The ethmoid bone is a tiny unpaired bone, located in the midline that the anterior cranium – the superior facet of the skull the encloses and protects the brain.

You are watching: This facial bone forms part of the nasal septum.

The hatchet ‘ethmoid’ originates from the Greek ‘ethmos’, definition sieve. This is reflect in its lightweight, spongy structure.

In this article, we shall look at the anatomy that the ethmoid bone – that is location, relations, and structure.


Anatomical Structure

The ethmoid bone is one of the 8 bones of the cranium. The is located at the roof the the nasal cavity, and between the two orbital cavities.

It contributes to the medial wall surface of the orbit and forms part of the anterior cranial fossa, whereby it off the sleep cavity (inferiorly) native the cranial cavity (superiorly). It additionally forms a far-reaching portion that the sleep septum and lateral nasal wall.

The olfactory nerve (CN I) has a close anatomical connection with the ethmoid bone. Its many nerve fibres pass through the cribriform plate of the ethmoid bone to innervate the sleep cavity through the feeling of smell.


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Fig 1 – The anatomical position and also relations the the ethmoid bone.


The ethmoid bone is comprised of three parts – the cribriform plate, the perpendicular plate, and also the ethmoidal labyrinth.

The cribriform plate forms the roof the the nasal cavity. It is pierced by many olfactory nerve fibres, which provides it a sieve-like structure. Projecting superiorly native the cribriform plate is the crista galli, which gives an attachment point for the falx cerebri (sheet that dura mater that separates the 2 cerebral hemispheres).

Another estimate of bone descends native the cribriform plate – the perpendicular plate. It forms the premium two-thirds that the sleep septum.

Lastly, the ethmoid bone includes two ethmoidal labyrinths. These are huge masses located at either next of the perpendicular plate, which contain the ethmoidal air cell (sinuses). 2 sheets of bone form each labyrinth:


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Fig 2 – The ethmoid bone in ~ the sleep cavity.


Articulations

The ethmoid bone articulates v 13 others:

Paired – nasal bones, maxillae, lacrimal bones, palatine bones, worse conchae.

Clinical relationship – Ethmoid Fracture

The ethmoid bone can be broken in situations of facial trauma – most commonly hitting the dashboard in a collision, or a loss from height. Some signs and symptoms the fracture are related to the anatomy the the ethmoid bone:

Fracture that cribriform plate – branches the the olfactory bulb might be sheared. This might cause anosmia (loss of feeling of smell).Fracture that the labyrinth – may allow communication in between the sleep cavity and the orbit. It is then feasible for air to get in the orbit and cause orbital emphysema.

Clinical relationship – CSF Rhinorrhoea

A fracture to the cribriform key may enable communication between the nasal cavity and the central nervous system. Consequently, cerebrospinal fluid (CSF) can enter the sleep cavity and drain the end from the nose. This manifests clinically as a clear watery discharge from one side of the nose – and is recognized as CSF rhinorrhoea.

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The leaks normally stop spontaneously and can be managed conservatively, but surgery is sometimes required. Spontaneous CSF rhinorrhoea can additionally occur due to congenital or obtained defects in the ethmoid bone.