King Ch 1 - Arterial supply

Question 1

What are the five pairs of arteries that supply the brain?

Answer 1

• Rostral cerebral artery
• Middle cerebral artery
• Caudal cerebral artery
• Rostral cerebellar artery
• Caudal cerebellar artery

Footnote

Question 2

From where do the four rostral arteries arise?

Answer 2

The cerebral arterial circle, also known as the circle of Willis

Rostral cerebral artery arises from basilar artery in horses

Question 3

Which artery is the largest cerebral artery in most mammals?

Answer 3

The middle cerebral artery

Question 4

Which pair of arteries does not arise from the arterial circle, and from where does it arise?

Answer 4

The caudal cerebral artery, which arises from the basilar artery

Question 5

Describe the pathway of the basilar artery

Answer 5

The ventral spinal artery courses towards the brain, and transforms into the basilar artery at the medullae, along the ventral midline. It courses under the pons and then divides into two branches, uniting with the caudal communicating arties to form the caudal portion of the arterial circle.

Question 6

Describe the pathway of the internal carotid arteries

Answer 6

They traverse the carotid canal in the tympanic part of the temporal bone and form a loop at the foramen lacerum, entering the middle cranial fossa ventral to the rostral end of the petrous temporal bone. It then courses rostrally through the cavernous sinus. It emerges through the dural dorsal to the cavernous sinus, enters the subarachnoid space, and divides into the rostral cerebral, middle cerebral, and caudal communicating arteries.

Question 7

What are the four potential incoming arterial channels to the cerebral arterial circle?

Answer 7

• Internal carotid artery
• Basilar artery
• Maxillary artery
• Vertebral artery

Blood distribution to the brain can be from mainly carotid, maxillary, vertebral, or a combination of these depending on species.

Question 8

What is the function of the maxillary artery’s anastomosing ramus?

Answer 8

It joins the maxillary artery to the internal carotid artery

Question 9

In most mammals, what supplies the rostral half of the brain and the caudal half of the brain?

Answer 9

• Rostral half: Internal carotid blood
• Caudal half: Vertebral blood

This is because the pressure gradients are such that the flow of blood in the basilar artery is rostral

Question 10

What happens to the internal carotid artery in sheep and cats after birth?

Answer 10

The lumen of the proximal two-thirds becomes obliterated

Question 11

How is the adult brain of sheep and cats supplied?

Answer 11

By maxillary blood via the anastomosing ramus of the maxillary artery

A rete mirable develops on the anastomatosing ramus.

Question 12

What is a rete mirabile?

Answer 12

A ‘marvellous network’ that occurs on the anastomosing ramus of the maxillary artery

In all species in which the supply from the maxillary artery is well developed. May be involved in thermoregulation.

Question 13

What is the significance of the vertebral artery as a source of blood to the brain in different species?

Answer 13

• In sheep and cats: Little or no vertebral blood reaches the brain
• In ox: Vertebral blood reaches all parts of the brain

In cats and sheep however, vertebral blood does reach the caudal half of the medulla oblongata.
In cows, supply to the whole brain is a misxture of maxillary and vertebral, via the anastamosing ramus of the maxillary and vertebral arteries (rete mirabile develops).

Question 14

What common feature exists in all species regarding the internal carotid artery and maxillary artery?

Answer 14

An inverse relationship: when one is large, the other is small

In all species, a vertebral–occipital anastomosis is present and well developed.

Question 15

Label this diagram

Answer 15

Question 16

True or False: Large pulsating arteries can be tolerated below the surface of the neuraxis.

Answer 16

False

Question 17

What is the primary reason for not having large arteries below the surface of the brain and spinal cord?

Answer 17

Large pulsating arteries would generate pressure waves below the surface

Question 18

What occurs in the blood supply to the brain when the common carotid artery is cut?

Answer 18

The vertebral–occipital anastomosis becomes functionally important

Question 19

What is the relationship between axons, cell bodies, and synapses regarding blood and oxygen consumption?

Answer 19

They have an increasing requirement for blood and oxygen consumption in that order

Question 20

Fill in the blank: The ancient parts of the neuraxis are typically _______ vascular than the recent parts.

Answer 20

less

Question 21

How much of total cardiac output is received by the brain?

Answer 21

About 16%

Question 22

What can anastomoses on the surface of the brain be useful for?

Answer 22

Can sometimes provide effective alternative channels around an obstruction

Question 23

How do the anastomoses on the surface of the spinal cord compare to those on the brain?

Answer 23

They are finer and generally inadequate as alternative pathways

Question 24

What is the status of deep arteries regarding anastomoses?

Answer 24

They rarely anastomose above capillary level

Question 25

What is the consequence of total obstruction of any artery below the surface of the neuraxis?

Answer 25

Death of all neurons in its territory within about 8 minutes

Question 26

What can result from injury to the roots of a spinal nerve?

Answer 26

Interference with its arteries, causing degeneration within the spinal cord

Question 27

What type of arteries supply the depth of the neuraxis?

Answer 27

Relatively small arteries that arise at right angles from large parent vessels

Question 28

Which arteries are most often involved in occlusion or hemorrhage ('stroke') in humans?

Answer 28

The striate arteries arising from the middle cerebral artery

Question 29

What areas do the striate arteries supply?

Answer 29

The basal nuclei (basal ganglia) and parts of the internal capsule

Question 30

How does hemorrhage into the brain affect tissue function?

Answer 30

It causes anoxia of the tissues and interferes with adjoining areas by pressure

Question 31

What are the two types of arteries that penetrate the surface of the spinal cord?

Answer 31

* Vertical arteries * Radial arteries

Question 32

What is one potential consequence of cardiac arrest during anesthesia?

Answer 32

Severe damage to the brain, particularly ischaemic necrosis of the cerebral cortex

Question 33

Which regions of the cerebral cortex are most severely affected by ischaemic necrosis?

Answer 33

The dorsal regions, including the visual area, and then the lateral regions

Question 34

What are two potential outcomes of damage to the brain during cardiac arrest?

Answer 34

Blindness and extensor rigidity

Question 35

What is the role of the rete mirabile in thermoregulation?

Answer 35

It helps cool the blood before it reaches the brain

Question 36

Label this diagram

Answer 36

Question 37

Describe the segmental arterial supply to the spinal cord

Answer 37

At each segment of the body, two arteries on the left, and two on the right side, supply the spinal cord. These are the dorsal root artery and ventral root artery on each side. These arteries arise from paired spinal arteries, which in turn spring from the paired lumbar arteries of the aorta, from the intercostal arteries, and from the vertebral arteries.

Question 38

What is the basic pattern of arterial supply in mammals for the spinal cord?

Answer 38

Founded on three longitudinal trunks; the ventral spinal artery and the paired dorsolateral arteries.

Question 39

What does the ventral spinal artery supply?

Answer 39

The inner vascular zone of the spinal cord

Question 40

Where do vertical arteries arise from and go to?

Answer 40

They arise from the ventral spinal artery, in the ventral fissure, towards the centre of the spinal cord. They supply most of the grey matter, and reach peripherally into the white matter also.

Question 41

Where do radial arteries arise from and go to?

Answer 41

The radial arteries arise from all the other arteries on the surface of the cord. They supply the white matter and the outer regions of the grey matter.

Question 42

What are the three vascular zones of the spinal cord, and what are they supplied by?

Answer 42

1. The inner vascular zone is supplied solely by the vertical arteries of the ventral spinal artery. 2. The middle vascular zone is supplied both by the vertical arteries of the ventral spinal artery, and by the radial arteries from all the other surface arteries. 3. The outer vascular zone is supplied by the radial arteries alone.