Blood Supply of Brain PDF

ARTERIAL SUPPLY OF THE BRAIN Dr. Amani A. Elfaki Professor of Anatomy Department of Anatomy  Blood Supply to the Brain The brain is one of the most metabolically active organs in the body, receiving 17% of the total cardiac output and about 20% of the oxygen available in...

ARTERIAL SUPPLY OF THE BRAIN Dr. Amani A. Elfaki Professor of Anatomy Department of Anatomy  Blood Supply to the Brain The brain is one of the most metabolically active organs in the body, receiving 17% of the total cardiac output and about 20% of the oxygen available in the body. The brain receives it’s blood from two pairs of arteries, the carotid and vertebral. About 80% of the brain’s blood supply comes from the carotid, and the remaining 20% from the vertebral. THE BRAIN IS SUPPLIED BY:- nTWO INTERNAL CAROTID ARTERIES – supplies anterior 2/3 of cerebral hemisphere and parts of diencephalon nTWO VERTEBRAL ARTERIES – supplies posterior 1/3 of cerebral hemisphere and parts of diencephalon, brain stem, spinal cord and cerebellum  INTERNAL CAROTID ARTERY Carotid canal Cavernous sinus Carotid sinus  The Internal Carotid Arteries The internal carotid arteries ascend vertically from the bifurcation of the common carotid arteries, entering the cranial cavity through the carotid canals in the temporal bones. They then pass through the cavernous sinus, piercing the roof to enter the sub-arachnoid space.  INTERNAL CAROTID ARTERY BRANCHES:- Ophthalmic Posterior communicating Choroidal Anterior cerebral Middle cerebral Ophthalmic Artery  Anterior Cerebral Artery Supplies Orbital and Medial Surfaces of Frontal and Parietal Lobes Joined the fellow of the opposite side by the anterior communicating artery Interruption cause – Paralysis of legs and feet – Difficulty in prefrontal lobe functions of cognitive thinking, judgment, motor initiation and self monitoring  Middle Cerebral Artery Direct continuation of carotid artery Cortical Branches – Temporal – Parietal – Frontal Therefore, symptoms include – Aphasia – Motor deficits q Anterior choroidal artery: passes backward, enters inferior horn of lateral ventricle, and ends in choroid plexus. q Posterior communicating artery : runs backward to join posterior cerebral artery  VERTIBRAL ARTERY The vertebral arteries originate from the subclavian artery, Ascend through the transverse foramen of the upper six cervical vertebra. It enters the foramen magnum. The arteries then run forward and unite at the caudal border of the pons to form the basilar artery.  VERTIBRAL ARTERY BRANCHES:- Meningeal Posterior spinal Anterior spinal Posterior inferior cerebellar medullary BASILAR ARTERY  BASILAR ARTERY BRANCHES:- Pontine Labyrinthine Anterior inferior cerebellar Superior cerebellar Posterior cerebelar  Posterior Cerebral Artery Supplies blood to anterior and inferior temporal lobes, uncus, inferior temporal gyri, inferior and medial occipital lobe Watersheds with middle cerebral artery Interruption causes – Homonymous hemianopsia – Possible total blindness – Cerebellar symptoms Circle of Willis  Cerebral arterial circle ( circle of Willis ) Connects Carotid and Basilar Systems Formation: formed by anterior communicating artery, both anterior cerebral arteries, internal carotid arteries, posterior communicating arteries, and posterior cerebral arteries Position: lies on sella turcica around optic chiasma, tuber cinereum and mamillary bodies CIRCLE OF WILLIS  Central Penetrating Arteries n Arise from cortical arteries or from Circle of Willis n Penetrate inferior surface of brain n Can form channels to facilitate blood supply n Central (Penetrating) Arteries n Supply – Thalamus – Hypothalamus – Basal Ganglia – Internal capsule – Choroid Plexus  Blood Supply to the Medulla The Medulla is supplied by the; 1. Anterior spinal artery, sends blood to the paramedian region of the caudal medulla. 2. Posterior spinal artery, supplies rostral areas, including the gracile and cuneate fasiculi and nuclei, along with dorsal areas of the inferior cerebellar peduncle. 3. Vertebral artery, bulbar branches supply areas of both the caudal and rostral medulla. 4. Posterior inferior cerebellar artery, supplies lateral medullary areas.  Blood Supply to the Pons The Pons is supplied by the; 1. The Basilar artery, contributions of this main artery can be further subdivided; a. paramedian branches, to medial pontine region b. short circumferential branches, supply anterolateral pons c. long circumferential branches, run laterally over the anterior surface of the Pons to anastomose with branches of the anterior inferior cerebellar artery (AICA). 