Prenatal Development Flashcards
last reading wang andfeigenson
people make an assuption that people are are result of learning and then born that way
Why study prenatal development
in an Infancy course?
Ilustrates some of the most important
facts of development
– Cell division
– Cell migration
– Cell differentiation
– Also: programmed cell death (apoptosis)
Principles to map facts on to
Illustrates some of the most important
principles of development
– Nature/Nurture
– Critical or sensitive periods
– Continuity/Discontinuity
– The lasting importance of early experience
* Fetal programming (e.g. Dutch Hunger Winter)
* Sleeper effects
prenatal development
- follows the cephalocaudal direction
- goes from simple to complex
**cephalocaudal direction **
develops from head to feet
Three Primary Stages of
Prenatal Development
-
Germinal Period: The Zygote
– fertilization to implantation -
Embryonic Period: The Embryo
– 12 days - 7/8 weeks -
Fetal Period:The Fetus
– 9 weeks - 40 weeks
prenatal development
starts at conception to birth
Fertilization
- Millions of sperm
- Most perish along the way
- Several hundred at the site of the egg
- With penetration, egg involved
– Egg creates barriers to additional sperm
– Pulls sperm into center, creates filaments to allow nucleii to join
the result of the sperm and egg joining is called a zygot
In vitro fertilization
an egg is extracted from a womens ulterus and a sperm is extracted and put together ‘‘artificially’’ and then implitation
1.Germinal Period : The Zygote #
within the first month of pregancy
Duration: 1-2 weeks
- Rapid cell division(zygot) > Extreme vulnerability
- By 4 days a ball of cells
- Creation of inner & outer masses of cells (blastocyst)
- 10-12 days: Implantation in the uterus wall
- 4-5 days:Differentiation of cells (before, all cells equipotential, embryonic stem cells)
- Outer layer will become Placenta, Amnion, & Umbilicus
- Inner cell mass will becomes the fetus
2. Embryonic Period
duration: 2-8weeks
- Placenta continues developing
- AT IMPLANTATION
- Embryo differentiates into:
– Ectoderm > skin, sense organs, PNS & CNS
– Mesoderm > muscles, circulatory system, skeletal, reproductive & excretory systems
– Endoderm >digestive system, lungs, urinary tract & glands - Heart & Neural Tube begin to form( not functioning)
- Remember – each cell has identical DNA
2. Embryonic Period
- By 7 weeks
– respond to external stimuli
– sexual differentiation begins (but reproductive system differentiation a few weeks later) - All major organ systems have begun to form and are in place
- By the end of this period, spontaneous movement occurs
- At 8 weeks, 3 cm long, 1 gram(tiny)
3.Fetal Period
- Begins around9 weeks
- Development and growth
- Skin and hair develop
- First movement felt at about 16 weeks
- Organization and establishment of :
– states of arousal by 4th month
– sleep/wake cycles by 28-30 weeks
– sensory systems
– learning
Prenatal experience effects
(nature and nurture; sensitive periods)
- Own movement impacts development
– *Experience Expectant; e.g. swallowing; breathing
– Hand movement involves bringing hand to mouth - Some continuity to after birth
– Fetuses with < heartbeat, later inhibited
– Hand thumb is sucked on, dominant hand
Prenatal experience effects#
(nature and nurture; sensitive periods)
- Positive: Diet, exercise, emotional well being
-
Teratogens: Harmful environmental agents (time of exposure is also important)
– Dose-Response relations
– Individual differences in genetic susceptibility -
the embryoric period is the most vulnerable
– Rapid differentiation
– Placenta not yet fully formed
