Lecture 2 - Interior Of The Skull And Dural Sinuses PDF

Interior of the Skull-CONTENTS ¨ The cranial cavity contains: 1. The brain and its meninges 2. Cranial nerves 3. Arteries and veins 4. Venous sinuses Cranial Cavity ¨ The interior of the skull is divided into three fossae: • Anterior Cranial Fossa • Middle Cranial Fossa • Posterior Cranial Fossa...

Interior of the Skull-CONTENTS ¨ The cranial cavity contains: 1. The brain and its meninges 2. Cranial nerves 3. Arteries and veins 4. Venous sinuses Cranial Cavity ¨ The interior of the skull is divided into three fossae: • Anterior Cranial Fossa • Middle Cranial Fossa • Posterior Cranial Fossa CRANIAL FOSSAE Anterior Cranial Fossa ¨ It contains: • Frontal lobes of the brain • Crista galli for attachment of the falx cerebrum • Cribiform plate for the olfactory nerve • Foramen cecum for emissary veins from the nasal mucosa to the dural sinuses of the brain (superior sagittal sinus) Middle Cranial Fossa ¨ It contains: • Temporal lobes of the brain • Optic canal (CN II, ophthalmic artery) • Superior orbital fissure (CN III, CN IV, V1, CN VI, superior ophthalmic vein) • Foramen rotundum (V2) • Foramen ovale (V3) • Foramen spinosum (middle meningeal artery and vein) • Foramen lacerum (fat) • Carotid canal (ICA, internal carotid nerve plexus) • Sella turcica (pituitary gland) • Groove for the middle meningeal artery (temporal bone opposite the pterion) Posterior Cranial Fossa ¨ It contains: • • • • Cerebellum Pons and medulla oblongata Tentorium cerebelli Foramen magnum (medulla oblongata, vertebral artery, and meningeal arteries) • Hypoglossal canal (CNXII) • Internal auditory meatus (CN VII, CN VIII) • Condylar canal and groove for the transverse sinus CRISTA GALLI FORAMEN CECUM CRIBIFORM PLATE OPTIC CANAL SUPERIOIR ORBITAL FISSURE FORAMEN ROTUNDUM SELLA TURCICA FORAMEN OVALE FORAMEN LACERUM FORAMEN SPINOSUM FORAMEN MAGNUM INTERNAL AUDITORY MEATUS JUGULAR FORAMEN HYPOGLOSSAL CANAL GROOVE FOR TRANSVERSE SINUS DURAL VENOUS SINUSES Dural Venous Sinuses ¨ ¨ ¨ These are venous channels located between the dura and the internal periostum lining of the skull. They contain no valves or muscles in their walls, and they drain the blood from the orbit, scalp, nose, brain, and pelvic region. The following veins drain into the dural venous sinuses: 1. 2. 3. 4. Vertebral venous plexus from the pelvis Emissary veins of the scalp Emissary veins of the nasal mucosa Angular vein via the superior ophthalmic vein from the face and nose Superior Sagittal Sinus ¨ It lies in the median plane, along the borders of the falx cerebri. ¨ It receives blood from the nasal cavity, scalp, meningeal vein and superior cerebral vein. The occipital sinus also drains into it. ¨ It continues with the transverse (right and left) sinuses. Inferior Sagittal Sinus ¨ Much smaller than the superior. ¨ It occupies the posterior two-thirds of the free edge of the falx cerebri. ¨ Joins the great cerebral vein to form the straight sinus, which empties in the confluence of sinuses. ¨ The confluence of sinuses is located at the internal occipital protuberance. Transverse Sinus ¨Begins at the internal occipital protuberance and it becomes the sigmoid sinus, which after exiting the jugular foramen, it becomes the internal jugular vein. Superior/Inferior Petrosal Sinuses ¨ Superior Petrosal Sinus: – It drains the cavernous sinus into the transverse sinus. ¨ Inferior Petrosal Sinus: – Exits the jugular foramen, and then it drains into the jugular vein. – It also drains the cavernous sinus. Cavernous Sinus TQ ¨ It is situated in the middle cranial fossa; lateral to the sphenoidal air cells and hypophyseal fossa. ¨ The internal carotid artery and CN VI run through the sinus (or horizontally), and CN III, IV, V1 and V2 run lateral to it (or vertically from superior to inferior). ¨ The superior and inferior ophthalmic veins, and the central vein of the retina drain into the cavernous sinus. OPTIC CANAL ICA CN III ICA CN VI CN V1 CN V2 ¨ Cavernous sinus problems may result from simple thrombosis, thrombophlebitis, maxillary sinus infections, arteriovenous fistula with the ICA, aneurysm of ICA, tumors, and mucormycosis in AIDS ¨ Cranial nerves III, IV, and VI are affected – Paresis of muscles supplied by these nerves results MIDDLE CEREBRAL VEIN STRAIGHT SINUS FALX CEREBRUM SUPERIOR SAGITTAL SINUS INFERIOR SAGITTAL SINUS OPHTHALMIC VEIN CONFLUENCE OF SINUSES SIGMOID SINUS CAVERNOUS SINUS OCCIPITAL SINUS INFERIOR JUGULAR VEIN SUPERIOR PETROSAL SINUS INFERIOR PETROSAL SINUS Vertebral Artery/Vertebral Vein ¨ VERTEBRAL ARTERY: – It is branch of the subclavian artery. – It passes through the transverse foramina of C6 to C1 to enter the foramen magnun of the skull. ¨ VERTEBRAL VEIN: – It begins inside the skull and passes through the foramina of C1 to C7 to drain into the subcalvian vein. ¨ Which of the following conditions results in ptosis? A. Bell’s palsy B. Fracture of the superior orbital fissure with compression to its contents CNIII, CN IV, CN V1, CN VI, superior ophthalmic vein C. Sympathetic chain lesions D. Horner’s syndrome E. More than one is correct