Human Embryology and Developmental Biology – Guest lecture Teratology by
Annelieke Schepens-Franke
..-03-18
Teratology: abnormalities in the development of embryos
Folding of the germ disc, results in the formation of the tube-within-a-tube body
plan.
Microcephaly: incredibly small head, due to zikavirus.
In order for the head region to form, you need to suppress signals that form the
thoracic region.
Teratology:
Morphogenesis dysmorphogenesis (birth defects in structures)
The study of congenital malformations
Teras: wonder, monster
In the middle ages:
Malborn babies were often thought of being a combination between animal and
human.
Nowadays:
Often accurate descriptions of conditions.
Rubella virus: rode hond can lead to congenital malformations and red dots on
the skin. first sign that influences of the mother (outside environment) could affect
development of the foetus.
Thalidomide (Softenon): drug prescribed for morning sickness malformations of
arms and legs. first sign that also medication could influence development of
embryos.
Most common severe congenital malformations/anomalies are: heart defects, neural
tube defects and Down syndrome.
Three possible causes of birth defects are:
1. Genetical
2. Environmental (teratogens, mechanical)
3. Multifactorial (both genetic and environmental, influencing each other)
1. Genetical:
Chromosomal and monogenic
Primordial germ cells:
- originate from oogenesis + spermatogenesis.
- Omnipotent are able to differentiate into any tissue.
- Around week 2: outside the embryo
- Around week 4-6: migration from the yolk sac, towards the genital ridge
(primitive gonad (testis/ovary)) become oocytes and sperm.
, Ploidy= number of copies of a chromosome
N number= number of copies of each DNA
Normal cells:
Diploid 2N
Sperm/oocyte:
Haploid N
During gametogenesis (spermatogenesis/oogenesis) processes can go wrong,
leading to chromosomal abnormalities.
Number of chromosomes:
Triploidy: instead of diploid cells, with two copies of each chromosome, you have
three copies of each chromosome. caused by 2 sperm cells fertilizing an
oocyte, or no formation of a 3rd polar body.
Triploidy is always lethal, during pregnancy, most of the fetuses have a fused 3 rd
and 4th finger.
Monosomy: Instead of diploid cells, with two copies of each chromosome, one of
your chromosomes has only one copy. Example: Turner Syndrome (vital) only
one sex chromosome
Trisomy: Instead of diploid cells, with two copies of each chromosome, one of
your chromosomes has three copies. Example: Down syndrome (vital) – Trisomy
21
Monosomy and trisomy are called nondisjunction.
The older the father the more gene mutations can occur. Especially: ADHD
2. Environmental:
Teratogen: agent that produce birth defects
- Critical period (at a certain stage in development: time dependent)
- Dose dependent
Organogenesis in pre-embryonal stage is the most critical period, the risk on inducing
congenital malformations (due to e.g. malformation of organs) is highly increased in
this stage.
Malformations that happen during growth stage, more affect the functioning of certain
organ systems.
Critical period: organ dependent.
Examples of teratogens:
Maternal infections:
- Rubella
- Toxoplasmosis
Chemical:
Annelieke Schepens-Franke
..-03-18
Teratology: abnormalities in the development of embryos
Folding of the germ disc, results in the formation of the tube-within-a-tube body
plan.
Microcephaly: incredibly small head, due to zikavirus.
In order for the head region to form, you need to suppress signals that form the
thoracic region.
Teratology:
Morphogenesis dysmorphogenesis (birth defects in structures)
The study of congenital malformations
Teras: wonder, monster
In the middle ages:
Malborn babies were often thought of being a combination between animal and
human.
Nowadays:
Often accurate descriptions of conditions.
Rubella virus: rode hond can lead to congenital malformations and red dots on
the skin. first sign that influences of the mother (outside environment) could affect
development of the foetus.
Thalidomide (Softenon): drug prescribed for morning sickness malformations of
arms and legs. first sign that also medication could influence development of
embryos.
Most common severe congenital malformations/anomalies are: heart defects, neural
tube defects and Down syndrome.
Three possible causes of birth defects are:
1. Genetical
2. Environmental (teratogens, mechanical)
3. Multifactorial (both genetic and environmental, influencing each other)
1. Genetical:
Chromosomal and monogenic
Primordial germ cells:
- originate from oogenesis + spermatogenesis.
- Omnipotent are able to differentiate into any tissue.
- Around week 2: outside the embryo
- Around week 4-6: migration from the yolk sac, towards the genital ridge
(primitive gonad (testis/ovary)) become oocytes and sperm.
, Ploidy= number of copies of a chromosome
N number= number of copies of each DNA
Normal cells:
Diploid 2N
Sperm/oocyte:
Haploid N
During gametogenesis (spermatogenesis/oogenesis) processes can go wrong,
leading to chromosomal abnormalities.
Number of chromosomes:
Triploidy: instead of diploid cells, with two copies of each chromosome, you have
three copies of each chromosome. caused by 2 sperm cells fertilizing an
oocyte, or no formation of a 3rd polar body.
Triploidy is always lethal, during pregnancy, most of the fetuses have a fused 3 rd
and 4th finger.
Monosomy: Instead of diploid cells, with two copies of each chromosome, one of
your chromosomes has only one copy. Example: Turner Syndrome (vital) only
one sex chromosome
Trisomy: Instead of diploid cells, with two copies of each chromosome, one of
your chromosomes has three copies. Example: Down syndrome (vital) – Trisomy
21
Monosomy and trisomy are called nondisjunction.
The older the father the more gene mutations can occur. Especially: ADHD
2. Environmental:
Teratogen: agent that produce birth defects
- Critical period (at a certain stage in development: time dependent)
- Dose dependent
Organogenesis in pre-embryonal stage is the most critical period, the risk on inducing
congenital malformations (due to e.g. malformation of organs) is highly increased in
this stage.
Malformations that happen during growth stage, more affect the functioning of certain
organ systems.
Critical period: organ dependent.
Examples of teratogens:
Maternal infections:
- Rubella
- Toxoplasmosis
Chemical:
