Development of mesoderm and neural crest cells Flashcards
What is a zygote?
Sperm and egg fuse together during fertilisation
What is cleavage?
Cells of zygote split without growing:
- 2 cells = blastomere
- 4 cells
- 8 cells
- 16 cells
What is a morula
16 cells mass resembling a mulberry
What happens after a morula is formed?
Form an outer cell mass - trophoblasts
Form an inner cell mass - embryoblasts
Embryoblasts clump together at one end, leaving a fluid filled cavity called a blastoceal. When this process ozzurs, the zygote forms a blastocyst
What stage comes after cleavage?
Blastulation
What processes occurs in blastulation?
- Zona pelucida disintegrates
- Inner cell mass of embryoblasts forms a cavity inside it called an amniotic cavity
- Embryoblasts closest to blastocyst differentiate and become hypoblasts
- Embryoblasts above hypoblast cells differentiate to form epiblasts
What is gastrulation?
- Formation of primitive streak marks gastrulation (site in epiblast layer start to migrate inside the bilaminar disk)
- Cells differentiate even more
What is a trilaminar disk?
- These are the 3 germ layers
- Ectoderm
- Mesoderm
- Endoderm
What occurs in neuralation?
- Further differentiation of cells occurs
- In centre of mesoderm, a notochord forms (forms some of intervertebral disks)
- Notochord induces a change in the ectoderm above it = thickening of the ectoderm to form the neural plate
- Neural plate cells dive into the mesoderm and form a tube = neural tube
- Cells from the neural tube break off and go into the mesoderm = neural crest cells – differentiate into special tissues
What is the blastoceal also known as?
primary yolk sac
What do embryoblasts form?
Embryo proper
What is the function of trophoblasts?
Form placenta and are associated with implantation
When is the bilaminar disk formed?
After 8 days of gestation
When is the trilaminar disk formed?
After the third week of development
Label this image
Label this image
What are neural crest cells?
• As the neural tube forms, a group of
cells separate from the
neuroectoderm (ectoderm destined
to form neural tissues).
• These cells have the capacity to
migrate and differentiate extensively
within the developing embryo, and
they are the basis for such
structures as the spinal sensory
ganglia, sympathetic neurones,
Schwann cells, pigment cells, and
meninges
What is thought to be critical for inducing the neural crest cascade?
bone morphogenetic proteins, Wnt (wingless homologue in
vertebrates), and fibroblast growth factor signalling pathways are
What do neural crest cells in he head region do?
In additionto assisting in the formation of the cranial sensory ganglia, they also
differentiate to form most of the connective tissue of the head.
How is embryonic connective tissue in the head different to that in other parts of the body?
Embryonic connective tissue elsewhere is derived from mesoderm and
is known as mesenchyme, whereas in the head it is known as
ectomesenchyme, reflecting its origin from neuroectoderm
Why is the correct migration of neural crest cells important in dentistry?
In a dental context the proper migration of neural crest cells is essential
for the development of the face and the teeth.
• In Treacher Collins syndrome, for example, full facial development does
not occur because the neural crest cells fail to migrate properly to the
facial region.
• All the tissues of the tooth (except enamel and perhaps some cementum) and its supporting apparatus are derived directly from neural crest cells, and their depletion prevents proper dental development.
