The human zygote undergoes cleavage during its movement along the fallopian tube. The cleavages in zygote are said to be holoblastic as the cleavage is equal. The first cleavage occurs usually within 30 hours after fertilization. The cleavage furrow is vertical passing through the animal pole to vegetal pole.
The two daughter cells so formed are called blastomeres. The second cleavage is also vertical but at right angles to the first one forming four blastomeres of equal size. Subsequent divisions occur in a rapid but orderly fashion producing a number of blastomeres.