2024 Meninges and Cranial Foramina YBOD200 PDF

Cranial Foramina and Meninges YBOD200 Ms AT Sebelebele  Objectives Identify and describe in detail the foramina of the skull and their contents if any Identify and describe in detail the structure and function of the meninges o Pia m...

Cranial Foramina and Meninges YBOD200 Ms AT Sebelebele  Objectives Identify and describe in detail the foramina of the skull and their contents if any Identify and describe in detail the structure and function of the meninges o Pia mater o Arachnoid mater o Dura mater o Subarachnoid spaces and cisterns Review the structure of the dural partitions: o Falx cerebri o Tentorium cerebelli o Falx cerebelli o Diaphragma sellae Discuss the innervation of the meninges  Cranial Fossae Cranial Foramina are found within Fossae at the base of the skull which forms the floor of the cranial cavity Floor of 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 Nerves CN I = Olfactory nerve Only CN II = Optic nerve One CN III = Oculomotor nerve Of CN IV = Trochlear nerve The CN V = Trigeminal nerve Two CN VI = Abducens nerve Athletes CN VII = Facial nerve Felt CN VIII = Vestibulochochlear nerve Very CN IX = Glossopharyngeal nerve Good, CN X = Vagus nerve Victorious, CN XI = Accessory nerve And CN XII = Hypoglossal nerve Happy CRANIAL FORAMINA  Anterior Cranial Fossa Foramina Consist of Olfactory foramina Located on the Cribriform plates of the ethmoid bone Contents: CN I (Olfactory nerves)  Middle Cranial Fossa Foramina Consist of : Optical canal Located on the sphenoid bone Contents: CN II (Optic nerve) and Ophthalmic artery Superior orbital fissure Located between greater and lesser wings of the sphenoid bone Contents: CN III (Oculomotor nerve); CN IV (Trochlear nerve); CN V1 (Ophthalmic division of the trigeminal nerve); CN VI abducent nerve; ophthalmic veins  Middle Cranial Fossa Foramina Consist of : Foramen rotundum Located on the greater wings of the sphenoid bone Contents: CN V2 (Maxillary division of trigeminal Foramen ovale Located on the greater wings of the sphenoid bone Contents: CN V3 (Mandibular division of the trigeminal nerve) and Accessory meningeal artery  Middle Cranial Fossa Foramina Consist of : Foramen spinosum Located on the greater wings of the sphenoid bone Contents: Middle meningeal artery and vein Foramen lacerum Located at the junction of temporal, sphenoid, and occipital bones Contents: Deep petrosal nerve, internal carotid artery, and greater petrosal nerve.  Posterior Cranial Fossa Foramina Consist of : Internal acoustic meatus Located on the greater wings of the sphenoid bone Contents: CN VII ( Facial nerve) and CN VIII (Vestibulocochlear nerve) Jugular foramen Located at the junction of temporal and occipital bones Contents: CN IX (Glossopharyngeal nerve), CN X (Vagus nerve) and CN XI ( Accessory nerve)  Posterior Cranial Fossa Foramina Consist of : Hypoglossal canal Located on the occipital bones Contents: CN XII (Hypoglossal nerve) Foramen magnum Located on the occipital bones Contents: CN XI (Accessory nerve), meninges, vertebral and spinal arteries, and medulla oblongata MENINGES  Meninges Meninges stabilize the shape and position of the central nervous system Cranial fossa and brain covered by meninges Three layers of meninges (Superficial to deep) Dura mater is the outermost layer Outer periosteal layer Inner meningeal layer Arachnoid mater is the intermediate layer Pia mater is the innermost layer Dura Mater May also be referred to as pachymeninx Outermost layer of the three Strongest layer protecting the brain and spinal cord Double-layered membrane Outer endosteal layer Inner meningeal layer  Dura Mater Outer endosteal layer ( Outer periosteal layer) Serves as the periosteum on the cranial inner surface It adheres tightly to the inner meningeal layer There is no clear boundary Except at the sinuses Two spaces exist around the dura mater 1. Epidural (Extradural) space lies between the cranium and periosteal layer 2. Subdural space between inner meningeal layer and arachnoid mater  Dura Mater Inner meningeal layer Separates from the periosteal layer and protrudes into the cranial cavity Separation creates double-layered dural folds May also refer to them as dural reflections/septa Dural Venous Sinuses Located where dural layers separate They are spaces into which cerebral veins drain Location of each sinus determined by dural fold attachment  Dural Venous Sinus 4 types of 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 Sinus Superior sagittal sinus Located on the attached edge of the falx cerebri Runs from anterior to posterior (Along the midsagittal plane) Anteriorly related to the foramen caecum Courses along the attached edge of the falx cerebri Posteriorly drains into the confluence of sinuses Drains veins draining the brain and cerebrospinal fluid  Dural Venous Sinuses Inferior sagittal sinus Located on the free edge of the falx cerebri Runs from anterior to posterior (Along the midsagittal plane) Courses along free edge of the falx cerebri Posteriorly drains into the straight sinus Drains veins draining the brain and cerebrospinal fluid  Dural Venous Sinuses Straight sinus Located at the junction of the falx cerebri and tentorium cerebelli Runs from anterior to posterior (Along midsagittal plane) Drains the cerebral, great cerebral, superior cerebellar veins and the inferior sagittal sinus Drains into the confluence of sinuses  Dural Venous Sinuses Confluence of sinuses Connecting point of Superior sagittal sinus, straight sinus and occipital sinus Located near the internal occipital protuberance Drains into the left and right transverse sinuses  Dural Venous Sinus Transverse sinuses Extend horizontally along the attached edge of tentorium cerebelli - From posterior to anterior Right transverse sinus usually drains the superior sagittal sinus  Dural Venous Sinus Left transverse sinus usually drains the straight sinus Sinuses also receive blood from the superior petrosal sinus Leave the surface of the occipital bone to become the sigmoid sinuses  Dural Venous Sinus Sigmoid sinuses Descends within the posterior cranial fossa - Towards the jugular foramen Sinus drains cerebral, cerebellar, diploic, and emissary veins Sinus drains into the internal jugular vein  Dural Venous Sinuses Cavernous sinuses Lies against the lateral aspect of the body of the sphenoid On either side of the sella turcica Receives blood from cerebral ophthalmic and emissary veins Left and right sinuses are connected by intercavernous sinuses (Anteriorly and posteriorly) Has several structures passing through it Structures passing through each sinus: Internal carotid artery and the abducent nerve Structures in the lateral wall of each sinus: Oculomotor, trochlear nerve, ophthalmic nerve, and maxillary nerve  Meninges: Arachnoid Mater Avascular membrane that lines the meningeal layer of the dura mater Thin process extend from it into the subarachnoid space It is continuous with the pia mater Lies over sulci and gyri Does not lie within the sulci  Meninges: Pia Mater Thin delicate layer that closely adheres to the brain surface Enters grooves and fissures of the brain  Innervation of Meninges Meningeal innervation is mainly from the meningeal branches of both the Trigeminal nerve and Vagus nerve Upper cervical spinal nerves contribute to meningeal innervation to a lesser degree Anterior cranial fossa Ophthalmic division of the trigeminal nerve Meningeal branches from the maxillary nerve (CN V2)  Innervation of Meninges 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 Always remember, You’ve got this!! 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