Fertilization, Cleavage Types (Meroblastic Discoidal in Birds) & Blastocyst Sequence

• Pre-Implantation Embryonic Development:

• Morula Formation (A): Cleavage divisions produce a solid spherical ball of $16 - 32$ blastomeres.
• Compaction (B): Blastomeres flatten and form tight intercellular junctions, creating distinct inner and outer cell populations.
• Blastulation (C): Fluid accumulation forms a blastocoel cavity, distinguishing the inner cell mass (embryoblast) and trophoblast.
• Zona Hatching (D): The blastocyst sheds the surrounding non-cellular zona pellucida envelope.
• Blastocyst Elongation (E): In domestic ruminants and pigs, the hatched spherical blastocyst elongates into a filamentous conceptus.
  • Sequence:

• nalysis:
• (A, B, C, D, E): Correct chronological order.

Correct option: (1) A,B,C,D.E