细胞分化的瞢這规:全能一能→单能 Cell differentiation occurs epidermis in multicellular organisms ectoderm- neuron Pigment sperm germ cell cardiac skeletal mesoderm elolkidney zygote blastocyst gastrulae smooth Human: 1014 cells pd creat >200 cell types endoderm cell细胞分化的普遍规律：全能→多能→单能