The sphenoid bone is a complex, sphenoid-shaped bone located in the middle of the skull, behind the nose and between the orbits (eye sockets). It forms the central part of the skull base and has numerous important attachments and functions.
Structure
The sphenoid bone is composed of several distinct parts, including the body, greater and lesser wings, pterygoid processes, and optic canal.
- The body of the sphenoid bone is a central, irregularly shaped section that forms the main part of the sphenoid. It is roughly triangular in shape and has numerous foramina (holes) for the passage of nerves and blood vessels. The body of the sphenoid also has a number of important articulations, including the sella turcica, which is a depression that houses the pituitary gland.
- The greater wings of the sphenoid bone are two large, wing-like extensions that project laterally from the body of the sphenoid. They form the lateral walls of the skull base and are involved in the formation of the orbits and the cranial base.
- The lesser wings of the sphenoid bone are two smaller, wing-like extensions that project inferiorly from the body of the sphenoid. They form part of the lateral walls of the nasopharynx (the upper part of the throat behind the nose) and provide attachments for the muscles of the head and neck.
- The pterygoid processes of the sphenoid bone are two projections that extend inferiorly from the body of the sphenoid and form part of the lateral walls of the nasopharynx. They provide attachments for the muscles of the head and neck and also contain the pterygoid fossae, which are shallow depressions that house the pterygoid muscles.
- The optic canal is a small, circular opening in the greater wing of the sphenoid bone that transmits the optic nerve and ophthalmic artery to the orbit.
Location
The sphenoid bone is located in the middle of the skull, behind the nose and between the orbits. It is situated between the frontal, parietal, temporal, and ethmoid bones and forms part of the skull base.
Function
The sphenoid bone has several important functions, including:
- Supporting the brain: The sphenoid bone forms part of the skull base, which supports the brain and protects it from trauma.
- Facilitating movement: The sphenoid bone has numerous articulations with other bones, including the occipital bone, temporal bones, and ethmoid bone. These articulations allow for movement of the skull and help maintain proper balance and alignment.
- Protecting the nerves and blood vessels: The sphenoid bone has numerous foramina, which allow for the passage of nerves and blood vessels. These include the optic canal, which transmits the optic nerve and ophthalmic artery to the orbit, and the foramen ovale, which allows for the passage of the mandibular nerve to the mandible (jawbone).
- Providing attachment points: The sphenoid bone has numerous attachment points for muscles, including the temporalis muscle, which is responsible for moving the jaw, and the pterygoid muscles, which help move the jaw and stabilize the skull.
Clinical significance
The sphenoid bone is involved in several clinical conditions, including:
- Fractures of the sphenoid bone can occur due to trauma or as a result of osteoporosis. Fractures can range from simple, linear fractures to complex, displaced fractures. Treatment depends on the type and severity of the fracture, but may include medications, immobilization, or surgery.
- Pituitary tumors: The pituitary gland, which is located in the sella turcica of the sphenoid bone, can develop tumors. These tumors can press on the optic nerves, causing vision problems, or secrete excess hormones, leading to hormonal imbalances. Treatment may include medications, radiation therapy, or surgery.
- The sphenoid sinuses, which are located within the sphenoid bone, can become infected or inflamed, leading to sphenoid sinusitis. Symptoms include headache, fever, and nasal congestion, and treatment may include antibiotics, decongestants, or nasal irrigation.
- Sphenoid dysplasia is a rare condition in which the sphenoid bone is malformed or underdeveloped.
- Sphenoiditis is an inflammation of the sphenoid bone, which can be caused by infection, trauma, or autoimmune disorders. Symptoms may include headache, fever, and nasal congestion, and treatment may include medications, such as antibiotics or corticosteroids, and surgery.
