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Region 4: Cranial Contents Calvaria: skull cap --Composed of three layers *Outer table: compact bone *Diploe: spongy bone containing diploic veins and marrow *Inner table: compact bone --Emissary Foramina for emissary veins: emissary veins connect dural venous sinuses within the cranium with the veins external to it Meninges: coverings of the brain which are exposed when the calvaria is removed --Dura mater (tough mother) *Periosteal layer: fused to bone *Meningeal Layer: the true layer of dura which reduplicates to form four projecting folds a. falx (sickle) cerebri: located b/w cerebral hemispheres b. falx cerebelli: between cerebellar hemispheres c. tentorium cerebelli: separates occipital lobes of cerebrum from cerebellum d. diaphragma (septum) sellae (saddle): forms roof of sella turcica *Dural Venous sinuses: lie b/w layers of dura and receive veins draining the brain to ultimately leave the skull via the interal jugular vein a. superior sagittal sinuses: along superior border of falx cerebri, drains into the confluens of the sinuses, unpaired b. inferior sagital sinus: along the inferior border of the falx cerebri, unpaired c. straight sinus: at junction of falx cerebri and tentorium cerebelli, unpaired, receives the greate cerebral vein of Galen, drains the inferior sagittal sinus, empties into the confluens of the sinuses d. intercavernous sinus: in diaphragma sellae, connects the left and right cavernous sinuses, unpaired e. transverse sinuses: at attachment of the tentorium cerebelli to skull, drains into the sigmoid sinus, paired f. sigmoid sinuses: connect the anterior end of the transverse sinuses with the interal jugular veins, paired g. cavernous sinuses: on each side of the sella tursica, paired h. superior petrosal sinuses: connects the cavernous sinus to the sigmoid sinus, paired i. inferior petrosal sinuses: connect the cavernous sinus to the internal jugular vein, paired *Cavernous Sinus a. lies on either side of the body of the sphenoid bone b. trabeculae from each layer cross the space giving it a cavernous apperance c. Contents of the cavernous sinus --Oculomotor Nerve (CN III) --Trochlear Nerve (CN IV) --Ophthalmic Nerve (CN V1) --Maxillary Nerve (CN V2) --Internal Carotid Artery --Abducens Nerve (CN VI) d. Drains: the superior ophthalmic veins, cerebral veins, and sphenoparietal veins --Subdural Space *space between the arachnoid and dura matter, contains very small amont of fluid --Arachnoid Mater *delicate membrane attached to the pia mater by trabeculae *arachnoid granulations: project into the dural sinuses to return CSF to the blood --Subarachnoid Space *actual space b/w the arachnoid and pia mater *filled with CSF (CSF is formed by choroid plexus in the brain’s ventricles) *communicates with the fourth ventricle of the brain by the median foramen of Magendie and the 2 lateral foramina of Luschka --Pia Mater *clings to the surface of the brain and follows all of its irregularities --Meningeal Arteries and veins: supply the dura and adjacent bone *Middle cranial fossa: the middle meningeal artery passes through the foramen spinosum and it supplies 4/5 of the dura Brain --Divisions a. telencephalon or cerebral hemispheres with the frontal, parietal, temporal, and occipital lobes *the olfactory bulb and tract are attached to the frontal lobe and are associated with the olfactory nerve (CN I) b. Deiencephalon: includes the thalamus, hypothalamus, optic chiasma (CN II), pituitary and pineal glands c. mesencephalon (mid-brain): gives the orging to oculomotor (CN III), and trochlear nerves (CN IV) d. metencephalon: consists of the pons and cerebellum *gives origin to trigeminal nerve (CN V), abducens (CN VI), facial (CN VII), and vestibulocochlear (CN VIII) nerves e. myelencephalon (medulla): origins of the glossopharyngeal (CN IX), vagus (CN X), and the cranial portion of accessory (CN XI) nerves and the hypoglossal nerve (CN XII) is immediately anterior to the inferior olive --The brain itself is insensitive to pain. --Blood Supply to the Brain a. vertebral arteries: enter the cranial cavity through the forament magnum, vessels from both sides join to form the basilar artery on front of the pons *Branches: --posterior spinal arteries (descend to supply the dorsal side of the spinal cord) --anterior spinal arteries (join and descend to supply the ventral surface of the spinal cord as a single artery) --posterior inferior cerebellar arteries (supply the cerebellum) b. Basilar artery: gives off several pairs of arteries before dividing into its larger paired terminal branches, the posterior cerebral arteries *Branches: --anterior inferior cerebellar artery --superior cerebellar artery --posterior cerebral artery (terminal branches of the basilar artery, communicates with the ipsilateral internal carotid artery by way of the posterior communicating artery) c. Internal Carotid artery: enters cranial cavity by passing through the carotid canal and then lying superior to the forament lacerum then passes through cavernous sinus, pierces the dura as it gives off the ophthalmic a. *Branches: --ophthalmic artery (enters the orbit through the optic foramen with the optic nerve) --posterior communicating artery (communicates with posterior cerebral artery) --anterior cerebral artery (small of 2 terminal branches, communicating with each other by way of unpaired anterior communicating artery) --middle cerebral artery: largest of the 2 terminal branches d. Cerebral Circle of Willis *anterior and posterior communicating arteries indirectly link up the basilar artery with the interal carotid arteries of both sides *arteries that make up the circle of Willis --posterior cerebral arteries --posterior communicating arteries --internal carotid arteries --middle cerebral arteries --anterior cerebral arteries --anterior communicating artery