• Length 0.1 -0.2 mm
• The above specimen is the blastocyst of the Macaque monkey.
• Stage 4, the onset of implantation, is reserved for the attaching blastocyst.
• Implantation includes:
  1. Dissolution of the zona pellucida, and contact and attachment (adhesion) between the blastocyst and endometrium.
  2. Penetration
  3. Migration of the blastocyst through the endometrium.
• Ovulation age: 5 - 6 days

Question: What are the three parts of implantation?

Developmental Stages in Human Embryos by Ronan O'Rahilly and Fabiola Müller.  Published by Carnegie Institution of Washington, Publication 637. 1987. Stage 4 (PDF)

Stage 3

Stage 5