Presentation on theme: "Ch. 46/47 Warm-Up (Ch. 46) How do oogenesis and spermatogenesis differ? (Ch. 46) How do these hormones affect the menstrual cycle? LH FSH Estrogen Progesterone."— Presentation transcript:
1 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.
3 What you must know: The events that occur when a sperm contacts an egg What occurs in cleavage, gastrulation, and organogenesisTwo structures derived from each germ layer
4 Mammalian Fertilization Sperm 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 egg
6 Cleavage: rapid mitotic cell division Zygote cytoplasm partitioned into smaller cells (blastomeres)Solid ball of cells = morulaBlastula (hollow ball of cells) filled with fluid (blastocoel)Blastocyst (human)
7 Gastrulation: rearrange cells to form 3-layered embryo w/primitive gut Three 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.
10 Gastrulation in a frog embryo SURFACE VIEWCROSS SECTIONAnimal poleBlastocoelDorsaltip ofblastoporeGastrulation in a frog embryoDorsal lipof blastoporeVegetal poleBlastulaBlastocoelshrinkingArchenteronEctodermMesodermBlastocoelremnantEndodermKeyFuture ectodermFuture mesodermYolk plugYolk plugFuture endodermGastrula
11 Gastrulation in a chick embryo EpiblastFutureectodermPrimitivestreakEndodermMigratingcells(mesoderm)HypoblastYOLK
12 Organogenesis: development of 3 germ layers into organs Notochord – 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 segmentation
14 Early organogenesis in a frog embryo Neural foldsEyeSomitesTail budNeuralfoldNeural plateSEMLMNeural tube1 mm1 mmNeuralfoldNeuralplateNotochordNeuralcrestNeural crestCoelomSomiteNotochordEctodermMesodermOuter layerof ectodermArchenteron(digestive cavity)EndodermNeural crestSomitesArchenteronNeural plate formationNeural tubeFormation of the neural tubeEarly organogenesis in a frog embryo
15 Amniotic 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 foodEmbryoAmnioticcavitywithamnioticfluidAllantoisAmnionAlbumenYolk(nutrients)Yolk sacChorionShell
16 Patterns of development Cytoplasmic 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