Embryology Flashcards
(14 cards)
What organisms does embryology take place in?
Animal kingdom
Why do we study embryology?
‘Ontology recapitulates phylogeny’ (Ernst Haeckel 1870s)- means the development of the embryo mirros the successive stages of evolution
Recapitulation theory (Meckel 1790s + Serres 1820s)- if you have the successive stages of fish development from egg, to embryo to adult
What does the evolutionary developmental biology state (evoe-devo)?
Changes in the timing and positioning of embryonic development affects the change of the shape of a descendants body compared to its ancestor
What happens in the early cell cleavage?
Fertilised egg or oocyte
Morula- solid ball of cells which develops from successive cleavage
Morula becomes a blastula- a hollow ball of cells around a blastocoel
Blastula forms a gastrula- a multi-layered ball of cells through invagination on the outside wall
What are the significant moments in embryogenesis?
Morulation
-formation of morula
-cell cleavage
Blastulation
-formation of blastula
Gastrulation
-formation of gastrula
-formation of germ cell layers
-formation of the mesoderm and the coelom
-fate of the blastopore
What happens in morulation?
Cleavage which can happen in two ways
Radial cleavage
-Cell divides. Cells remain on the polar axis. Origin cell below the new cell
Spiral cleavage
-As cell divides along the polar axis, there is a twist that develops. Creates a more spiral view
What happens in gastrulation?
Forms the cell layers of the gut
Point of invagination of outer wall
Blastopore becomes either the mouth, anus or both
What happens in blastulation?
Blastopore develops into one of 3 things
Diploblastic- mouth and anus
Triploblastic enterocoelom- anus
Tripoblastic schizocoelom- mouth
What organisms in the animal kingdom are undergo no cleavage, where the mouth and anus is formed?
Coelenterates- sponges, jellyfish, corals
What organisms in the animal kingdom undergo spiral cleavage, where the blastopore forms the mouth?
Protostomes- molluscs, annelids, arthropods
What organisms in the animal kingdom undergo radial cleavage, where the blastopore forms the anus?
Deuterostomes- starfish, vertebrates
What is a summary of embryogenesis in coelenterates?
Germ layer- diploblastic
Cell cleavage- none
Coelom- acoelmate
Blastopore- mouth and anus
What is a summary of embryogenesis in protostomes?
Germ layers- triploblastic
Cell cleavage- spiral
Coelom- schizocoelom
Blastopore- mouth
What is a summary of embryogenesis in deutrostomes?
Germ layers- triploblastic
Cell cleavage- radial
Coelom- enterocoelom
Blastopore- anus
