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UNT BIOL 4330 - Neural Crests
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BIOL 4330 1st Edition Lecture 11 Outline of Last Lecture I. Central Nervous System and Neural CrestII. NeuroblastsIII. Cerebellar OrganizationIV. Spinal CordOutline of Current Lecture I. Neural Crest CellsII. Regionalization of the Neural CrestIII. Bone FormationIV. Intramembraneous BonesCurrent LectureThe Neural Crest- Derived from the ectoderm - Leads to the jaws, face, skull and sensory ganglia of the vertebrates - Transient structure - Adults and later stage embryos do not have neural crest - Cells undergo an epithelial-mesenchymal transition from the dorsal tube and then migrate to form many different cell types.A portion of the dorsal ectoderm is specified to become neural ectoderm and the cells are columnar - this region of the embryo is called the neural plate – on the surface of the embryo. The process by which the neural plate forms a neural tube (rudiment of the central nervous system) is called neurulation; the embryo is called a neurula. Neural tube forms the brain anteriorly and the spinal cord posteriorly.Studies by Patthey and colleagues (2008, 2009) have shown that if Wnts induce BMPs and Wnt signaling is turned off, the cells become committed to be anterior placodes, whereas if the Wnt signaling induces BMPs but stays on, the cells become neural crest.Regionalization of the Neural Crest These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.1) Cranial (cephalic) neural crest – craniofacial mesenchyme differentiates into cartilage, bone, cranial neurons, glia and connective tissues of the face. Cells also enter the pharyngeal arches and pouches and give rise to the thymic cells, odontoblasts of the tooth primordia and bones of the middle ear and jaw.2) Cardiac neural crest- subregion of the cranial neural crest and extends from the otic (ear) placodes to the third somites-develop into melanocytes, neurons, cartilage, and connective tissue-and produce the large arteries that arise from the heart, contribute to the septum that separates the pulmonary circulation from the aorta. 3) Trunk neural crest- two major pathways: 1) forms the sclerotomes (from somites are blocks of mesodermal cells that will become cartilagenous discs of the spine), some of these form the the dorsal root ganglia containing sensory neurons, sympathetic ganglia, adrenal medulla and nerve clusters surrounding the aorta. 2) Others form the precursors of melanocytes (pigment cells) which move through the dermis from the dorsum to the belly 4) Vagal and sacral neural crest generate the parasympathetic (enteric) ganglia of the gut-failure of neural crest to migrate to the gut results in absence of peristalsisCranial migrates to pharangeal arches. Forms - Neurons, cartilage, bone, and muscles –cranial nervesVagal n.c. – (s 1-7) & sacral n.c. (>s.28) –parasympathetic nerves Of the gut. Cardiac n.c.- (s. 1-3) – make the Division b/w aorta & pulmonary Artery Trunk n.c. – (s. >6) make Sympathetic neurons & Melanocytes – a subset (s. 18-24) forms the Medulla of the adrenal gland CNeural Crest – Cranial vs Trunk - Cranial and Trunk neural crest are not equal. - Cranial neural crest can form cartilage and bone while trunk neural crest cannot.- Both can generate neurons, melanocytes and glia.- Expression of Hox genes in the trunk n.c. cause these cells to fail to make skeletal tissue- To form bone may have been a primitive property and may have been critical for forming bony armor in extinct fish species Both are multipotentMechanisms of trunk migration 1) What signals initiate migration?2) When does the migratory agent become competent to respond to these signals?3) How do the migratory agents know the route to travel?4) What signals indicate that the destination has been reached?Paracrine factors encountered in the environment help specify the different neural crest - derived lineages in the trunk.Ventral Pathway: segmental restriction of neural crest cells and motor neurons by the ephrin proteins of the sclerotome.Bone Formation - Bones form in 2 major ways1) Bones in the trunk and back of the skull are made from mesoderm - mesodermal mesenchymal cells become cartilage, which is replaced by bone (endochondral ossification)2) mesenchymal cells form bone directly (intramembranous ossification)Intramembranous bones 1) Sesamoid bone (e.g. patella) forms as a result of mechanical stress/force 2) Periostal bone- adds thickness to the long bones; 3) Dermal bone -forms in the dermis of the skin 1. and 2. are characteristic of mesodermal cells Dermal bones of the face and skull originate from cranial neural crest are derived mesenchymal cells.During craniofacial development, mesencephalic cranial neural crest cells migrate to become the mesenchyme of the future face and much of the skull.Cardiac N.C. -The septa that separate the truncus arteriosus into the pulmonary artery and aorta form from cells of the cardiac neural crest.The septum that separates the truncus arteriosus into the pulmonary artery and the aorta forms from cells of the cardiac neural


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UNT BIOL 4330 - Neural Crests

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