Basic Principles of Development Flashcards
What is conceptus?
Product of conception including embryo/fetus and fetal membranes
What is the embryonic period?
1st cleavage of zygote to establishment of major organ systems
What is the fetal period?
Consists of growth and organ refinement up to the point of birth
What are the 2 major events required for embryonic development?
- Increase in cell number or cell proliferation
- Cell specialization of differentiation
What is occuring during cell proliferation?
Mitosis
What is differntiation?
A gradual process whereby specialized cell types develop from less specialized ones
Two key parts to cordination via communication?
Timing
Amount (intensity)
of communication
4 Response to cell signalling?
Change Morphology
Divide
Differentiate
Apoptosis
5 Types of signaling
Paracrine
Contact-dependent
Autocrine
Synaptic
Endocrine
What is paracrine signaling?
Short range, however, doesnt require direct cell to cell contact
What is contact-dependent signaling
Short range, cell giving off signal must be in direct contact with target cell
3 forms of contact-dependent signaling
Membrane protein on one cell binding to specific receptor on adjacent cell
Secretion of ligand into the extracellular matrix that binds receptor on target cell
Signal directly being transmitted from the cytoplasm of one cell into the cytoplasm of another via gap junctions
What is autocrine signaling?
Cell(s) can send molecules to cells of similar type or even to themselves
Why is autocrine signaling very pertinent for development?
Groups of a particular cell type signal to a group of similar cells to follow a common developmental fate
Difference between endocrine signalling and synaptic
Endocrine is slow acting but long lived
What must first occur in order for differentiation to occur?
Cells first need to become committed to a specific cell fate
What are two aspects of cell commitment?
Cell specification - reversible process
Cell determination - irreversible
What is differentiation regulated by?
Difference in gene expression
All cells in embryo have same genome, however, some individuals have genes that re repressed
What is induction
Process by which presence of one tissue influences the development of others
What is cell competency?
Cell can only be induced when the signaling molecules moving to the target cell can be interpreted
ie., Induction of lens by optic vesicle
What is the critical period?
Window of Time durring which signaling molecules and or signaling receptors are present to cause induction
What is cellular totipoteny?
Blastomeres that can form all cells of embryo proper
What are blastomeres?
Zygote and first few genearations of cells that develop
What is pluriopotency?
Durring development cells become more restricted in developmental potential
What is gastrulation?
Formation of 3 germ layers
What is multipotency?
Cells within germ layers exibit several developmental potentials
What is unipotency
Tissue-specific precursor cells that produce single types of differentiated cells
eg. satelite cells producing skeletal muscle cells
What is terminal differentiation?
When cells reach a specific stage of development where they have fully matured and no longer divide
What is patterning?
Process of embryonic cells organizing into tissues and organs
What drives patterning?
Regional gene expression
What is regional gene expression?
Differential expression of genes in different parts of the embryo
What are homeobox containing genes?
180bp conserved DNA sequence shared by some genes
Specify the identity of a particular body segment
What do hox genes control>
The segmental development of the embryo
The fine patterning of the dorso-ventral axis of the developing nervous system results from the relative concentrations of which two factors?
- TGF-beta family members
- Sonic hedghog (Shh)
What is morphogenesis?
Mechanism by which tissues and organs are shaped
Relationship of patterning and morphogenesis?
Patterning gathers cells into regions to form organs while morphogenesis internaly shapes them
