Sphenoid Bone Anatomy PDF

# The Sphenoid Bone ## The Sphenoid Bone - Anatomy ### **Overview** - The sphenoid bone is a complex, butterfly-shaped bone that forms the base of the skull. - It articulates with all other cranial bones except the mandible. - It contains several important cavities and foramina that transmit ne...

# The Sphenoid Bone ## The Sphenoid Bone - Anatomy ### **Overview** - The sphenoid bone is a complex, butterfly-shaped bone that forms the base of the skull. - It articulates with all other cranial bones except the mandible. - It contains several important cavities and foramina that transmit nerves, blood vessels, and other structures. ### **Key Features** #### **Body of the Sphenoid Bone** - Located in the center of the bone. - Contains the sphenoidal sinuses (air-filled cavities). #### **Greater Wings** - Extend laterally from the body of the bone. - Form part of the floor of the middle cranial fossa, temporal fossa, and orbit. #### **Lesser Wings** - Project anteriorly from the body of the bone. - Form part of the floor of the anterior cranial fossa and orbit #### **Pterygoid Processes** - Two downward projections from the body of the bone. - They support muscles of mastication and provide attachment points for the soft palate. ### **Foramina** - **Foramen Rotundum:** Transmits the maxillary nerve (V2). - **Foramen Ovale:** Transmits the mandibular nerve (V3), accessory meningeal artery, and emissary vein. - **Foramen Spinosum:** Transmits the middle meningeal artery and vein. - **Superior Orbital Fissure** : Transmits the oculomotor nerve (III), the trochlear nerve (IV), the abducent nerve (VI), the ophthalmic nerve (V1), and the superior ophthalmic vein. - **Foramen Opticum:** Transmits the optic nerve (II) and ophthalmic artery. - **Foramen Lacerum:** Transmits cranial nerves (some branches of V and IX), the internal carotid artery (ICA) and sympathetic nerves. - **Foramen Magnum:** Largest foramen in the skull, allowing passage of the spinal cord, spinal arteries, and vertebral arteries. ### **Surfaces** #### **Superior or Cerebral Surface** - Forms part of the floor of the middle cranial fossa. - Contains the following features: - **Sella Turcica:** A saddle-shaped depression that houses the pituitary gland. - **Dorsum Sellae:** Posterior wall of sella turcica. - **Tuberculum Sellae:** A small elevation at the anterior part of the sella turcica. - **Hypophyseal Fossa:** Houses the pituitary gland. #### **Anterior or Orbital Surface** - Forms part of the roof of the orbit. - **Optic canal:** Transmits the optic nerve and ophthalmic artery. - **Superior Orbital Fissure:** Transmits cranial nerves III, IV, VI, and V1. #### **Lateral or Temporal Surface** - Forms part of the floor of the middle cranial fossa. - **Foramen ovale:** Transmits the mandibular nerve (V3), accessory meningeal artery, and emissary vein. - **Foramen spinosum:** Transmits the middle meningeal artery and vein. #### **Inferior or Spheno-Palatine Surface** - Forms part of the roof of the pharynx. - **Sphenopalatine foramen:** Transmits the sphenopalatine artery and nerve, and nasopalatine nerve. - **Pterygoid processes:** Support muscles of mastication and provide attachment points for the soft palate. ### **Muscles** - **Lateral Pterygoid:** Assists with protraction of the mandible and opening of the mouth. - **Medial Pterygoid:** Assists with elevation of the mandible. - **Tensor Veli Palatini:** Stretches the soft palate and widens the eustachian tube. - **Tensor Tympani:** Tenses the tympanic membrane within the ear. ## **Clinical Significance** - **Fractures** - Usually occur in conjunction with other skull fractures. - May damage structures passing through foramina, leading to neurological deficits. - **Tumors** - Sphenoid bone tumors are rare, but can compress critical structures such as optic nerve or brain stem.