Ch 3 - Vascular Anatomy

Question 0

arterial branches arising from what location supply the majority of blood to the brain?

Answer 0

the circle of Willis and proximal basilar a.

Question 1

3 typical arterial pathways for blood to the brain

Answer 1

1. internal carotid artery
2. maxillary artery (remember it anastomoses with the internal carotid)
3. basilar artery (composed primarily from large contributions of paired vertebral a.)

Question 2

the cerebellum is supplied by 2 pairs of cerebellar arteries. what are they?

Answer 2

1. rostral cerebellar arteries - branch off caudal communicating a.
2. caudal cerebellar arteries - branch off the basilar a. it supplies the caudal portions of the cerebellum.

Question 3

there are 5 main intracranial branches supplying the brain and brain stem. what are they?

Answer 3

1. rostral cerebral a. - supply the rostral & medial portions of the cerebral hemispheres. branches supply cortex & medullary substance.
2. middle cerebral a. - the largest of cerebral a. and largest terminal branches of the intracranial internal cranial a. branches supply cortex and medullary substance. the central branches supply the basal nuclei and adjacent tracts.
3. caudal cerebral a. - supplies the caudomedial portions of the cerebral hemispheres
4. rostral cerebellar a. - supplies the rostral and middle portions of the cerebellum.
5. caudal cerebellar a. - supplies the caudal portions of the cerebellum.

Question 4

why is it that blood from the left internal carotid typically only supplies the left hemisphere?

Answer 4

despite the circular distribution of arteries from the circle of willis, blood from from the circle of willis to the hemispheres remains laterally segregated unless pressure profiles are significantly modified.
anastomoses are not sufficient to support long term brain function during occlusion of parent cerebral vessels.

Question 5

species variations of the circle of willis: dog/horse/human

Answer 5

• the extracranial internal carotid aa. connect to & supply much of the circle of willis
• significant contribution to the internal carotid aa. is made by an anastomotic branch of the maxillary a.
• a rudimentary rete is formed by the maxillo-carotid anastomosis
• the vertebrobasilar system supplies blood to the caudal portion of the cerebral hemispheres via caudal cerebral a.
• smaller contributions to the internal carotid a. are often made by ascending pharyngeal a. & anastomotic branches of the external opthalmic & external ethmoidal a. V

Question 6

species variations in arterial supply of the brain: cat/small ruminants

Answer 6

• blood supply to the cranial portions of the circle of willis is covered by numerous small dorsal branches of the maxillary a.
• they form the rostral epidural rete mirabile. this coalesces into the intracranial carotid a which supply the rostral, middle and caudal cerebral a.
• blood flow in the basilar a. is directed caudad and the blood supplying both cerebral hemispheres sources from the intracranial internal carotid a.
• the circulation provided by the verebrobasilar connections are reduced in comparison to the dog.

Question 7

species variation in arterial supply of the brain: cow

Answer 7

• internal carotid a. replaced by dorsal branches of the maxillary a.
• these branches are separated into rostral and caudal branches all of which supply the rostral epidural rete mirabile
• the intracranial internal carotid a. reconstitute from the rostral epidural rete mirabile.
• a caudal epidural rete mirabile connects the to the rostral rete.
• vertebral and spinal branches of the vertebrobasilar connections contribute to the caudal rete.
• *since the caudal rete is connected to the rostral supply of the brain via the rostral rete, the vertebrobasilar system contributes to whole brain blood supply**

Question 8

how many separate anastomoses occur between the extracranial and intracranial arteries contributing to blood brain supply?

Answer 8

• at least 5 separate anastomoses between extracranial and intracranial arteries can contribute to brain supply.

Question 9

name the 5 anastomoses that occur between extracranial and intracranial a. contributing to brain supply

Answer 9

1. occipital & vertebral a.
2. ascending pharyngeal & internal carotid a.
3. intracranial vessels & maxillary a.
4. anastomotic a. between the maxillary & internal carotid a.
5. ophthalmic anastomosis between external & internal carotid a.

Question 10

5 typical venous pathways for blood draining from the brain

Answer 10

1. internal jugular veins - begins as sigmoid and ventral petrosal sinuses and exits the skull and joins the vertebral veins
2. maxillary vein - receives numerous intracranial emissary veins, including ones from the temporal dural sinus and ventral petrosal and cavernous dural sinuses.
3. vertebral veins - drains the sigmoid sinus and the hypoglossal canal.
4. Internal vertebral venous plexus (IVVP) - the bilateral basilar sinuses become the IVVP as they leave the skull via the foramen magnum. consists of a L & R vein which extend along the ventral aspect of the neural canal along their course to the caudal vertebrae
5. emissary veins - two main ones: 1. connects cavernous sinus to maxillary vein. 2. leaves cavernous and joins opto, pterygoid & palatine plexus

Question 11

the intracranial veins that drain the majority of the cerebrum can be divided into two veins:

Answer 11

1. cortical veins

2. central veins

Question 12

what are cortical veins divided into?

Answer 12

dorsal and ventral cerebral veins which drain into the dorsal sagittal and dorsal petrosal sinus

Question 13

what are the central veins made up of and where do they drain into?

Answer 13

made up of: basal, corpus callosal, internal cerebral, thalamostriate

drain into: great cerebral vein

Question 14

the cavernous sinuses contain with their lumen portions of which arteries?

Answer 14

internal carotid a., middle meningeal a., and anastomotic branches of the external ophthalmic a.

Question 15

a significant portion of blood from the dural sinus drains where?

Answer 15

into the neural canal of the vertebral column

Question 16

which plexuses receive a large volume of blood draining from the CNS?

Answer 16

the internal (epidural) and external (perivertebral) vertebral plexuses

Question 17

describe the arterial blood supply to the spinal cord

Answer 17

1. all parent arteries originate from the aorta
2. once they reach the vertebral column bilateral arteries branch off the parent arteries
3. these branches enter the neural canal and bifurcate into dorsal and ventral root arteries.
4. the ventral root arteries empty into the median ventral spinal artery and the dorsal root artery join the paired dorsal spinal arteries.
5. countless anastomoses exist between all 3 spinal arteries forming the pial (coronal) network. this is what supplies the actual spinal cord.

Question 18

which artery supplies the gray matter of the spinal cord?

Answer 18

the ventral spinal artery

Question 19

which artery supplies the white matter of the spinal cord?

Answer 19

the pial network

Question 20

describe the venous drainage of the spinal cord

Answer 20

1. a median ventral spinal vein accompanies the equivalent artery
2. the spinal veins are connected to dorsal and ventral root veins (ie medullary veins)
3. the medullary veins drain into the ventral internal vertebral plexus
4. which is subsequently drained by the intervertebral veins into an external vertebral plexus which surrounds the vertebrae.

Question 21

name the important path of collateral drainage of blood from the CNS.

Answer 21

the highly anastomosing networks of the internal (epidural) and external (perivertebral) vertebral plexuses drain the blood from the spinal cord into the various parent veins (eg. vertebral,azygos, lumbar)

Question 22

Name the 3 tissues that make up the CNS

Answer 22

blood, neural tissues, and cerebrospinal fluid.

Question 23

the basic idea of pressure in the CNS as declared by teh Monro-Kellie doctrine

Answer 23

any increase in volume of one of the 3 tissues that make of the CNS will result in an increase in intracranial pressure. to avoid damage to the CNS due to this increase in pressure, any increase in the volume of one of those tissues requires a reduction in the volume of another tissue.