Midterm Suggested SA Flashcards
Name 4 differences between differentiation and morphogenesis (hint: definition, level at which it occurs, control and cellular movement)
Differentiation:
definition - refers to the process by which cells become specialized
level - cellular level
control - transcription factors
movement - does not play a role
Morphogenesis:
definition - process that determines the shape of an organism
level - tissue, organ or organism level
control - spatial/temporal control of embryo mechanics
movement - cell movement is critical to morphogenesis
State the key properties of cells for morphogenesis
cell adhesiveness - tendency of cells to stick together and to their environment. interaction involves cell adhesion molecules
cell shape - cell can actively change shape by means of internal connections
cell migration - the ability of a cell to move from one location to another
How does cell adhesion regulate the cell behaviour in morphogenesis
all cells have surface tension at their membrane where they encounter extracellular environment. the particular cell adhesion molecule expressed by a cell will determine which cells it can stick to
Define sorting out different cell types
separation of embryonic tissues with different adhesive properties. the sorting out is the combine result of differences in surface tensions. cadhesions can provide adhesive specificity
How do cadherins provide adhesive specificity?
cell type specific cadherins. only those expressing same cadherin adhere together
What are the major structures arising out of three germ layers?
endoderm - gut and its derivatives (lung and liver)
mesoderm - kidney, muscles, CT, skeleton, etc
ectoderm - endoderm of skin and nervous system
How does embryo get nourishment
the mammalian embryo is a small, non-yolky embryo, and when it attaches to the uterine wall, it receives nourished from the fluids present in the oviduct and uterus for some days. otherwise the yolk provides nourishment for birds, amphibians, reptiles
List the features that birds and mammals resemble each other and differ from amphibian in early embryo
Birds and mammals:
- blastula is not hollow, but is a layer of epithelium called the epiblast
- no distinct regions of epiblast that correspond to future germ layers
Amphibians:
- hollow blastula
- distinct regions that will develop into future germ layers
Discuss the different cleavage patterns in different animal groups
- radial cleavage: when the cell cleave at right angles to the eggs surface and the first few cleavages produce tiers of blastomeres that sit directly over each other. (ex-sea urchins)
- spiral cleavage: successive divisions that are at slight angles to each other producing spiral arrangement of cells (ex-mollusks and annelids)
Define planar cell polarity with example
planar cell polarity (PCP) is the polarization of a cell within a plane or tissue. ex - stereocillia in human inner ear
Define convergent extension with example
convergent extension is the process by which the tissue of an embryo is restructured to converge along one axis and extend along perpendicular axis by cellular movement
ex- the anteroposterior axis becomes longer as the lateral tissue moves in toward the dorsal midline
What is the role of the Apical ectodermal ridge during limb development?
the apical ectodermal ridge (AER) is one of the main signalling centres during limb development. it controls outgrowth and patterning in the proximo-distal axis.
