|an extraordinary or unusual thing, person, or event; an exceptional example or instance.|
|an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle.|
ectoderm ec·to·derm (ěk'tə-dûrm')
The outermost of the three primary germ layers of an embryo, from which the epidermis, nervous tissue, and sense organs develop. Also called ectoblast.
|ectoderm (ěk'tə-dûrm') Pronunciation Key
The outermost of the primary germ layers of an animal embryo. In vertebrates, the ectoderm gives rise to the epidermis and associated tissues (such as hair and sweat glands), enamel of the teeth, sense organs, nervous system, and lining of the nose, mouth, and anus. Compare endoderm, mesoderm.