ethmocranial (ethmokranial)

[ ethmofrontal (eth-mō-frontal), a. [ II. n. A bone of the cranium, situated in the middle line of the skull, in advance of the sphenoid, above the basicranial axis, transmitting the filaments of the olfactory nerve, and constituting the bony skeleton of the organ of smell: so called because, in the human subject and mammal i a generally, it has a cribriform plate perforated with numerous holes for the pa age of the olfactory nerves. The human ethmoid is comparatively small, of a cubical figure, with its cribriform plate horizontal. It consists of a median perpendicular plate or mes ethmoid, and of the horizontal or cribriform plate, from which latter the main body of the bone depends on either side, forming the so-called lateral ma es, or ethmoturbinals. The texture of these is extremely light and spongy, full of large cavities con necting with the frontal and sphenoidal sinuses, and lined with mucous membrane, the Schneiderian membrane, upon which the olfactory nerves ramify after leaving the cranium through the in the cribriform plate. (See cut under nasal.) The so-called os planum of the ethmoid is simply the exterior surface of these lateral ma es, which contributes to the inner wall of the orbit of the eye. The lateral ma es are each partially divided into two, called the superior and middle turbinate bones, or scroll-bones (the inferior turbinate being a different bone), which respectively overlie the corresponding nasal meatuses. (See cut under mouth.) The ethmoid is wedged into the ethmofrontal notch of the frontal bone, and also articulates with the vomer, sphenoid, sphenoturbinals, nasals, maxillaries, lacrymals, palatals, and maxilloturbinals. It is developed from three o ific centers, one for the perpendicular plate, and one for each lateral ma . In other animals the ethmoid exhibits a wide range of variation in size, shape, and connections, and below mammals loses much or all of the particular characters it presents in man. (See cut under Esox.) It is relatively larger and more complicated in mammals of keen scent, as car nivores and ruminants.