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CRANIATE EMBRYOGENESIS

CRANIATE EMBRYOGENESIS. Mrs. Ofelia Solano Saludar Department of Natural Sciences University of St. La Salle. Benjamin Disraeli on life history:. YOUTH IS A BLUNDER, MANHOOD A STRUGGLE, OLD AGE A REGRET. TYPES OF EMBRYONIC DEVELOPMENT.

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CRANIATE EMBRYOGENESIS

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  1. CRANIATE EMBRYOGENESIS Mrs. Ofelia Solano Saludar Department of Natural Sciences University of St. La Salle

  2. Benjamin Disraeli on life history: YOUTH IS A BLUNDER, MANHOOD A STRUGGLE, OLD AGE A REGRET.

  3. TYPES OF EMBRYONIC DEVELOPMENT OVIPARITY- egg-laying; contains yolk and albumen to support development VIVIPARITY- offspring is born alive EUVIVIPARITY- maternal tissues provide nutrition, e.g. histotrophic (embryotrophic) nutrition derived from glandular secretions, e.g. placenta OVOVIVIPARITY- egg provides nourishment throughout pregnancy, mother provides protection and oxygen; e.g. shark

  4. INTERNAL VS. EXTERNAL FERTILIZATION censored • EXTERNAL- oviparous forms • INTERNAL- viviparous forms • Spermatophore- gelatinous packet of sperm is placed in the cloaca of female by the male, or picked up by lips of female’s cloaca, e.g. urodeles • Spermathecae- crypts in the female tract containing stored sperm which may fertilize eggs when conditions become suitable

  5. EGG TYPES BASED ON YOLK CHARACTERISTICS MICROLECITHAL, OLIGOLECITHAL or ISOLECITHAL- little amount of yolk; yolk evenly distributed: echinoderms, Amphioxus, mammals MESOLECITHAL- moderate amount of yolk found in vegetal pole: many fishes, lampreys, amphibians MACROLECITHAL- large amounts of yolk found: shark, monotremes TELOLECITHAL- yolk concentrated on one pole; birds, reptiles, most nontherian craniates

  6. TYPES OF CLEAVAGE DUE TO YOLK CONTENT PATTERNS OF CLEAVAGE

  7. EARLY EMBRYOGENESIS

  8. CLEAVAGE

  9. GASTRULATION

  10. GASTRULA TO NEURULA

  11. NEURULATION AMPHIOXUS AMPHIBIAN

  12. TADPOLE

  13. BIRD EMBRYOGENESIS

  14. MAMMALIAN DEVELOPMENT

  15. EXTRAEMBRYONIC MEMBRANES YOLK SAC-surrounds the yolk; Meckel’sdiverticulum is vestigial yolk sac of man CHORION- lines eggshell or mother’s uterus AMNION- prevents dessication of embryo and buffers fetus against mechanical trauma ALLANTOIS- respiratory organ, site of exchange of nutrients and metabolic wastes between mother and embryo; proximal part becomes urinary bladder

  16. PLACENTAa device which allows an embryo to obtain food from the mother. In return the embryo provides bodily waste and eventually, birth pains, stretch marks & sleepless nights. SIMPLE YOLK SAC-serves as a membrane for absorbing oxygen and nourishment from maternal tissues; e.g. viviparous anamniotes CHORIOVITELLINE- yolk sac lies against the chorion; e.g. marsupials CHORIOALLANTOIC- chorioallantoic membrane is in direct contact with maternal uterine lining; reptiles, monotremes, eutherians NONDECIDUOUS vs. DECIDUOUS-fetal membranes peel away without shedding of uterine lining (ungulates), or disengage with bleeding from the invaded tissues of uterine lining (man) CHORIONIC VILLImaybe arranged in cotyledonary (patches), zonary (band), diffuse, or discoidal patterns

  17. Feeding the kids to be…

  18. EPIGENETICS The mutual associations established among cells and tissues determine the eventual developmental outcome. NEU RAL TUBE SPI NAL CORD SCLEROTOMES CARTI LAGES VERTE BRAE INDUCTION-stimulatory effect between developing parts of the embryo

  19. INDUCTION MORPHOGENS- inductor (signaling) proteins expressed by specific homeotic genes that induce organization of the germ layers and participate in the differentiation of specialized tissues from embryonic mesenchyme. HOMEOTIC GENES-Hox gene clusters determine the fates of individual segments in Drosophila and craniates Sonic Hedgehog- participate in differentiation of the notochord, early neural tube, fins or limbs Chordin- secreted by genes in the dorsal lip of the blastopore; body axis-forming activity in early gastrulation

  20. DIFFERENTIATION MORPHOGENS MESENCHYME dendritic, undifferentiated embryonic cells BLASTEMA totipotent mesenchymal aggregates

  21. ECTODERMAL DERIVATIVES EPIDERMIS NEURAL PLATE NEURAL CREST Telencephalon- cerebral hemispheres Diencephalon- thalamus; Mesencephalon-optic lobes Metencephalon- cerebellum Myelencephalon- medulla oblongata Olfactory, otic, optic, epibranchial placodes and neuromasts Neural tube- spinal cord Epidermis Stomodeum- mouth; Rathke’s pouch; mammalian enamel Proctodeum- cloacal opening Extraembryonic membranes Ganglionic neural crest Neuroglia (Schwann cells) Ectomesenchyme-melanocytes Visceral skeleton Adrenal medulla

  22. MESODERMAL DERIVATIVES EPIMERE MESOMERE HYPOMERE Somato pleure Splanchno pleure SOMITE NEPHROTOME Dermatome- dermis Myotome- body musculature Sclerotome- vertebral column Kidney and urogenital ducts: pronephric tubules and duct, mesonephric tubules, renal cortex Limbs Parietal peritoneum Genital ridge- gonads CT of skeleton and body wall Blood vascular- heart, vessels Visceral peritoneum Mesenteries Extraembryonic membranes

  23. ENDODERMAL DERIVATIVES FOREGUT MIDGUT HINDGUT Pharynx- oral and nasal cavities and derivatives; pharyngeal pouches Posterior foregut- esophagus, lungs buds (trachea) Stomach Liver Pancreas Small and large intestines Allantois- urinary bladder Urogenital sinus- cloaca

  24. QUESTIONS?

  25. Quiz next meeting. Next… The Integument

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