Pre-embryonic: week 1 - week 2

- Developing human called pre-embryo

Embryonic: week 3 - week 8

- Developing of human called embryo

Fetal: week 9 - birth

- Developing of human called fetus

Fertilization (when sperm fuses with egg).

200 - 600 million sperm per ejaculation.

Fertilized Ovum is called zygote.

Zygote undergoes cleavage before implantation

Each egg carries an X chromosome.

Each sperm carries an X or a Y chromosome.

If Y chromosome fuses with X = boy

If X chromosome fuses with Y = girl

Pre-embryonic period (part2)

Zygote goes through cleavage before implantation.

After fertilization and implantation zygote splits

Becomes pre-embryo

zygote splits down the center to form 2 cells, then 4, then 6, etc.

After it reaches 12, it is known as Morula

Morula keeps dividing and eventually implants in the endometrial lining.

If implantation is successful, pregnancy begins.