Organogenesis Flashcards
What is organogenesis? (2)
o During organogenesis, various regions of the germ layers develop into rudimentary organs.
o Organogenesis- formation of organs in their proper location.
What does the adoption of particular developmental fates may cause…
cells to change shape or even migrate to a new location.
How can a cell’s fate be established?
A cell’s fate can be established by the inheritance of cytoplasmic determinants or by interaction with neighbouring cells (induction).
To understand organogenesis in vertebrates, we will consider ____ and _____.
neurulation
somitogenesis
Describe the process of neurulation in frogs. (7)
- Neurulation begins with the development of a dorsal nerve rod called the notochord.
- The notochord forms from the dorsal mesoderm.
- The notochord is a rod of cartilage that supports the body of the developing
embryo. - Signaling molecules secreted by the mesoderm causes the ectoderm to form a neural plate.
- Neural plate formation is an example of induction.
- The neural plate cells change shape and curve inward, forming the neural tube.
- The neural tube will become the central nervous system (brain and spinal cord)
What are neural crest cells? (2)
o A set of cells develop along the border of the neural tube and are called the Neural crest.
o These cells migrate to form various parts of the embryo (nerves, parts of teeth, skull bones).
What happens while the neural tube is forming? (2)
o While the neural tube is forming the rest of the body is being established.
o A group of mesoderm cells next to the notochord separate into blocks called somites.
What do somites end up forming? (2)
o Somites form the segmented structure of the vertebrate body.
o These somite cells end up forming the vertebrae, ribs and associated muscles.
Neurulation in ____ and humans is similar, the three layers fold and pinch to form the neural tube.
chicks
What is spina bifida & what can it lead to?
o Spina bifida is a birth defect resulting from faults during neurulation:-
the neural tube fails to develop or does not close properly
o This can lead to nerve damage and paralysis.
o During organogenesis the cells of the three gem layers _______ to form these organs
differentiate
What does organogenesis rely on?
o Organogenesis relies in cell migration (e.g. cells of the neural crest).
What cell components are essential to cell migration?
> Microtubules and microfilaments are essential to cell
migration.
These are found in the cytoskeleton and they:
o Bringing about changes in cell shape.
o Enabling a cell to migrate to a new location.
How do somite cells and neural crest cells migrate?
Somite cells and neural crest cells migrate to various location by “crawling” using the cytoskeletal fibres.
What is the function of cell-adhesion molecules in neurulation?
o Cell adhesion molecules (glycoproteins) play a role by promoting cell-cell interactions.
How does invagination occur? (3)
o Microtubules orientate themselves from the dorsal to ventral side in a sheet of ectodermal cells.
o At the epical end of the cell is a bundle of actin filaments which contract to give the cells a wedge shape.
o This process bends the ectodermal layer inward developing an invagination.
What is convergent extension?
o Convergent extension- rearrangement that causes a sheet of cells to become narrower and longer.
o E.g. the formation of the primitive streak.
o The cells elongate with their ends pointing in the direction they will travel.
o Cell wedge together to form fewer columns
