CH 4 Cranial Vascular: Anatomy and Physiology Flashcards
Vascular structure of the brain includes:
Carotid arteries, vertebral arteries, the circle of willis and the venous sinuses.
80% of blood supply from the carotid artery.
20% from vertebral artery.
cerebral arterial blood supply is predominantly directed to the basal ganglia at the early stages of development and then to the white matter later.
Internal carotid arteries (ICA) course along each side of the neck, bifurcate to form
the anterior (ACA) and middle cerebral arteries (MCA) at the medial end of the sylvian fissure.
The anterior cerebral arteries supply:
the medial cortex, the medial portions of the frontal lobes and the superior medial parietal lobes.
ACA is seen curving around the corpus callosum.
Pericallosal artery
is the terminal end of the ACA and arches around the genue of the corpus callosum and runs along the longitudinal fissure anterior to posterior.
Heubner’s artery
important branch of the ACA supplies the anteriomedial part of the head of the caudate nucleus.
*main nutrient vessel of the caudate
ACA and pericallosal arteries best seen
in mid-sagittal plane through the anterior fontanelle.
*power doppler is best for evaluating the ACA because it provides a more accurate image.
Direction of flow in anterior cerebral artery (ACA) when performing TCD
is away from transducer
TCD is done in children when
child with sickle cell
Middle cerebral arteries
largest and most terminal branches of the ICA and the longest branch which helps form the circle of willis. the MCA supply the majority of the cerebrum.
MCA runs
laterally in the sylvian fissure as a continuation of the intracranial ICA and carries 80% of blood flow to the cerebral hemispheres. supplies a major part of the basal ganglia and its branches and lateral surface of the cerebral hemispheres.
MCA visualized
*the one intracranial vessel that can be evaluated most accurately
is seen at the level of the cerebral peduncles running anteriolaterally toward the lateral edge of the orbits.
MCA branches
tree-like small branches that bring blood to entire lateral aspect of each cerebral hemisphere, including the areas of speech (brocas area)
*small branches M3 branches “stroke arteries” because damage to them can cause major disabilities including paralysis.
Transtemporal position for TCD
best approach to image MCA
window is parallel to MCA and the blood flow is seen flowing towards the transducer.
Medial and lateral branches of the MCA supply
the basal ganglia and thalamus and are very thin, thus more prone to hemorrhage.
Posterior cerebral arteries supply
the occipital lobe of the brain and inferior aspects of the temporal lobes, the midbrain and thalami
Anterior communicating artery (AcomA) and Posterior communicating artery (PcomA) arise from
ICA
Anterior communicating artery (AcomA)
joins the anterior cerebral arteries (aca) which are branches of the ICA of each hemisphere
Posterior communicating artery (PcomA)
joins the MCA’s to the posterior cerebral arteries, which are part of the basilar artery system. Runs from the posterior cerebral arteries(PCA) to ICA
ECA
supply face, high resistance
ICA
supply the brain along with the verts, which help to form the circle of willis. low resistance.
Circle of willis
brains own collateral pathway and decrease blood pressure in brain. Important role in the pressure equilibrium of the cerebral vasculature.
Circle of willis formed by
blood carried by 2 ICA’s and basilar system come together and redistributed by the ACA, MCA, and PCA, with 2 AcomA and 2 PcomA.
formed by the anterior comm. artery, 2 anterior cerebral arteries, 2 ICA’s, 2 posterior comm arteries and 2 posterior cerebral arteries.
Basilar and MCA supply the brain…
they are not considered part of the circle of willis
Vertebral arteries
enter through the foramen magnum into the brain. just inferior to pons they join to become the basilar artery
Basilar artery
give off to R and L posterior cerebral arteries at superior level of the pons.
It can be seen pulsating in the notch of the cerebral peduncles.
Chorodial arteries
arise from the basilar and ICA
*supply the choroid plexes.
damage to these arteries can affect the CSF production
cerebral bloodflow autoregulation
brainstem better at autoregulation
pressures ranging from 50mmHg - 160 mmHg
- the cerebral cortex suffers at low pressures.
- the cerebral vasculature dilates when oxygen content is reduced, but this is limited.
Venous drainage of brain
superficial and deep drainage through veins and venous sinuses.
veins in brain have thin walls and no valves.
cerebral veins
superficial and deep.
superficial lie on surface and drain into SSS and deep veins drain internal structures of the brain into the straight sinus.
Superior cerebral veins
drain the superior, lateral and medial surfaces of the brain and open into the SSS
Middle cerebral vein
runs along the lateral cerebral fissure and is *connected with the SSS and transverse sinus
Internal cerebral vein formed:
from choroid vein and terminal or thalmostriate vein.