Download Aim: How does fertilization and embryonic development occur

Aim: How does fertilization and
embryonic development occur?
Zygote – fertilized egg
- undergoes a series of mitotic cell
division
- overall size of embryo remains the
same but the cells get smaller after
each division
- cells before implantation are
considered totipotent (can become any
type of body cell)
Stages of embryo development
1. Zygote
2. Morula – solid ball of cells (enters
uterus at this stage)
3. Blastocyst – hollow ball of cells
a. Outer layer called trophoblast
cells (responsible for embryo
implantation into the uterine
lining – secretes digestive
enzymes…..and secretes hCg –
human chorionic gonadotropin –
pregnancy hormone)
b. hCG targets the corpus luteum
– stimulates the production of
progesterone (keep uterine wall
thick).
Placenta
a. site of material exchange between
mother and fetus
b. blood does not mix between mother
and child – if it did it would cause
an immune response and mother or
baby could be at risk of death
c. composed of the chorion of baby
and the uterine wall of the mother
Umbilical cord
a. connects fetus to the placenta – an
artery and vein
Fetal development and cell
differentiation (cells become
specialized…you know skin, nerves,
muscle…other stuff …get it?
a. Process of gastrulation
i. Different layers of the body
form
1. ectoderm – skin and
nervous system
2. mesoderm – connective
tissue and muscle
3. endoderm – lining of
the organs