Embryogenesis

• Embryoblast


  The inner cell mass of a blastocyst (the suffix "blast" means "to make")
• Zona pellucida disappearance


  Allows the ball of cells, now called a blastocyst, to grow and change shape
• Blastula


  The term for the blastocyst stage in non-mammal animals
• Pluripotent


  Cells in the inner cell mass can eventually turn into cells of any body tissue (muscle, brain, bone, etc)
• Cell differentiation in the second week

  Cells differentiate further in the epiblast and the hypoblast, which are the two layers of the bilaminar disc
• Bilaminar disc


  A flat slice across the developing sphere, splitting the environment into two cavities
• Hypoblast


  The layer facing the blastocoel
• Epiblast


  The layer on the other side of the bilaminar disc
• Primitive yolk sac


  The cavity on the side of the hypoblast
• Amniotic cavity


  The cavity on the side of the epiblast, which will eventually surround the fetus
• Trophoblast


  The outermost layer of the sphere
• Gastrulation


  The three germ layers form; the cell mass is now known as a gastrula
• Primitive streak formation


  During gastrulation
• Notochord formation


  During gastrulation
• Germ layers


  Ectoderm (outer), mesoderm (middle), endoderm (inner)
• Ectoderm


  Derivatives: epidermis (outer layer of skin), hair, nails, brain, spinal cord, peripheral nervous system
• Mesoderm


  Derivatives: muscle, bone, connective tissue, notochord, kidneys, gonads, cardiovascular system
• Reproduction


  The process where the exchange of genetic material between individuals can result in the formation of a new life
• Reproduction


  1. Conception

  2. Pregnancy

  3. Birth
• Embryogenesis


  The process by which the meeting of an egg and sperm results in an embryo
• Embryo


  The collection of cells that develops into a fetus within the womb of the female, which occurs during pregnancy
• Embryogenesis Stages


  • Fertilization
  • Cleavage formation and Blastocyst formation (Blastulation)
  • Implantation
  • Gastrulation
  • Neurulation
  • Placentation
• Gastrulation

  Transformation of the bilaminar germ disc/layers into the trilaminar germ disc/layers
• Germ layers


  • Endoderm
  • Mesoderm
  • Ectoderm
• Endoderm


  • Develops into digestive tract, liver, pancreas, part of lungs, inner lining of abdominal cavity
• Mesoderm


  • Develops into muscle, skeletal elements, reproductive organs, kidneys, cardiovascular system
• Ectoderm


  • Develops into outer layer of body, central nervous system
• Gastrulation is the stage at which the developing offspring becomes positioned within the womb
• Embryogenesis


  The first eight weeks of development after fertilization, transforming from a single cell to an organism with a multi-level body plan
• During embryogenesis, the circulatory, excretory, and neurologic systems all begin to develop
• Zygote


  The single cell formed when an egg and a sperm cell fuse
• Cleavage


  Very rapid cell division in the first 12-24 hours after zygote formation
• Blastulation


  The mass of cells forms a hollow ball
• Cell differentiation


  Cells begin to differentiate and form cavities
• Trophoblast


  The outer shell layer that helps the growing embryo implant in the mother's uterus
• Inner cell mass


  The inner collection of cells that will continue to differentiate and become the embryo
• Blastocoel


  The fluid-filled cavity within the blastocyst
• Gastrulation


  1. Formation of primitive streak

  2. Bilaminar disc as two-layered cake

  3. Cutting into epiblast layer

  4. Primitive streak cuts from caudal to rostral end

  5. Primitive streak determines midline and separates left and right sides

  6. Cells move from epiblast to between epiblast and hypoblast
• Primitive streak


  • Cuts from caudal (anus) end to rostral (head) end
  • Determines midline of body
  • Separates left and right sides
• Humans


  • Have bilateral symmetry