Blood Supply and Cerebral Blood Flow Flashcards
Which veins have little supporting structure and are vulnerable to injury forming a subdural hematoma?
Superior cerebral veins. These cross the subdural space (from arachnoid to superior sagittal sinus)
Which veins connect the dural sinuses (superior sagittal sinus or cavernous sinus) with extracranial veins of the scalp and face?
Emissary veins
Why do emissary veins have a greater potential for spreading infection (e.g. meningitis) from outside the cranium to venous sinesus within?
Emissary veins have no valves and allow for free communication between these venous systems
Veins of which features roughly follow the arterial system?
Veins of the brainstem, cerebellum and spinal cord
What is a potential consequence of the absence of valves in spinal cord veins?
Since there are no valves, flow is easliy reversed. This provides a means through which metastases from the pelvis, kidney, or lung may spread to vertebral bodies or to the CNS.
The brain, brainstem, and cerebellum are supplied by which two major arteries?
The internal carotid arteries and vertebral arteries.
Occlusion of these arteries or smaller branches causes damage to areas of the CNS supplied by these vessels.
Approximately what percentage of blood to the cerebrum is supplied by vertebral arteries?
15%. These vessels enter the foramen magnum, penetrate the dura mater and arachnoid; then enter the subarachnoid space.
Which arteries supply most of the brainstem through their branches?
vertebral arteries
The Anterior spinal artery (a single, unpaired artery) supplies blood to what part of the spinal cord?
It supplies blood to the anterior 2/3 of the spinal cord (running in a rostral to caudal direction in the ventral medial fissure of the spinal cord)
Which arteries branch off the vertebral artery; descend caudally as separate trunks and serve the posterior 1/3 of spinal cord?
The Posterior spinal arteries (paired)
Which arteries branch off the vertebral arteries before joining to form the basilar artery and provide blood to the posterior part of cerebellar hemispheres, vermis, and lateral and posterior medulla?
Posterior inferior cerebellar arteries
What are the four main branches of the basilar artery?
a. Anterior inferior cerebellar artery
b. Pontine arteries
c. Superior cerebellar arteries
d. Posterior cerebral arteries
The anterior inferior cerebellar artery (branch of the basilar artery) supplies blood mainly to which structures?
inferior cerebellum and deep cerebellar nuclei and part of the pons
The pontine arteries (branches of the basilar artery) supply blood mainly to which structures?
They penetrate the pons and supply this region of brainstem and all nuclei located there, including the reticular formation.
The superior cerebellar arteries (branches of the basilar artery) supply blood mainly to which structures?
They supply the dorsum of the cerebellum and deeper structures, midbrain, pons and superior cerebellar peduncle
The posterior cerebral arteries (branches of the basilar artery) supply blood mainly to which structures?
They supply the inferior surface of temporal lobe and medial occipital lobe to parieto-occipital fissure, thalamus, midbrain, internal capsule, cerebral peduncle, substantia nigra, and red nucleus.
What do the Posterior communicating arteries connect?
They connect the internal carotid system to the vertebral-basilar system; (and are part of the circle of Willis)
Which blood vessels are reponsible for supplying about 85% of the blood to the Cerebrum?
Internal carotid arteries
The internal carotid arteries branch to form which two main blood vessels?
Middle cerebral arteries and the anterior cerebral arteries
Middle cerebral arteries provide blood to…
the tip of temporal lobe, lateral surface of cerebral hemispheres and insula. Also supply globus pallidus, putamen, internal capsule, corona radiata, and caudate nucleus.
The MCA supplies all of the motor cortex (area 4) and the somatosensory cortex (areas 1, 2, 3) except the lower extremity LE area.
The anterior cerebral arteries are joined near the rostrom of the corpus callosum by…
the anterior communicating artery
The anterior cerebral arteries supply…
the medial surface of the cerebral hemisphere (i.e., the LE area) and deeper structures including the internal capsule, corpus callosum, and caudate nucleus.
Components of the circle of Willis:
A. Basilar artery B. Posterior cerebral arteries C. Posterior communicating arteries D. Internal carotid arteries E. Anterior cerebral arteries F. Anterior communicating artery
Blood supply of spinal cord (midline anterior spinal artery)
The midline anterior spinal artery, branches off the vertebral artery and supplies the anterior 2/3 of the upper cervical levels of the SC with blood from the vertebral artery.
Blood supply of spinal cord (short and long circumferential branches)
branch off the anterior spinal artery and carry blood to the depths and lateral edges of the anterior 2/3 of the SC, including all of the ventral horn and reaching the base of the posterior horn. The area of supply includes a variable part of the lateral corticospinal tract.
Blood supply of spinal cord (paired posterior spinal arteries)
branch off of the vertebral arteries or the posterior inferior cerebellar arteries. The posterior spinal arteries supply the posterior 1/3 of the SC with blood from the vertebral arteries. The supply area includes the dorsal horn, substantia gelatinosa, and also a variable part of the lateral corticospinal tract.
Below the upper cervical levels, the 3 spinal arteries form anastomoses with…
radicular arteries which branch off of the aorta.
The great radicular artery or artery of Adamkiewicz may provide the entire arterial supply for…
the lumbosacral SC. This artery is sometimes inadvertently damaged during thoracic surgery, resulting in ischemic myelyopathy, and rendering the subject paralyzed below the affected level of the spinal cord.
Spinal arteriovenous malformations may result in…
low back pain, sensory or motor problems, and/or impaired micturition.
The brain consumes approximately what percentage of the body’s oxygen?
20%
The brain comprises only 2% of the body weight, yet receives approximately what percentage of the cardiac output?
15-20%
What are the main factors that have an effect on cerebral blood flow (F)?
pressure gradient (P) and cerebral vascular resistance (R)
What is the relationship between the pressure gradient and cerebral vascular resistance?
The relationship described by Ohm’s law.
In the case of blood flow, Ohm’s law is F = P/R
Resistance to blood flow is a function of both…
Resistance to blood flow is a function of both blood viscosity and vascular resistance
Pressure is regulated by…
circulatory reflexes (e.g., the baroreceptor reflex, mediated by CN X).
