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A mouth ulcer (also termed an oral ulcer, or a mucosal ulcer) is an ulcer that occurs on the mucous membrane of the oral cavity. Mouth ulcers are very common, occurring in association with many diseases and by many different mechanisms, but usually there is no serious underlying cause. The two most common causes of oral ulceration are local trauma (e.g. rubbing from a sharp edge on a broken filling) and aphthous stomatitis ("canker sores"), a condition characterized by recurrent formation of oral ulcers for largely unknown reasons. Mouth ulcers often cause pain and discomfort, and may alter the person's choice of food while healing occurs (e.g. avoiding acidic or spicy foods and beverages). They may form individually or multiple ulcers may appear at the same time (a "crop" of ulcers). Once formed, the ulcer may be maintained by inflammation and/or secondary infection. Rarely, a mouth ulcer that does not heal for many weeks may be a sign of oral cancer. == Definition == An ulcer (; from Latin ''ulcus'', "ulcer, sore")〔(【引用サイトリンク】title=''Ulcer'' Origin )〕 is a break in the skin or mucous membrane with loss of surface tissue, disintegration and necrosis of epithelial tissue.〔(【引用サイトリンク】url=http://www.merriam-webster.com/medlineplus/ulcer )〕 A ''mucosal ulcer'' is an ulcer which specifically occurs on a mucous membrane. An ulcer is a tissue defect which has penetrated the epithelial-connective tissue border, with its base at a deep level in the submucosa, or even within muscle or periosteum.〔 An ulcer is a deeper breach of the epithelium than an erosion or an excoriation, and involves damage to both epithelium and lamina propria.〔 An ''erosion'' is a superficial breach of the epithelium, with little damage to the underlying lamina propria. A ''mucosal erosion'' is an erosion which specifically occurs on a mucous membrane. Only the superficial epithelial cells of the epidermis or of the mucosa are lost, and the lesion can reach the depth of the basement membrane.〔 Erosions heal without scar formation.〔 ''Excoriation'' is a term sometimes used to describe a breach of the epithelium which is deeper than an erosion but shallower than an ulcer. This type of lesion is tangential to the rete pegs and shows punctiform (small pinhead spots) bleeding, caused by exposed capillary loops. 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「mouth ulcer」の詳細全文を読む スポンサード リンク
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