The two-cell stage occurs with the first cleavage of the zygote. As it reaches the 30-hour mark (that is, 30 hours after fertilization), the zygote undergoes additional divisions as it moves toward the uterus (endometrium).
Join our Newsletter and receive our free ebook: Guide to Mastering the Study of Anatomy
Thank you for subscribing! Now please check your email to confirm your subscription.
We hate spam as much as you do. Unsubscribe at any time.