Fetal Development Flashcards
(50 cards)
What is happening during the foetal period?
Growth and physiological maturation of the structures created during the embryonic period. It involves preparation for the transition to independent life after birth
When is pregnancy counted from?
Pregnancy weeks are calculated from the date of LMP, i.e., conception weeks +2, so term is 40 pregnancy weeks.
Which weeks mark the pre-embryonic, embryonic, and fetal stages?
Pre-embryonic = weeks 1-2, embryonic = weeks 3-8, fetal = week 9 onwards.
When do the lungs start to develop?
The lungs develop relatively late, after the cardiac system.
When is the bronchopulmonary tree created?
Embryonic development creates only the bronchopulmonary tree (trachea & main bronchi).
When does functional specialization occur in lung development?
Functional specialization occurs in the foetal period.
What is the embryological origin of the lungs?
The lungs originate from the primitive gut tube (endoderm).
Describe lung development from the gut tube.
Lungs are a diverticulum of the gut tube and separate after forming a septum (tracheoesophageal septum).
Describe lung development in the foetal period.
W8-16: bronchioles; W16-26: respiratory bronchioles; W26-term: terminal sacs, alveoli type I and II cells.
When are surfactants produced and by which cells?
Surfactants are produced in week 26 by alveoli type II cells, reducing surface tension in the lungs.
Why are there breathing movements if no gas exchange is occurring in T2&3?
Gas exchange is conducted at the placenta, but lungs must be prepared for the full burden at birth. Breathing movements condition the respiratory musculature and allow lungs to become fluid-filled by inhaling amniotic fluid, crucial for normal lung development.
What is respiratory distress syndrome?
It often affects infants born prematurely due to insufficient surfactant production, leading to increased surface tension.
What is the treatment for RDS?
If pre-term delivery is unavoidable, glucocorticoid treatment of the mother can increase surfactant production in the fetus.
What are developmental disorders/birth defects?
They are present at birth and can be structural, functional, or metabolic, with a wide range of causes, most of which are unknown.
What are teratogens? Give 4 examples.
Teratogens are agents that can interfere with normal development. Examples include congenital infections (TORCH, rubella, Zika, CMV), drugs and environmental pollutants, maternal metabolic diseases (e.g., diabetes), and radiation exposure.
How can birth defects be classified?
Classified by timing: pre-embryonic (pre-week 2, lethal or no effect), early effects (2-4 weeks, scattered pattern), later effects (4-8 weeks, localized effects), and foetal period (>week 9, organ growth and functional maturation affected).
At which period is the baby most at risk of teratogenic disruption?
The embryonic period, with the exception of effects on the CNS, which continues developing past the embryonic period.
What causes congenital anomalies to occur?
Congenital anomalies occur when normal development is disrupted.
Define deformation, disruption, sequence, and malformation.
Deformation: late changes in previously normal structures (mechanical effect) e.g., talipes. Disruption: secondary disturbance due to early influence of external factors e.g., amniotic bands. Sequence: primary defect leads to a cascade of further anomalies e.g., Potter sequence. Malformation: primary disturbance of embryogenesis.
What are antenatal examinations/tests?
- Screening: non-invasive (little/no risk), blood tests, and obstetric ultrasound screening. 2. Diagnostics: invasive, including amniocentesis/chorionic villus sampling (CVS) for definitive results.
When do combined tests need to be carried out and what do they test?
Combined tests need to be done before 14 weeks, covering maternal age, nuchal translucency, serum free bhCG, and PAPP-A, reporting the chance of T21 and T18/T13.
What do quadruple tests test?
Quadruple tests assess maternal age, hCG, unconjugated E3, inhibin A, and AFB, testing for T21 only.
What is a non-invasive prenatal test (NIPT)?
Foetal DNA fragments are extracted from maternal plasma, sequenced, and mapped to the genome, with statistical analysis performed on the number of reads from the chromosome(s) of interest.
What can happen to single genes?
Mutation in gene or deletion of gene.
