The Meninges and Blood Vessels of Brain and Spinal Cord, and the Cerebrospinal Fluid

The Meninges of Brain and Spinal Cord The spinal cord and brain are surrounded by three membranes, the meninges. Named from the outside inward they are the dura mater, arachnoid, and pia mater.

The meninges of spinal cord Spinal dura mater Spinal arachnoid mater Spinal pia mater

Spinal dura mater Characters Above, attached to circumference of foramen magnum Below, becomes thinner at level of S2, invests filum terminale to attach at back of coccyx

Epidural space Subdural space Position: lies between spinal dura mater and periosteum of vertebral canal Contents: a quantity of loose connective tissue, fat, lymphatic vessels and vertebral venous plexus, the spinal nerves on each side pass through the epidural space which is applicable for block anesthesia Subdural space

Spinal arachnoid mater Characters A thin, delicate, tubular membrane loosely investing spinal cord Above, it is continuous with cerebral arachnoid mater

Subarachnoid space Position: lies between pia and arachnoid maters containing cerebrospinal fluid Terminal cistern : the largest part of subarachnoid space extending from termination of spinal cord to level of S2, where it is occupied by nerves of cauda equina, so it is the best site for a lumbar puncture

Lumbar spinal puncture (spinal tap)

Spinal pia mater A delicate vascular membrane that closely invests the spinal cord Denticulate ligament: consist of 21 pairs triangular ligaments extending from spinal cord on each side between anterior and posterior roots of spinal nerves to spinal dura mate; these ligaments help to fix position of spinal cord. Filum terminale: an extension of pia beyond conus medullaris

The Meninges of Brain Cerebral dural mater Cerebral arachnoid mater Cerebral pia mater

Cerebral dural mater Characters A thick and dense inelastic membrane that composed of two layers, an inner or meningeal and outer or endosteal It is in loose contact with calvaria, and most strongly adherent to base of skull

Four septa Cerebral falx Tentorium of cerebellum－in front there is a gap, the tentorial incisure , for passage of midbrain Cerebellar falx Diaphragma sellae

Sinuses of duramater Superior sagittal sinus Inferior sagittal sinus Straight sinus Confluence of sinus

Transverse sinus Sigmoid sinus Superior petrosal sinuses inferior petrosal sinuses

Position: lies on each side of sella turcica Cavernous sinus Position: lies on each side of sella turcica Relations of cavernous sinus: Internal carotid artery and abducent nerve run through the sinus Oculomotor and trochlear nerves and ophthalmic and maxillary divisions of trigeminal nerve lie in the lateral wall of the sinus

Cavernous sinus nerves

The flowing of the blood in dural sinus Sup. sagittal sinus Inf. sagittal sinus Straight sinus Confluence of sinus Transverse sinus Sup. petrosal sinus Sigmoid sinus Cavernous sinus Inf. petrosal sinus Internal jugular vein

Cerebral arachnoid mater Characters: a delicate membrane covering brain loosely, passing over sulci and entering only cerebral longitudinal and transverse fissures

Arachnoid granulations － project into sinuses of dura mater, serve as sites where cerebrospinal fluid diffuses into bloodstream

Subarachnoid cisterns Cerebellomedullary cistern Interpeduncular cistern Pontine cistern Superior cistern

Cerebellomedullary cistern

Cerebral pia mater Closely invests brain surface, in some areas the pia invaginates into ventricles to take part in the formation of choroids plexus

Circulation of cerebrospinal fluid (CSF) Cerebrospinal fluid is a clear colorless fluid, which acts as a transport medium for nutrients and vaster products and provides a protective fluid cushion for the central nervous system. Production: produced by the choroids plexuses within the lateral, third and fourth ventricles

Circulation of cerebrospinal fluid interventricular foramina CSF drains from lateral ventricle third ventricle mesencephalic aqueduct median and two lateral apertures fourth ventricle arachnoid granulations subarachnoid space superior sagittal sinus vein

Blood vessels of brain and spinal cord

Arteries of brain Two sources Internal carotid artery: supplies anterior 2/3 of cerebral hemisphere and parts of diencephalon Vertebral artery: supplies postterior 1/3 of cerebral hemisphere and parts of diencephalon, brain stem and cerebellum

Internal carotid artery Hypophysial a. Ophtalmic a. Anterior cerebral artery Middle cerebral artery Anterior choroidal artery Posterior communicating artery

