人的唾液有何功能?

2025-02-17 08:42:54
推荐回答(1个)
回答1:

唾液(saliva)由唾液腺所分泌的液体。人一昼夜分泌量约为1000~1500毫升。其中大唾液腺约分泌5/6,小唾液腺分泌占1/6。其去路乃自觉与不自觉的被咽入胃中,绝大部分被重吸收,以维持体液平衡。唾液分泌有一定节律,夜间静止,清晨较少,下午4~6时达高峰。唾液成分中99.4%为水,其中固体物约0.6%,无机物0.2%,包括Na+、K+、Cl-、HCO-3等。有机物有粘蛋白、球蛋白、氨基酸、尿酸、尿素、肌酸酐和酶。下颌下腺及腮腺唾液的蛋白质含量为0.1~0.5克/100毫升。以粘液蛋白居多,其次为唾液淀粉酶和少量免疫蛋白(IgA)。酶有唾液淀粉酶、麦芽糖酶、ATP酶、5′-核苷酸酶、脂酶、激肽释放酶、碱性磷酸酶、氨基氧化酶等。唾液淀粉酶仅存在于人、类人猿、猪、兔、大鼠、小鼠、豚鼠的下颌下腺及腮腺唾液中,而狗、猫、牛、马、山羊及绵羊的唾液中则含量极少或不含此酶。下颌下腺唾液中含有与红细胞同样的血型凝集原A、B、O等物质,其浓度为10~20毫克/升。来自下颌下腺粘液细胞。
唾液的功能为:湿润口腔,调和润湿食物,使食物溶解并引起味觉,便于吞咽;淀粉酶可水解淀粉及糖原,起到消化作用;在胃内此种淀粉酶仍可持续作用10~30分钟,直到pH降至4.5,在酶失活前,食物中约60~70%淀粉转变成麦芽糖、糊精、麦芽三糖等。唾液可防止口腔干燥,清除食物残渣,洁净口腔;其中溶酶体硫氰酸盐及蛋白质抗体可杀灭细菌。唾液可中和胃酸保护胃壁。唾液中含的氟化物可减少龋齿发生率,保护牙齿。唾液中含的ABO血型物质可测定血型。唾液中(已知成年雄性小鼠)含神经生长因子和表皮生长因子可有助于创面收缩,伤口愈合。唾液还有助于医学诊断。在某些缺乏汗腺的动物(如狗),唾液分泌还可调节体温及水的平衡。

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