Chick Embryo

• Living part of the chicken egg

  Blastoderm
• The blastoderm is surrounded by the area pellucida and area opaca
• Transparent portion of the embryo

  Area pellucida
• Darker portion of the embryo, where extra embryonic blood vessels are forming

  Area opaca
• The primitive streak is a clear line flanked by parallel dark lines toward the center of the area pellucida
• Groove between 2 primitive folds

  Primitive groove
• 2 ectodermal elevations

  Primitive folds
• Deep anterior pit where groove terminates

  Hensen's node
• The notochord is a slightly darkened triangular area anterior to the Hensen's node
• Formed throughout the area opaca, irregularly shaped accumulations of mesodermal cells

  Blood islands
• Will form the blood vessels and primitive blood cells

  Blood islands
• In how many hours will the somites be present?

  ~ 21
• In this stage, the specimen is divisible into an inner area pellucida and an outer area opaca

  33 Hour Chick Embryo
• Clear area anterior to the head of the embryo

  Proamnion
• Biggest difference between 48 hour and 33 hour chick embryo

  Cephalic flexure
• In the 48 hour chick embryo, there are now optic cups and about 20 to 28 somites
• After 72 hours, the chick embryo will now have:

  1. Limb buds
  2. Tail
  3. Paired wing
  4. Sac-like allantois
• The allantois acts as an embryonic lung
• Day 1

  • Head fold formation
  • Hensen's node regression
  • Separation of embryo from extraembryonic tissue
• Day 2

  • Blood islands
  • Heart primordium
  • Closing of neural tube
• Day 3

  • Start of blood circulation
  • Appearance of extraembryonic fold
• Day 4

  • Limb bud and allantoic vesicle formation

  Day 9

  • C-shaped embryo
  • Appearance of claws
  • Budding of first feather follicles
• The ff image shows the blastodisc:

  
• Single reproductive cell

  Blastodisc
• Four membranes of the amniotic egg:

  1. Chorion
  2. Amnion
  3. Yolk sac
  4. Allantois
• Encases the embryo in a fluid-filled cavity

  Amnion
• Blood vessel formation is attributed to:

  1. Vasculogenesis
  2. Angiogenesis
• Branch point density =

  branch points in a blood vessel segment / length of a blood vessel segment
• Distance between each branch point

  Intercapillary distance