Question

1. The first and shortest stage of prenatal development is __________, where the the zygote begins to grow in complexity during the first two weeks of conception. 2. The ___________ stage lasts from 2 - 8 weeks following fertilization, when major organs and basic anatomy begin to develop. 3. The __________ stage lasts from 8 weeks until birth and involved the differentiation of major organs.

Answer 1

Answer:

The first and Shortest stage of prenatal development is Germinal stage, where the zygote begins to grow in complexity during first two weeks of conception.

The embryonic stage lasts from 2-8 weeks following fertilisation,when major organ and basic anatomy begin to develop.

The fetal stage lasts from 8 weeks until birth and involved the differentiation of major organs.

Explanation:

Periods of pregnacy and major events are as follows:

• Implantation follows the germinal stage.
• Embryonic stage begins at 2 weeks and following events occur:

• End of one month : Embryo's heart begins to beat.
• End of second month: limbs become paddle like.
• Fetal stage begins:
• first trimesters: major organ systems established.
• End of fourth month: nerve fibre formation begins.
• End of fifth month: First movement of foetus,; eruption of hair.
• End of sixth month: Fine hairs appear on body, eyelids separate.
• End of eighth month: Testes descends into scrotum.
• End of ninth month: Foetus completely developed and ready for birth