Growth and Development
second trimester
continued development makes movement in the womb possible and facial features become apparent
sperm
male gamete
conception
occurs when the male gamete fertilizes the female gamete
third
the respiratory system becomes mature
embryo
after the zygote divides into two cells
how many are contained in the nucleus of each cell in the human body?
46
first trimester
a sac called a placenta forms around the embryo and is connected to the embryo with an umbilical cord and the placenta begins absorbing nutrients and oxygen from the mother's body
egg
female gamete
the male and female gamete each contribute a _____ of the zygote's DNA material
half