Vascular and Ventricular Systems

Ventricular System

• chambers

• Communicating system of cavities lined with ependyma and filled with CSF

• Responsible for production, transport and removal of CSF

Cerebrospinal Fluid

• circulates in the surfaces of the brain and spinal chord (SUBARACHNOID SPACE)

• Produced by the choroid plexus

• For:

  • Shock absorption

  • Mechanical buoyancy

  • Nourishment

  • Metabolite removal

  • Pineal secretion pathway

150 mL

• normal amount of CSF in circulation at a time

400-500 mL

• amount of CSF produced and reabsorbed per day

70-180 mm H20

• normal mean pressure of CSG

Spinal Tap

• diagnostic procedure done to collect spinal fluid to check for brain infections and content of fluid

• Done at L3-L4 or L4--L5

Lateral Ventricle

• Supplies CSF to the cerebral cortex

3rd Ventricle

• Supplies CSF to the diencephalon

4th ventricle

• Supplies CSF to the brainstem and cerebellum

Anterior Horn

• Part of the lateral ventricle that supplies CSF to the frontal lobe

Posterior Horn

• Part of the lateral ventricle that supplies CSF to the occipital lobe

Inferior horn

• Part of the lateral ventricle that supplies CSF to the temporal lobe lobe

Arachnoid Villi

• Absorbs the CSF

Dural Venous Sinuses

• Reabsorbs the CSF

Venous Sinus Pressure

• absorption is initiated when the CSF pressure exceeds __

Blood-brain Barriers

• isolates the nervous system from the blood supply

• Prevent poisonous or toxic substances from entering the brain

Circumventricular organs

• structures centered around the ventricles of the brain lacking blood-brain barriers

Blood-CSF Barriers

• Permeable to Water, Gas, Electrolytes, and glucose

• Impermeable to proteins and large organic molecules

• More permeable in children than adults

Bilirubin

• Passage to blood-csf barrier may cause brain damage in premature children

Alcohol

• Passage to blood-csf barrier may cause cerebellar damage in premature children

Hydrocephalus

• abnormal buildup of CSF volume in the ventricles

• Can be:

  • Communicating

  • Non-communicating

  • Normal pressure __

  • __ ex-vacuo

Communicating type

• Type of hydrocephalus

• less obstruction in the brain

• Overproduction or under-absorption

Non-communicating type

• Type of hydrocephalus

• More obstruction in the brain

  • Cerebral aqueduct

  • Interventricular foramen

  • Foramen of magendie and luschka

Normal pressure hydrocephalus

• Type of hydrocephalus

• Often caused by tumor, head injury, hemorrhage, infection, or inflammation

• No increase in intracranial pressure but with increase in CSF

Hydrocephalus Ex Vacuo

• Type of hydrocephalus

• often in degenerative conditions and brain damage is caused by head injury or stroke

• Ventricles enlarge as compensatory action

Shunting

• Hydrocephalus management

• transfer fluid from ventricles to peritoneal cavity

• For communicating, NPH, HEV types

Surgery

• Hydrocephalus management

• Remove the obstruction

• For non-communicating type

Papilledema

• swelling of the optic disc due to elevated intracranial pressure → optic nerve compression

• Leads to blindness or optic atrophy

18%

• the brain receives this much blood from the heart

20%

• the brain uses this much oxygen absorbed in the lungs

Circle of Willis

• hexagonal network of arteries at the base of the brain that gives rise to all major cerebral arteries

Internal Carotid Artery

• anterior circulation

• Receive and supplies 80% of blood

Common Carotid Artery

• where the bifurcation of the ICA begins

Vertebral Artery

• posterior circulation

• Receive and supplies 20% of the blood

Subclavian Artery

• where the bifurcation of the vertebral artery begins.

Ophthalmic Artery

• first branch of ICA

• Provides blood to:

  • Eyes, other orbital structures

  • Frontal Scalp area

  • Ethmoid and frontal sinuses

  • Dorsum of nose

Anterior Cerebral Artery

• involved in asymptomatic stroke

• Provides blood to:

  • Medial aspect of the hemisphere

  • Anterior frontal lobe

  • Basal ganglia

Middle cerebral artery

• largest and terminal branch, most commonly occluded

• Provides blood to:

  • Lateral aspect of hemisphere (ex. Occipital lobe)

  • Basal Ganglia

Anterior Choroidal Artery

• Provides blood to:

  • Choroid plexus

Posterior Inferior Cerebellar Artery

• largest branch

• Posterior inferior quarter of cerebelllum

• Medulla oblongata

Anterior Inferior Cerebellar Artery

• Provides blood to:

  • Anterior inferior quarter of cerebellum

  • Inferior pons

Basilar and Pontine Arteries

• Provides blood to:

  • Thalamus

  • Midbrain

  • Pons

  • Medulla Oblongata

Superior Cerebellar Artery

• Provides blood to:

  • Superior half of cerebellum

  • Superior Pons

  • Midbrain

Posterior Cerebral Artery

• Provides blood to:

  • Occipital lobe

  • Lower temporal lobe

  • Lateral and third ventricles

  • Thalamus

  • Midbrain

Anterior spinal artery

• larger; supplies 2/3 of the spinal cord

• Along anterior median fissure

Posterior Spinal Arteries

• supply the posterior ½ of spinal cord

• Close to nerve roots

Radicular Arteries

• Arise from segmental spinal artery

• Enter the intervertebral foramina and white and gray matter

Anterior Sulcal Artery

• Branches from the corona artery that supplies blood to the anterior gray horns and lateral columns

Artery of Adam Kiewicz

• nutritional artery

• Unilateral and only seen in the left side

• Arises from the aorta at level T8-L4 → major source of blood supply to the lower 2/3 of the spinal cord

Vasocorona

• hugs the spinal cord; irregular rings of arteries with vertical connections

• Made up of segmental arteries that are connected to the ASA and PSA

Veins of the Brain

• thin walls

• No muscular tissue or valves

• Emerge from the brain and travel in the subarachnoid space

• Pierce other meningeal layers and drain into the cranial venous sinuses

Superior Cerebral Veins

• Superficial vein

• 8-12 branches that pass upward over the lateral surface of the cerebral hemiphere

• Empty into the Superior Sagittal Sinus

Superficial Middle Cerebral Vein

• drains the lateral surface of the cerebral hemisphere

• Travels within the sylvian fissure into 3 veins/sinuses

Dural venous sinuses

• sinuses in the dura mater

• Between the periosteal and meningeal layers

• CSF drainage

Confluence of Sinuses

• also known as torcular herophili or torcula

• Connecting point of

  • Superior sagittal sinus

  • Straight sinus

  • 2 transverse sinuses

  • Occipital sinus

• Corresponds to the internal occipital protuberance of the occupiral bone of the skull

• Drains straight to the R transverse sinus

Midbrain Veins

• drains into the great cerebral vein or basal vein

Pontine Vein

• one medial, two lateral

• Drain into the basal vein, cerebellar veins, or neighboring sinuses

Medulla Oblongata Veins

• drain into spinal veins, occipital sinus, or neighboring sinuses

Superior Group

• drains straight to the straight sinus or great cerebral vein

• Drains to the transverse and superior petrosal sinuses

Inferior Group

• Drains to straight or sigmoid sinuses

Spinal Cord

• irregular external plexus in the epidural space

• Usually follows the arteries

• Drain into the vertebral venous plexus or vena cava