Also found in: Medical, Wikipedia.


A platelike epithelial thickening, frequently marking, in the embryo, the anlage of an organ or part.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Among them, Gbx is especially important in the development of the otic placode (9).
Riley, "Zebrafish fgf3 and fgf8 encode redundant functions required for otic placode induction," Developmental Biology, vol.
Proboscis lateralis usually occurs in association with absence of the nose on the same side [3, 5]; however, it may occur from an accessory nasal placode as seen in our case.
Pax2 transcripts were previously shown to be initially distributed uniformly throughout the epithelium of the otic placode [23].
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.
In mouse it begins at14th day of gestation by local proliferation of epidermis forming thickenings (placode stage) followed by hair germ stage then hair peg stage (dermal papilla formation) and finally hair follicles are formed.10For chemoprevention or treatment of skin disorders including malignant conditions retinoids are found to be effective agents.
Wallingford, "A family of Xenopus BTB-Kelch repeat proteins related to ENC-1: new markers for early events in floorplate and placode development," Gene Expression Patterns, vol.
During embryonic development, these cells originate from an extracerebral region, namely, the nasal placode, and migrate to the hypothalamus, closed to olfactory-vomeronasal nerves (VNNs) [2, 3].
An effective assay for high cellular resolution time-lapse imaging of sensory placode formation and morphogenesis.