PSY 302 Lecture 2: lec2
Chapter 2: Prenatal Development and the Newborn Period
Outline of Chapter
Prenatal Development
Hazards to Prenatal Development
The Birth Experience
The Newborn Infant
Prenatal Development
* epigensis : emergence of new structures and fxns in the course of dev
• Aristotle: studied chicken eggs development there is dev of new structures and fxns -- humans are
not conceived as small humans and grow in size until birth and then keep growing
Conception
Gametes (germ cells): Reproductive cells—egg and sperm—that contain only half the genetic material of
all other cells in the body
Meiosis: Cell division that produces gametes
In meiosis, 23 chromosomes from mother and 23 chromosomes from father leads to conception—23 pairs
of chromosomes.
Conception: The union of an egg from the mother and a sperm from the father; fertilization
Zygote: A fertilized egg cell
• Ejaculation has about 500 million sperm
• Approx 200 sperm get close ot the egg
• Only one will penetrate the egg outer coat and form zygote
Developmental Processes
Four developmental processes that transform a zygote to embryo to fetus
Mitosis: Cell division resulting in two identical daughter cells
Cell migration: Newly formed cells move away from point of origin
• For further dev
Cell differentiation: Cells start to specialize in structure and function
• Embryonic cell will specialize and cell fate is determined ie: some will become muscle cell, skin
cell, neural cell etc
• Prior to differentiation- they are stem cell, they have the ability to become anything bc cell fate
hasn’t been determined yet
Apoptosis: Genetically programmed death of cells
• Contributed by skin cells being killed off so there’s no tissue btwn the fingers
• Hormonal influence ex: at 8th week, testes produce androgens→ productin of male genitalia
Developmental Processes **
Germinal 1-3 week
Embryonic 3-8 week
Fetal- 9th week to birth
Early Development
Identical Twins
Twins that result from the splitting in half of the zygote
Each of the two resulting zygotes have exactly same set of genes
Fraternal Twins
Twins that result when two eggs happen to release in fallopian tubes at the same time
Fertilized by two different sperm
Fraternal twins have only half their genes in common
• Ie: broters and sisters
•
Early Development
Implantation
Differentiation of the embedded ball of cells
the inner cell mass embryo
The rest of the cell amniotic sac and placenta
Top layer: Neural tube: A groove formed in the top layer of differentiated cells in the embryo that
eventually becomes the brain and spinal cord
Middle layer - becomes muscle, bones, circulatory system and other internal organs
Bottom layer - become gi tract, lungs, urinary tract and glands
• The rest of cells→ will become the amniotic sac and placenta ( inner cell mass become amniotic
sac, placenta )
Amniotic sac: A transparent, fluid-filled membrane that surrounds and protects the fetus
Placenta: A support organ for the fetus that permits the exchange of materials (nutrient and waste
products) carried in the bloodstreams of the fetus and mother
• Estrogen released by placenta and mproves the flow of oxygenated blood to uterus
• Progesterone : suppress uterine contraction occuring in the uterus to prevent premature birth
Umbilical cord: A tube containing the blood vessels connecting the fetus and placenta
Embryo at 4 weeks
Cephalocaudal development
• * primitive heart
• Arm buds
• Less distinct leg buds
• Organs closer to the head will develop before organs further from head
Face Development from 5½ to 8½
At 5½-week: nose, mouth, and palate are differentiating
At 8½ week: nose and mouth are fully formed.
Cleft palate
* may develop in some children which could be a result to a teratogen that the pregnant mother
has while fetus is dev
Fetus at 9 weeks
Bulging forehead
Rapid brain growth
Rudimentary eyes and ears
All internal organs are present
• Still need to undergo further dev
Further development
Sexual differentiation has started
Ribs are visible
Fingers and toes have emerged
Nails are growing
Spontaneous movements
