Developmental Biology Introduction PDF

Embryology DEVELOPMENTAL Biology (An Introduction) ABI 3109 – Developmental Biology Developmental Biology Comparative Embryology study of processes the study of how whereby a single cell...

Embryology DEVELOPMENTAL Biology (An Introduction) ABI 3109 – Developmental Biology Developmental Biology Comparative Embryology study of processes the study of how whereby a single cell anatomy changes divides and selectively during the activates expression of development of genes to produce complete different organisms organism initiation and modes of construction of organisms reproduction: discipline that studies – oviparity, viviparity, embryonic and ovoviviparity developmental processes cleavage pattern CLEAVAGE PATTERN  Comparative Embryology Von Baer’s principles on vertebrate development  the three germ layers give rise to different organs, and this derivation of the organs is constant Comparative Embryology Comparative Embryology 1. The general features of a large group of 3. The embryo of a given species, instead of animals appear earlier in development passing through the adult stages of lower than do the specialized features of a animals, departs more and more from them smaller group 2. Less general characters develop from the 4. The early embryo of a higher animal is more general, until finally the most never like a lower animal, but only like its specialized appear early embryo Comparative Embryology Evolutionary Embryology trace the movement and positioning of cells study of how changes in development may cause evolutionary changes and of how an organism's ancestry may constrain the types of changes that are possible  tracing of cell lineages: following individual cells to see what they become …“Fate Map”  Evolutionary Embryology embryos contributed to our understanding of evolutionary relationships  Darwin's evolutionary interpretation of von Baer's laws established a paradigm that was to be followed for many decades, namely, that relationships between groups can be discovered by finding common  Larval forms had been used for taxonomic classification embryonic or larval forms. Evolutionary Embryology Evolutionary Embryology homologous or analogous structures Teratology & Medical Embryology Teratology & Medical Embryology the study of birth defects syndrome (piebaldism) malformation – gene mutation – chromosomal aneuploidy – translocation disruption Syndrome: anemia, sterility, unpigmented regions of the skin and hair, deafness, and the absence of the nerves that cause peristalsis in the gut.  Effects of Chernobyl nuclear power plant Teratology & Medical Embryology catastrophe Disruptions (teratogens) Teratology Phocomelia –missing long bones eg. Thalidomide Mathematical Modeling Isometric vs Allometric Growth seeks to describe developmental phenomena in terms of equations patterns of growth and differentiation can be explained by interactions whose results are mathematically predictable whorl were 1 inch in breadth at one point on a radius and the angle of the spiral were 80°  History of Embryology Preformation & Epigenesis Aristotle Epigenesis – first embryologist the organism develops in a – classified animals by type stepwise fashion from an of birth unorganized state – Epigenesis organs of the embryo are formed de novo at each generation Preformation & Epigenesis Preformationists Preformation Jan Swammerdam (1672) the organism is preformed as 17th century Dutch a complete miniature microscopist structure in the sperm or the demonstrated insect egg and simply grows larger development as it develops the organs are already present, in miniature form within the egg (or sperm) Preformationists: Spermistand Preformationists ovist Nicolaas Hartsoeker (1694) Marcelo Malpighi Dutch mathematician and physicist Early microscopist invented the screw-barrel microscope Discovered “Spermatoids” with described early structures in Leeuwenhoek chick embryos Homunculus -animalcule One of the first scientists to study structures such as the Charles Bonnet (1762) lungs, kidneys, spleen, brain, Swiss lawyer, naturalist, philosopher and skin ovist  Determinants: Cytoplasm or Epigeneticists Nucleus William Harvey (1651) Edmund Wilson (1894) blood circulation and Essay on the Generation of Animals Pierre Maupertuis (1745) French mathematician and biologist proposed that the embryo goes through a number of distinct developmental stages. Thomas Morgan (1897) Determinants: Cytoplasm or Nucleus History of Development Edmund Wilson Waldeyer (1863) Discovered haematoxylin his pioneering research on the development of teeth and hair Tonsillar ring Wilhelm His (1870) – Invented the precision microtome – the first scientist to study embryos using paraffin histology, serial sectioning and three‐dimensional modelling. treated the cell as an organism subject to ontogenetic and phylogenetic processes History of Development History of Development Spemann Theory of Organizers Weismann’s Germplasm Theory – protoplasm of egg is destined to give rise to – primordial germ cells which are destined to specific structures give rise to the gonads are segregated very – the organizer plays a critical role in the early in cleavage and that they contain the development of an embryo. “determinants” necessary for development – The organizer contains embryonic cells that influence the development of cells and tissues in the embryo  EMBRYONIC DEVELOPMENT Sperm Figure 47.2 Zygote Adult Egg frog Metamorphosis Blastula Larval Gastrula stages Tail-bud embryo Directional and Anatomical Terms: A Review