Week 2: Foundations Of Development Flashcards
What are genes?
They synthesise enzymes and proteins that regulate the body
Determine timing of development
Where are genes?
Located on chromosomes
Every cell in the body contains…
Chromosomes (located in cell nucleus)
How many chromosomal pairs do humans have?
23 pairs: 22 autosomal and 1 sex chromosome pair
What are autosomal chromosome pairs?
They make us who we are
Encode skills, looks etc
What is a genotype?
Actual genetic makeup
What is a phenotype?
How these genes are expressed
Explain identical twin genetics
Monozygotic: come from the same zygote
100% genetic overlap and if reared together, possibly 100% environmental overlap
Explain fraternal twin genetics
Come from two different zygotes (dizygotic)
50% genetic overlap (like normal siblings) as well as possibly 100% environmental overlap
How do ordinary siblings and fraternal twin siblings differ?
Fraternal twins are different than ordinary siblings because they were born and raised at the same time
What are sesquizygotic twins?
Semi identical
2 sperm simultaneously fertilise same ovum
Same material from Mum but different from dad
What is canalisation?
Behaviour follows a genetic blueprint
Some things are more/less susceptible to environmental forces
Eg. Walking age is strongly canalised/genetically coded
What is niche picking?
Seeking environmental niche that suits genetics - we choose an environment that further improves our genetic makeup
Makes it hard to then seperate nature form nurture
What is reaction range?
Genes set the boundaries for environmental effects
An ability range, environment then determines where you sit on that range
Explain conception
1 of 360 million sperm cells attaches to ovum surface
Sperm and egg release chromosomes
Join to form a new cell or a ‘zygote’
When is the germinal stage?
From conception - 2 weeks
Explain what happens in the germinal stage
The zygote divides and redivides (rapid cell replication) so that when it reaches the uterus it consisted of hundreds of cells (blastocyst) - then implants into the uterine wall
Explain the structure of a blastocyst
Made of 2 layers:
- Outer/trophoblast layer: fluid filled cavity that then develops into tissue to support and protect the embryo
- Inner cell mass: embryonic disk (cells that become the embryo)
What happens when the blastocyst reaches the uterus?
Trophoblast cells put out branches that bury into the spongy wall of the uterus to make contact with maternal blood vessels
How many blastocysts implant?
Only 1/2 become fully implanted
What weeks are within the embryonic stage?
Weeks 3-8
What happens in the embryonic stage?
Basic organs are formed
Begin to respond to direct stimulation
Very rapid development
The embryonic disk begins to differentiate into 3 layers
What are the 3 layers of the embryonic disk?
Ectoderm (outside): nervous system, skin and hair
Mesoderm (middle): muscles, bones, circulation system, internal organs
Endoderm (inside): digestive system, lungs, urinary tract, glands
Give some examples of what happens in the first and second month in the embryonic stage
- The brain starts developing as well as the heart which then starts beating
Form muscles, start of the spine, ribs and digestive system and limb buds form - Starts to develop eyes, nose mouth and neck
From the limb buds, limbs start to form
Bones harden and start moving
all basic organs and tissues are present
What is a fully implanted blastocyst referred to as?
Embryo
Which weeks of pregnancy are considered the foetal stage
Weeks nine until birth
What happens during the foetal stage
Organs take on the final form and begin function
Bones and small features start to develop
Becomes responsive to external stimuli such as light or touch
What week of pregnancy does sex differentiation occur
Week 13
Is determined at conception but can’t tell in scans until week 12-13
What are some distinctive features of the end of trimester two
The baby has suck and swallow reflexes they can hear and open and close their eyes
All of their organs are fully formed apart from the central nervous system
Which weeks of pregnancy is birth safe
38 to 40 weeks
What happens during birth
The uterine wall begins to contract
Over 10 to 20 hours contractions become stronger and the baby eventually emerges through the birth canal
When is the baby‘s physical condition assessed and how
Immediately after birth
Through Apgar scale (1min and 5min after birth)
What is the apgar scale
Looks at functions such as heart rate, effort to breathe, reflex irritability, skin colour and muscle tone
Different scores mean different things for functioning
What does an apgar score of 7 to 10 indicate
Indicates good functioning
What does an apgar score of 4-6 indicate
Fair condition
Moderate central nervous system depression or some muscle flaccidity
May need to establish respiration
What does an apgar score of 0-3 indicate
Very poor condition
resuscitation is required immediately
the survival of the infinite is in doubt
What is a teratogen?
A substance or environmental influences that can damage embryos development
May cause serious malformation or even death
Will teratogens always have the same affect
Different ones have different effects of different times in development or pregnancy
Explain teratogenic sensitive periods
Each organs sensitivity varies over time, may not be effected during some periods and really effected at another
Explain tissue specific effects of teratogens
May work in specific ways on certain tissues
Eg. Mercury is bad for baby brain development
Explain teratogenic effects on the mother
Often she notices no adverse effects. Eg. May have a very mild virus and not notice but harms the baby
5% of women catch an infection while pregnant the most experience know if fracture but some can cause serious problems
For example viruses bacteria infections parasites maternal maternal diseases such as diabetes
Explain the dose-response relationship of teratogens
The greater the dose, the worse it’s effect
Medicinal drug teratogens?
Some drug molecules are small enough to cross the placental barrier to affect the fetus
Such as aspirin, quinine (lead to deafness), and thalidomide (drug used for morning sickness but lead to limb defects as morning sickness most common during weeks limbs are developing)
Non-medicinal drug teratogens?
Alcohol, tobacco, heroine, cocaine
Babies born to users at risk for many health problems such as prematurity low-birth-weight and addiction
Why is foetal learning research limited
You have relative inaccessibility to the fetus because you don’t want to be poking and prodding too much
Learning in utero? Explain
The fetus can habituate to repetitive sounds and we know this because of things such as changes in heartbeat or kicking rate
And this does persist after birth babies prefer the things they had before birth
Stories and learning in utero
The rate of sucking on a dummy to control which story they were hearing show babies can learn that if they want to hear more, to suck more
if they didn’t they would actually stop sucking
they did have a preference
The taste of anise and carrot? Learning in utero
The amniotic fluid can taste like this And if given a taste those that are used to it will enjoy it
Babies from cultures that use a lot of spice, the babies will likely be used to the taste and will enjoy it they can gain a sense of familiarity towards culture even before birth
