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The ethmoidal labyrinth is divided by multiple obliquely oriented, parallel lamellae. The first lamellae is equivalent to the uncinate process of ethmoid bone, the second corresponds the ethmoid bulla, and the third is the basal lamella, and the fourth is equivalent to the superior nasal concha. [5]
The ethmoidal labyrinth or lateral mass of the ethmoid bone consists of a number of thin-walled cellular cavities, the ethmoid air cells, arranged in three groups, anterior, middle, and posterior, and interposed between two vertical plates of bone; the lateral plate forms part of the orbit, the medial plate forms part of the nasal cavity.
Its sides are smooth, and sometimes bulging due to the presence of a small air sinus in the interior. The crista galli projects upwards from the middle line of the cribriform plate. The long thin posterior border of the crista galli serves for the attachment of the falx cerebri. On either side of the crista galli, the cribriform plate is narrow ...
Paranasal sinuses are a group of four paired air-filled spaces that surround the nasal cavity. [1] The maxillary sinuses are located under the eyes; the frontal sinuses are above the eyes; the ethmoidal sinuses are between the eyes and the sphenoidal sinuses are behind the eyes.
The ethmoid bone (/ ˈ ɛ θ m ɔɪ d /; [1] [2] from Ancient Greek: ἡθμός, romanized: hēthmós, lit. 'sieve') is an unpaired bone in the skull that separates the nasal cavity from the brain. It is located at the roof of the nose, between the two orbits. The cubical bone is lightweight due to a spongy construction.
The medial surface of the labyrinth of ethmoid consists of a thin lamella, which descends from the under surface of the cribriform plate, and ends below in a free, convoluted margin, the middle nasal concha (middle nasal turbinate).
The openings to the posterior ethmoidal sinuses exist under the superior meatus. [3] The sphenoid sinus ostium exists medial to the superior turbinate. [5] The middle conchae are smaller but have the most complex anatomy of the nasal turbinates. They originate from the lateral edge of the cribriform plate of the ethmoid bone.
This space continues laterally as a three-dimensional slit-like space - the ethmoidal infundibulum. This is bounded by the uncinate process, medially, the orbital lamina of ethmoid bone (lamina papyracea), laterally, and the ethmoidal bulla, posterosuperiorly. This concept is easier to understand if one imagine the infundibulum as a prism so ...