Differentiation of the Ectoderm and Organ development Flashcards
What does the ectoderm differentiate into?
Non neural ectoderm and neural ectoderm
What does non-neural ectoderm form once fully developed?
Epidermis of the skin and all the components associated with it (e.g. hair, nails, tooth enamel)
What does neural ectoderm form?
Nervous system, neural plate border
What kind of ectoderm is found exclusively in the head? What does it form?
Ectodermal placodes Lens of the eye, ear (structures of the head)
The cells on the ectoderm that are placed along or near the midline become what kind of tissue? How does the cell shape change? What is the tissue that is next to it?
Becomes neural plate Tall columnar cell shape Tissue next to on either side is non-neural ectoderm
What does the neural plate develop into?
Most of the tissue will form the nervous system
How does the neural plate vary along the rostral caudal axis? What different structures does this develop?
It is wider at the rostral end and thinner at the caudal end Forms the brain at the rostral end and the spinal cord at the caudal end
How does the neural plate change as development proceeds? What does it form? What is the process called?
The central area of the neural plate folds downwards (creating a ‘ditch’ in the neural plate) and the outer edges rise and curl upwards and inwards It forms a neural tube Process is called primary neurulation
Is the neural tube a closed cylinder? Explain
No, it has the rostral/anterior neuropores and caudal/posterior neuropores still open (e.g. the top and bottom ends are still open)
What is the condition where the rostral neuropores don’t close? What is its lethality?
Anencephaly It is lethal
What is the condition where the caudal neuropores don’t close?
Spina bifida
What is chance of a neural tube not closing properly?
1 in 1000 live births
Where does the neural tube form in relation to the non-neural ectoderm?
The neural tube is covered over by the non-neural ectoderm
Where is the neural tube located in the embryo?
It runs from the caudal to rostral end
What forms at the rostral end of the neural tube? What will this develop into?
The forebrain, midbrain and hindbrain vesicle Will develop into the brain
What does the neural tube that does not develop into the vesicles develop into?
The spinal chord
What happens to the cells on the edge of the neural plate as the neural plate rises? What do they develop into?
Goes from being epithelial like cells to mesenchymal cells and come out of the forming neural tube, migrating around the entire body form the peripheral nervous system, melanocytes and other neural tissue
What kind of hox gene expression occurs from below the midbrain?
Hox gene patterning
What are hox genes?
A type of transcription factors
What kind of hox gene is expressed in the forebrain and midbrain?
There are no hox genes expressed in these regions
Where does the head start? What determines this?
It is debatable as it could start from the midbrain where hox genes are not expressed OR it could start from the hindbrain where the somites are the beginning on non-brain neural tissue
What does secondary neurulation form?
Forms the neural tube from the caudal end
How does secondary neurulation form a neural tube?
A rod like condensation of mesenchymal cells beneath the dorsal ectoderm (ectoderm on the back of the embryo) in the tail bud forms and a cavity opens up in the centre of the rod
How does primary and secondary neurulation differ?
Primary starts at rostral end and ectoderm folds over itself to form a tube, secondary starts at caudal and is a rod the then develops a central canal throughout he rod