Ventricles, Meninges, CSF, Blood Vessels of the Brain

Non terminal branches in the brain

1) posterior inferior cerebellar (PICA) artery 2) Anterior spinal artery 3) Anterior inferior cerebellar artery (AICA) 4) Labyrinthine 5) Superior cerebellar artery

Blood Supply to the Brain

2 pairs of arteries in the subarachnoid space: Vertebral and internal carotid. Also the circle of willis

Cavernous Sinuses

2- Large venous sinuses located on either side of the sella turcicia

Sigmoid Sinuses

2- direct continuation of transverse sinuses -Takes on an S shaped apearence and enters into the jugular foramen -changes names into the internal jugular vein

Transverse Sinuses

2- found at the posterior border of the tentorum cerebelli -start to head inferiorly after wrap around -changes names into the sigmoid sinuses

Superior Petrosal Sinuses

2- heads posteriorly from the cavernous sinus to dump into the junction of the tranverse sinous and sigmoid sinus

4th Ventricle

3 openings- 2 lateral and 1 medial apetures. CSF can get into the subarachnoid space through any of these

Cerebral arterial circle (Circle of Willis)

Anastamosis formed at the base of the brain by the vertebral and internal carotid arteries. Composed of: anterior communicating artery between the anterior cerebrals, internal carotid, anterior cerebral arteries, posterior communicating arteries, posterior cerebral artery

Internal carotid arteries

Arise from the common carotid in the neck to serve the internal skull, does not branch until in the skull. Goes through the carotid canal and foramen lacerum -branch into middle cerebral and anterior cerebral arteries -anterior circulation of the brain -80% of the circulation to the brain

Ventricles of the brain

Arise from the expansion of the lumen of the neural tube. Telencephalon- Forms the C shaped lateral ventricles Diencephalon- forms the third ventricle Mesencephalon- forms the cerebral aqueduct Meten/myelencephalon forms the 4th ventricle -The choroid plexuses hang off ventricles

Posterior Cerebral artery

Basil Artery -supplies the inferior surface of the temporal lobes and the occipital lobes

Occipital Sinus

Brings blood into the confluence, vv small

Hemorrhages

Cause pressure on the brain tissue -leads to drowsiness, loss of consciousness, coma, etc. -Can also force the brain stem through the foramen magnum -surgery can correct it

Ependymal cells

Close together so nothing leaks between them, gives the specificity to CSF- chooses what passes into the brain from blood plasma

Straight Sinus

Connection of the inferior sagittal sinus and great cerebral vein -runs along the attachment of falx cerebri to the tentorum cerebelli -brings blood posterioly to the confluence

Meninges

Cover and protect the brain and spinal cord, blood vessels and encloses dural venous sinuses. Contains cerebrospinal fluid and partitions the skull 1) Dura Mater 2) Arachnoid Mater 3) Pia mater

Inferior Petrosal Sinuses

Dump into the junction of sigmoid and jugular vein

Falx Cerebri

Dural septa: structure is shaped like a sickle, largest of the septa, sits or dips into the longitudinal fissure between the cerebral hemispheres. Attaches to the cristi galli anteriorly

Inferior Sagittal Sinus

Found along the inferior edge of the falx cerebri, running the posterior 2/3 -Connects with the great cerebral vein, merge to create the straight sinus

Dural Venous sinuses

Gaps within the dura mater where venous blood can collect. As blood goes out of the brain it will drain into one of the venous sinuses: a) Superior sagittal sinus b) inferior sagittal sinus c) straight sinus d) occipital sinus e) transverse Sinus f) sigmoid sinus g) superior petrosal sinus h) inferior petrosal sinus i) cavernous sinus

Subarachnoid Space

In the brain: actual space between the arachnoid and pia mater. Location of CSF and blood veins that serve the brain. -blow to the head can cause subarachnoid hemorrage or hematoma, 70% is a rupture from an annurism (dilated blood vessel)

Subdural Space

In the brain: potential space between the dura and arachnoid maters. CSF pressure keeps the arachnoid up against the dura mater. -blows to the head can open the space by rupturing the cerebral vein

Epidural space

In the brain: potential space between the periostial layer of the dura mater and skull -Some dieseases open the space -hemorrhages and hematomas occur when blood collects in this space from the meningeal artery tearing. Leads to compression of brain tissues

