Early Development

StudyBlue printing of Early Development html, body, div, span, applet, object, iframe, h1, h2, h3, h4, h5, h6, p, blockquote, pre, a, abbr, acronym, address, big, cite, code, del, dfn, em, font, img, ins, kbd, q, s, samp, small, strike, strong, sub, sup, tt, var, b, u, i, center, fieldset, form, label, legend, table, caption, tbody, tfoot, thead, tr, th, td { margin: 0; padding: 0; border: 0; outline: 0; font-size: 100%; background: transparent; } body { line-height: 1; } blockquote, q { quotes: none; } blockquote:before, blockquote:after, q:before, q:after { content: ''; content: none; } /* remember to define focus styles! */ :focus { outline: 0; } /* remember to highlight inserts somehow! */ ins { text-decoration: none; } del { text-decoration: line-through; } /* tables still need 'cellspacing="0"' in the markup */ table { border-collapse: collapse; border-spacing: 0; } /* end RESET */ .header { min-width:800px; } .logo { padding:6px 20px 2px 20px; margin:0; font-size:25px; font-weight:bold; color:#808285; position:relative; border-bottom: 1px solid #c5c5c5; } .logo-blue { color:#70adc4; } .logo-desc { font-weight:normal; font-size:19px; color:#cccccc; margin-top:50px; position:absolute; display: none; } .back-button { position:absolute; top:20px; right:20px; font-size:13px; line-height:25px; color:rgb(0,175,225); font-weight:normal; } .back-button a { color:rgb(0,175,225); } .instructions { padding:0; margin:0; width:100%; position:relative; color:rgb(100,100,100); } .step-holder { border-left:1px solid #ededed; margin-left:20px; } .steps { padding:15px 0; float:left; width:24%; border-right:1px solid #ededed; text-align:center; } .steps-01 { } .steps-02 { } .steps-03 { } .steps-04 { } .label { padding:5px 10px; } .print-button { } .print-button a { background-color:rgb(0,175,225); color:white; line-height: 19px; padding:9px 8px 5px 30px; font-size:14px; text-decoration:none; background-image: url(images/printer.png); background-repeat: no-repeat; background-position: 7px 50%; -moz-border-radius: 5px; -webkit-border-radius: 5px; } .print-button a:hover { background-color:black; } .theNote .content { width: 8.0in !important; margin: 5px auto; padding:20px; background-color:white; } .theNote .header { border-bottom: 1px dashed #C8C8C8; font-size: 17px; padding: 0 0 10px; line-height: 19px; color: #00ADE1; min-width:500px; } .theNote .body { font-size: 14px; line-height: 19px; padding: 10px 0; } .theNote{ padding:6px 0; clear:both; background-color: rgb(200,200,200); } .theNote h3{ color: rgb(100,100,100); } .theNote h1, .theNote h3{ background-color:white; padding:2px 20px; width:8.0in !important; margin: 0 auto; font-size: 15px; } .theNote h1{ padding-top: 10px; font-size: 15px; } .theNote h1:first-child{ font-size: 20px; } .theNote h3 { font-size: 14px; font-weight: normal; } #options { border: 3px double #ccc; padding: 5px 12px; margin: 10px 50px 10px 20px; float: left; } #info { border-top: 1px solid #ccc; padding-top: 5px; font-style: italic; } li { margin: 5px 10px 5px 25px; } ul li { list-style: disc; } ol li { list-style: decimal; } img { border: 0; } table { clear: both; width: 100%; border: 1px solid #c5c5c5; border-width: 1px 0; margin: 0; page-break-after: always; } table#page { page-break-after: auto; } td { text-align: center; font-size: 12px; border-bottom: 1px dashed #c5c5c5; height: 1.75in; width: 50%; padding-left: 15px; } .leftside { border-right: 1px solid #cccccc; padding: 0 15px 0 0; } .bottom td { border-bottom: none; } .clearfix { clear:both; line-height:1px; height:1px; } img { max-width:80%; max-height:150px; margin:20px; } @media print {.header { display: none; } .content .header{ display:inherit; } table { border: 1px dashed #bbb; border-width: 1px 0; } .theNote{ background-color:white; } } Chapter 22: Key Terms anencephalyA congenital defect of neural tube closure, in which much of the brain fails to develop. diencephalon Portion of the brain that lies just rostral to the midbrain; comprises the thalamus and hypothalamus. ectoderm The most superficial of the three embryonic germ layers; gives rise to the nervous system and epidermis. endoderm The innermost of the three embryonic germ layers. Gives rise to the digestive and respiratory tracts and the structures associated with them. fibroblast growth factor (FGF) A peptide growth factor, originally defined by its mitogenic effects on fibroblasts; also acts as an inducer during early brain development. floorplate Region in the ventral portion of the developing spinal cord; important in the guidance and crossing of growing axons. forebrain The anterior portion of the brain that includes the cerebral hemispheres (includes the