Blood Supply of CNS PDF

Blood Supply of Brain and Spinal Cord
Dr. Amir M Ali Associate Professor of Anatomy and Embryology  Arterial Supply of Brain  Brain is 2% of TBW  Consumes 15% of normal Card. Output  Consumes 25% of body oxygen  More than 90% distributed in the cortical tissue (gr...

Blood Supply of Brain and Spinal Cord
Dr. Amir M Ali Associate Professor of Anatomy and Embryology  Arterial Supply of Brain  Brain is 2% of TBW  Consumes 15% of normal Card. Output  Consumes 25% of body oxygen  More than 90% distributed in the cortical tissue (gray matter)  Arterial Supply of Brain The brain receives blood from two sources:  Internal carotid  Vertebral arteries Circle of Willis  Internal Carotid Artery  Main source  Arises from common carotid artery in the neck, entering the skull via the carotid canal, and terminates at bifurcation into the anterior cerebral artery and middle cerebral artery  Extracranial part  from the origin of the ICA to the skull base  Intracranial part  Is divided into petrous, cavernous, subaraclinoid portions  Vertebral arteries  Arises at the root of the neck from the first parts of the subclavian artery. Basilar. a  Ascends through the foramina transeversum of cervical vertebrae  Enter the skull through the Vertebral. a foramen magnum. Subclavian. a  Arterial Supply of Brain (Circle of Willis)
 The internal carotid arteries branch to form, the anterior and middle cerebral arteries  The right and left vertebral arteries come together on the ventral surface of the brainstem to form the midline basilar artery  The basilar artery joins the blood supply from the internal carotids in an arterial ring at the base of the brain called the circle of Willis  The posterior cerebral arteries arise at this confluence, as do two small bridging arteries, the anterior and posterior communicating arteries  Circle of Willis Formed by:  6 large arteries  Rt.& Lt. anterior cerebral arteries  Rt.& Lt. internal carotid arteries  Rt.& Lt. posterior cerebral arteries  3 communicating arteries (one anterior & two posterior) Physiological Significance  The arrangement of the brain's arteries into the Circle of Willis creates collaterals in the cerebral circulation, if one part of the circle or its branches becomes blocked or narrowed (stenosed)  Middle cerebral  Continuation of internal carotid  Emerge from lateral sulcus to supply most of superiolateral surface.  Exception the most (superior + inferior).  Supplies  All motor + sensory areas except the lower limb.  Deep nuclei  Internal capsule  Lateral + third ventricles Dr. Amir  Anterior Cerebral  Medial aspect of brain.  Superior margin of cortex which supply foot  Supplies importance regions :  The motor and sensory areas for lower limp , corpus callosum Dr. Amir  Posterior Cerebral Supplies  The posterior cortex, and the brainstem  The whole visual cortex in occipital lobe , center of smell in the uncus  Most of the thalamus and midbrain  Most of the choroid plexuses of the lateral and 3rd ventricle  Blood Supply to Cerebellum  Superior cerebellar artery (SCA) from basilar artery  Anterior inferior cerebellar artery (AICA) from basilar artery  Posterior inferior cerebellar artery (PICA) from vertebral artery  Blood Supply to Spinal Cord  The spinal cord is supplied with blood by three longitudinal arteries anterior spinal artery, right and left posterior spinal arteries  These travel in the subarachnoid space and send branches into the spinal cord  They anastamose via the anterior and posterior segmental medullary arteries, which enter the spinal cord at various points along its length Extra-dural Hemorrhage o It results from injuries of the meningeal arteries or veins o most common is the anterior branch of the middle meningeal artery Sub-dural Hemorrhage o It results from tearing of the superior cerebral veins at their entrance into the superior sagittal sinus o Cause is a blow on the front or back of the head causing anteroposterior displacement of the brain within the skull