Lecture 30: Development of the nerve system3 Flashcards
whats a 16 celled human embryo called?
morula
what day is fertilisation?
Day 0
what happens in Day 1 of the embryo ?
first cleavage
what happens in Days 2, 3 , 4 ?
2 - two cell stage and4 cell stage
3 - 8 cell uncompacted morula
4- 8 cell compacted morula
when is an early blastocyst formed?
Day 5
what happens in days 6 - 7?
late stage blastocyst
In day 5 what forms in the embryo?
inner cell mass
by days 6 - 7 what can be found in the embryo?
polar trophectoderm
epiblast
primitive endoderm
mural trophectoderm
what happens to a 7.5 day blastocyst?
Endometrium erodes
cells of embryonic disk separated from amnion by a fluid filled space
what happens to a 12 day blastocyst ?
This is when implantation is complete, extra embryonic mesoderm is forming a discrete layer beneath the cytotrophoblasts.
what happens to a 16- day embryo?
cytotrophoblast and mesoderm = chorion, chorionic villi elaborate.
embryo contains three germ layers, yolk sac, and allantois, which forms basis of umbilical cord
what forms the embryonic disc?
epiblast (ectoderm)
mesoderm
prospective endoderm
endoblasts
what does the endoderm layer become?
- digestive system
- liver
- pancreas
- lungs (inner layers)
what does the mesoderm layer become?
- circulatory system
- lungs (epithelial layers)
- sekeltal system
- muscular system
what does the ectoderm layer become?
hair
nails
skin
nervous system
what three things also occur during development?
cells differentiate
cells migrate and aggregate
cells form functional relationships
what does it mean when cells differentiate?
Some become muscle cells, some become neurones, and so on.
what happens when Cells Migrate & Aggregate
?
They make their way to appropriate sites and to form structures.
what happens when Cells form Functional Relationships?
They form integrated and interconnected systems that mediating complex tasks.
what are the 5 phases in which the nervous system develops?
Neurulation
Neural Proliferarion
Neural Migration, Aggregation & Differentiation
Neurite Growth
Neuronal Death & Synapse Rearrangement
what is neurulation?
formation of the neural tube
what is a neural plate?
a patch of ectodermal tissue on the dorsal surface of the developing embryo
what forms from the neural plate?
neural grooves
what happens after the neural groove is formed?
- The walls of the neural groove (neural folds) come together and fuse.
- Some ectodermal tissue is pinched off and forms the neural crest.
at what day is the neural tube fully formed?
24 days
Neural Proliferation
During the early embryonic stage, the nervous system consists of __ ______ _____.
3 interconnected chambers
Neural Proliferation
The 3 chambers will form the ______ and the tissue surrounding them will form the ____ _____ and _______.
ventricles
forebrian
mid brain
hindbrain
what ventricles link to the forebrain ?
lateral
third
what ventricle links to the midbrain?
Cerebral Aqueduct
what ventricle links to the hindbrain?
fourth
what happens once the Once the neural tube has completely fused together ?
cells of the ventricular zone begin to multiply
Neural Migration, Aggregation & Differentiation
what happens to new neurones formed ta this stage?
migrate away from the inner surface of the neural tube, guided to new location either physically (along glial cells) or chemically.
Neural Migration, Aggregation & Differentiation
Why does the thickness of the neural tube increase?
brain structures begin to form and coalesce
Neural Migration, Aggregation & Differentiation
what cells in the Ventricular zone?
progenitor cells
Neural Migration, Aggregation & Differentiation
whats found in the Intermediate zone?
subcortical structures and white matter
Neural Migration, Aggregation & Differentiation
whats found at the cordial plate?
cerebral cortex
Neural Migration, Aggregation & Differentiation
Once developing neurons have migrated, they must ____ ___ ___ _____ in the same region.
align with other neurones
Neural Migration, Aggregation & Differentiation
what mediates aggregation ?
cell adhesion molecules
Neural Migration, Aggregation & Differentiation
what ability do cell adhesion molecules have?
ability to recognise proteins on other neurones and stick to them.
what do Extracellular molecular signals help to give pyramidal cells ?
distinctive shape
A protein called _____ is released by cells up in the marginal zone that ___ axons and ____ dendrites thus altering the morphology of pyramidal cells.
semaphoring 3A
repels
attracts
migration, aggregation and differentiation continue causing?
the brain to start to take shape.
what make stem shape of the brain?
- flexures (bends)
- Differentiation and enlargement of the various brain regions.
- Growth of portions of the cerebral hemispheres over the diencephalon, midbrain, and cerebellum.
- The formation of sulci and gyri in the cerebral and cerebellar cortices.
where does the first major change to the brain occure?
first major changes occur in the forebrain, telencephalon extends laterally and posteriorly.
what also develops early on?
the visual and olfactory systems
How do the cerebral hemispheres grow?
cerebral hemispheres grow laterally to cover the diencephalon.
_______ bulbs and _____ stalks sprout.
olfactory
optic
what happens By the beginning of the third trimester?
structures of the brain are clearly distinguishable
The development of the ____ outpaces the capacity of the ______ to accommodate it!
cortex
cerebrum
