Cranial Fossae and Foramina Quiz

Cranial Fossae

• The floor of the cranial cavity is divided into 3 fossae:
  • Anterior Cranial Fossa: Frontal bone, ethmoid bone, sphenoid bone (Lesser wings and body)
  • Middle Cranial Fossa: Temporal bone and sphenoid bone (Greater wings and sella turcica)
  • Posterior Cranial Fossa: Temporal bones, occipital bones, with small contributions from the sphenoid and parietal bones

Cranial Foramina

• Anterior Cranial Fossa Foramina
  • Olfactory foramina: Located on the Cribriform plates of the ethmoid bone, contains CN I (Olfactory nerves)
• Middle Cranial Fossa Foramina
  • Optical canal: Located on the sphenoid bone, contains CN II (Optic Nerve) and Ophthalmic artery
  • Superior orbital fissure: Located between greater and lesser wings of the sphenoid bone, contains CN III (Oculomotor nerve), CN IV (Trochlear nerve), CN V1 (Ophthalmic division of the trigeminal nerve), CN VI (Abducent nerve), and ophthalmic veins
  • Foramen rotundum: Located on the greater wings of the sphenoid bone, contains CN V2 (Maxillary division of trigeminal)
  • Foramen ovale: Located on the greater wings of the sphenoid bone, contains CN V3 (Mandibular division of the trigeminal nerve) and Accessory meningeal artery
  • Foramen spinosum: Located on the greater wings of the sphenoid bone, contains Middle meningeal artery and vein
  • Foramen lacerum: Located at the junction of temporal, sphenoid, and occipital bones, contains Deep petrosal nerve, internal carotid artery, and greater petrosal nerve
• Posterior Cranial Fossa Foramina
  • Internal acoustic meatus: Located on the greater wings of the sphenoid bone, contains CN VII (Facial nerve) and CN VIII (Vestibulocochlear nerve)
  • Jugular foramen: Located at the junction of temporal and occipital bones, contains CN IX (Glossopharyngeal nerve), CN X (Vagus nerve), and CN XI (Accessory nerve)
  • Hypoglossal canal: Located on the occipital bones, contains CN XII (Hypoglossal nerve)
  • Foramen magnum: Located on the occipital bones, contains CN XI (Accessory nerve), meninges, vertebral and spinal arteries, and medulla oblongata

Meninges

• Meninges are layers of tissue that protect and stabilize the brain and spinal cord
• Dura Mater
  • Outermost layer
  • Strongest layer
  • Double-layered membrane
    • Outer endosteal layer (Outer periosteal layer): Functions as the periosteum on the cranial inner surface, adheres tightly to the inner meningeal layer
    • Inner meningeal layer: Separates from the periosteal layer and protrudes into the cranial cavity creating dural folds
  • Dural Venous Sinuses: Spaces formed by the separation of dural layers, where cerebral veins drain
  • Dural folds:
    • Falx cerebri: Sickle-shaped fold between cerebral hemispheres
    • Falx cerebelli: Partially extends between cerebellar hemispheres
    • Tentorium cerebelli: Horizontal fold between the cerebrum and cerebellum
    • Diaphragma sellae: Overlies pituitary fossa, allows infundibulum of the pituitary gland through
  • Dural Venous Sinuses:
    • Superior sagittal sinus: Runs from anterior to posterior, drains veins draining the brain and cerebrospinal fluid
    • Inferior sagittal sinus: Runs from anterior to posterior, drains veins draining the brain and cerebrospinal fluid
    • Straight sinus: Runs from anterior to posterior, drains the cerebral, great cerebral, superior cerebellar veins and the inferior sagittal sinus
    • Confluence of sinuses: Connecting point of Superior sagittal sinus, straight sinus and occipital sinus, drains into the left and right transverse sinuses
    • Transverse sinuses: Extend horizontally along the attached edge of tentorium cerebelli, drains the superior sagittal sinus (right) and straight sinus (left)
    • Sigmoid sinuses: Descend within the posterior cranial fossa, drains cerebral, cerebellar, diploic, and emissary veins
    • Cavernous sinuses: Lies against the lateral aspect of the body of the sphenoid, receives blood from cerebral ophthalmic and emissary veins, has several structures passing through it
• Arachnoid Mater
  • Avascular membrane that lines the meningeal layer of the dura mater
  • Continuous with the pia mater
  • Lies over sulci and gyri
• Pia Mater
  • Thin delicate layer that closely adheres to the brain surface
  • Enters grooves and fissures of the brain

Innervation of Meninges

• Meninges are innervated primarily by the meningeal branches of the Trigeminal nerve and Vagus nerve
• Upper cervical spinal nerves also contribute to meningeal innervation
  • Anterior cranial fossa: Ophthalmic division of the trigeminal nerve, Meningeal branches from the maxillary nerve (CN V2)
  • Middle cranial fossa: Meningeal branches of ophthalmic, maxillary, and mandibular divisions of the trigeminal nerve
  • Posterior cranial fossa: Meningeal branches from the vagus nerve (CN X) and glossopharyngeal nerve (CN IX) supply the inferior surface of the tentorium and dura of the posterior fossa

Test your knowledge on the anatomical features of the cranial cavity, specifically the various fossae and foramina. This quiz covers the anterior, middle, and posterior cranial fossae along with their respective foramina and associated cranial nerves. Perfect for students of anatomy and neuroanatomy.