Oral histo quiz

• Bilaminar embryo will be formed by inner cell mass of blastocyst
• Chorion is a double-layered membrane formed by the trophoblast
• Allantois is an extension from the embryo and forms the umbilical cord
• Notochord formation provides skeletal support for the developing embryo
• Neurulation marks the beginning of nervous system development
• Somites give rise to the vertebral column and associated musculature
• Organogenesis involves the development of different structures from the 3 germ layers
• Pharyngeal arches and pouches give rise to various structures in the head and neck region
• First pharyngeal arch (mandibular arch) forms the bony mandible and muscles of mastication
• Second pharyngeal arch (hyoid arch) gives rise to structures like the stapes and stylohyoid ligament
• Third pharyngeal arch contributes to the greater horn of the hyoid bone and the stylopharyngeus muscle
• Fourth pharyngeal arch forms the thyroid cartilage and cricothyroid muscle
• Pharyngeal pouches give rise to structures like the middle ear, parathyroid glands, and thymus gland
• External auditory meatus forms from the first pharyngeal groove
• Cleavage stage:

  • Cells increase in size
  • Morula: Cells are called blastomeres
  • Cells start to differentiate
  • Cell migration
  • Formation of fluid-filled cavity called blastocoel
• Blastulation:

  • Migration
  • Blastocyst
  • Zona pellucida
  • Bilaminar embryo will be formed by inner cell mass of blastocyst
  • Amniotic cavity
• Bilaminar embryo:

  • Epiblast
  • Hypoblast
  • Implantation:
  • Epiblast
  • Hypoblast
  • Primitive streak
  • Bilaminar germ disc
• After floating for 2-3 days in the lumen in the uterus, the embryo implants

  • Formation of bilaminar embryo second week
  • Cells in epiblast are high columnar cells
  • Hypoblast cells are cuboidal cells
  • A small space appears between the inner cell mass and the invading trophoblast called amniotic cavity
• Amnion:

  • Lines amniotic cavity
  • Holds amniotic fluid
  • Forms as a layer of epiblast cells expands towards embryonic pole and differentiates into a thin membrane
• Chorion:

  • A double-layered membrane formed by the trophoblast
  • Surrounds the amnion, embryo, and other membranes
  • Gives rise to the fetal part of the placenta
• Allantois:

  • Is an extension from the embryo
  • Together with the remnants of the yolk sac, it forms the umbilical cord
  • Function is to collect the liquid waste from the embryo as well as to exchange gases by the embryo
• Neurulation:

  • Gastrulation will mark the beginning of neurulation
  • First to develop is the nervous system
  • Process by which the ectoderm layer forms the neural tube
• Notochord formation:

  • Is a round which the vertebral column will develop
  • Provides skeletal support for the developing embryo but will disappear eventually
  • Notochord forms where the primitive streak used to be
• Development of somites:

  • Paraxial mesoderm thickens on each side of the notochord as the notochord and neural tube form
  • End of the third week, the paraxial mesoderm breaks up into segmented pairs of blocks called somites
  • Somites give rise to the vertebral column and associated musculature as well as adjacent dermis of skin
• Organogenesis:

  • Different structures develop from 3 germ layers
  • A different series of events takes place in the head region
  • The neural tube undergoes massive expansion to form the forebrain, midbrain, and hindbrain
• Craniofacial development:

  • Migration of neural crest cells provides the embryonic connective tissue needed for craniofacial development
  • Neural crest cells arise from the midbrain and the first 2 rhombomeres as two streams
  • Development of brachial arches and pharyngeal arches
• Pharyngeal arches:

  • Stomodeum is limited by the first pair of pharyngeal arches bounded by frontal prominence and caudally by the developing heart
  • The arches are seen clearly as bulges on the lateral aspect of the embryo
  • Each arch has its own cartilage, nerves, muscle, and artery (aortic arch artery)
• 
  

  • The pharyngeal pouches are balloon-like diverticula that form between the pharyngeal arches
  • The pairs of pouches develop in a craniocaudal sequence between arches
  • Different derivatives of each pharyngeal pouch
• Cleavage stage: Cells increase in size
• Morula:

  • Cells are called blastomeres
  • Cells start to differentiate
• Formation of fluid-filled cavity called blastocoel
• Blastulation

  • Bilaminar embryo will be formed by inner cell mass of blastocyst
• Bilaminar embryo:

  • Epiblast
  • Hypoblast
• Implantation:

  • Epiblast
  • Hypoblast
  • Primitive streak
  • Bilaminar germ disc
  • After floating for 2-3 days in the lumen in the uterus, the embryo implants
• Formation of bilaminar embryo second week
• Cells in epiblast are high columnar cells
• Hypoblast cells are cuboidal cells
• As implantation continues, a small space appears between the inner cell mass and the invading trophoblast called amniotic cavity
• Amnion:

  • Lines amniotic cavity
  • Holds amniotic fluid
• Chorion:

  • A double-layered membrane formed by the trophoblast
  • Surrounds the amnion, embryo, and other membranes
  • Gives rise to the fetal part of the placenta