Sphenoid

Sphenoid bone

The sphenoid bone is an unpaired bone of the neurocranium. It is situated in the middle of the skull towards the front, in front of the temporal bone and basilar part of the occipital bone. The sphenoid bone is one of the seven bones that articulate to form the orbit. Its shape somewhat resembles that of a butterfly or bat with its wings extended.

Structure

The sphenoid bone consists of a central part, the body, and six distinct processes with two arising from the sides, the greater and lesser wings, and four from its upper surface, the pterygoid processes.

Body

The body, more or less cubical in shape, is hollowed into two cavities, the sphenoidal sinuses, which are separated from each other by a septum.

Greater wings

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.

Lesser wings

The lesser wings of the sphenoid are two thin triangular plates, which arise from the upper and anterior parts of the body, and, projecting lateralward, end in sharp points.

Pterygoid processes

The pterygoid processes, one on either side, descend perpendicularly from the regions where the body and the greater wings unite.

Function

The sphenoid bone assists with the formation of the base and the sides of the skull, and the floors and walls of the orbits. It is also an attachment site for the muscles of mastication.

Clinical significance

Due to its location, fractures of the sphenoid bone may damage the cranial nerves, leading to loss of vision, movement, or sensation. Infections may also spread from the nasopharynx to the sphenoid bone, leading to sphenoiditis.

See also

• Cranial bones
• Human skull
• Sphenoidal sinuses

References

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