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A platelike epithelial thickening, frequently marking, in the embryo, the anlage of an organ or part.



the rudiment of a sense organ or ganglion in humans, vertebrates, and some invertebrates. Placodes are paired thickenings of the outermost embryonic germ layer, the ectoderm; they arise as the nervous system is laid down in the early stages of embryogeny. In vertebrates, placodes give rise to the olfactory organ, the crystalline lens of the eye, the inner ear, the auditory ganglion, and the ganglia of the facial, glossopharyngeal, and vagus nerves. In cyclostomes, fishes, and many amphibians, placodes give rise to the lateral-line organs in addition to the aforementioned structures.

References in periodicals archive ?
Mouse eya homologues of the Drosophila eyes absent gene require Pax6 for expression in lens and nasal placode.
3, where the KAL-1 gene encodes Anosmin 1, which plays a role in normal migration of both GnRH secreting neurons and axons of olfactory neurons from the olfactory placode to the brain, thus linking anosmia with hypogonadotropism.
Neural crest cells and other embryonic cells called placode cells display just the sort of run-and-chase behavior that enables effective migration, Mayor said.
The brain is an ancient structure, and the anterior placode has been considered to be an innovation of vertebrates or chordates.
Because CSF passes through the open distal placode, even though ventriculomegaly may be present, progressive increased ICP is rarely a problem prenatally.
A conserved role for FGF signaling in chordate otic/atrial placode formation.
An effective assay for high cellular resolution time-lapse imaging of sensory placode formation and morphogenesis.
Wise promotes coalescence of cells of neural crest and placode origins in the trigeminal region during head development.
Our inner ear develops in the embryo from a simple flap of skin called the otic placode into a complex, three dimensional structure that enables balance and hearing.
Nicotine inhibition of pulsatile GnRH secretion is mediated by GABAA receptor system in the cultured rat embryonic olfactory placode.
Included in the areas of proposed origin are Jacobson organ (vomeronasal organ), sphenopalatine (pterygoid palatine) ganglion, olfactory placode, and the ganglion of Loci (nervus terminalis).
The supernumerary nostril is result of the abnormal developmental process in the formation of the nose and nasal cavity, which may be in the form of total duplication of the nasal placode or the fissuring of the lateral nasal process.