Prenatal development Flashcards
Developmental psycholoy
how we change physically, cognitively, behaviourally and socially over time due to biological, individual and environmental differences
Ontogenetic development
the development of an individual over their lifetime (onto= one= individual)
Microgenetic development
Changes that occur over very brief periods of time
Phylogenetic development
changes over evolutionary time
stages of development?
prenatal = conception to birth infancy = birth to 2yrs preschool = 2 - 4 childhood = 5-12 adolescence= 12-18 young adulthood = 18-40 middle adulthood = 40-65 late adulthood = 65+
preformationism
the popular belief (until 17th century) that miniature people lived in sperm and started to grow when sperm met an egg
epigenesis
new organs and structures develop through a series of stages during prenatal development (what we know now)
Stages of prenatal development?
germinal stage = conception - 2 weeks
embryo = 2-8 weeks
foetus = 9weeks - birth
Germinal stage
- when
- what happens
conception - 2 weeks
journey through fallopian tube to womb, the zygote doubles its cells twice a day
at 2 weeks it attaches to uterus wall and becomes an embryo
when sperm penetrates ovum they combine = half from dad, half from mums DNA
sperm forms membrane to prevent other sperm penetrating ovum
fewer than 1/2 ovums survive
Embryo
- when
- what happens
2-8 weeks
period of rapid growth when key organs and structures develop
once zygote has attached to uterine wall it becomes an embryo
inner cell mass becomes embryo, the rest becomes the amniotic sac and placenta
placenta= exchange of materials via bloodstream through blood vessels that make up umbilical cord
-inner cells divide into 3 layers:
1= ectoderm (top layer) - becomes nervous system,nails, teeth, inner ear,lens of eyes and skin
2= mesoderm (middle) - muscles, bones, circulatory system, inner layers of skin and internal organs
3= endoderm (bottom) - digestive system, lungs, urinary tract and glands
After - a U-shaped groove forms down centre of the top layer and top of grooves fuse = neural tube (becomes brain and spinal cord)
Foetus
- when
- what happens
9 weeks - birth
growth and development in organs
areas near head develop earlier
during last 5 months the lower parts develop more rapidly = movement from foetus
development of sexual organs takes place early in this period
all human foetuses can develop either male or female genetalia (depends on presence or absense of adrogens that cause male genetalia to develop eg. testosterone)
chromosomes
every cell has 23 pairs (1/2 from mum and 1/2 from dad)
genes are short segments of chromosomes - molecule of DNA that hold genetic info
Sex determination
the 23rd pair of chromosomes determine a persons sex
females = XX, males = XY
(gender determined by whether sperm is X or Y)
sperm that carry Y are lighter and so swim faster
so, 120-150 males : 100 females conceived
BUT only 106 males : 100 females born
WHY?
because boys are more vulnerable in the womb - more susceptible to stress and more likely to be miscarried + have birth complications
WHY?
- because they only have one X chromosome. Therefore, if they have one defective gene on the X chromosome they don’t have a functioning copy to balance this out
Twins
MZ identical twins - when growing cell cluster breaks apart early in development = 2 clusters with identical genes (from same zygote = share placenta)
DZ fraternal twins - 2 eggs fertilized at the same time, chance determines which of the 23 pairs of chromosomes goes to a reproductive cell, so there are about 8 mil chromosome possibilites in each parent
