In this chapter you will: Describe the acrosomal reaction; describe the cortical reaction; distinguish among meroblastic cleavage and holoblastic cleavage; compare the formation of a blastula and gastrulation in a sea urchin, a frog, and a chick; list and explain the functions of the extraembryonic membranes.
Ch 46/47 Warm-Up (Ch 46) How oogenesis and spermatogenesis differ? (Ch 46) How these hormones affect the menstrual cycle? a) LH b) FSH c) Estrogen d) Progesterone (Ch 47) Describe the process of fertilization Chapter 47 Animal Development What you must know: • The events that occur when a sperm contacts an egg • What occurs in cleavage, gastrulation, and organogenesis • Two structures derived from each germ layer 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 polyspermy Sperm + Egg Fuse Cortical reaction: sperm + egg fusion triggers release of Ca2+ cortical granules fuse with z.p z.p hardens to form fertilization envelope = slow block to polyspermy Ca2+ release also triggers activation of the egg Fertilization in mammals Cleavage: rapid mitotic cell division • Zygote cytoplasm partitioned into smaller cells (blastomeres) • Solid ball of cells = morula • Blastula (hollow ball of cells) filled with fluid (blastocoel) Blastocyst (human) Gastrulation: rearrange cells to form 3-layered embryo w/primitive gut Three Embryonic Germ Layers* Ectoderm Mesoderm Endoderm • Skin, nails, teeth • Lens of eye • Nervous system (brain, spinal cord) • Skeletal, muscular • Epithelial linings of systems digestive, respiratory, excretory tracts • Notochord • Liver, pancreas • Excretory, circulatory • Reproductive system • Blood, bone, muscle * For AP Test, you should know at least derivatives of each germ layer Organogenesis: development of germ layers into organs • Notochord – stiff dorsal skeletal rod, forms from mesoderm • Neural plate neural tube brain and spinal cord • Neurulation – forms hollow dorsal nerve chord • Somites – blocks of mesoderm arranged along notochord; sign of segmentation Early human embryonic development Amniotic embryos (reptiles, birds, mammals) • Develop in fluid-filled sac w/in a shell or uterus • Amnion: fluid protects embryo – prevent dehydration, cushions mechanical shock • Yolk : nutrients in egg • Mammalian eggs: little stored food Amnion Allantois Embryo Amniotic cavity with amniotic fluid Albumen Shell Yolk (nutrients) Chorion Yolk sac Patterns of development • Cytoplasmic determinants: chemical signals such as mRNAs and transcription factors, influence pattern of cleavage • Induction: interaction among cells that influences their fate, cause changes in gene expression • Totipotent cells: capable of developing into all the different cell types all cells of mammalian embryos are totipotent until the 16-cell stage .. .Chapter 47 Animal Development What you must know: • The events that occur when a sperm contacts an egg •... circulatory • Reproductive system • Blood, bone, muscle * For AP Test, you should know at least derivatives of each germ layer Organogenesis: development of germ layers into organs • Notochord – stiff... polyspermy Ca2+ release also triggers activation of the egg Fertilization in mammals Cleavage: rapid mitotic cell division • Zygote cytoplasm partitioned into smaller cells (blastomeres) • Solid