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The sphenethmoid bone forms as three bones: the lesser wings and the anterior part of the base. These two parts of the sphenethmoid may be distinguished as orbitosphenoids and presphenoid, respectively, although there is often some degree of fusion. Only the parasphenoid appears to be entirely absent in mammals.
The sphenoethmoidal recess is a small triangular space superior to the superior nasal meatus of the nasal cavity into which the sphenoidal sinus [1] [2] [3] opens. [4] The sphenoethmoidal recess is situated supero posterior to the superior nasal concha, [3] [2] between the superior nasal concha and the anterior aspect of the body of the sphenoid bone.
The sphenoethmoidal suture is the cranial suture between the sphenoid bone and the ethmoid bone. It is located in the anterior cranial fossa. External links
It is located in the midsagittal line, and articulates with the sphenoid, the ethmoid, the left and right palatine bones, and the left and right maxillary bones. The vomer forms the inferior part of the nasal septum in humans, with the superior part formed by the perpendicular plate of the ethmoid bone . [ 3 ]
Each spehoid sinus is in the body of sphenoid bone, just under the sella turcica. The sphenoid sinuses are separated from each other medially by the septum of sphenoidal sinuses, which is usually asymmetrical. [2]: 500 An opening of sphenoidal sinus forms a passage between each sphenoidal sinus [2]: 500 and the nasal cavity.
The lateral pterygoid plate of the sphenoid (or lateral lamina of pterygoid process) is broad, thin, and everted and forms the lateral part of a horseshoe like process that extends from the inferior aspect of the sphenoid bone, and serves as the origin of the lateral pterygoid muscle, which functions in allowing the mandible to move in a lateral and medial direction, or from side-to-side.
The greater wings of the sphenoid are two strong processes of bone, which arise from the sides of the body, and are curved upward, laterally, and backward; the posterior part of each projects as a triangular process that fits into the angle between the squamous and the petrous part of the temporal bone and presents at its apex a downward-directed process, the spine of sphenoid bone.
The larger bone is the cleithrum. The cleithrum (pl.: cleithra) is a membrane bone which first appears as part of the skeleton in primitive bony fish, where it runs vertically along the scapula. [1] Its name is derived from Greek κλειθρον = "key (lock)", by analogy with "clavicle" from Latin clavicula = "little key".