Pre-Natal Development Flashcards
Where have living things come from?
They have evolved from common ancestors
What species are humans?
Chordates
Why are humans are chordates?
They have a spinal cord
How many species do chordates comprise?
1/10th
What is the history of pre natal development?
Most processes were un known
1590’s - Microscope development
1695 - Hartsoeker and the preformation theory
19th - Improvements demonstrated development didn’t involve simple processes but substantial differentiation
What is the preformation theory?
Looked in microscope at sperm and thought he saw a tiny human, belief of womb as an oven where humans wait till they are right size to be born
What did the debate around pre natal development lead too?
Scientific debate eg. scala naturae
What is scala naturae?
When species are arranged hierarchically
What is the recapitulation theory?
Development occurs in stages. Human embryo’s took form of animals lower down the ladder - all animals do this then are born
What has technology done?
Allowed us to see changes - photos show that animals look very different when bored, can’t rely on drawings from scientists
What are the 3 stages?
Geminal Period
Period of the embryo
Period of the foetus
What is the geminal period?
Conception to implantation
Conception begins when sperm fertilises the egg in the Fallopian tube, the zygote moves down into uterus, this multiples and turns into morula. in the first few stages, morula gets smaller and smaller and turns into stem cells. then takes a new shape - blastocyst
What is the period of the embryo?
Implantation to 2 weeks
Cell differentiation at 2 weeks - different organ systems in the body develop such as the ectoderm, mesoderm and endoderm
At 3 weeks - different tissues develop
At 7 weeks - area of rapid growth in digestive tract, brain expands
What is the period of the foetus?
2 months to birth
Further development and growth occurs here
4 months - organism can respond to sound at 250-500hZ
Touch forming, capable of moving, ears/eyes develop
8 months - reflex is strong, maintains a preferred position in the womb, has a sense of where it is
What is a zygote?
A fertilised egg
What are the variations from typical development?
WHO states that 50% or cases are unknown 50% of the time
Genes
Environment
Genetic factors affecting development
Mitosis vs mieosis - function of this is to produce a series of gametes that only have half chromosomes from mum, half from dad
Chromosomal variations - usually have 23 pairs, males have XY, females have XX
Can have different chromosomal variations which aren’t always incapable with life, there is a huge range
some lead to birth deficits, some to pubertal deficits
What are the types of chromosomal variations?
Trisomy 21 - Down syndrome
Trisomy 18 - Edwards syndrome
Trisomy 13 - Patau syndrome
90% die in first year
What are chromosomal variations called?
Aneuploidy - having more or less
Environmental factors affecting development
Taratogens
Fetal alcohol syndrome
Taratogens
Substances than cause deficits at birth
Till the zygote is in the uterate wall, it is free from influences as not sharing the blood at mum, but once implantation occurs, substances effect them
The central nervous system is vulnerable throughout all trimesters, limbs only vulnerable in some
Thalidomide tragedy
Developed in 1954 to treat headaches, morning sickness. By 1961, 20,000 children in 46 countries were born with misshapen limbs. thought it was caused by atomic bombs. In Us, it was never approved on Dr Frances Kelsey refused it - HERO as only 40 cases in US.
these were prescribed in last trimester, when limbs are most vulnerable
Fetal alcohol syndrome
Effects the CNS (vulnerable the whole way)
Causes brain problems, vision, hearing, learning difficulties
Children survive but have problems
Fetal learning
DeCasper and Spence - Training: read 2 stories per day. Testing: 2.5 days after birth, 8 babies hear familiar story, associated with faster sucking, shows they prefer familiarity
Hepper - mothers who watched neighbours, when played there were significant differences in the movements of babies 2 days after
