الفهرس 
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Abstract
The ethmoid bone is one of the most complicated structures in the
human body, and its anatomy is very complex.
A brief review of the available literatures on this structure in man
and dog is given.
”’:<’t- o~mprehensrive descrniption 0 f’ cnsta gaIII’,
perpen icular plate and ethmoidal labyrinth is given.
cribriform plate,
The present work gives a precise study on the morphological
features of the ethmoid bone in comparative study with that of the dog.
The morphological study of both man’s and dog’s ethmoid bone was
done using ten fresh dried skulls of human being, and other ten fresh dried
SkullS;:t~
The sense of smell in carnivora especially dogs affords an adequate
ea for the purposes of olfaction in comparison to man. This was proved
by ~ study in the following points which also show the aspects of
difference of the ethmoid bone in man and dog :
_Projection of the nose of the dog anteriorly.
_Great length of the nasal cavity in the dog.
_ The ethmoid bone of man lies between the two orbits while in the dog iY ~
situated between the maxillary bones.
_ The ethmoid bone in man is cuboidal III shape, while in the dog it is
elongated.- The crista galli
low crest. is well developed in man while in dog it ifdimemary
_ The perpendicular plate is triangular in shape and lies more anteriorly in
dog, while in man it is rectangular in shape and lies posteriorly.
_ The cribriform plate in man extends from the frontal bone anteriorly to
the sphenoid bone posteriorly, while in the dog it extends from the i:mer
plate of the medial chamber of the frontal sinus dorsally, to the inner
plate of the presphenoid bone ventrally.
_ The forward protrusion of the nose of the dog pulling with it the midline
of the cribriform plate causing it to be concave in shape, pulling also the
frontal bone antro-ventrally and the sphenoid bone antro-dorsally.
Hence the frontal sinus is expanded and formed from medial and lateral
chambers and the sphenoid bone consists of pre and basisphenoid.
_ The cribriform plate in man is elongated while in the dog it is deep and
concave. ~
_ The lamina cribrosa in man is narrow with few foramina iicontrary with
that of the dog where it is broad, wide, with great surface are a and
contains numerous perforations .
_ The ethmoidal labyrinth in man consists of ethmoidal air cells while in
the dog it consists of endo and ectoturbinates. Each turbinate IS
convoluted to provide a wide surface area for the olfactory mucosa,
_ The turbinate bones extend into the cavity of the frontal sinus and the
presphenoid bone in the dOg~ in turn increas~~the available surface
with olfactory extensions.