after implantation, a placenta is formed in the uterine lining, here, nutrients and oxygen pass from the mother's blood into the embryo's blood, and the waste produced by the embryo passes into the mother's blood. the placenta is connected to the embryo through the umbilical cord.
the embryo is protected by a bag of fluid called amniotic fluid.
during labour, the muscles of the uterus umbilical cord strongly to push the foetus out through the vagina.
a newborn baby cannot take care of itself, parental care is very important for the healthy growth of a baby.
we show some common characteristics of our parents because our body cells contain the genetic materials from our parents.
identical twins have the same genetic materials ,they are of the same sex and look like each other.
non-identical twins have different genetic materials. they may be of the same sex or different sexes. they may not looking like each other.
in general, girls enter puberty earlier than boys.
at puberty, our body begins to produce more sex hormones, this causes body changes that show important male and female characteristics, these characteristics are called secondary sexual characteristics.
boys at puberty may experience nocturnal emission.
during a menstrual cycle , the thickness of the uterine lining changes.
if the egg is not fertilized, the tissues of the uterine lining break down and pass out of the body with the egg. this is called menstruation.
