This document contains detailed lecture notes from PSYC302 (Infancy) Modules 3 and 4, offering a comprehensive look into the early stages of human development.
Module 3 focuses on prenatal development, covering the germinal, embryonic, and fetal stages, and the factors influencing them. The note...
PSYC302 – Infancy Lecture Notes
Module 3 - Prenatal Development, Birth, and the Newborn Baby
Lesson 6: Prenatal Development
Conception
- Sperm and ovum unite
- Ovum is released from ovaries every 28 days
survives for one day
- Sperm live in fallopian tube for up to six days
- Most conceptions result from intercourse on
day of ovulation or during two days
preceding it
Milestones of Prenatal Development
1. Germinal (0-2 weeks)
Weeks 1 – 2
Fertilization and formation of the
zygote
Implantation of the blastocyst
Development of nourishing and protective structures:
o Amnion: membrane forming a fluid-filled cavity (amniotic sac) that
encloses the embryo, protecting the developing baby from the mother's
body and provides nutrients, immune protection, waste removal, and
gas exchange for the growing baby.
o Chorion: membrane that surrounds a developing fetus in conjunction
with the amnion, plays a key role in the exchange of blood and gases
between mother and fetus and develops into the fetal aspect of the
placenta.
o Yolk sac: structure that develops inside uterus, provides embryo with
nourishment (food), circulates gasses between mother and embryo,
produces cells that turn into important structures, like umbilical cord,
blood cells and reproductive organs.
o Placenta: temporary organ that develops during pregnancy, attaches to
the lining of uterus and delivers oxygen and nutrients to growing baby
through umbilical cord.
o Umbilical cord: tube that connects mother to baby during pregnancy
three blood vessels: one vein carries food/oxygen from placenta to baby
and two arteries carry waste from baby back to placenta.
2. Embryonic (3-8 weeks)
Forebrain, midbrain, hindbrain formed
Central nervous system, internal organs, muscles, skeleton begin to form
o Heart begins pumping blood
o Neurons develop rapidly
External features form: eyes, ears, nose, limbs
3. Fetal (9 weeks-birth)
First trimester:
o Organs, muscles, and nervous system organize
o Lungs begin to expand and contract
o Sex of fetus detectable with ultrasound
Second trimester:
o Fetus is active; mother can feel movement
, o Neurons rapidly form synapses
o Sensitivity to sound and light emerges
Third trimester:
o Age of viability: 22 – 26 weeks
o Substantial growth and weight gain
o Rapid gains in neural connectivity and organization
o Expanding sensory and behavioural capacities, signs of developing
temperament
Placenta and Umbilical Cord
- At the end of the germinal period and the beginning of the embryonic period, the
placenta develops
- The umbilical cord connects the fetus to the placenta
Permits transfer of food and oxygen
Takes waste products away
- A membrane separates the mother’s blood from the embryo’s blood
Prenatal Environmental Influences
Teratogens
- Environmental agents that cause damage during the prenatal period
- Effects depend on:
Dose “the dose make the poison”
Heredity
Presence of other negative factors
Age and prenatal sensitive periods
Teratogenic Substances
- Drugs
Prescription and Non-prescription
o Isotretinoin (acne treatment)
o Aspirin
o Caffeine
o Antidepressants
Illegal
o Cocaine
o Heroin
- Tobacco
10% of the US women smoke while pregnant
Low birth weight is more known effect
Increase risks of miscarriage, prematurity, abnormalities, heart rate and
breathing problems, infant death, later asthma and cancer, and long-term
cognitive and behaviour problems
Passive exposure also increases risk
- Alcohol
- Radiation and environmental pollution
Radiation
o Even low-level exposure is harmful
o Examples: industrial leakage, medical X-rays
Environmental pollution
, o Many babies are “born polluted”
o Examples: mercury, PCBs, dioxins, lead, traffic-related fumes
Can cause variety of physical defects and cognition impairments increases
chances of later illnesses
- Infectious diseases
Rubella
HIV/AIDS
Herpes
Toxoplasmosis
The Thalidomide Crisis
- Early 1960s
- Canada widely prescribed a sedative drug, thalidomide, to reduce morning sickness
- It was later found to cause severe deformities
- About 7,000 infants worldwide were affected before it was removed from the market
Cannabis
- Use is increasing in Canada due to legalization
- Linked with numerous development delays and difficulties
- Lasting consequences not well-established
Crucial Maternal Factors
- Nutrition
Prenatal malnutrition can lead to damaged organs and CNS, increased
chances of illness and disease later in life
Vitamin-mineral enrichment is crucial, e.g., folic acid supplementation
reduces neural abnormalities and defects by 70%
- Emotional stress/distress
Deprives fetus oxygen and nutrients
Stress hormones cross the placenta causing dramatic rise in fetal stress
hormones
Associated with negative behavioural outcomes in children and youths and
with susceptibility to later illness
Social support reduces risk of complications
- Maternal age
Importance of Prenatal Care
- Can detect and treat complications
- Reduces likelihood of low birth weight and fetal death
- Culturally sensitive practices also helpful
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