人体的九个生理秘密

　　一，人为什么有四种肤色

　　皮肤可能呈乳白色，表皮中的血管为肌肤添加了红色，黄色色素又补充了些底色。最后，皮肤会由于紫外线照射导致黑色素聚集而呈现黑色。这四种颜色以不同的比例混合搭配就产生了不同的肤色。

　　二，笑能增强交际纽带

　　哈欠和笑都能“传染”。听到笑声可以刺激大脑中与面部活动有关的区域。在社会交往中，模仿起着重要的作用。笑、哭泣和打哈欠都是在群体内增强交际纽带的方式。

　　三，姿势影响记忆力

　　专家指出，当身体处于与往事发生时类似的姿势时，人们就容易记起当时的情景。此外，气味或声音都可能唤醒遥远的记忆。

　　四，天冷会使人鼻涕不断

　　人身体内的纤毛对许多器官的运转都有帮助。在鼻子中，纤毛能帮助把黏液从鼻腔排到咽喉。寒冷的天气会减缓排液进程，造成黏液阻塞，使人鼻涕不断。

　　五，胃里隐藏着腐蚀酸

　　任何机场的安检设施都查不出你身上的一种危险液体———胃酸。工业中，盐酸用来浸洗金属。而我们胃壁内的黏液却可将这种毒液安全地储存在消化系统内，帮助人们分解食物。

　　六，数万卵细胞遭浪费

　　年轻女性平均有3.4万个不成熟的卵泡，然而终其一生，只有约350个会发育成熟，其余数万个卵泡都浪费了。

　　七，青春期容易闹情绪    

　　当人处于青春期时，容易出现情绪波动、态度冷漠、决策力低下等现象。这是因为各种荷尔蒙会影响大脑中神经细胞的发育，而大脑结构的变化则会导致各种行为的发生。

　　八，大脑缺氧导致中风

　　大脑占人体体重的2%，却要消耗20%的氧和能量，三条主要的脑动脉必须持续向脑部供氧。若其中一条受阻或断裂，脑细胞就会因缺氧而无法正常工作，从而导致中风。

　　九，骨质为身体补钙

　　骨骼不但能支撑身体的各种器官和肌肉，还能调节体内钙的含量。骨骼中含有磷和钙，而钙是肌肉和神经系统必需的。若体内钙含量不足，特定的激素就会令骨质分解，从而提高体内的钙含量。

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