Medical brain notes 24

  Blood Supply of Central Nervous System          The nervous system is richly supplied with blood. Interruption of blood supply even for a short period can result in damage to nervous tissue. Traditionally it has been taught that lymphatics are not present in nervous tissue, but some workers have recently challenged this view. Blood Supply of the Spinal Cord        The spinal cord receives its blood supply from three longitudinal arterial channels that extend along the length of the spinal cord (Fig. 21.1). The anterior spinal artery  is present in relation to the anterior median fissure. Two  posterior spinal arteries  (one on each side) run along the posterolateral sulcus (i.e., along the line of attachment of the dorsal nerve roots). In addition to these channels the pia mater covering the spinal cord has an arterial plexus (called the  arterialvasocorona ) which also sends branches into t...

  Arteries Supplying the Brain        The brain is supplied by branches of the internal carotid  and the  vertebral  arteries(Figs. 21.3, 21.4). Each internal carotid arterygives off two major branches to the brain. Theseare the  anterior cerebral  and middlecerebral  arteries.         The two vertebral arteries ascend on theanterolateral aspect of the medulla. At the lowerborder of the pons they unite to form the basilar  artery         The basilar artery lies in the midline, ventralto the pons. At the upper border of the pons itbifurcates into two  posterior cerebral  arteries          The internal carotid and vertebro-basilarsystems are connected by the  posteriorcommunicating  arteries. The two anteriorcerebral arteries are connected by the  anterior communicating  artery. As ...

  Arterial Supply of the Cerebral Cortex        The cerebral cortex is supplied by cortical branches of the anterior, middle and posterior cerebral arteries. Superolateral surface          The greater part of the superolateral surface is supplied by the middle cerebral artery (Fig. 21.5). The areas  not  supplied by this artery are as follows. (a)               A strip half to one inch wide along the superomedial border extending from the frontal pole to the parieto-occipital sulcus is supplied by the anterior cerebral artery. (b)            The area belonging to the occipital lobe is supplied by the posterior cerebral artery. (c)             The inferior temporal gyrus (excluding the part adjoining the temporal pole) is also supplied b...

  Internal capsule          The main arteries supplying the internal capsule are the medial and lateral striate branches of the middle cerebral artery, the recurrent branch of the anterior cerebral, and the anterior choroidal artery. The internal capsule may also receive direct branches from the internal carotid artery, and branches from the posterior communicating artery (Fig. 21.8).           The  upper parts  of the anterior limb, the genu, and the posterior limb are supplied by striate branches of the middle cerebral artery. The  lower parts  of these regions are supplied as follows. 1.                The lower part of the anterior limb is supplied by the recurrent branch of the anterior cerebral artery. 2.                The lower part ...

  Medulla          The medulla is supplied by various branches of the vertebral arteries. These are the anterior and posterior spinal arteries, the posterior inferior cerebellar artery, and small direct branches (Fig. 21.11). The anterior spinal artery supplies a triangular area next to the midline. This area includes the pyramid, the medial lemniscus, and the hypoglossal nucleus. The posterior spinal artery supplies a small area including the gracile and cuneate nuclei. The posterior inferior cerebellar artery supplies the retro-olivary region. This region contains several important structures including the spinothalamic tracts, the rubrospinal tract, the nucleus ambiguus, the dorsal vagal nucleus, and descending autonomic fibres. The posterior inferior cerebellar artery also supplies part of the inferior cerebellar  peduncle. The rest of the medulla is supplied by direct bulbar branches of the vertebral arteries. Clinical:   ...

  Venous Drainage of the Brain          The veins draining the brain open into the dural venous sinuses (Fig. 21.12). These are the superior sagittal, inferior sagittal, straight, transverse, sigmoid, cavernous, sphenoparietal, petrosal and occipital sinuses. Ultimately, the blood from all these sinuses reaches the sigmoid sinus which becomes continuous with the internal jugular vein. The intracranial venous sinuses communicate with veins outside the skull through emissary veins. For details about intracranial venous sinuses see the author’s Textbook of Anatomy.         The venous drainage of individual parts of the brain is described below. Veins of the Cerebral Hemisphere        The veins of the cerebral hemisphere consist of two sets, superficial and deep.         The superficial veins drain into neighbouring venous sinuses. The  superi...