微动脉是指毛细血管前的阻力血管。在微循环中，起“总闸门”的作用，平滑肌纤维的舒缩可控制管径的大小，其口径决定了微循环的血流量。管径小于300μm的小动脉叫微动脉。
微动脉在绒毛顶部与微静脉有交通支，构成动静脉吻合。
At the tip of the villus, arterioles send out one branch to form an arteriovenous anastomosis with the vein.
目的探讨脑出血时脑小动脉、微动脉病变的分布与严重的程度。
Objective To investigate the extent and degree of lesions of small intracerebral arteries and arterioles.
外源给NO可轻微扩张脑微动脉和提睾肌微动脉，但对其缺氧反应无影响。
Exogenous no could slightly dilate the brain and cremaster muscle arterioles, but had no effect on their hypoxic responses.
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