The medial joins the lateral pterygoid plate about the sixth month.Ībout the fourth month, a center appears for each lingula and speedily joins the rest of the bone. Soon after, the centers for the postsphenoid part of the body appear, one on either side of the sella turcica, and become blended together about the middle of fetal life.Įach medial pterygoid plate (except its hamulus) is ossified in membrane, and its center probably appears about the ninth or tenth week the hamulus becomes chondrified during the third month, and almost at once ossifies (Fawcett). The orbital plate and that part of the sphenoid, which is found in the temporal fossa, as well as the lateral pterygoid plate, are ossified in membrane (Fawcett). One makes its appearance in each wing between the foramen rotundum and foramen ovale about the eighth week. The first ossific nuclei are those for the great wings ( alisphenoids). The sphenoidal conchae are each developed from a center that makes its appearance about the fifth month at birth they consist of small triangular laminae, and it is not until the third year that they become hollowed out and coneshaped about the fourth year they fuse with the labyrinths of the ethmoid bone, and between the ninth and twelfth years they unite with the sphenoid bone. There are fourteen centers in all, six for the presphenoid and eight for the postsphenoid.īy about the ninth week of fetal development an ossific center appears for each of the small wings (orbito-sphenoids) just lateral to the optic foramen this is followed by the appearance of two nuclei in the presphenoid part of the body. The greater part of the bone is ossified in cartilage. Until the seventh or eighth month of fetal development, the body of the sphenoid consists of two parts: one in front of the tuberculum sellæ, the presphenoid, with which the small wings are continuous the other, consisting of the sella turcica and dorsum sellae, the postsphenoid, with which are associated the great wings, and pterygoid processes. ĭevelopment Figure 4 : Sphenoid bone at birth, posterior aspect. Medially, terminates in the anterior clinoid process.Posterior surface projects into the Sylvian point.Inferior surface forming upper boundary of superior orbital fissure.Superior surface forming floor of anterior cranial fossa.Tip forming the lateral end of the wing. These are two triangular wings projecting laterally from anterosuperior part of the body. This forms the posterior wall of the orbit Lesser wings This is divided into (by infratemporal crest): This forms the floor of the middle cranial fossa. See also: Greater wing of the sphenoid bone Superior or cerebral surface Sphenoidal sinuses are asymmetrical air sinuses in the body of the sphenoid, closed by sphenoidal conchae. Sphenoidal crest articulates with the perpendicular plate of ethmoid leading to formation of a part of the septum of nose.īasilar part of occipital bone Lateral surface Ĭarotid sulcus lodging cavernous sinus and internal carotid artery Sphenoidal sinuses Vaginal processes of medial pterygoid plate.Superior or cerebral surface Īrticulates with ethmoid bone anteriorly and basilar part of occipital bone posteriorly. The sphenoid articulates with the frontal, parietal, ethmoid, temporal, zygomatic, palatine, vomer, and occipital bones and helps to connect the neurocranium to the facial skeleton.
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