What is a placode in biology?
Anatomical terminology. A neurogenic placode is an area of thickening of the epithelium in the embryonic head ectoderm layer that gives rise to neurons and other structures of the sensory nervous system. Placodes are embryonic structures that give rise to structures such as hair follicles, feathers and teeth.
What is an ectodermal placode?
Introduction. Ectodermal placodes are focal thickenings of the cranial ectoderm that generate many different components of the sensory systems of the head. The emergence and utilisation of these embryonic structures have long been viewed as being important for the evolution of the vertebrates.
What is the optic placode and where does it originate?
An evagination (the optic vesicle) expands from the wall of the forebrain towards the overlying ectoderm, which has formed a placode (optic, lens placode). The optic vesicle remains attached to the forebrain by an optic stalk.
Is the olfactory Placode a neurogenic Placode?
20.1. Almost all placodes can be classified into two groups, namely (a) the neurogenic placodes and (b) the olfactory, lens, and otic placodes that contribute to sensory organs. The olfactory placode emerges in front of the neural plate adjacent to the forebrain and invaginates to form olfactory pits.
What is the Neuroectoderm?
: embryonic ectoderm that gives rise to nervous tissue.
Where is the ectoderm?
Ectoderm, the outermost of the three germ layers, or masses of cells, which appears early in the development of an animal embryo.
What does the otic Placode form?
The inner ear is derived from the otic placode, which invaginates to form the otocyst, a closed vesicle located within the temporal bone. The otocyst, surrounded by mesenchyme, condenses during development and differentiates into the otic capsule.
What develops from mesoderm?
The mesoderm gives rise to the skeletal muscles, smooth muscle, blood vessels, bone, cartilage, joints, connective tissue, endocrine glands, kidney cortex, heart muscle, urogenital organ, uterus, fallopian tube, testicles and blood cells from the spinal cord and lymphatic tissue (see Fig. 5.4).
What induces neuroectoderm?
Formation of the neuroectoderm is first step in the development of the nervous system. The neuroectoderm receives bone morphogenetic protein-inhibiting signals from proteins such as noggin, which leads to the development of the nervous system from this tissue.
What does mesoderm turn into?
What is the meaning of the word placode?
Also found in: Encyclopedia, Wikipedia. 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).
What is the medical term for placode thickening?
Medical definition of placode: a platelike thickening of embryonic ectoderm from which a definitive structure develops.
What is the meaning of the nasal placode?
nasal placode. an oval area of thickened ectoderm on either ventrolateral surface of the head of the early embryo, constituting the first indication of the olfactory organ.
Is the placode a sense organ or ganglion?
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] Medical Dictionary for the Health Professions and Nursing © Farlex 2012