Protection & Supply Apparatusesfor Central Nervous System

Meninges of Brain and Spinal CordCerebral Spinal Fluid (CSF) Circulation Blood Vessels of Brain and Spinal Cord

Guo Ling , MD, PhD

Department of Anatomy

Meninges of Brain and Spinal Cord

Concept ： they are the connective tissue membranes covering the brain and the spinal cord (three layers)Meninges of brain & spinal

cord(out inward)

Spinal meninges

dura materarachnoidpia mater

cerebral dura mater

arachnoidcerebral pia

mater

spinal duramater

arachnoidspinal pia mater

Cerebral meninges

Cerebral pia mater

Arachnoid

Cerebral dura mater

Spinal pia mater

Spinal dura

arachnoid

Spaces Formed by Meninges & Relative Contents

1.Epidural Space Location: lying between spinal dura and internal periosteum of the vertebral canal. Contents: roots of spinal nerve,venous plexuses,rich fat Feature: minus atmospheric pressure.

2.Subarachnoid Space

Location: lying between arachnoid

and pia mater.

Contents: cerebrospinal fluid (CSF)

Features: plus pressure equal to the

normal atmospheric pressure Locally enlarged spaces(5):

terminal cistern(L2—S4)

cerebellomedullary cistern

interpeduncular cistern

pontine cistern

superior cistern

Grains:

arachnoid granulations

5 positions

Specific Structures Formed by Cerebral Dura Mater 1.Inclusion: cerebral falx cerebellar falx cerebellar tentorium dural sinuses 2.Communications among the sinuses:

Sup.sagittal sinus

Inf.sagittal sinus→straight sinus→confluence of sinuses→transverse sinus→sigmoid sinus→inter jug v

Cavernous sinus → sup.petrosal sinus

inf.petrosal sinus

2.Communications among the sinuses:

3.Cavernous Sinus(1) Position: lying on each side of sella turcica

(2) Contents: internal carotid artery & abducent nerve run through it ; and oculomotor,trochlear,

ophthalmic(V1) & maxillary(V2) nerves pass through its lateral wall into the orbit.

(3) Communication: facial v –-superior & inferior ophthalmic veins—--cavernous sinus

(4) Clinical significances: bacterial or viral infection in the dangerous facial trigone may spread to

the sinus via the above pathway causing sepsis & thrombosis in it and even negtively affecting

the ajacent crainal nerves,in which relative symptoms & signs will appear.

Cerebrospinal Fluid(CSF) 1.Producing Position CSF is secreted by the choroid plexuses in all ventricles. 2. Circulation R&L lateral ventricles

↓interventricular

↓foramina third ventricle

↓ cerebral aqueduct fourth ventricle

↓ R/L lateral foramina

↓ median foramen subarchnoid space

↓ arachnoid granulations superior sagittal sinus

↓ internal jugular vein

3.Clinical Significances If the pathways of CSF circulation are blocked, CSF will not be able to return to the epidural sinuses, and will stagnate in

cerebral ventricular system, leading to the swellen brain (hydrocephalus) especially in infants or children and to a high intrcranial pressure in adults in which the disfunctions

of brain or cerebral hernias may appear,resulting to sudden death. .

Arteries of CNS

I. Brain Arteries 1.Origin two sets of arteries

internal carotid artery

vertebral artery

Blood Vessels in CNS

The above branches of the artery collectively provide blood for the anterior 2/3 part of cerebral hemisphere including eyes, & anterior portion of thalamus.

(1) anterior cerebral a

(3) anterior choroidal a

(4) optic a

(5) posterior communicating a

(2) middle cerebral a

2. Branches of Internal Carotid Artery

(1)Anterior cerebral a supplies the medial surface of

cerebrum & upper part of dorsal surface of the cerebrum.

(2)Middle cerebral a supplies most part of the dorsolateral surface of cerebral hemisphere.

(3) anterior

choroidal a

(4) optic a

(5) posterior

communicating a

The three branches supply the areas with the same arterial names.

3. Cerebral Arterial Circle(Willis`s) 1) Composition(5 parts, 9 branches ): anterior communicating A ， bilateral anterior cerebral As, bilateral internal carotid As ， bilateral posterior communicating As, bilateral posterior cerebral As.

2) Location:

The circle lies on

inferior surface of

cerebrum & encircles

optic chiasma,

tuber cinereum &

mammillary bodies.

3)Functions ：

The circle regulates

blood flow of both

cerebral hemispheres.

4.Two Kinds of Arterial Branches Anterior ,middle and posterior cerebral arteries and the cerebral arterial circle all possesses the following:

cortical branches central branches (IC,BN)

Few anastomoses exist among separate branches . If a branch is blocked or broken, the target area suffers a deadly attact,either stroke or bleeding, resulting in losses of sensation & paralyses.

5. Clinical Significances   1. The branches of cerebral arteries hardly establish anastomoses (so-called terminal As ). When one of them is blocked, the supplied regions of brain will completely lack blood supply, leading to neuronal necroses & apoptoses . 2. The arteries of brain seldom beat, which may link to their thin walls & their curved routes, bringing about no palpable pulses from the arteries. 3. The branches for internal capsule are easily broken and this may result in a worse bleeding, because they directly arise from middle cerebral A at a right angle and and their walls have to put up with the powerful rush force and high blood pressure from torrent blood flow.

II.Arteries of Spinal Cord

1.Four Origins Vertebral A Ascending cervical A Intercostal A Lumbar A

2. Branches of Vertebral Artery & Basilar Artery

(1)anterior spinal artery (1) (2) posterior spinal arteries (1)

(3) posterior inferior cerebellar arteries (2) (4) anterior inferior cerebellar arteries (2)

(5) labyrinthine arteries (2) (7) pontine arteries (3 or 4 pairs ) (8) superior cerebellar arteries (2)

(9) posterior cerebral arteries (2)

The above branches collectively provide blood for the posterior 1/3 portion of cerebral hemisphere and posterior part of thalamus as well as the cerebellum, brain stem & spinal cord.

Artery (1) ~ artery (5) are the branches of vertebral artery

Artery (7)~ Artery (9) are the branches of basilar artery

Vertebral A

Ant.spinal A

labyrinthine A

posterior cerebral A.

pontine A

superior cerebellar A

Ant.inf cerebellar A

Post.inf.cerebellar A

Post.cerebral A

3.It supplies most parts of occipital and temporal lobes.

Vertebral AAnt.spinal A

Basillar A

Post. Spinal A

Post. Intercostal A

Lumbar A

Ascending cervical A

4.Arterial Distribution Patterns in Spinal Cord

Ant. Spinal A

Post spinal A

Coronary A of spinal cord

III.Veins of Brain 1. Features (1) They own no relatively accompanying arteries. (2) There are two sets----superficial and deep veins. 2.Division (1) Superficial Vein ( 3 branches : sup, mid & inf ) They lie on the surface of the cerebrum and drains the blood from the cerebral cortex to venous sinuses : a. superior cerebral v (on the surface above LS ) →superior sagittal sinus b. middle cerebral v (situated in lateral sulcus--LS ) →cavernous sinus c. inferior cerebral v (on the surface under LS ) →cavernous sinus & transverse sinus

Superior cerebral V

Middle cerebral V

Inferior cerebral V

Sup.sagittal sinus

Transverse sinus

Sigmoid sinus

(2)Deep veins drain the blood from the deep medullar matter to venous sinuses:a.Internal cerebral V b.Great cerebral V straight sinus (lying in postoinferiorpart of corpus callosum) c.Basilar V.

Great cerebral vein is also called Galen`s vein.