Answer
The sphenoid bone is situated in the floor of the cranium and articulates with the other cranial bones-- ethmoid, temporal, occipital and parietal. It has been described as "butterfly-shaped" but sphenoid comes from a Greek word that means " wedge-shaped."
The important structural parts of the sphenoid bone are the body, the greater wings, and the and lesser wings. The body is the cuboidal central part of the bone. At the point of its articulation with the ethmoid bone, it has two sphenoidal sinuses that open into the nasal cavity. The sella turcica is a saddle-shaped depression on the surface of the body. Three important features of the sella are the tuberculum sellae, the dorsum sellae and the hypophyseal fossa. The tuberculum sellae forms the anterior wall of the sella turcica, and the dorsum sellae forms its posterior wall. The hypophyseal fossa is the deepest part of the sella; it is a depression which contains the pituitary gland ( hypophysis ). the master gland of the endocrine system.
The dura mater stretches over the sella turcica and attaches to the anterior clinoid processes. The pituitary stalk has to pierce the dura to connect the pituitary gland with the brain (hypothalamus).
The greater wings of the sphenoid form part of the lateral surface of the cranium just anterior to the temporal bone. The other set of wings, the lesser wings form the posterior margin o the anterior cranial fossa. they border the orbit posteriorly, and contain the optic canal ; it is through this canal that the important structures of the optic nerve, and ophthalmic artery travel to the orbital cavity.
Work Step by Step
Some important openings in the sphenoid are the superior orbital fissure (posterior wall), the foramen rotundum, foramen ovale, foramen spinosum, foramen lacerum, the choanae, and the sphenoidal sinuses
Superior orbital fissure: this an opening in the posterior wall of the orbit which serves as a passage for three nerves that supply the muscles of the eye--oculomotor, the abducens and the trochlear;
The foramen rotundum connects the middle cranial fossae with the pterygoid-palatine plates.
The foramen ovale is an opening in the base of the greater wing of the sphenoid; it permits passage of
optic ganglion, the mandibular nerve (CN V3), accessory nerve and other structures.
The foramen spinosum also opens in the middle cranial fossa; it permits passage of middle meningeal
artery and vein, and the meningeal branch of the mandibular nerve.
The foramen lacerum: in life, this is a cartilage covered opening at the juncture of sphenoid, temporal
and occipital bones.
The sphenoid sinus one of the four paired paranasal sinuses situated at the back of the nasopharynx, behind the eye. They filter and clean inhaled air.
The final notable features of the sphenoid bone are the pterygoid and palatine structures and the choanae. The choanae ( sing. choana)are openings of the nasal cavity in the inferior surface of the skull, near the nasopharynx and anterior to the basal aspect of the occipital bone. Lateral to each of these posterior nasal apertures exist the medial and lateral pterygoid plates . The pterygoid plates and processes provide sites of attachment for jaw muscles.
