Introduction

It is a median bone of the base of cranium, it is in the notch ethmoïdale frontal bone. It also belongs to the wall médiale of the orbit and the walls of the nasal fossae. It is composed of four parts: the vertical or perpendicular blade, the horizontal sifted blade, two side masses.

the Vertical Blade

Composed of two segments: cranial and nasal. the cranial segment form ahead the process crista galli, not of fastener of the false brain. the segment extracrânien (=nasal) form the high part of the partition of the nasal fossae. The cranial segment is directed in a sagittal plan antéro posterior: base lower, posterior top, 2 side faces. The nasal segment is pentagonal (5 sides)

the Horizontal or Sifted Blade

It is perforated by many openings in which the nervous nets of the olfactive ways pass. It includes/understands a face higher endocrânienne in contact with the olfactive nerve, first pair of cranial nerve (I) and a lower or nasal face. The posterior edge is articulated with the bone sphénoïde. The former edge is articulated with the frontal bone.

Side Masses

Two blocks in the shape of hulls fixed at the sifted blade (often compared with a catamaran). Dug by the cells ethmoïdales: aeric cavities cuts some and variables number, forming a labyrinth systematized by the partitioning roots of certain reliefs of the face médiale (horns, process unciforme, bubble ethmoïdale).

Six faces

1. Nasal Face médiale/: irregular, marked by reliefs, carries the horns superior and means who are the osseous blades in the shape of conches delimiting the higher MEATUSES and inferiors where the ostiums of the paranasaux sines open.
2. side/orbital Face: belongs to the wall médiale of the orbit, also called bone planum.
3. former Face/jawbone: articulated with the frontal process of the jawbone.
4. posterior Face/sphénoïdale: articulated with the sphénoïde.
5. higher Face/Endocrânienne: covered partially by the hard mother of the base of cranium.
6. lower Face/jawbone: articular with the jawbone ahead, the palatine one behind.

Simple: Ethmoid bone