Chicken Embryo Development

24-Hour Chick Embryo Development

  • Incubation:
    • Eggs are incubated at a constant temperature of 100100 degrees Fahrenheit or 37.837.8 degrees Celsius to facilitate embryo development.
  • Preparation:
    • Fertilized eggs are used (unlike grocery store eggs).
    • The egg is immersed in a culture dish containing a saline solution (salt water) warmed to 100100 degrees Fahrenheit or 37.837.8 degrees Celsius.
    • The shell is gently cracked, and the saline solution is allowed to enter.
  • Separation:
    • The shell is carefully separated from the egg.
  • Embryonic Structures:
    • Yolk: The yellow part of the egg.
    • Yolk Membrane: The membrane containing the yolk.
    • Albumin: The clear, thick liquid surrounding the yolk.
    • Blastoderm: The small white circle in the center of the yolk; the group of cells that form the chick embryo.
    • Chalaza: A strand of white tissue beside the yolk; holds the egg in place within the shell (there are two chalazae on opposite sides of the yolk).
  • Staining:
    • Neutral red solution (a dye) is added to the yolk to stain the blastoderm for better visibility under a microscope (approximately 30 drops).
    • The solution is allowed to sit for five minutes to allow absorption into the blastoderm tissue.
  • Isolation of Blastoderm:
    • The chalaza is located and held with tweezers to stabilize the yolk.
    • The yolk membrane around the blastoderm is carefully cut with quick incisions (avoiding damage to the blastoderm).
    • The blastoderm is lifted out of the saline solution and placed in a petri dish.
  • Removal of Yolk:
    • A small amount of saline solution is added to the petri dish to help separate the blastoderm from any remaining yolk.
    • Excess saline solution and yolk are carefully withdrawn from the petri dish to prevent glare under the microscope.
  • Microscopic Observation:
    • The petri dish containing the blastoderm is placed on the stage of a stereo microscope.

Microscopic View of 24-Hour Blastoderm

  • Blastoderm Structure:
    • The blastoderm appears as a short tube surrounded by a flat disc.
  • Embryo: The tube-like structure.
  • Area Pellucida: The disc surrounding the embryo; forms the circulatory system of the chick.
  • Neural Crest: A flap of tissue at the top of the embryo; the beginning of the chick's brain.
  • Neural Groove: A dark line running the length of the embryo; the beginning of the chick's spinal cord.
  • Primitive Streak: A light line in the center of the neural groove; a row of cells that form the digestive organs, nervous system, and muscles of the chick.
  • Somites: Rows of cell clusters on each side of the neural groove (about halfway down the neural structures); develop into the bones, ligaments, and tendons of the chick.

48-Hour Chick Embryo Development

  • Preparation: The same steps are followed as with the 24-hour embryo to prepare it for observation.
  • Observed Developments:
    • Neural Fold: Developing into the forebrain, midbrain, and hindbrain at the anterior end of the embryo.
    • Eye and Ear: Developing behind the brain.
    • Spinal Cord: Descending from the brain on the left side of the image.
    • Heart: Visible near the midsection of the embryo on the right side of the image.
    • Somites: Still visible.
    • Tail Bud: Developing into the chick's tail and tail feathers.

72-Hour Chick Embryo Development

  • Observed Developments:
    • Brain, Eyes, Ears, Spinal Cord: More developed compared to the 48-hour embryo.
    • Somites: Still visible.
    • Wing Buds: Visible; will become wings.
    • Leg Buds: Visible; will become legs.
    • Tail Bud: Grown longer.
    • Heart: More developed.
    • Blood Vessels: Two sets of blood vessels are visible.