not move, surgery is avoided. If the tear has caused a change in position, they will need to be treated surgically. The small, fragile lacrimal bone is less likely to be fixed with plates and fixed by connecting them to the surrounding bones with wire. Where the orbicular eyes are separated from the posterior lacrimal crest, the tendon of this muscle is fixed using screw holes and sutures. In type III fractures, the most serious type of nasoorbitoethmoidal (NOE) fracture, primary bone grafts are often needed to replace lost or damaged bone.

Any tear duct wound must be closed carefully to avoid permanent blockage of the nasolacrimal duct.

In cases of obstructions due to congenital malformations, the passages can be accessed through the interior of the nostrils or through the corner of the eye. A dacryocystorhinostomy is the name of the procedure that opens the duct; sometimes a stent is placed to keep the duct open.

Definebiology.com

Lacrimal bone- Function, Border, Where is the Lacrimal Bone?

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