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The middle cerebral artery (MCA) is one of the three major paired arteries that supply blood to the cerebrum. The MCA arises from the internal carotid and continues into the lateral sulcus where it then branches and projects to many parts of the lateral cerebral cortex. It also supplies blood to the anterior temporal lobes and the insular cortices. The left and right MCAs rise from trifurcations of the internal carotid arteries and thus are connected to the anterior cerebral arteries and the posterior communicating arteries, which connect to the posterior cerebral arteries. The MCAs are not considered a part of the Circle of Willis.〔Moore KL, Dalley AR. ''Clinically Oriented Anatomy'', 4th Ed., Lippincott Williams & Wilkins, Toronto. Copyright 1999. ISBN 0-683-06141-0.〕 ==Structure== The middle cerebral artery can be classified into 4 parts: *M1: The ''sphenoidal'' segment, so named due to its origin and loose lateral tracking of the sphenoid bone. Although known also as the ''horizontal'' segment, this may be misleading since the segment may descend, remain flat, or extend posteriorly the anterior (dorsad) in different individuals. The M1 segment perforates the brain with numerous ''anterolateral central'' (lateral lenticulostriate) arteries, which irrigate the basal ganglia. *M2: Extending anteriorly on the insula, this segment in known as the ''insular'' segment. It is also known as the ''Sylvian'' segment when the opercular segments are included. The MCA branches may bifurcate or sometimes trifurcate into trunks in this segment which then extend into branches that terminate towards the cortex. *M3: The ''opercular'' segments and extends laterally exteriorly from the insula towards the cortex. This segment is sometimes grouped as part of M2. *M4: These finer ''terminal'' or ''cortical'' segments irrigate the cortex. They begin at the external of the Sylvian fissure and extend distally away on the cortex of the brain. The M2 and M3 segments may each split into 2 or 3 main trunks (terminal branches) with an ''upper trunk'', ''lower trunk'' and occasionally a ''middle trunk''. Bifurcations and trifurcations occurs in 50% and 25% of the cases respectively. Other cases include duplication of the MCA at the internal carotid artery (ICA) or an accessory MCA (AccMCA) which arise not from the ICA but as a branch from the anterior cerebral artery. The ''middle trunk'' that exist in parts of the population, when present provides the ''pre-Rolandic'', ''Rolandic'', ''anterior parietal'', ''posterior parietal'' and the ''angular artery'' for irrigation instead of the ''upper'' and ''lower trunks''. The branches (ramus) of the MCA can be described by the areas that they irrigate. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「middle cerebral artery」の詳細全文を読む スポンサード リンク
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