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Blood supply to the brain The cerebrospinal fluid (CSF) Mark Kozsurek, M.D., Ph.D. [email protected] 19/09/2011, EM II. Extremly high demand for oxygen and nutrients: human brain represents 2% of the body weight, but receives 15% of the cardiac output, 20% of total body oxygen consumption and 25% of total body glucose utilization. Cerebrovascular deseases and stroke are among the major causes of death. Arteries supplying the brain 2 sources of blood: ICA and VA Vertebro-basilar system atlas laterally axis upward backward C6 CTA: CT angiography C6 C7 C5 C4 cavernous sinus (C3) C2 C7 C6 C5 cavernous sinus carotid canal C4 C3 ant. clinoid proc. C2 C1 foramen lacerum X-ray angiogram ant. cerebral ant. communicating middle cerebral striate post. communicating ophthalmic ant. choroidal inf. hypophyseal sup. hypophyseal caroticotympanic Circle of Willis Circle of Willis Circle of Willis pituitary stalk optic chiasm oculomotor n. mamillary bodies abducens n. 1. Circle of Willis encloses the optic chiasm, pituitary stalk and mamillary bodies. 2. Oculomotor nerve exits between the post. cerebral and sup. cerebellar arteries. 3. Vertebral arteries of the two sides unite to form the basilar artery at the ponto-medullary junction. The root of the abducens nerve and initial segment of the ant. inf. cerebellar artery can also be found here. A2 A1 pericallosal br. A3 A2 A1 ant. communicating recurrent artery of Heubner Heubner’s pericallosal br. A3 A2 A1 ant. communicating recurrent artery of Heubner M3 M2 M3 M2 M3 M3 ACA PCA MCA PCA anterior cerebral middle cerebral posterior cerebral oculomotor n. PCA sca BA aica VA sca: superior cerebellar pica aica: anterior inferior cerebellar pica: posterior inferior cerebellar Veins drainig the brain SUPERFICIAL VEINS superior cerebral veins superficial middle cerebral vein inferior cerebral veins Similarly, there are superior and inferior celebellar veins for the cerebellum. Superior cerebral veins open into the superior sagittal sinus or into the adjacent lateral lacunae. 1. 2. 3. 4. Inferior cerebral veins drain mainly into the sphenoparietal (1), cavernous (2), superior petrous (3), and transverse (4) sinuses. superior sagittal sinus TROLARD’S VEIN LABBE’S VEIN cavernous sinus transverse sinus DEEP VEINS ant. cerebral deep middle cerebral basal (Rosenthal) great cerebral (Galen) of septum pellucidum thalamostriate int. cerebral * choroid great cerebral v. of septum pell. great cerebral vein Almost the total volume of veinous blood collected from the brain leaves the skull through the jugular foramen and the internal jugular vein. If the jugular foramen and/or the internal jugular vein is getting occluded, blodd may escape through the diploic and emissary veins connecting the dural sinuses with the veins of the scalp skin. Diploic veins (frontal, anterior and posterior temporal, occipital): form a network between the external and internal compact bony layers of the skull and connect dural sinuses with the external veins. emissary diploic Emissary veins (occipital, parietal, condylar, mastoid): pearce the skull directly and connect dural sinuses with external veins. Blood-brain barrier (BBB) The extracellular fluid of the CNS is separated from the blood by the BBB ensuring strictly controlled and mainly carrier protein assisted transport of macromolecules. Is formed by endothelial cells attached to one other by tight junctions, basement membrane, astrocytic endfeet. Protects the CNS from possibly toxic agents but makes development of medicines acting on the CNS difficult (e.g. antibiotics in infections). Life outside the BBB: the circumventricular organs „Circumventricular” = around the ventricles Incomplet or missing BBB Highly capillarized structure Secretion of neurohormons or detection of hormons, glucose, ions, etc. Subfornical organ sensory fluid regulation Organum vasculosum sensory, secretory detects peptides, fluid regulation Median eminence secretory regulates the anterior pituitary through the release of neurohormones Neurohypophysis secretory store and secretes the hormones oxytocin and ADH into the blood, but does not synthesize either hormone Subcommissural organ secretory secretes certain proteins into the cerebrospinal fluid, its specific function is as yet unknown. Pineal gland secretory stimulated by darkness to secrete melatonin and is associated with circadian rhythms Area postrema sensory the vomiting centre of the brain (can detect noxious substances in the blood and stimulate vomiting in order to rid the body of these toxic chemicals) The cerebrospinal fluid (CSF) Provides mechanical protection for the brain and the spinal cord. When floating in the CSF brain weights only 50g (!) according to the Archimedes’ principle. internal and external CSF spaces internal = ventricles external = subarachnoidal space Surface of a choroid plexus post. choroidal from PCA ant. choroidal from ICA or MCA choroidal a. of the 4th ventricle from pica median aperture of Magendi cerebellomedullary (or great) cystern lateral aperture of Luschka lateral pontine (or pontocerebellar) cystern Site of CSF resorption: arachnoid granulations in the superior sagittal sinus and lateral lacunae. Thank You !!!