Sinh học - Chương 46: Warm - Up

Ch. 46/47 Warm-Up(Ch. 46) How do oogenesis and spermatogenesis differ?(Ch. 46) How do these hormones affect the menstrual cycle?LHFSHEstrogenProgesterone(Ch. 47) Describe the process of fertilization.Chapter 47Animal DevelopmentWhat you must know:The events that occur when a sperm contacts an eggWhat occurs in cleavage, gastrulation, and organogenesisTwo structures derived from each germ layerMammalian FertilizationSperm binds to receptors in zona pellucida (extracellular matrix of egg)Acrosomal reaction: sperm releases hydrolytic enzymes to digest z.p. (Sea Urchins) Depolarization of membrane: prevent other sperm from binding = fast block to polyspermySperm + Egg FuseCortical reaction: sperm + egg fusion triggers release of Ca2+cortical granules fuse with z.p.  z.p. hardens to form fertilization envelope = slow block to polyspermyCa2+ release also triggers activation of the eggFertilization in mammalsCleavage: rapid mitotic cell divisionZygote cytoplasm partitioned into smaller cells (blastomeres)Solid ball of cells = morulaBlastula (hollow ball of cells) filled with fluid (blastocoel)Blastocyst (human)Gastrulation: rearrange cells to form 3-layered embryo w/primitive gutThree Embryonic Germ Layers*EctodermMesodermEndodermSkin, nails, teethLens of eyeNervous system (brain, spinal cord)Skeletal, muscular systemsNotochordExcretory, circulatoryReproductive systemBlood, bone, muscleEpithelial linings of digestive, respiratory, excretory tractsLiver, pancreas* For AP Test, you should know at least 2 derivatives of each germ layer.Future ectodermKeyFuture mesodermFuture endodermArchenteronBlastocoelremnantEctodermMesodermEndodermYolk plugYolk plugGastrulaBlastocoelshrinkingBlastocoelDorsal tip of blastoporeCROSS SECTIONAnimal poleDorsal lipof blastoporeVegetal poleBlastulaSURFACE VIEWGastrulation in a frog embryoFutureectodermEpiblastMigratingcells(mesoderm)YOLKHypoblastEndodermPrimitivestreakGastrulation in a chick embryoOrganogenesis: development of 3 germ layers into organsNotochord – stiff dorsal skeletal rod, forms from mesodermNeural plate  neural tube brain and spinal cordNeurulation – forms hollow dorsal nerve chordSomites – blocks of mesoderm arranged along notochord; sign of segmentationEarly human embryonic developmentNeural foldsNeuralplateLMNeuralfold1 mmNeuralfoldNotochordArchenteronNeural plate formationEndodermMesodermEctodermNeural plateNeural tubeFormation of the neural tubeNeural crestOuter layerof ectodermNeural crest1 mmNotochordArchenteron(digestive cavity)Neural tubeNeural crestEyeSomitesTail budSEMCoelomSomiteSomitesEarly organogenesis in a frog embryoEmbryoAmnioticcavitywithamnioticfluidAllantoisAmnionAlbumenYolk(nutrients)Yolk sacChorionShellAmniotic embryos (reptiles, birds, mammals)Develop in fluid-filled sac w/in a shell or uterusAmnion: fluid protects embryo – prevent dehydration, cushions mechanical shockYolk : nutrients in eggMammalian eggs: little stored foodPatterns of developmentCytoplasmic determinants: chemical signals such as mRNAs and transcription factors, influence pattern of cleavageInduction: interaction among cells that influences their fate, cause changes in gene expressionTotipotent cells: capable of developing into all the different cell typesall cells of mammalian embryos are totipotent until the 16-cell stage