The medial joins the lateral pterygoid plate about the sixth month. The sphenoid bone forms important parts of the underside, and outside of the skull; and it forms part of the orbit. The lateral margin of the anterior surface is serrated, and articulates with the lamina papyracea of the ethmoid, completing the posterior ethmoidal cells; the lower margin articulates with the orbital process of the palatine bone, and the upper with the orbital plate of the frontal bone. The lateral surfaces of the body are united with the great wings and the medial pterygoid plates. On each side the palatine bone forms the posterior part of the hard palate, and part of the side wall of the nasal cavity.
The posterior clinoid processes deepen the sella turcica, and give attachment to the tentorium cerebelli. The superior or temporal portion, convex from above downward, concave from before backward, forms a part of the temporal fossa, and gives attachment to the Temporalis; the inferior or infratemporal, smaller in size and concave, enters into the formation of the infratemporal fossa, and, together with the infratemporal crest, affords attachment to the Pterygoideus externus. The sphenoid bone is extremely complex! The underside of the lesser wing forms this small but important part of the back of the orbit. The sphenoid bone primarily consists of a central body containing the pituitary gland and two pairs of wing-shaped extensions projecting laterally. Occasionally, they extend into the basilar part of the occipital nearly as far as the foramen magnum. There are seven bones that form the orbit eye socket , and the sphenoid is one of these bones.
The pterygoid processes, one on either side, descend perpendicularly from the regions where the body and great wings unite. The temporal surface of the greater wing of the sphenoid is the attachment site for the temporalis muscle. Its upper surface is concave, and looks toward the cavity of the sinus; its under surface is convex, and forms part of the roof of the corresponding nasal cavity. The greater wing of the sphenoid forms the front wall and part of the floor of the middle cranial fossa. Behind the dorsum sellæ is a shallow depression, the clivus, which slopes obliquely backward, and is continuous with the groove on the basilar portion of the occipital bone; it supports the upper part of the pons.
The pterygoid canal transmits the greater and deep petrosal nerves from the middle cranial fossa to the pterygoid ganglion in the pterygopalatine fossa. The greater wings curve upwards, laterally and backwards to form a prominent concavity or fossa in the middle of the cranial floor. The central part of the sphenoid includes the clinoid processes, and the pituitary fossa. This serves to moisten the air we breathe through our noses. The sphenoid sinuses are located in the sphenoid bone near the optic nerve and the pituitary gland on the side of the skull. The sphenoidal conchæ are two thin, curved plates, situated at the anterior and lower part of the body of the sphenoid. On either side of the dorsum sellæ is a notch for the passage of the abducent nerve, and below the notch a sharp process, the petrosal process, which articulates with the apex of the petrous portion of the temporal bone, and forms the medial boundary of the foramen lacerum.
In front of the spine the circumference presents a concave, serrated edge, bevelled at the expense of the inner table below, and of the outer table above, for articulation with the temporal squama. Additionally, the , the , and the all travel through this same triangular opening. It contains the sphenoid sinuses and a large depression for the pituitary gland. The mucus secretions produced in the sinuses are continually being swept into the nose by the hair-like structures on the surface of the respiratory membrane lung lining tissues. It transmits the oculomotor, trochlear, and abducent nerves, the three branches of the ophthalmic division of the trigeminal nerve, some filaments from the cavernous plexus of the sympathetic, the orbital branch of the middle meningeal artery, a recurrent branch from the lacrimal artery to the dura mater, and the ophthalmic vein. The pterygoid fossa is a space between the lateral and medial plates of each pterygoid process of the sphenoid bone. Each bone articulates in front with the ethmoid, laterally with the palatine; its pointed posterior extremity is placed above the vomer, and is received between the root of the pterygoid process laterally and the rostrum of the sphenoid medially.
It is also housed in the sella turcica. However, this may affect the quality of your user experience by limiting your possibilities, as some parts of the site may no longer function properly. The inferior surface forms the back part of the roof of the orbit, and the upper boundary of the superior orbital fissure. The lateral surface is pierced by the foramen ovale and foramen spinosum, and features the downward projecting sphenoidal spine. Projecting backward from near the middle of the posterior edge of this plate is an angular process, the processus tubarius, which supports the pharyngeal end of the auditory tube.
By the twenty-fifth year the sphenoid and occipital are completely fused. The sphenoidal sinuses are present as minute cavities at the time of birth Onodi , but do not attain their full size until after puberty. The inferior margin of the orbital surface forms the posterolateral margin of the inferior orbital fissure, while its medial margin forms the inferolateral edge of the superior orbital fissure. The greater part of the bone is ossified in cartilage. The orbital surface of the greater wing of the sphenoid bone faces anteromedially, and forms the posterior part of the lateral wall of the orbit. Behind the chiasmatic groove is an elevation, the tuberculum sellæ; and still more posteriorly, a deep depression, the sella turcica, the deepest part of which lodges the hypophysis cerebri and is known as the fossa hypophyseos.
The lesser wing, which is the highest part of the sphenoid bone, forms the sphenoid ridge, which separates the anterior and middle cranial fossae. The lateral plate of the pterygoid process is the lateral division of the pterygoid process where the pterygoid muscles attach, the lateral pterygoid muscle to the lateral aspect, and the medial pterygoid muscle - to the medial aspect of the lateral plate. The lateral surface of this plate forms part of the pterygoid fossa, the medial surface constitutes the lateral boundary of the choana or posterior aperture of the corresponding nasal cavity. The hypophysial fossa or pituitary fossa is a depression on the superior surface of the sphenoid body occupied by the hypophysis. On the outside the greater wing forms this part of the temporal, and infratemporal fossae, and it also forms this large part of the lateral wall of the orbit. On either side of the crest is an irregular opening leading into the corresponding sphenoidal air sinus.
It enables gliding action of tendon associated with tensor veli palatine muscle and aids in tensing the palate during the act of swallowing. The anterior border is serrated for articulation with the frontal bone. It extends all the way from one side of the skull to the other. Its upper surface is concave, and looks toward the cavity of the sinus; its under surface is convex, and forms part of the roof of the corresponding nasal cavity. The medial pterygoid plate is narrower and longer than the lateral; it curves lateralward at its lower extremity into a hook-like process, the pterygoid hamulus, around which the tendon of the Tensor veli palatini glides. It somewhat resembles a bat with its wings extended, and is divided into a median portion or body, two great and two small wings extending outward from the sides of the body, and two pterygoid processes which project from it below. The greater part of the bone is ossified in cartilage.