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

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

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


Anatomical Structure

The ethmoid bone is one of the 8 skeleton of the cranium. That is positioned at the roof of the nasal cavity, and also between the two orbital cavities.

It contributes to the medial wall of the orbit and forms component of the anterior cranial fossa, whereby it separates the nasal cavity (inferiorly) indigenous the cranial cavity (superiorly). It additionally forms a significant portion the the sleep septum and lateral sleep wall.

The olfactory nerve (CN I) has a nearby anatomical partnership with the ethmoid bone. Its plenty of nerve fibres pass with the cribriform key of the ethmoid bone come innervate the sleep cavity through the feeling of smell.


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


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

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

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

Lastly, the ethmoid bone has two ethmoidal labyrinths. These are huge masses located at either side of the perpendicular plate, i m sorry contain the ethmoidal air cells (sinuses). Two sheets that bone type 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 relevance – Ethmoid Fracture

The ethmoid bone have the right to be broken in situations of facial trauma – many commonly hitting the dashboard in a collision, or a loss from height. Part signs and symptoms that fracture are concerned the anatomy the the ethmoid bone:

Fracture of cribriform plate – branches that the olfactory bulb might be sheared. This may cause anosmia (loss of sense of smell).Fracture that the labyrinth – may allow communication in between the nasal cavity and also the orbit. That is then possible for wait to enter the orbit and cause orbital emphysema.

Clinical relationship – CSF Rhinorrhoea

A fracture to the cribriform plate may enable communication in between the nasal cavity and also the central nervous system. Consequently, cerebrospinal liquid (CSF) can enter the nasal cavity and drain out from the nose. This manifests clinically together a clean watery discharge from one next of the nose – and also is known as CSF rhinorrhoea.

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The leaks typically stop spontaneously and can be controlled conservatively, but surgery is sometimes required. Voluntary CSF rhinorrhoea can additionally occur as result of congenital or gained defects in the ethmoid bone.