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Neurogenic Placodes
In embryology, 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. The term "neurogenic placode" generally refers to cranial placodes that have neurogenic potential - i.e. those that give rise to neurons associated with the special senses and cranial ganglia. Cranial placodes include a diverse range of structures found across chordates, but the neurogenic placodes found in vertebrates arose later in evolution. The region in the ectoderm of the developing head that contains all the precursor cells for the cranial placodes is known as the preplacodal region. In humans The cranial placodes that have neurogenic potential (i.e. give rise to neurons) can be divided into two groups, the dorsolateral placodes and the epibranchial placodes. * dorsolateral ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ectoderm
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. The word ectoderm comes from the Greek language, Greek ''ektos'' meaning "outside", and ''derma'' meaning "skin".Gilbert, Scott F. Developmental Biology. 9th ed. Sunderland, MA: Sinauer Associates, 2010: 333-370. Print. Generally speaking, the ectoderm differentiates to form epithelial tissue, epithelial and nervous system, neural tissues (spinal cord, nerves and brain). This includes the Epidermis (skin), skin, linings of the mouth, anus, nostrils, sweat glands, hair and nails, and tooth enamel. Other types of epithelium are derived from the endoderm. In vertebrate embryos, the ectoderm can be divided into two parts: the dorsal surface ectoderm also known as the external ectoderm, and the neural plate, which inv ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dorsolateral Placodes
Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek language, Greek roots, describe something in its standard anatomical position. This position provides a definition of what is at the front ("anterior"), behind ("posterior") and so on. As part of defining and describing terms, the body is described through the use of anatomical planes and anatomical axes, axes. The meaning of terms that are used can change depending on whether a vertebrate is a biped or a quadruped, due to the difference in the neuraxis, or if an invertebrate is a non-bilaterian. A non-bilaterian has no anterior or posterior surface for example but can still have a descriptor used such as proximal or distal in relation to a body part that is nearest to, or furthest from its middle. International organisations have determined vocabularies that are often used as standards for subdisciplines of anatomy. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cranial Nerve IX
The glossopharyngeal nerve (), also known as the ninth cranial nerve, cranial nerve IX, or simply CN IX, is a cranial nerve that exits the brainstem from the sides of the upper medulla, just anterior (closer to the nose) to the vagus nerve. Being a mixed nerve (sensorimotor), it carries afferent sensory and efferent motor information. The motor division of the glossopharyngeal nerve is derived from the basal plate of the embryonic medulla oblongata, whereas the sensory division originates from the cranial neural crest. Structure From the anterior portion of the medulla oblongata, the glossopharyngeal nerve passes laterally across or below the flocculus, and leaves the skull through the central part of the jugular foramen. From the superior and inferior ganglia in jugular foramen, it has its own sheath of dura mater. The inferior ganglion on the inferior surface of petrous part of temporal is related with a triangular depression into which the aqueduct of cochlea opens. On th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inferior Ganglion Of Glossopharyngeal Nerve
The inferior ganglion of the glossopharyngeal nerve (petrosal ganglion) is a sensory ganglion. It is larger than and inferior to the superior ganglion of the glossopharyngeal nerve. It is located within the jugular foramen. The pseudounipolar neurons of the inferior ganglion of the glossopharyngeal nerve provide sensory innervation to areas around the tongue and pharynx. More specifically: # innervation of taste buds on the posterior 1/3 of tongue # general sensory innervation of posterior 1/3 of tongue, soft palate, palatine tonsils, upper pharynx and Eustachian tubes # innervation of baroreceptor cells in the carotid sinus # innervation of glomus type I chemoreceptor cells in the carotid body The central processes of the neurons which provide taste sensation synapse in the rostral portion of the solitary nucleus (also called the gustatory nucleus). The central processes of the neurons which provide general sensory information synapse in the spinal trigeminal nucleus. Finally ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Petrosal Placode , in various animals referred to as the petrosal bone
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Petrosal may refer to: * Inferior petrosal sinus * Petrosal process * Petrosal nerve (other) * Petrous ganglion * Petrous part of the temporal bone The petrous part of the temporal bone is pyramid-shaped and is wedged in at the base of the skull between the sphenoid and occipital bones. Directed medially, forward, and a little upward, it presents a base, an apex, three surfaces, and three ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cranial Nerve VII
