Blood supply to the brain The cerebrospinal fluid (CSF) Mark Kozsurek, M.D., Ph.D. mark@kozsurek.hu 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 CTA: CT angiography atlas axis laterally upward backward C6

C6 C5 C7 C4 (C3) cavernous sinus C2

C1 C2 C3 C4 C5 C6 C7 ant. clinoid proc. cavernous sinus foramen lacerum carotid canal X-ray angiogram

ant. cerebral middle cerebral striate ant. communicating 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. abducens n. pituitary stalk optic chiasm mamillary bodies

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

parietooccipital sulcus callosomarginal br. pericallosal br. A3 A2 A1 ant. communicating recurrent artery of Heubner

Heubner’s

parietooccipital sulcus callosomarginal br. pericallosal br. A3 A2 A1 ant. communicating recurrent artery of Heubner

M3 M3 M2 M2 M3 M3

parietooccipital sulcus ACA PCA MCA

PCA

anterior cerebral middle cerebral posterior cerebral

oculomotor n. PCA sca BA aica VA pica sca: superior cerebellar aica: anterior inferior cerebellar pica: posterior inferior cerebellar

Veins drainig the brain

superficial middle cerebral vein superior cerebral veins SUPERFICIAL 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. Inferior cerebral veins drain mainly into the sphenoparietal (1), cavernous (2), superior petrous (3), and transverse (4) sinuses. 2. 3. 4.

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

ant. cerebral deep middle cer. v. of septum pell. choroid thalamostriate internal cerebral basal 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).

the circumventricular organs 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 store and secretes the hormones oxytocin and ADH into the blood, but does not synthesize either hormone Subcommissural organ secretes certain proteins into the cerebrospinal fluid, its specific function is as yet unknown. Pineal gland stimulated by darkness to secrete melatonin and is associated with circadian rhythms Area postrema 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

ant. choroidal from ICA or MCA post. choroidal from PCA choroidal a. of the 4th ventricle from pica

(or pontocerebellar) cystern median aperture of Magendi lateral aperture of Luschka cerebellomedullary (or great) cystern lateral pontine (or pontocerebellar) cystern

Site of CSF resorption: arachnoid granulations in the superior sagittal sinus and lateral lacunae.

Thank You !!!