Chapter 2 Prenatal development and the newborn
period
Prenatal development
Epigenesis = the emergence of new structures and functions in the course of
development.
Conception
Conception = the union of an egg from the mother and a sperm cell from the father.
Gametes (germ cells) = reproductive cells (egg and sperm) that contain only half the
genetic material of all the other cells in the body.
Meiosis = cell division that produces gametes.
Zygote = a fertilized egg cell
Developmental processes
1. Mitosis = cell division that results in two identical daughter cells.
2. Cell migration = movement of newly formed cells away from their point of
origin.
3. Cell differentiation = specialization of embryonic stem cells (can develop in
any type)
4. Apoptosis = cell death
Hormones also play a role → androgens (= hormones including testosterone)
causes development to go one way or another.
Early development
0-2 weeks: Zygote
- migration to uterus
- cell division: occurs twice daily
- implantation in the uterine wall: cells become a hollow sphere with inner cell
mass
- hCG is secreted
Twins:
1) Identical twins develop when the inner cell mass splits in two (genetically
identical)
2) Fraternal twins develop during conception, when two egg cells are present
and fertilized (similar to regular sibling)
3-8 weeks: Embryo
- Inner cell mass forms 3 layers → different parts of the body
- Formation of neural tube (later becomes brain and spinal cord)
- Support system develops: placenta (provides important elements and
removes waste products from fetus), umbilical cord, amniotic sac
- Organ systems develop: vulnerable for environmental influences (teratogens)
9 weeks - birth: Fetus
period
Prenatal development
Epigenesis = the emergence of new structures and functions in the course of
development.
Conception
Conception = the union of an egg from the mother and a sperm cell from the father.
Gametes (germ cells) = reproductive cells (egg and sperm) that contain only half the
genetic material of all the other cells in the body.
Meiosis = cell division that produces gametes.
Zygote = a fertilized egg cell
Developmental processes
1. Mitosis = cell division that results in two identical daughter cells.
2. Cell migration = movement of newly formed cells away from their point of
origin.
3. Cell differentiation = specialization of embryonic stem cells (can develop in
any type)
4. Apoptosis = cell death
Hormones also play a role → androgens (= hormones including testosterone)
causes development to go one way or another.
Early development
0-2 weeks: Zygote
- migration to uterus
- cell division: occurs twice daily
- implantation in the uterine wall: cells become a hollow sphere with inner cell
mass
- hCG is secreted
Twins:
1) Identical twins develop when the inner cell mass splits in two (genetically
identical)
2) Fraternal twins develop during conception, when two egg cells are present
and fertilized (similar to regular sibling)
3-8 weeks: Embryo
- Inner cell mass forms 3 layers → different parts of the body
- Formation of neural tube (later becomes brain and spinal cord)
- Support system develops: placenta (provides important elements and
removes waste products from fetus), umbilical cord, amniotic sac
- Organ systems develop: vulnerable for environmental influences (teratogens)
9 weeks - birth: Fetus
