Regarding fertilization and early development, which of the following are TRUE?

• A. True
• B. False: The morula forms before, not after, the blastocyst.
• C. True
• D. False: The ovum is viable about 24 hours, not a week.
• E. False: During cleavage there is no growth, so cells get smaller with each division.

Fertilization and early development

Sequence and timing

• Fertilization occurs in the fallopian tube (oviduct).
• Zygote -> cleavage -> morula (~day 4) -> blastocyst -> implantation (~day 7) - so the morula forms before the blastocyst.
• During cleavage there is no growth, so cells get smaller with each division.
• The ovum is viable about 24 hours (sperm ~48-72 hours) - not a week.

Why A is true

Fertilization occurs in the tube.

Why B is false

The morula forms before the blastocyst.

Why C is true

Implantation is ~1 week after fertilization.

Why D is false

The ovum is viable ~24 hours, not a week.

Why E is false

During cleavage cells get smaller, not larger.