Topic 6.5 : CNS Protection & Vascular Supply

Five protective structures and systems safeguarding the CNS

Cranium, vertebral column, meninges, CSF, and blood-brain barrier

Three connective tissue layers forming the meninges

Dura mater, arachnoid mater, and pia mater

Alternative anatomical name for the dura mater

Pachymeninx

Collective anatomical name for arachnoid mater and pia mater together

Leptomeninges

Number of layers forming the cranial dura mater

Two layers (periosteal/parietal and meningeal/visceral)

Vascular structures located between the two cranial dural layers

Meningeal arteries/veins and dural venous sinuses

Venous vessel into which dural venous sinuses ultimately empty

Internal jugular vein

Extent of dural sheath coverage on spinal nerve roots

Covers roots until their exit through intervertebral foramina

Inferior fibrous structure enveloped caudally by the dura mater

Filum terminale

Vertical sickle-shaped dural reflections within the cranium

Falx cerebri and falx cerebelli

Horizontal tent-like dural reflections within the cranium

Tentorium cerebelli and diaphragma sellae

Venous sinus contained between dural layers at the diaphragma sellae

Cavernous sinus

Dural cavity located immediately adjacent to the cavernous sinus

Meckel's cave

Vascularity characteristic of the arachnoid mater

Avascular

Arachnoid protrusions penetrating dural sinuses to filter CSF

Arachnoid villi (granulations)

Vascular inner meningeal layer closely following brain sulci and fissures

Pia mater

Intraventricular structures formed by pia mater and ependymal cells

Choroid plexuses

Meningeal space located between bone and dura mater

Epidural space

Key anatomical difference regarding epidural space cranial presence

Present in spinal canal; absent in cranium under normal conditions

Meningeal space located between dura mater and arachnoid mater

Subdural space

Fluid normally contained inside the subdural space

Lubricating serous fluid

Meningeal space located between arachnoid mater and pia mater

Subarachnoid space (leptomeningeal space)

Enlarged subarachnoid compartments containing cerebrospinal fluid

Cisterns

Normal total adult volume of cerebrospinal fluid in circulation

Approximately 150 mL

Normal daily production rate of cerebrospinal fluid

600 to 700 mL per day

Primary site of CSF production and its percentage contribution

Choroid plexuses of the four ventricles (70%)

Cerebral ventricles producing the largest proportion of CSF

Lateral ventricles

Percentage of CSF produced by ependymal lining and arachnoid mater

20%

Percentage of CSF produced by brain capillaries crossing the BBB

10%

Primary site of cerebrospinal fluid reabsorption into venous blood

Arachnoid villi of the superior sagittal sinus

Interventricular openings connecting lateral ventricles to third ventricle

Interventricular foramina (of Monro)

Narrow channel connecting third ventricle to fourth ventricle

Cerebral aqueduct (aqueduct of Sylvius)

Median aperture connecting fourth ventricle to cisterna magna

Foramen of Magendie

Lateral apertures connecting fourth ventricle to subarachnoid space

Foramina of Luschka

Two primary cellular components forming the blood-brain barrier

Vascular endothelial cells and astrocytes

Intercellular junctional structures maintaining BBB impermeability

Tight junctions

Specific brain regions naturally lacking a blood-brain barrier

Near third ventricle (neurohypophysis, pineal gland) and fourth ventricle

Physiological purpose of brain regions lacking a blood-brain barrier

Allows neuroendocrine sensing and autonomic feedback regulation

Two major arterial systems supplying blood to the brain

Carotid system (anterior) and vertebrobasilar system (posterior)

Aortic origin of the left common carotid artery

Aortic arch

Aortic origin of the right common carotid artery

Right brachiocephalic trunk

Cranial fossae supplied by the internal carotid artery territory

Anterior and middle cranial fossae

Parent arterial trunks giving rise to the vertebral arteries

Subclavian arteries

Aortic origin of the left subclavian artery

Aortic arch

Aortic origin of the right subclavian artery

Right brachiocephalic trunk

Cranial fossa supplied by the vertebrobasilar arterial territory

Posterior cranial fossa

Arterial polygon interconnecting carotid and vertebrobasilar systems

Circle of Willis

Brain structures encircled within the Circle of Willis ring

Optic chiasm, optic tract, hypothalamus, and pituitary gland

Four parent arterial trunks contributing to the Circle of Willis

Two internal carotid arteries and two vertebral arteries

Three major branches arising from internal carotid artery in the circle

Anterior cerebral, middle cerebral, and posterior communicating arteries

Artery interconnecting the two anterior cerebral arteries

Anterior communicating artery

Artery formed by the confluence of the right and left vertebral arteries

Basilar artery

Brainstem level where the basilar artery divides into posterior cerebrals

Midbrain level

Artery connecting the internal carotid to the posterior cerebral artery

Posterior communicating artery

Arterial source supplying the cervical spinal cord

Vertebral arteries

Arterial source supplying the thoracic spinal cord

Intercostal arteries

Arterial source supplying the lumbar spinal cord

Lumbar arteries

Number and course of anterior spinal arterial vessels

Single vessel running longitudinally (anterior spinal artery)

Number and course of posterior spinal arterial vessels

Two vessels running longitudinally (posterior spinal arteries)

Two vascular systems collecting venous blood from the brain

Dural venous sinuses and meningeal veins

Three anatomical convergence points of dural venous sinuses

Confluence of sinuses (posteriorly) and two cavernous sinuses (anteriorly)

Anatomical location of confluence of sinuses (torcular Herophili)

Posteriorly near the internal occipital protuberance

Cranial foramen through which the internal jugular vein exits the skull

Jugular foramen

Venous drainage sequence from internal jugular vein to heart

Internal jugular to common jugular, subclavian, and superior vena cava

Course of spinal veins relative to the spinal arteries

Run parallel to the arteries