placode


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placode

 [plak´ōd]
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).

plac·ode

(plak'ōd),
Local thickening in the embryonic ectodermal layer; the cells of the placode ordinarily constitute a primordial group from which a sense organ or ganglion develops.
[G. plakōdēs, fr. plax, anything flat or broad, + eidos, like]

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

(plak'ōd)
Local thickening in the embryonic ectodermal layer; the cells of the placode ordinarily constitute a primordial group from which a sense organ or ganglion develops.
[G. plakōdēs, fr. plax, anything flat or broad, + eidos, like]

placode

a plate-like embryonic structure from which a particular organ, such as the eye, 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.
References in periodicals archive ?
Canonical WNT signaling promotes mammary placode development and is essential for initiation of mammary gland morphogenesis.
The goal of the zebrafish research is to understand at the molecular level, how and why otic placode cells decide to become neuronal, non-sensory or sensory cells.
Where possible, the placode is then reconstituted, followed by a careful, layered, watertight closure of the dura and myofascial tissue.
Morphogenesis of feather follicle initiated from the basal epidermal placode appearing above a condensation of dermal cell (Prum, 1999), the increasing of the dermal condensation and the thickening of the epidermal played an essential role in the induction of feather follicles (Wolpert, 1998).
The nasal placodes (olfactory placodes) arise from the medial aspect of the lower portion of the frontal prominence, and the lens placodes arise from the lateral aspect of the lower portion of the frontal prominence.
It becomes more superficial and rostral as it proceeds ventrally, and it ends adjacent to the deep surface of the epibranchial placode on the dorsal and caudal aspect of the first branchial groove.
1,2] Should inner ear development be interrupted between the fourth and fifth weeks of gestation after differentiation of the auditory placode into the otocyst, but before division of the latter into the primordium of the cochlea, vestibule, and semicircular canals--a "common cavity" forms that has no internal architecture (figure).
The lens placodes form the lenses of the eyes in week 5, and the primary lens fibers reach the anterior wall of the lens vesicle by the end of week 7.
Stage Y&K Description 1 14 Late gastrula 2 16 Head fold 3 17 Optic vesicle 4 20 Optic cups 5 21 Auditory placodes 6 22 Lens 7 23-25 Otoliths, heartbeat, black pigment in retina and iris is strongest in periphery.
Vertebrate structures such as the neural crest and the placodes further the development of the head and the brain, which reaches an unprecedented complexity in humans.
Londt (1983)--Revised Daspletis, presenting a key to six species: hermanni (transferred from Microstylum), hirtus, setithoracicus (established within the genus as a consequence of the synonymy of Neodysmachus), vulpes, and two new species, placodes and stenoura, both from South Africa.
Antennae 30 antennomeres, longer than body, the basal flagellomeres about 3 times as long as wide, the following slightly shorter, Fp about 2 times as long as wide; the setae as long as the segment width; in lateral view 3 placodes visible.