Foetal Development Flashcards
List the events that take place in the first 4 weeks of gestation
1st week - sperm + ovum = fertilisation - morula - blastocyst - implantation 2nd week - bilaminar germ disc, epiblast/hypoblast (clinical gestation week 4) 3rd week - gastrulation - ectoderm/mesoderm/endoderm - neurulation - by end of 4th week
What structures are formed form the following:
- ectoderm
- mesoderm
- endoderm
Ectoderm - skin - neural tissue - pigment cells Mesoderm - cardiac muscle - skeletal muscle - tubule cell of kidney - red blood cells - smooth muscle Endoderm - alveolar cell - thyroid cell - pancreatic cell
Describe the folding of the embryonic disc
- flat trilaminar disc –> cylindrical embryo
- cephalo-caudal folding
- lateral folding
When and what events occur during:
- the embryonic period
- the foetal period
Embryonic period
- organogenesis
- establishment of main organ systems
- post-fertilisation weeks 3-8 (clinical gestation weeks 5-10)
Foetal period
- maturation and growth of tissues and organs
- post-fertilisation week 9-38 (clinical gestation 11-40 weeks)
What are birth defects?
What are the three types?
Birth defects = developmental disorders present at birth, not only physical defects Types: - structural = congenital anomaly - function = organ dysfunction - metabolic = enzyme/cellular defect
What are the causes of birth defects?
Genetic
Environmental
Multi-factorial inheritance - interaction between genetic constitution and environmental factors
Describe the following congenital anomalies:
- Malformation
- Disruption
- Deformation
Malformation
- incomplete or abnormal formation of structure
- complete or partial absence of a structure
- alteration of its normal configuration
Disruption
- morphological alterations of already formed structure
- destructive process e.g amniotic bands
Deformation
- mechanical factors e.g. positional talipes w
Describe the chromosomal/genetic causes of birth defects
Decribe Syndromes, Associations and Sequence
- multiorgan involvement
- usually lethal/significant defects
Syndromes - a group anomalies with a known specific cause
- e.g. Down’s syndrome
Association - abnormalities which tend to occur together but the cause is not determined e.g. CHARGE
Sequence - when a defect leads to a cascade of further abnormalities e.g. Potters sequence (kidneys don’t form, then no urine, no amniotic fluid, no lungs, other physical changes)
What are the clinics features of Down’s syndrome?
- craniofacial appearance = flat nasal bridge, upslanted palpebral fissures, epicanthic folds, brush field spots)
- single palmar creases
- hypotonia
- congenital heart defects
- duodenal atresia
- variable learning difficulties
- Alzheimer’s/malignancy
What are the two major causes of Down’s syndrome/
Maternal non-disjunction
Robertsonian translocation
Define teratogens
What are the determining factors of teratogenic effect?
- agents that can cause predispose to a birth defect
- single or few systems involved
Determining factors - timing
- dosage
- genetic constitution of the embryo
What are the types of teratogen?
Drugs - include alcohol, cocaine, thalidomide, anticonsulsants, antipsychotics, ACE inhibitors, warfarin Environmental chemicals - e.g. organic mercury, lead Infectious agents - e.g rubella, CMV, zika Radiation - high levels of ionising radiation Maternal factors - SLE, poorly controlled pre-existing DM Mechanical factors - e.g. malformed uterus, oligohyrdramnios, amniotic band
What are the different effects of timing and insult during foetal life?
Prior to post-fertilisation week 2
- either miscarriage or no effect
Organogenesis period (week 3-8)
- period of greatest sensitivity to malformation
- different organ systems have different periods of peak sensitivity
- leading to birth defects
Fetogenesis period (week 9-38)
- main effect on growth and functional maturation
- usually not leading to birth defect
What are the classifications of spina bifida?
Occulta
Meningocoele
Myelomeningocoele
Draw neural tube formation
see lecture
