The =nasal bones= (Ossa nasalia) are situated in front of the frontal
bones and form the greater part of the roof of the nasal cavity. They
have an elongated triangular outline, wide behind, pointed in front.
Each presents two surfaces, two borders, a base, and an apex.
The =external= or =facial surface= is smooth and is convex transversely;
the profile contour is usually slightly wavy, with a depression about
its middle and a variably prominent area in front.
The =internal= or =nasal surface= is smooth and concave from side to
side. About in its middle it presents the =superior turbinal crest=
(Crista conchalis dorsalis), which is parallel with the inner border,
and has the superior turbinal bone attached to it. Most of this surface
faces into the nasal cavity, but its posterior part enters into the
formation of the frontal sinus; the latter area is marked off by an
oblique ridge.
The =internal border= is straight, and meets the opposite bone at the
=nasal suture=.
The =external border= is irregular. Its anterior third is free and
concurs with the nasal process in forming the =naso-maxillary notch=
(Incisura naso-maxillaris). Behind this it is scaly for articulation
with the end of the nasal process, the maxilla, and the lacrimal,
forming the =naso-maxillary= and =naso-lacrimal sutures=.
The =base= or posterior end is beveled and overlaps the frontal bone,
forming the =naso-frontal suture=.
The =apex= is pointed and thin.
=Development.=—Each nasal bone ossifies in membrane from a single
center. The nasal suture does not close completely even in old age. In
some cases the two plates separate to inclose a small air-space in the
posterior part.