维生素A属于脂溶性维生素,也称抗干眼病维生素。它的生理功能主要表现在以下几个方面: 第一,构成视觉细胞的视紫红质。 在人的视网膜中有两种感光细胞:一种是锥细胞,另一种是杆细胞。在杆细胞中有一种对弱光敏感的叫视紫红质的化学物质,其中就含有维生素A。维生素A缺乏时,视紫红质合成减少,不能感受弱光,在黄昏时看不清东西,也就是易患夜盲症。 Vitamin A is a fat-soluble vitamins, also known as anti-dry eye vitamins. Its physiological function mainly in the following areas: First, the visual cells constitute the rhodopsin. In the human retina there are two types of photoreceptor cells: one is a cone cell and the other is a rod cell. There is a weak light-sensitive chemical called rhodopsin in rod cells, which contains vitamin A. Vitamin A deficiency, rhodopsin synthesis reduced, can not feel weak light, do not see things at dusk, which is susceptible to night blindness.