BS- Ethmoid bone

what is the ethmoid bone and where is it located?

single bone- contributes to middle third of back of face
part of nasal septum- roof and lateral wall of nasal cavity
medial wall of orbit
floor of anterior cranial fossa

what parts make up the ethmoid bone?

1. perpendicular plate
2.cribiform plate
3.ethmoidal labrynths x2
chonchae are also part of the ethmoid

what is the perpendicular plate?

thin quadrilateral plate- descends from cribiform plate
forms upper part of nasal septum

what bones does the perpendicular plate articulate with?

anterior- nasal bone and septal cartillage
posterior- sphenoidal crest
inferior- vomer

what structures are loacted in the cribiform plate?

numerous foramina- olfactory nerve
crista galli - foramen caecum- when in articulation with the alae

what are the ethmoidal labrynths?

hang from the lateral margins of the cribiform plate
have network of air cells separated by tuberculae
covered by bone: anterior articulates with frontal(tops of them) and the posteriors with sphenoid and occipital bone

what bones do ethmoidal labrynths articulate with?

superior- frontal bone
posterior- sphenoid and palatine bones

ossification of the ethmoid bone

ossifies endochondrally- 3 centres
5 months-centre for each ethmoidal labrynth
after birth- centre for crista galli and perpendicular plate
2 years- join/unite as one

what bones does the ethmoid articulate with?

chonchae- part of it
superior- frontal bone
inferior-maxilla
posterior- sphenoid

What are alae?

wing like projections that come anteriorly from the crista galli
contribute to foramen caecum