placode /plac·ode/ (plak´ōd) a platelike structure, especially a thickened plate of ectoderm in the early embryo, from which a sense organ develops, e.g., otic p. (ear), lens p. (eye), and nasal p. (nose).
plac·ode (pl k  d )n. An area of thickening in the embryonic epithelial layer from which some organ or structure later develops. |
placode
a platelike structure, especially a thickening of the ectoderm marking the site of future development in the early embryo of an organ of special sense, e.g. the auditory placode (ear), lens placode (eye) and olfactory placode (nose).
lens placode
the ectodermal thickening which develops into the lens vesicle and later the lens.
nasal placode
one of a pair of ectodermal thickenings which are the forerunners of the external nares and nasopharyngeal epithelium.
olfactory placode
an ectodermal thickening of the embryo which ultimately provides the sensory nerves for the olfactory region of the nasal mucosa.
otic placode
one of the pair of ectodermal thickenings in the vertebrate embryo which invaginates and is a major contributor to the internal ear.
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