A cranial bone is called the sphenoid bone. It is located in the middle region of the skull.
What is the sphenoid bone?
The sphenoid bone is a bone of the cranium that is located relatively deep in the middle section of the skull. The bone also goes by the name Os sphenoidale or Os sphenoides. Together with the occipital bone, the sphenoid bone serves to form the base of the skull as well as the posterior orbital region. The term Os sphenoidale is said to have come about in the Middle Ages through the misspelling of a monk. Thus, Os sphekoidale, the Greek word for “wasp leg,” became Os sphenoidale, the Greek term for “sphenoid bone.” However, the skull bone more closely resembles a wasp because of its wings.
Anatomy and structure
The basic shape of the sphenoid bone is mostly square. Internally, there are two cavities separated by an enclosure (septum). These spaces are called sphenoid sinuses. On the anterior sphenoid bone are the bilateral wings, which in humans are called ala minor. They are relatively small and form part of the posterior orbit. They are traversed by the optic canal. The optic nerve can pass through it. The course of each wing extends into a process called the anterior clinoid process. Attached to the processes is the cerebellar tentorium (tentorium cerebelli), which is part of the hard meninges. Larger than the wings of the anterior sphenoid are the wings of the posterior sphenoid (Ala major). The wings house the foramen ovale. It functions as an exit for the mandibular nerve, which belongs to the main branches of the 5th cranial nerve. The foramen rotundum, on the other hand, houses the maxillary nerve, another branch of the 5th cranial nerve. In the posterior sphenoid wing, the foramen spinosum occurs. Through the foramen, the median meningeal artery can exit toward the cranial cavity. Positioned between the sphenoid wings is the superior orbital fissure, which is a fissure-like opening. From this opening, some cranial nerves run to the orbit. From the wings of the posterior sphenoid bone (Ala magna) is formed the middle cranial fossa, which is also called the fossa cranii media. The middle cranial fossa houses the diencephalon as well as the midbrain. From the posterior cuneiform body is formed a structure that has the shape of a saddle. For this reason, it is also called the Turk’s saddle (sella turcica). The characteristic feature of the turquoise saddle is a central pit. It contains the pituitary gland, also known as the pituitary gland. It is called the hypophysial fossa. The hypophysial fossa is covered by a dura-mater septum whose name is diaphragma sellae. It separates the pituitary gland from the brain. In front of the sella turcica is the sulcus chiasmatis. This is a groove that acts as a junction of the optic nerves. Also part of the sphenoid bone is the sphenoid sinus. It is part of the nasal sinuses.
Function and tasks
Developmentally, the sphenoid bone is composed of two bones, which are the anterior and posterior sphenoid bones. Even before birth, however, the two bones fuse. The sphenoid bone is considered the central bone of the craniosacral system. Thus, it has connections to almost all other bones of the skull, which is due to its unique anatomical structure. There is a direct connection to the hard palate via the wing processes, which are adjacent to the palatine bones. If the sphenoid bone does not align correctly, this can have a negative effect on the palatal structures and, consequently, on the upper dentition and jaw. Of particular importance is the pituitary gland, which rests directly on the sphenoid bone. Via the endocrine system, it has a great influence on numerous physiological processes. A slight rocking motion of the sphenoid bone ensures that warm blood is removed from the pituitary gland. This cooling is exceedingly important, as even small increases in temperature can have a negative effect on the functions of the pituitary gland.
Diseases
Malpositions of the sphenoid bone affect numerous areas of the human body.If there is excessive pressure on the ganglia, which are located between the sphenoid processes and the palatine bone, this has an effect on the nasal mucous membranes because they are innervated by the ganglia, as are the nasal cavities and the nasopharynx. This becomes noticeable through rhinitis or rhinorrhea. Some people then also react more sensitively to allergens they inhale. Disorders of the sphenoid bone not infrequently also affect the pituitary gland. For example, misalignments of the skull can have consequences for the cooling of the pituitary gland. For example, the pituitary gland is located outside the brain because it requires a cooler environment than the brain. But the temporomandibular joint can also be affected by sphenoid problems. The outer wing muscles of the sphenoid bone directly affect the mandible. A dysbalance of the muscles therefore negatively affects the position of the sphenoid bone. If its position changes, this leads to disturbances in the functions and movements of the Os sphenoidale. A possible consequence of malpositions is visual disturbances. Thus, structures of the orbit are partially formed by the Os sphenoidale. In addition, cranial nerves that influence eye movements and visual acuity pass through the sphenoid bone. Among the most common injuries of the sphenoid bone is the skull base fracture. Thus, the sphenoid bone is part of the skull base, which means that it is often damaged due to a corresponding fracture.
