Infarction

Also written as infarction, it refers to a sudden blockage of a terminal artery that does not have any anastomotic branches connecting them, causing blood circulation problems in the tissues in the peripheral basin controlled by the artery and resulting in localized necrosis.

Blood vessel blockage is generally caused by embolism or thrombosis. In this case, the shape of the necrotic focus is unique, and corresponds to the area controlled by the blood vessel, and is cone-shaped with the occluded artery at its apex, and its base often faces the surface of the organ.

Because tissues fall into ischemic necrosis due to impaired blood flow, they are often anemic and appear white, and are called anemic infarction or white infarction. They are seen in the kidneys, spleen, heart, brain, etc., and in particular infarctions in the coronary arteries, i.e. myocardial infarction and cerebral infarction, can cause severe symptoms and can sometimes be fatal. In addition, when congestion or damage to the blood vessel walls is accompanied by hemorrhagic changes and the infarction appears red, it is called hemorrhagic infarction or red infarction, and is mainly seen in the lungs.

[Keiji Takeuchi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

硬塞とも書き、おもに互いに連絡する吻合枝(ふんごうし)をもたない終末動脈が急に閉塞され、その動脈が支配する末梢(まっしょう)流域の組織に血行障害をおこして限局性の壊死(えし)がみられるものをいう。

　血管の閉鎖は一般に塞栓や血栓によることが多い。この場合における壊死巣の形は特有で、血管の支配領域に一致し、閉塞された動脈部を頂点とした円錐(えんすい)形で、その底面は臓器の表面に向かう場合が多い。

　組織の血行障害によって虚血性壊死に陥るため、貧血性で白色を呈することが多く、貧血性梗塞または白色梗塞とよばれる。腎臓(じんぞう)、脾臓(ひぞう)、心臓、脳などにみられ、とくに冠状動脈にみられる梗塞、すなわち心筋梗塞や脳梗塞は重篤な症状を呈し、ときに致命的となる。また、うっ血や血管壁の障害を伴い出血性変化が加わり、赤色を呈するものは出血性梗塞または赤色梗塞とよばれ、おもに肺にみられる。

［竹内慶治］

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