Prenatal Development Flashcards
When does development begin?
Traditionally thought at birth, more recently - in the womb.
Some argue it begins before conception with influence of social, economic and cultural factors
Germinal stage
sperm and egg unite in the fallopian tube to form the zygote
Weeks 1-2, zygotic stage
The fertilised egg travels down the fallopian tube, at the same time it divides and implants itself in the uterine wall
Two process which sperm undergo as they travel through fallopian tubes
Capacitation - where it’s outer layer is changed
Hyperactivation - which changes the way the sperm’s tail moves.
To enter the egg, the sperm must do two things:
- Break through a group of cells known as the cumulus oophorous that surround the egg. The sperm dissolves these cells using an enzyme.
- Break through the outer membrane of the egg. The sperm essentially fuses to and digests this membrane using an enzyme.
The sperm’s nucleus
Where chromosomes are stored. Enters the egg cell looking for the egg’s nucleus. Once it meets the egg, the nuclei from the egg and sperm merge and share their genetic material.
Implantation
It takes 6-12 days for the fertilized egg to travel to the uterus and attach to the uterus. The egg is pushed back towards the uterus by the cilia. The egg must attach to the uterus to become a viable pregnancy.
When the uterus defects the blastocyst
It releases enzymes to break down the blastocyst’s outer membrane. Once the barrier is broken down, the blastocyst can attach to the endometrium.
Weeks 3-5, embryonic stage
Embryo is just 2/3mms long and has a yolk sack. By the end of the 2nd week the chorion develops - a protective layer surrounding the amnion; small blood vessels emerge from it and later form the placenta
Nutrients to the embryo
At first the embryo uses nutrients from the yolk sac and then once the placenta develops, uses that for oxygen and nutrients.
Outer layer =
Ectoderm
Central Nervous System and skin, nails, eye lenses, tooth enamel
Middle layer
Mesoderm
Muscles, skeleton, and circulatory system, organs
Inner most layer
Endoderm
Digestive system, lungs and respiratory system, urinary tract, glands, stomach
Gastrulation
The ectoderm develops a groove and folds, creating a tube aka the neural tube - this will become the brain and spinal cord.
embryo at 3-5 weeks
Has some blood vessels; some start to connect to the uterus and will become the umbilical cord. The embryo is surrounded by fluid inside the amniotic sac, that is the sac that becomes the placenta.
Weeks 6-9 embryonic
Rapid development of the beginnings of:
- CNS
- Limbs
- Eyes, ears, nose
- General development of systems and organs
Weeks 9-12, foetal stage
- placenta is now fully formed
- organs connect
- foetus moves
- finer details such as nails, eyelids and ears form
- at the end of week 12, all the structures are there, now they have to mature and the foetus has to gain weight
Week 12 when 2nd trimester starts
At this point the embryonic stage is over, all the ground work is laid out and the foetus can start maturing, gain weight and strength
Teratogen
an environmental agent (e.g., a substance) that can cause damage during prenatal period.
Sensitive/critical period
Each body part forms at a particular time. During that time, it is very sensitive to damage. A period of time when a part of the body of the developing organism (embryo/foetus) is developing and is particularly vulnerable and sensitive.
Prescription drug
Any drug with molecules small enough to penetrate the placenta can enter the embryonic or foetal bloodstream. However, many people continue to take over the counter medication.
Non prescription drugs can potentially cause
Contractions of the uterus which can affect blood supply, which in turn can cause pre-term birth, birth defects, miscarriage.
Tobacco
Nicotine constricts blood vessels, lessens blood flow and affects placenta. This affects nutrients being delivered to the foetus and it can develop poorly.
Tobacco consequences
Low birth weight, premature birth, impaired heart rate and breathing, infant death, asthma in later childhood.
Low birth weight
The stronger and more developed the child is, the higher chances of following typical developmental trajectories and not being delayed.
Organs may not be dully developed, or simply not strong enough. The baby may need to be in an incubator, on ventilators or even intubated to help it breathe.
Neonatal abstinence syndrome
Babies are born addicted to the drug. Suffer withdrawal after birth. May last 1 week to 6 months.
Alcohol
Foetal alcohol spectrum disorders is a term that encompasses a range of physical, behavioural and mental outcomes caused by prenatal alcohol. CNS damage, distinct facial features, slow growth, low IQ, lifelong health problems.
Foetal alcohol syndrome characterised by
Slow growth, Three specific facial features (short eye lid openings, thing upper lip, smooth or flat philtrum), brain injury
Maternal factors
Age - over 50s
Nutrition - malnutrition can cause miscarriage, CNS damage, organ damage, lower birth weight
Exercise - moderate: increased birth weight, vigorous: low birth weight
Intense anxiety
Higher rate of miscarriage, premature birth, low birth weight, respiratory and digestive illnesses, sleep disturbances.
Low concentration of cortisol
leads to reduced physiological capacity to cope with stress
Depression
growth delays, prematurity, low birthweight, sleep problems. difficult temperament, attentional, emotional and behavioural problems.
