A bone lying in the centre of the base of the SKULL, and supporting the others like a wedge or keystone.
a bone forming the base of the cranium behind the eyes. It consists of a body, containing air spaces continuous with the nasal cavity (see paranasal sinuses); two wings that form part of the orbits; and two pterygoid processes projecting down from the point where the two wings join the body. See skull.... sphenoid bone
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