Foetal Development Flashcards
What is a cordocentesis?
A cordocentesis is a procedure used to take a sample of fluid from the base of the umbilical cord.
List the events that occur in week 1 of gestation.
Week 1:
1 - Fertilisation.
2 - Blastocyst formation.
3 - Implantation.
What occurs in week 2 of gestation?
In week 2 of gestation, the bilaminar germ disc forms, comprising the epiblast and hypoblast.
What occurs in week 3 of gestation?
In week 3 of gestation, gastrulation occurs to form the trilaminar germ disc:
- Endoderm – formed by epiblast cells that migrate through the primitive streak and displace the hypoblast cells.
- Mesoderm – formed by epiblast cells that migrate through the primitive streak and lie between the epiblast layer and the newly created endoderm.
- Ectoderm – formed by the epiblast cells that remain in position.
- The hypoblast disappears.
What occurs in week 4 of gestation?
In week 4 of gestation, neurulation occurs (the transformation of the neural plate into the neural tube explain later in more detail).
List 2 tissues / organs that originate from the ectoderm.
The ectoderm gives rise to:
1 - The epidermis.
2 - Neural tissue.
List 5 tissues / organs that originate from the mesoderm.
The mesoderm gives rise to:
1 - Cardiac muscle.
2 - Skeletal muscle.
3 - Smooth muscle.
4 - Kidney tubules.
5 - Red blood cells.
List 6 tissues / organs that originate from the endoderm.
The endoderm gives rise to:
1 - Lungs.
2 - Thyroid gland.
3 - Pancreas.
4 - Liver.
5 - Colon.
6 - GIT.
How does the trilaminar disc fold to form a cylindrical embryo?
- Cephalocaudal folding occurs in the longitudinal direction.
- Lateral folding occurs in the lateral / transverse direction.
List the phases of foetal development (different to the phases of foetal growth as seen in the last lecture).
1 - Embryonic period (weeks 3-8):
- Organogenesis.
- Establishment of the main organ systems
2 - Foetogenesis (weeks 9-38):
- Maturation and growth of tissues.
List the types of birth defect.
1 - Structural birth defect.
2 - Functional birth defect.
3 - Metabolic birth defect.
What is the difference between a malformation, disruption and deformation?
- Malformation refers to abnormal formation of a structure.
- Disruption refers to alterations to an already-formed structure due to an intrinsic destructive process.
- Deformation refers to alterations to an already-formed structure due to an extrinsic mechanical factor.
What is the difference between a syndrome, association and sequence?
- A syndrome is a group of abnormalities which tend to occur together with a specific known cause.
- An association is a group of abnormalities which tend to occur together without a specific known cause.
- A sequence is a cascade of abnormalities.
Which chromosome is affected in Down’s syndrome?
Down’s syndrome is caused by trisomy of chromosome 21.
List 6 features of Down’s syndrome.
1 - Congenital heart defects.
2 - Duodenal atresia (closure of the duodenum).
3 - Learning difficulties.
4 - Early onset Alzheimer’s.
5 - Single palmar crease.
6 - Wide sandal gap.
How does the trisomy occur in Down’s syndrome?
- 94% of trisomy 21 is caused by nondisjunction.
- 6% of trisomy 21 is causes by robertsonian translocation.
Define teratogen.
A teratogen is an agent that can predispose to a birth defect.
List 6 teratogenic drugs.
1 - Alcohol.
2 - Cocaine.
3 - Thalidomide.
4 - Anticonvulsants.
5 - Antipsychotics.
6 - Warfarin.
List 2 teratogenic infectious agents.
1 - Rubella.
2 - CMV.
List 2 teratogenic maternal factors.
1 - SLE.
2 - Poorly controlled pre-existing DM.
List 3 teratogenic mechanical factors.
1 - Malformed uterus.
2 - Oligohydramnios.
3 - Amniotic band syndrome.
What is amniotic band syndrome?
Amniotic band syndrome is a birth defect in which bands of tissue in the amniotic sac tangle the foetus.
How do teratogens affect foetal development at different points in development?
- Prior to organogenesis, teratogens either cause miscarriage or have no effect.
- Organogenesis is the period of greatest sensitivity to teratogens, and is where most birth defects arise.
- During foetogenesis, the foetus is only significantly sensitive to functional birth defects.
How does spina bifida arise?
Spina bifida arises from failure of closure of the caudal end of the neural tube.
*Anencephaly is caused by failure of closure of the rostral end of the neural tube.
