L7: CNS Arterial Supply and Venous Drainage

Blood supply to the brain is derived from the ___ ____ artery

Internal carotid (ICA)

The ICA branches from what artery?

The common carotid artery

The ICA passes through the ____ canal to enter the cranium

Carotid

The ICA provides (anterior/posterior) circulation?

Anterior

Some blood supply to the brain is also derived from the ____/____ artery

Vertebral/basilar

The vertebral/basilar artery passes through the ____ foramina of the ____ vertebra and then through the ____ ______ to enter the cranium.

Transverse, cervical, foramen magnum

The vertebral/basilar artery provides (anterior/posterior) circulation?

Posterior

In the event of vessel blockage, what structure provides collateral circulation?

Circle of Willis

Venous blood from the brain drains into the ___ ____ sinuses

Duran venous

The dural venous sinuses are vessels lined with what tissue?

Endothelium

The dural venous vessels are located within the ___ layers

Dura

What six structures comprise the dural venous sinuses?

1- superior sagittal sinus

2- inferior sagittal sinus

3- straight sinus

4- confluences of sinuses

5- transverse sinuses

6- sigmoid sinuses

Deeper veins drain into ____ cerebral veins

Superficial

Where are superficial cerebral veins located?

Within the subarachnoid space

What do superficial cerebral veins drain into?

Dural venous sinuses

Blood eventually drains into the ____ ____ vein by passing through the _____ foramen

Internal jugular, jugular

What veins run from extracranial tissues to the dural venous sinuses?

Emissary veins (can carry infection from the scalp into the cranial cavity)

What are the veins that drain blood from the cerebral veins on the brain surface into the sinuses?

Bridging veins

Because the brain can move within the cranium, shearing of ____ ____ is possible

Bridging veins

The shearing of a bridging vein would result in a ______ hematoma

Subdural

Epidural hematomas result from damage to what artery?

Middle meningeal artery

Subdural hematomas occur from stretching or tearing of what veins?

Bridging veins

Subarachnoid hemorrhage results when?

Arterial blood fills the arachnoid space

What are usual causes/associations with subarachnoid hemorrhages?

• usually from a rupture of an aneurysm

• Can be associated with head trauma or cranial fractures and cerebral lacerations

Which artery branches from the vertebral artery to supply 2/3 of the cross-sectional area of the spinal cord?

Anterior spinal artery

Which artery branches from the posterior inferior cerebellar artery or vertebral artery to supply blood to the posterior 1/3 of the cross-sectional area of the spinal cord?

Posterior spinal arteries

The largest posterior spinal artery and the major supplier of the inferior spinal card is called?

Artery of Adamkiewicz (great anterior segmental medullary artery)

Spinal veins running longitudinally on the surface of the spinal cord drain into what veins?

Intervertebral veins

What plexus contains valveless eins located in the epidural space throughout the length of the spine?

Vertebral venous plexus

What plexus communicates with the intercranial venous system, pelvic veins, and extraspinal veins via the intervertebral veins (through the IVF)

Vertebral venous plexus

Where is CSF produced?

By ependymal cells in the choroid plexus

What is the function of CSF?

• cushions and protects the CNS from trauma and nourishes it

• Provides mechanical buoyancy and support for the brain

• Removes neuronal metabolites from the CNS

True or False: Normally, CSF contains a lot of protein and WBC.

FALSE: Normally, CSF contains very little protein and WBC

Circulation of CSF involves a pressure gradient created by ____ and _____, as well as arterial pulsations, ______, and ependyma cilia movement.

Production

Absorption

Respiration

In terms of absorption of CSF, is CSF pressure greater than or less than venous blood pressure and/or lymph pressure?

GREATER

Impaired absorption of excessive production of CSF leads to _____ and a consequential (increase/decrease) in ICP?

Hydrocephalus

Increase

What is the Monroe-Kellie hypothesis?

The skull is an enclosed structure that does not permit expansion and contains 3 volumes (brain tissue, CSF, and blood volume) whose sum is CONSTANT

What hypothesis says that if one volume of either brain tissue, CSF, or blood volume increases, one of the other volumes will increase to compensate?

Monroe-Kellie hypothesis

If there is an excessive change in volume, then compensation becomes exhausted, resulting in?

increased ICP

Increased ICP can lead to?

• Decreased cerebral profusion

• Herniating of brain tissue

What is the name for an area where the subarachnoid space is enlarged and contains CSF?

Subarachnoid cistern

What are the four subarachnoid cisterns?

1- quadrigeminal

2- interpenduncular

3- pontine

4- cisterns magna

What is the approximate location of the quadrigeminal cistern?

Posterior to the midbrain

What is the approximate location of the interpenduncular cistern?

Anterior to the midbrain, between the two cerebral peduncles

What is the approximate location of the pontine cistern?

Anterior to the pons

What is the approximate location of the cisterna magna cistern?

Between the lower part of the cerebellum and the medulla