telencephalon and diencephalon). gastrulation The cell movements (invagination and spreading) that transform the embryonic blastula into the gastrula. germ layers The three primary layers of the developing embryo from which all adult tissues arise: ectoderm, mesoderm, and endoderm. holoprosencephaly Disrupted regional differentiation of the forebrain during development resulting in severe brain malformations. homeotic genes Genes that determine the developmental fate of an entire segment of an animal. Mutations in these genes drastically alter the characteristics of the body segment (as when wings grow from a fly body segment that should have produced legs). Hox genes A group of conserved homeotic genes characterized by a specific DNA sequence—“the homeobox”—and that specify body axis and segmentation patterns in the developing embryo. Hox genes are found among the vertebrates, in Drosophila , and in some other animal groups. hydrocephalus Enlarged cranium as a result of increased cerebrospinal fluid pressure (typically due to a mechanical outflow blockage). medulloblastoma Childhood brain tumor associated with mutations of Sonic hedgehog and other genes in the Shh signaling pathway. mesoderm -The middle of the three germ layers; gives rise to muscle, connective tissue, skeleton, and other structures. midbrain The most rostral portion of the brainstem; identified by the superior and inferior colliculi on its dorsal surface, and the cerebral penduncles on its ventral aspect. Also called the mesencephalon. neural crest A group of progenitor cells that forms along the dorsum of the neural tube and gives rise to peripheral neurons and glia (among other derivatives). neural plateThe thickened region of the dorsal ectoderm of a neurula that gives rise to the neural tube. neural stem cell A precursor cell type that can give rise to the full complement of cell classes found in neural tissue—i.e., neurons, astrocytes, and oligodendroglia, as well as more neural stem cells. neural tube The primordium of the brain and spinal cord; derived from the neural ectoderm. neuroblast A dividing cell, the progeny of which develop into neurons. neuromere A segment of the rhombencephalon (synonym for rhombomere). neurulation The process by which the neural plate folds to form the neural tube. notochord A transient, cylindrical structure of mesodermal cells underlying the neural plate (and later the neural tube) in vertebrate embryos. Source of important inductive signals for spinal cord. primitive pit The thickened anterior end of the primitive streak; an important source of inductive signals during early development. primitive streak Axial thickening in the ectoderm of the gastrulas of reptiles, birds, and mammals; the mesoderm forms by the ingression of cells at this site. prosencephalon The part of the brain that includes the diencephalon and telencephalon (derived from the embryonic forebrain vesicle). radial glia Glial cells that contact both the luminal and pial surfaces of the neural tube, providing a substrate for neuronal migration. retinoic acid A derivative of vitamin A that acts as an inducer during early brain development. rhombencephalon The part of the brain that includes the pons, cerebellum, and medulla (derived from the embryonic hindbrain vesicle). rhombomere Segment of the developing rhombencephalon. segmentation The anterior-posterior division of animals into roughly similar repeating units. somatic stem cell A cell that can divide to give rise to more cells like itself, but also can divide to give rise to a new stem cell plus one or more differentiated cells of a distinct tissue type (e.g., a hematopoeitic stem cell that gives rise to all types of blood cells; see also neural stem cell). Sonic hedgehog (Shh)An inductive signaling hormone essential for development of the mammalian nervous system; believed to be particularly important for establishing the identity of neurons in the ventral portion of the developing spinal cord and hindbrain. spina bifidaA congenital defect in which the neural tube fails to close at its posterior end. telencephalon The part of the brain derived from the anterior part of the embryonic forebrain vesicle; includes the cerebral hemispheres. transcription factors A general term applied to proteins that regulate transcription, including those that are basal and that interact with the RNA polymerase to initiate transcription, as well as those that bind elsewhere to stimulate or repress transcription. transforming growth factor (TGF)A class of peptide growth factors that acts as an inducer during early development. ventricular zone The sheet of cells closest to the ventricles in the developing neural tube.