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 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

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

Cavernous sinus

Sup. petrosal sinus

Inf. petrosal sinus Internal jugular vein

Sigmoid sinus

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

CSF drains from lateral ventricle interventricular foramina third ventricle

mesencephalic aqueduct fourth ventricle median and two lateral apertures

subarachnoid space arachnoid granulations superior sagittal sinus vein

Blood vessels of brain and spinal cord

Arteries of brainTwo 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

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, ponsmidbrain) receives the bulk of itsblood supply from the vertebrobasilar system. Exceptfor the labyrynthine branch,all other branches supply thebrain stem and cerebellum

The posterior cerebral has onlya small contribution, its maintarget being the posteriorcerebral hemispheres

Branches of the Basilar Artery

1. Anterior Inferior Cerebellar Arteries (AICA), originates near the lower borderof the Pons just past the union of thevertebral arteries.

Distribution: a. supplies anterior inferior surface andunderlying white matter of cerebellum b. contributes to supply of centralcerebellar nuclei c. also contributes to upper medullaalso contributes to upper medullaand lower pontine areasand lower pontine areas

Branches of the Basilar Artery

2. Pontine arteries, numerous smallerbranches that can be subdivided intoParamedian and Circumferential pontinearteries. The Circumferential can be further subdivided into Long and Shortpontine arteries.

Distribution:

a. paramedian pontine - basal pons b. circumferential pontine - lateral ponsand middle cerebellar peduncle, floorof fourth ventricle and pontine tegmentum

Branches of the Basilar Artery

3. Superior Cerebellar arteries, originatesnear the end of the Basilar artery, close to the Pons-Midbrain junction.

Runs along dorsal surface of cerebellum

Distribution:

a. cerebellar cortex, white matter andcentral nuclei b. Additional contribution to rostralAdditional contribution to rostralpontine tegmentum, superior cerebellarpontine tegmentum, superior cerebellarpeduncle and inferior colliculuspeduncle and inferior colliculus

Branches of the Basilar Artery

4. Posterior cerebral arteries, the terminalbranches of the Basilar artery. Theyappear as a bifurcation of the Basilar, just past the Superior Cerebellar arteriesand the oculomotor nerve.

Curves around the midbrain and reachesthe medial surface of the cerebralhemisphere beneath the splenium of thecorpus callosum

Distribution: a. mainly neocortex and diencephalonb. some contribution to interpeduncularsome contribution to interpeduncularplexusplexus

Branches of the Basilar Artery

5. Labyrynthine arteries, may branchfrom the basilar, but variable in its origin. Supplies the region of the innerear

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

Blockage

Area of oxygendeprives brain

Thrombus

Plaque

Subarachnoid hemorrhage

Microaneurysm

Lenticulostriate arteries

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