L7-9 quiz

• cleavage divisions occur during passage down the oviduct during human embryonic development
• inner cell mass forms the embryo in human embryonic development
• hatching of the embryo occurs before implantation
• trophoblast forms part of the placenta in human embryonic development
• skin and the nervous system are derived from the ectoderm
• cortical reaction:

  • release of high concentration of solutes into the perivitelline space
  • loss of adherence between the plasma membrane and the vitelline membrane
  • cortical granule is released
  • egg plasma membrane is depolarised in contact and fusion of the sperm and egg
  • is the slow block to polyspermy
• Spemann's organiser:

  • is needed to enable neural plate formation
  • releases BMP inhibitors
  • when transplanted to another gastrula is able to induce formation of an entire extra embryo
• vertebrate limb development:

  • ZPA controls the anterior-posterior polarity of the limb
  • high concentrations of Shh give rise to posterior digits
• the blastocyst consists of two cell layers, the inner cell mass (ICM) and the outer layer called trophoblast
• the initial period of cell division with no associated increase in the size of the embryo is called cleavage
• extraembryonic membrane is the outer layer of the blastocyst that forms the placenta
• extraembryonic membrane:

  • amnion
  • chorion
  • yolk sac
  • allantois
• the endometrium is the lining of the uterus that is shed at the end of the menstrual cycle
• during the acrosomal reaction during se urchin fertilisation:

  • release of hydrolytic enzymes
  • membrane depolarisation
  • fast block to polyspermy
• fertilisation membrane is formed when the oocyte is developed
• gastrulation in the chick-> hollow crater formed along the surface of the embryo is called the

  primitive streak
• in the Xenopus blastula, BMP 4 is needed for ventral development
• the fast block polyspermy in sea urchins in effective for approximately a minute
• in all vertebrates, the neural tube develops in the ectoderm directly above the notochord
• in vertebrate limb development, the Apical Ectoderm Ridge (AER) is important for limb outgrowth