Concepts In Embryology Flashcards
(28 cards)
What are the three approaches to embryology?
Anatomical, experimental, genetic
How do embryos develop?
New structures arise progressively
What is Von Baer’s first law?
The general characters of an animal group appear earlier in the embryo than the specialised characters do
What is Von Baer’s second law?
Less general characters develop from more general until finally the most specialised appear
What is Von Baer’s third law?
The embryo of a given species, instead of passing through the adult stages of lower animals, departs more and more from them
What is Von Baer’s fourth law?
Therefore the early embryo of a higher animal is never like a lower animal, but only like its early embryo
What is ontogeny?
The sequence of events involvd in the development of an individual organism
What is phylogeny?
The sequence of events involved in evolutionary development of a taxonomic group
Wo discovered the ovum and when?
Von Baer in 1827
When wa sperm discovered?
1677
What is the signalling centre?
The organiser for gastrulation
In what specie was the organiser discovered?
In frog embryos
What is gastrulation?
The process where the cells of the embryo reorganise to allow the development of different cell types
Where is the organiser in frog embryos?
The dorsal blastopore lip
What was the result of grafting the frog dorsal blastopore lip onto the ventral side of a host embryo?
The host embryo developed normally but with a second embryonic axis on the ventral side from the dorsal bastopore lip
What is metamerism?
An initial subdivision of the embryonic body into an ordered series of equal segements (metameres)
What is somitogenesis?
Segementation of the embryonic body into structures of interest in vertebrates
What cell type segements into somites either side of the neural tube?
Mesoderm
What three precursor cell types develop from somites?
Cells of the vertebrae, dermis and skeletal muscle
What gene family sets up the segmented body plan?
Hox genes
Where are Hox genes expressed?
Along the anterior - posterior axis
What germ layer develops into the CNS?
Ectoderm
What germ layer develops into the skin?
Ectoderm
What germ layer develops into the muscles?
Mesoderm
