Embryology 2 Flashcards
What is the primitive streak?
Raised groove on the dorsal surface of the epiblast.
What is gastrulation?
Formation of 3 germ layers as an embryo
What are the 3 germ layers that derive from the epiblast?
Ectoderm
Mesoderm
Endoderm
How does the notochord form?
The ectoderm thickens and dips down to form a solid tube, leading to the formation of the notochord.
What is the role of the notochord?
It induces ectodermal cells in the midline to form the neural tube.
What does the notochord release?
Shh gene
What does the neural tube induce?
It induces the mesoderm to thicken
What are the 3 parts of the mesoderm?
Paraxial mesoderm
Intermediate plate mesoderm
Lateral plate mesoderm
What does the paraxial mesoderm give rise to?
Axial skeleton
In what weeks of development of the organogenetic period?
4th - 8th week
What happens to the lateral plate mesoderm?
Splits into 2 leaves and form a cavity in between
What does the endoderm form?
Gut and respiratory system
What do somites differentiate into?
Sclerotome (bone)
Myotome (muscle)
Dermatome (dermis of skin)
What does the lateral plate mesoderm form?
Splanchnic and somatic mesoderm
What does the intermediate plate mesoderm form?
Urogenital system (eg. kidneys, reproductive system)
What are teratogens?
Substances that cause birth defects
What is congenital rubella syndrome caused by?
Contraction of german measles whilst pregnant.
What are causes of genetic birth defects?
Maternal age
Environmental factors (e.g radiation)
Which weeks of development have the greatest sensitivity to teratogens?
3 - 8 weeks
What are the prenatal methods of diagnosis of malfunctions?
Alpha-fetoprotein (AFP)
Blood test
Ultrasound scan at 12 weeks
Chronic villus sampling
Amniocentesis
What are the postnatal methods of diagnosis of malfunctions?
Hip stability
Testes (descent)
Fingers and toes
Hearing test
