Principles Arteries & Veins of the CNS LO14

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1 Principles Arteries & Veins of the CNS LO Identify (on cadaver specimens, models and diagrams) and name the principal arteries and veins of the CNS:

2 Why is it important to understand blood supply to the brain? The brain does not store glucose/oxygen thus is dependent on a continuous blood supply. Brain has no alternative. Which area of the brain required a greater proportion of blood (grey or white matter)? Gray matter as location of cell bodies which is where metabolism takes place. Name the 4 major arteries that deliver blood to the brain? Right and left vertebral arteries. Right and left internal carotid arteries. What space is the Circle of Willis located? Subarachnoid space. If you have a subarachnoid hemorrhage then you have a bleeding in this space. Name the blood vessels of the Circle of Willis The arterial circle is formed sequentially in an anterior to posterior direction by the: Anterior communicating artery Anterior cerebral arteries Internal carotid arteries Posterior communicating arteries Posterior cerebral arteries Middle cerebral NOT part of the Circle of Willis as it is a terminating branch of the MCA

3 Artery Origin Course Termination Major Area Supplied Pathology Vertebral arteries Internal carotid arteries The vertebral arteries begin in the root of the neck (the prevertebral parts of the vertebral arteries) as the first branches of the first part of the subclavian arteries. The internal carotid arteries arise in the neck from the common carotid arteries at the superior border of the thyroid cartilage. Can be distinguished from the external carotid branch because of the large bulge or sinus at the birducation of the common carotid. Enters the cranium in the foramen magnum in the posterior cranial fossa. The cervical part of each artery ascends vertically through the neck, without branching, to the cranial base. Each internal carotid artery enters the cranial cavity through the carotid canal in the petrous part of the temporal bone in the middle cranial fossa. Paired right and left. Join at the base of the pons to for the basilar artery. The terminal branches of the internal carotid arteries are the anterior and middle cerebral arteries. Considered to be the posterior circulation supplies occipital lobe, brain stem and cerebral. Internal carotid artery called the anterior circulation. Gives branches to walls of cavernous sinus, pituitary gland, and trigeminal ganglion; provides primary supply to brain. Occlusion or hemorrhage to these arteries will impact on the functions of the area supplied. In the event of a hemorrhage increased intracranial pressure could lead to further complications affecting other areas of the brain. In fractures of the cranial base, the internal carotid artery may be torn, producing an arteriovenous fistula within the cavernous sinus. Arterial blood rushes into the cavernous sinus, enlarging it and forcing retrograde blood flow into its venous tributaries, especially the ophthalmic veins. Most subarachnoid hemorrhages result from rupture of an aneurysm such as an aneurysm of the internal carotid artery. Subarachnoid hemorrhage is an extravasation of blood, usually arterial, into the subarachnoid space. These two paired vessels anastomose on the inferior surface of the brain to form the Circle of Willis Only 2 vessels that provide the internal surface of the skull with oxygenated blood.

4 Circle of Willis: See LO15

5 Basilar artery and major branches Formed by the union of the left and right vertebral arteries. Mid line on the pons is a single fissure where the basilar artery lies It ends by dividing into the two posterior cerebral arteries. Brainstem, cerebellum, and cerebrum. Aneurysms can occur at the bifurcation of the basilar artery into the posterior cerebral arteries. The most common type of aneurysm is a berry aneurysm. Sudden rupture of an aneurysm is a hemorrhagic stroke and occurs when the weak part of the wall of the aneurysm bursts due to hypertension. Anterior cerebral artery Branch of internal carotid artery It curves backward over the corpus callosum Occlusion or hemorrhage of these arteries will affect the areas supplied i.e. cerebral

6 and, finally, anastomoses with the posterior cerebral artery The cortical branches supply all the medial surface of the cerebral cortex as far back as the parieto-occipital sulcus The anterior cerebral artery thus supplies the leg area of the precentral gyrus. hemispheres (frontal lobes, parietal lobes, temporal lobes NOT occipital lobe) Middle cerebral artery Branch of internal carotid artery Is the major artery supplying most of lateral surface of cerebral hemispheres and temporal lobe. All the motor and sensory area except the leg area. Central branches enter the Occlusion or hemorrhage of these arteries will affect the areas supplied i.e. lateral surface of cerebral hemispheres and temporal lobe

7 Posterior cerebral artery Terminal branch of basilar artery anterior perforated substance and supply the lentiform and caudate nuclei and the internal capsule Inferior aspect of cerebral hemisphere and occipital lobe.

8 Great cerebral vein The great cerebral vein (of Galen) is a single, midline vein formed inside the brain by the union of two internal cerebral veins; it ends by merging with the inferior sagittal sinus to form the straight sinus.

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10 Vertebro-Basilar System Predominately supplies the posterior cerebral Also the supply for the cerebellum and brain stem Little arteries branching off are called ponteen arteries They are lining up to the cranial nerves Any disruption to blood supply in this area then these are the cranial nuclei which will be affected.