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Premedical Biology Individual development in humans Different types of cells have the same genetic information, create different proteins as result of regulatin of transcription. Tissue specific proteins / determinated [differentiated] cells Maternal molecules in cytoplasm and local cell signalling regulate transcription General principles have being studied on model organisms Model organisms Drosophila melanogaster - fruit fly Xenopus laevis - frog Caenorhabditis elegans – nematode Mus musculus Management Zygote / embryonal development means cell division, cell differentiation and morphogenesis/ create a form genetic information for many types of cells, for threedimensional form / morfogenetic movements 1. Maternal determinants in egg: protein molecules, RNA, mRNA….= cytoplasmatic imformation molecules Cytoplasmatic determinants 2. Signal molecules/ induction are coded of offspring genome, Process is accomplished by chemical signals – have target cells / local signalling and cell surface interactions - responsible of early diferentiation, early development Induction / signalling / regulation of gene expression Positional information • determine the location relative to body axes and cell’s ability to respond to signals • anteriorposterior and dorsoventral axe is done by gradients of maternal morphogenes= =products of genes, transcription factors Group of genes 1. egg-polarity genes - bicoid Segmentation genes 2. Gap genes 3. Pair-rule genes 4. Segment polarity genes Homeotic genes / Homeobox • identity of body parts • evolutionarily highly conserved HOX genes: origin of transctiption factors with homeodomain able to bind to DNA / switch on or off Development Zygote - cleavage Morula - blastomers Blastula / blastocoel / blastocyst Gastrula – gastrulation Organogenesis – primitive organs Specific changes of shape, position and adhesion Polarization / animal vegetal pole Gastrulation Epiblast - embryo Hypoblast - yolk sac Germ layers / invagination Ectoderm – nervous system, skin Endoderm – pancreas, epitels of digestive system Mesoderm – kidneys, heart, muscle ectoderm forms the outer layer of gastrula endoderm lines the digestive tract and mesoderm fills the space between the ectoderm and endoderm Gastrulation Archenteron Blastoporus Animal kingdom Porifera - sponges Cnidaria – jellyfish, corals, anemones Ctenophora – coma jellies Platyhelminthes – flatworms Rotifera Nematoda – roundworms Nemertea – ribbon worms Bryozoa two germs layers Radial three germs layers Schizocoelom Bilateral Protostomia / mouth from blastopore Pseudocoelom Phoronida Brachiopoda Mollusca – clams, snails, octopuses Annelida – segmented worms Arthropoda – crustaceans, insects, spiders Echinodermata – sea stars, sea urchins Chordata – lancelets, tunicates, vertebrates Coelom without segmetation Coelom with segmentation Segmentation homonomously Sedmentation herenomously Deuterostomia / anus from blastopor, mouth secondarily Body cavity Space between digestive tract and outer body wall Organogenesis - chordata Primitive organs from germ layers folds, clefts, dense clumps – mechanisms Neural tube - ektoderm – centre of nerve system, brain and spinal cord Notochord – mesoderm – backbone Somites - mesoderm - the muscle segments arrange along each side of notochord neural tube notochord somites archenteron Gastrulation Chicken, mammals Primitive streak “blastoporus” a rapidly proliferating mass of cells that spreads between the ectoderm and endoderm, giving rise to the mesoderm layer. Amniotic egg / reptiles, birds and mammals Extraembryonic membranes: Amnion / protection Allantois / wastes and gas exchange Chorion / gas exchange Yolk sac Human embryo a slow rate of division - between 12 and 24 hours Blastocyst – 7 days, more than 100 cells Trofoblast – placenta Primitive streak Ectoderm: nervous system and epidermis Endoderm: digestive tract and associated organs Mesoderm: kidney, heart, muscles, inner layer of skin In vertebrates, the ectoderm has three parts: external ectoderm (also known as surface ectoderm), the neural crest, and neural tube. The latter two are known as neuroectoderm. The body organs, tissues and systems derived from the mesoderm: • bones • cartilage • most of the circulatory system, including the heart and major blood vessels • connective tissues of the gut and integuments • mesenchyme • mesothelium • muscles • peritoneum (lining of the abdominal cavity) • reproductive system • spleen • urinary system, including the kidneys The following chart shows the products produced by the endoderm. Gastrointestinal tract Respiratory tract Endocrine glands and organs (liver and pancreas) The endoderm forms the epithelial lining of the entire alimentary canal except part of the mouth, pharynx and the terminal part of the rectum (which are lined by involutions of the ectoderm), the lining cells of all the glands which open into the digestive tube, including those of the liver and pancreas, the epithelium of the auditory tube and tympanic cavity, of the trachea, bronchi, and alveoli of the lungs, of the urinary bladder and part of the urethra, and that which lines the follicles of the thyroid gland and thymus. Vertebrates • Sensory organs • Cuticle [skin] of more levels and with derivatives • Special blood cells carry oxygen, closed circulatory system • Pairing kidneys of mesoderm origin • Nervous system and system of glands of internal secretions operate all life functions • Ability to deposite of molecules of high energy - Land vertebrate have egg with amniotic sac and allantois, Agnatha and Gnathostomata from pharyngeal slits • Mammals, birds, reptiles, amphibians, classes of fishes Mammalia Perfect thermoregulation - adaptation to fluctuating tamperatures Cornification of skin, hair Epidermic glands, lactic, milk glands Two-generation set of teeth Two atrias, two ventriculi, left alveolar arch Non-nucleated erythrocytes Diaphragma Placenta / placental mammals and marsupials Thank you for your attention Campbell, Neil A., Reece, Jane B., Cain Michael L., Jackson, Robert B., Minorsky, Peter V., Biology, Benjamin-Cummings Publishing Company, 1996 – 2010.