2. Some reinforcing contributions by the anterior inferior cerebellar and superior cerebellar arteries  Blood Supply to the Midbrain The major blood supply to the midbrain is derived from branches of the basilar artery; 1. Posterior cerebral artery, forms a plexus with the posterior communicating arteries in the interpeduncular fossa, branches from this plexus supply a wide area if the midbrain 2. Superior cerebellar artery, supplies dorsal areas around the central gray and inferior colliculus with support from branches of the posterior cerebral artery. 3. Quadrigeminal, (some posterior choroidal) a branch of the posterior cerebral, provides support for the tectum (superior and inferior colliculi) 4. Posterior communicating artery, derived from the internal carotid, joins the posterior cerebral to form portions of the circle of Willis (arterial circle). Contributes to the interpeduncular plexus 5. Branches of these arteries are best understood when grouped into paramedian, short circumferential and long circumferential VEINS OF THE BRAIN  The veins of the brain have no muscular tissues in their very thin walls. They possess no valves. Emerge from brain to the subarachnoid space. Pierce the arachnoid & dura to drain into the cranial venous sinuses.  Veins of the Brain Superficial veins drain the cortex and subcortical white matter -> Superior Sagittal Sinus and tran Sinus -> -> Internal Jugular Vein Deep veins drain internal structures -> Great Cerebral vein of Galen -> Straight sinus -> -> Internal Jugular Vein  External cerebral veins Superior cerebral vein superior sagittal sinus Superficial cerebral vein cavernous sinus  Superior Superior cerebral sagittal sinus veins Confluence of Sinus (torcula) Superior anastomotic vein Superficial Superior petrosal middle Carvenous Inferior petrosal Occipital cerebral sinus Inferior anastomotic Transverse vein vein sinus Internal Jugular Sigmoid vein sinus Inferior sagittal sinus Straight sinus Thalamostriate vein and choroidal vein Deep veins Internal cerebral veins Great cerebral vein of Galen Basal veins of Rosenthal Anterior cerebral vein and deep middle cerebral vein  Internal cerebral veins Deep middle cerebral + Anterior cerebral + Striate vein = Basal vein Straight sinus Thalamostriate veins + choroid vein = Internal cerebral vein Internal cerebral vein + Internal cerebral vein = Great cerebral vein  Cerebrovascular Disease The most common neurologic disorder encountered in the United States. Causes 10% of all deaths annually. The 3rd leading cause of death behind heart disease and cancer. Stroke is the general clinical term. qTwo types: Ischemic or Hemorrhagic  Common Vascular Pathology qAtherosclerosis - Narrowing and/or occlusion of vessel lumen due to a build-up of fatty, fibrous plaque (atheromatous plaque) on the vessel wall - Prevalent in diabetic and/or hypertensive patients - Most commonly found in the large arteries in or near the Circle of Willis Anterior Cerebral Middle Cerebral Posterior Cerebral Basilar Internal carotid Vertebral Common carotid Innominate Aorta q Thrombosis The formation of a clotted mass of blood in the cardiovascular system. The mass itself is termed a thrombus. q Embolism Free floating plaque or other substances that blocks the blood vessels,e.g., blood clot, fat, tumor, air. qIntracranial Arterial Aneurysms - abnormal localized dilation of the arterial lumen - Most common in the Circle of Willis Berry Aneurysms - Caused by developmental anomalies or damage to the arterial wall due to atherosclerosis or embolisms qHemorrhagic Lesions - Intracranial bleeding - Commonly caused by rupture of an intracranial aneurysm or developmental defects of blood vessels.  Transient Ischemic Attack (TIA) TIA is a medical emergency because a stroke can occur within the next few hours or days. TIA is a sign of generalized atherosclerotic disease. In fact, the primary cause of death following a TIA is coronary artery disease. Thus, a patient with a TIA should undergo carotid and cardiac evaluation.  Hemorrhage subarachnoid hemorrhage – blood vessel on surface of brain leaks – bleeding into space between brain & skull cerebral hemorrhage (10%) – Defective artery in brain bursts Causes: – aneurysm (blood-filled pouches that balloon out from weak spot in artery) – advancing age, congenital malformation – aggravated by hypertension – head injury  Stroke and Hemiplegia Right-Hemisphere Stroke – The right hemisphere controls the movement of the left side of the body as well as analytical and perceptual tasks Left-Hemisphere Stroke – The left hemisphere controls the movement of the right side of the body as well as speech and language abilities  Stroke: Signs & Symptoms Paralysis on one side Limb Weakness Paresthesias/Sensory loss (numbness or tingling) Ataxia – Gait Disturbance – Uncoordinated fine motor movements  Signs & Symptoms, continued nSpeech Disturbance nVision Problems nHeadache nConfusion/Agitation nDizziness/Vertigo  Blood Brain Barrier Not everything in the blood should reach the neurone. Barrier between CSF and blood Located in capillaries of arachnoid and CSF Barriers between blood and brain tissue.