Arachnoid Mater

Loose brain covering, middle layer just deep to Dura Mater. -Looks like a spider web -Connected to the pia mater by web-like projections -Only dips into the longitudinal and transverse fissures, not the sulci -Subdural space: between the arachnoid and dura maters -Subarachnoid space: CSF flows around between arachnoid and pia mater, largest blood vessels serving the brain found here

Superior Sagittal Sinus

Median/midsagittal plane, found along the superior end of the falx cerebri -runs the length of cerebri: blood flows anterior to posterior, all the way back to the confluence of the sinuses -begins at crista galli -small pieces of arachnoid mater portude into the sinus (arachnoid villi for reabs of CSF)

Dural Septa

Meningeal layer pulling away from the periosteal layer to form partitions or walls within the cranial cavity. -Limits excessive mvmnt of the brain within the skull, supports part of the brain's weight a) falx cerebri b) falx cerebelli c) Tentorium cerebelli d) sellar diaphragm

Vertebral Arteries

Pass through the transverse foramen and foramen magnum to unite at the caudal border of the pons, forms the Basilar Artery -Branches into 2 posterior cerebral arteries -20% of the circulation to the brain

Arachnoid villi/granulations

Projections into the superior sagittal sinus where CSF is reabsorbed into the bloodstream

Cerebrospinal Fluid

Provides 3 types of protection: 1) Mechanical- buoyancy to structures 2) chemical- provides specific environment for neurons to function 3) circulation- Carries nutrients and waste Clear colorless liquid formed from specific nutrients in blood plasma. Created through the choroid plexuses which are a network of capillaries. -Reabsorbs through the superior sagittal sinus through the arachnoid vili. -Constantly produced, replaced every 4-6 hours (20ml/hr, 80-150mL in an adult)

CSF Flow Chart

Right/Left ventricle--> 3rd vent--> cerebral aqueduct--> 4th vent--> subarachnoid space--> superior sagittal sinus--> confluence of the sinuses (along with occipital sinus, inferior saggital sinus-->sinus rectus/straight sinus)--> Right/Left transverse sinus--> Sigmoid sinus--> subclavian on each side. - on the right side: right sigmoid--> subclavian--> brachiocephalic--> superior vena cava

Tentorum Cerebelli

Second largest dural septa. Sits in the transverse cerebral fissure between the cerebral hemis and cerebellum, separating occipital lobes and cerebellum. -Holds up weight of the occipital lobes so they aren't sitting on cerebellum

Falx Cerebelli

Separates the cerebellar hemispheres, much smaller than falx cerebri

Blood supply

Since vision and motor control is contralateral, if blood flow stopped to one side, wont be able to see out the other eye or move the other side

Sellar Diaphragm

Smallest dural septa. forms the roof over the hypofisseal fossa which is the hole or opening for the passage of the infrandibulum -Stock of hypothilamic tissue (from hypothalimus) that connects hypothalimus to pituitary gland

Anterior cerebral artery

Terminal branch of the internal carotid -enters the longitudinal fissure, runs over the corpus collosum to supply most of the medial and superior surfaces of cerebral hemis

Middle Cerebral artery

Terminal branch of the internal carotid - passes between the temporal and frontal lobes to rach the lateral part of the cerebral hemispheres

Dura Mater

Tough, strongest of the meninges. Opaque, superficial, made of dense connective tissues. Made of two fused layers: 1) Periosteal layer- more superficial layer, this is the periosteum of the skull, so the dura mater of the brain is directly attached to the skull. Not adhered in the vertebral column 2) Meningeal layer- more deep, continues through the foramen magnum into the vertebral column to surround the spinal cord.

Pia Mater

Very thin, adhered directly to the brain and spinal cord -Shiny -Follows the contours, goes into fissures and sulci -Almost impossible to dissect away from the spinal cord

Hydrocephalus

Water on the brain caused by excess of CSF. -Can be from excess production, problem with flow or reabs -Caused by tumors, inflammation, head injuries, etc Common in infants in cerebral aqueduct or Monroe -More dire in adults since skull can't expand

Superior cerebellar artery

comes off the basilar artery to supply the superior cerebellum surface

Labyrinthine artery

comes off the basilar artery, enters the internal acustic meatus with cranial nerves 7,8 to supply the inner ear

Anterior inferior cerebellar artery (AICA)

comes off the basilar to supply the inferior cerebellum

Anterior spinal artery

comes off the vertebral artery, two branches come together to supply the spinal cord

posterior inferior cerebellar (PICA) artery

off the vertebral arteries, supplies the inferior cerebellum