The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue. The nerve typically travels from the pons through the facial canal in the temporal bone and exits the skull at the stylomastoid foramen. It arises from the brainstem from an area posterior to the cranial nerve VI (abducens nerve) and anterior to cranial nerve VIII (vestibulocochlear nerve). The facial nerve also supplies preganglionic parasympathetic fibers to several head and neck ganglia. The facial and intermediate nerves can be collectively referred to as the nervus intermediofacialis. The path of the facial nerve can be divided into six segments: # intracranial (cisternal) segment (from brainstem pons to internal auditory canal) # meatal (canalicular) segment (within the i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geniculate Ganglion
The geniculate ganglion (from Latin ''genu'', for "knee") is a bilaterally paired special sense ganglion of the intermediate nerve component of the facial nerve (CN VII). It is situated within facial canal of the head. It contains cell bodies of first-order unipolar sensory neurons which convey gustatory (taste) afferents from taste receptors of the anterior two-thirds of the tongue by way of the chorda tympani, and of the palate by way of the greater petrosal nerve, From the ganglion, the proximal fibres proceed to the gustatory (i.e. superior/rostral) part of the solitary nucleus where they synapse with second-order neurons. Anatomy Structure The geniculate ganglion is conical in shape. The greater petrosal nerve diverges from CNVII and the lesser petrosal nerve diverges from CN IX at the geniculate ganglion. Relations It is located close to the internal auditory meatus. It is covered superiorly by the petrous part of the temporal bone (which is sometimes abse ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pharyngeal Groove
A pharyngeal groove (or branchial groove, or pharyngeal cleft) is made up of ectoderm unlike its counterpart the pharyngeal pouch on the endodermal side. The first pharyngeal groove produces the external auditory meatus The ear canal (external acoustic meatus, external auditory meatus, EAM) is a pathway running from the outer ear to the middle ear. The adult human ear canal extends from the auricle to the eardrum and is about in length and in diameter. Str ... (ear canal). The rest (2, 3, and 4) are overlapped by the growing second pharyngeal arch, and form the floor of the depression termed the cervical sinus, which opens ventrally, and is finally obliterated. See also * Branchial cleft cyst * Collaural fistula References Animal developmental biology Pharyngeal arches {{developmental-biology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Geniculate Placode
The geniculate ganglion (from Latin ''genu'', for "knee") is a bilaterally paired special sense ganglion of the intermediate nerve component of the facial nerve (CN VII). It is situated within facial canal of the head. It contains cell bodies of first-order unipolar sensory neurons which convey gustatory (taste) afferents from taste receptors of the anterior two-thirds of the tongue by way of the chorda tympani, and of the palate by way of the greater petrosal nerve, From the ganglion, the proximal fibres proceed to the gustatory (i.e. superior/rostral) part of the solitary nucleus where they synapse with second-order neurons. Anatomy Structure The geniculate ganglion is conical in shape. The greater petrosal nerve diverges from CNVII and the lesser petrosal nerve diverges from CN IX at the geniculate ganglion. Relations It is located close to the internal auditory meatus. It is covered superiorly by the petrous part of the temporal bone (which is sometimes absent o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Otic Vesicle
Otic vesicle, or auditory vesicle, consists of either of the two sac-like invaginations formed and subsequently closed off during embryonic development. It is part of the neural ectoderm, which will develop into the membranous labyrinth of the inner ear. This labyrinth is a continuous epithelium, giving rise to the vestibular system and auditory components of the inner ear. During the earlier stages of embryogenesis, the otic placode invaginates to produce the otic cup. Thereafter, the otic cup closes off, creating the otic vesicle. Once formed, the otic vesicle will reside next to the neural tube medially, and on the lateral side will be paraxial mesoderm. Neural crest cells will migrate rostral and caudal to the placode. The general sequence in formation of the otic vesicle is relatively conserved across vertebrates, although there is much variation in timing and stages. Patterning during morphogenesis into the distinctive inner ear structures is determined by homeobox transc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Otic Pit
The auditory pit, also known as the otic pit, is the first rudiment of the internal ear. It appears shortly after that of the eye, in the form of a patch of thickened ectoderm 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 o ..., the auditory plate, over the region of the hind-brain. The auditory plate becomes depressed and converted into the auditory pit (or otic pit). References Embryology of nervous system {{developmental-biology-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
