What are neurogenic Placodes?
Neurogenic placodes are specialized regions of the embryonic ectoderm that are central to the development of the cranial sensory systems of vertebrates. These structures generate many of the sensory neurones of the head and also, in some instances, the associated sensory receptor cells.
How do placodes form?
The cranial placodes are localized ectodermal thickenings that develop by apicobasal elongation of cuboidal cells in the inner layer of the ectodem in the head of vertebrate embryos. They are involved in formation of sense organs (eye, nose, ear) and cranial sensory ganglia.
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 is a placode in biology?
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.
Where is the ectoderm located?
The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, and is superficial to the mesoderm (the middle layer) and endoderm (the innermost layer). It emerges and originates from the outer layer of germ cells.
Where does the otic vesicle develop from?
cranial placode
Development. The otic vesicle is derived from the cranial placode. The early otic vesicle is characterized as having broad competence and can be subdivided into sensory, non-sensory, and neurogenic components. Sensory epithelial cells and neurons are derived from the proneurosensory domain.
What is Placodal ectoderm?
The ectodermal placodes are focal thickenings of the cranial embryonic ectoderm that contribute exten- sively to the cranial sensory systems of the vertebrates. The ectodermal placodes have long been thought of as representing a coherent group, which share a developmental and evolutionary history.
What is the difference between nerve and ganglia?
Difference Between a Nerve and a Ganglion Both nerves and ganglia are structures found in the nervous system. However, a ganglion refers to a collection of nerve cells outside of the CNS whereas a nerve is the axon of a neuron.