Prenatal Development (5)* Flashcards
Prenatal development stages***
- Ovulation (9-16 days of the menstrual cycle)
- Fertilisation (24hrs after this)
- Male + female chromosome material unite (24-30hrs)
- Egg cell divides
- 2 cells (36hrs after fertilisation)
- 4 cells (48hrs after fertilisation)
- Cluster of 16-32 cells (3 days)
- Hollow ball of about 100 cells (4 days)
- Zygote enters the uterus (4-5 days)
- Zygote begins to attach to the wall of the uterus (6-7 days)
- Zygote is completely implanted in the uterine wall (12-14 days)
3 stages of prenatal development
Zygote (up to 2 weeks)
Embryo (2-8)
Foetal (from 2 months)
Zygote
A single cell embryo
How many chromosomes does an embryo contain
46
Heart appears
18 days after fertilisation
When are major features (such as hands, arms, fingers, eyes…) defined
8 weeks (end of embryo stage)
The brain and spinal chord… what stage
Embryo stage
Forebrain
Cerebral hemispheres, hypothalamus, thalamus
Midbrain
Superior + inferior colliculi, substancia nigra
Hindbrain
Medulla oblongata, pons
3 weeks…brain and spinal chord
Neural plate thickens first at the head and then folds into the neural tube which forms the brain and spinal chord
Movement
Even though mother typically doesn’t feel it for another 10 weeks, embryo starts moving at 5-6 weeks
XX
Female
XY
Male
6 months… unfolding in the cortex
- sulci + gyri
- increases surface area
- frontal, parietal + occipital lobes differentiated
Cerebral cells mature by..
27 weeks
Touch sensitive by…
13-14 weeks
Responds to growing medley of sounds
20 weeks
Respond to taste
25 weeks
Sweet substances in fluid…
Increase swallowing
Bitter substances in fluid…
Decrease swallowing and alter facial expressions
Chemosensory
Taste and smell
Eyelids fused until
5-7 months
Teratogons*
Substances which, if ingested by mother, can adversely affect their unborn child
Types of teratogens
Diseases/infections e.g. rubella
Drugs/medicine e.g. aspirin
Which stage are defects most common?
Embryonic -> foundations of all body parts
Common features of foetal alcohol syndrome (according to Connor et al)
Over activity
Impaired motor control
Attention deficits
Memory problems
Language impairments
How many pairs of autonomes
22
What is the embryo stage crucial for
Organ formation, sexual development
What drives the formation of organs
Chemical reactions
When does the heart begin to beat
3 weeks and 1 day
How many heart beats per minute (by 4 weeks)
105-121
When are major features defined e.g arms, hands, fingers…
8 weeks
Day neural plate begins to form
18
Neurogenisis
Cells are continually born within the neural tube
When does neurogenisis and migration continue to
6 months
Reflexive movements controlled by
Midbrain
When does cerebral cortex start developing
9 weeks - covers whole brain by mid pregnancy
Additional volume in cerebral due to..
Increases in cell body size, synaptogenisis, myelination (month 6)
Foetus swallows and sucks thumb
9 weeks
Sense light touch
9 weeks
When do gender differences emerge
14 weeks - female foetuses move their jaws more
When do foetuses start to learn
24 weeks - respond + habituate
Continually moving by
13 weeks
Distinct patterns of rest and activity
34 weeks
Quiet sleep
Motionless, steady heart beat, rhythmic breathing
Active sleep
Lots of different body movements, eyes moving and sometimes open, heart rates and breathing irregular and responsive to stimulation
Exposure learning
If a newborn responds to a stimuli they heard/ experienced in the womb
Righting reflex (balance) by..
25 weeks - head down birthing orientation
Effects of Dutch famine study
2x more likely to develop heart disease
Schizophrenia, obesity, diabetes, cancer, stress-related illnesses