Anterior cerebral artery Joined the fellow of the opposite side by the anterior communicating artery Cortical branches: supply all medial surface of the cerebral cortex as far back as the parietooccipital sulcus and superior border of the suprolateral surface of the cerebral hemisphere Central branches: supply caudate nucleus, anterior part of lentiform nucleus and anterior limb of internal capsule

Middle cerebral artery Cortical branches: supply most of superolateral surface of cerebral hemisphere and insular lobe Central branches: supply lentiform and caudate nuclei, genu and posterior limb of internal capsule (lenticulostriate artery)

Anterior choroidal artery: passes backward, enters inferior horn of lateral ventricle, and ends in choroid plexus. It supplies lateral geniculate body, posterior limb of internal capsule, middle 3/5 of crus cerebri,and globus pallidus Posterior communicating artery: runs backward to join posterior cerebral artery

Vertebral artery Cranial branche Branches of basilar artery Anterior and posterior spinal arteries Posterior inferior cerebellar artery Branches of basilar artery Anterior inferior cerebral artery Labyrinthine artery Pontine arteries Superior cerebellar artery Posterior cerebral artery

Blood Supply to the Brain Stem The brain stem (medulla, pons midbrain) receives the bulk of its blood supply from the vertebrobasilar system. Except for the labyrynthine branch, all other branches supply the brain stem and cerebellum The posterior cerebral has only a small contribution, its main target being the posterior cerebral hemispheres

Branches of the Basilar Artery 1. Anterior Inferior Cerebellar Arteries (AICA), originates near the lower border of the Pons just past the union of the vertebral arteries. Distribution: a. supplies anterior inferior surface and underlying white matter of cerebellum b. contributes to supply of central cerebellar nuclei c. also contributes to upper medulla and lower pontine areas

Branches of the Basilar Artery 2. Pontine arteries, numerous smaller branches that can be subdivided into Paramedian and Circumferential pontine arteries. The Circumferential can be further subdivided into Long and Short pontine arteries. Distribution: a. paramedian pontine - basal pons b. circumferential pontine - lateral pons and middle cerebellar peduncle, floor of fourth ventricle and pontine tegmentum

Branches of the Basilar Artery 3. Superior Cerebellar arteries, originates near the end of the Basilar artery, close to the Pons-Midbrain junction. Runs along dorsal surface of cerebellum Distribution: a. cerebellar cortex, white matter and central nuclei b. Additional contribution to rostral pontine tegmentum, superior cerebellar peduncle and inferior colliculus

Branches of the Basilar Artery 4. Posterior cerebral arteries, the terminal branches of the Basilar artery. They appear as a bifurcation of the Basilar, just past the Superior Cerebellar arteries and the oculomotor nerve. Curves around the midbrain and reaches the medial surface of the cerebral hemisphere beneath the splenium of the corpus callosum Distribution: a. mainly neocortex and diencephalon b. some contribution to interpeduncular plexus

Branches of the Basilar Artery 5. Labyrynthine arteries, may branch from the basilar, but variable in its origin. Supplies the region of the inner ear

Posterior cerebral artery Cortical branches: supply medial and inferior surfaces of temporal lobe and occipital lobe Central branches: supply dorsal thalamus, medial and lateral geniculate bodies, hypothalamus and subthalamus

Cerebral arterial circle ( circle of Willis ) Formation: formed by anterior communicating artery, both anterior cerebral arteries, internal carotid arteries, posterior communicating arteries, and posterior cerebral arteries Position: lies on sella turcica around optic chiasma, tuber cinereum and mamillary bodies

Area of oxygendeprives brain Blockage Thrombus Plaque

Microaneurysm Lenticulostriate arteries Subarachnoid hemorrhage

Intracerebral hemorhage Arteriovenous malformation

Classification of cerebral vein Superficial cerebral veins Superior cerebral veins Inferior cerebral veins Superficial middle cerebral veins Deep cerebral veins Internal cerebral vein Basal vein (Rosenthal) Great cerebral vein (Of Galen)

Veins of brain Superficial cerebral veins Drain blood from cortex and subcortical medullary substance and empty into adjacent sinuses of dura mater

Veins of brain Deep cerebral veins: drain deeper parts of hemispheres, basal nuclei, internal capsule, diencephalon and choroid plexus, ultimately form great cerebral vein which enter straight sinus