Neurulation and Somitogenesis Flashcards
What is Neurulation
Formation of the vertebrate nervous system in embryos
Explain the process of Neurulation
1- Notochord induces formation of CNS by signalling the ectoderm above it to form the neural plate
2- neural plate folds in on itself to form the neural tube
3- neural tube differentiates into the brain and spinal cord
4- neural crest cells derived from neural tube , migrate and form PNS and other structures such as melanocytes and cartilage in head
What is Gastrulation
The formation of the 3 embryonic layers : ectoderm , mesoderm and endoderm
What is the neural plate composed of
neuroectoderm
Where does the notochord arise from
Mesoderm, arises from the midline & extends to the cranial region
Where does the neural tube arise from
Ectoderm
Explain the development of the Notochord & What Day it would happen
Day 15-16
Some Mesodermal cells migrate cranially in the midline of the mesodermal layer and form rod-like notochord process
At What Day is the Development of the neural tube
Day 21
Explain in detail the development of the neural tube
1- Neuroectodermal tissue will differentiate from ectoderm and thicken into neural plates
2- Neural plate border separates the ectoderm from neural plate via a neural plate border
3- neural plate will bend dorsally with two ends eventually joining at the borders = now called neural crest ( made of neural plate border )
4- Closure of neural tube disconnects neural crest form ectoderm & the neural plate from both the neural crests and the ectoderm
5- Neural crest cells differentiate to form PNS
6- Notochord degenerates and only stays as the nucleus pulpous of intervertebral discs
7- other mesoderm cells differentiate into somites , precursors for axial skeleton and skeletal muscle
What are neural crests cells composed of
Neural plate border that has been separated form he neural plate
What is the function of the notochord
It’s an inductive structure that turns the overlying ectodermal tissue around it into neural tissue
The region of the ectoderm under the influence of the notochord to turn into neural tissue is called what
Neural Plate
Pluripotent neural crest cells migrate and give rise to which nervous structures
1- Spinal Ganglia ( dorsal root ganglia )
2- Ganglia of autonomic nervous system
3- Ganglia of some cranial nerves
4- Sheaths of peripheral nerves
5- Meninges of brain and spinal cord
6- Melanocytes
7- Suprarenal medulla ( of the adrenal gland )
8- Skeletal muscular components in the head
What is BMP
Bone morphogenetic Protein
- morphogen released by notochord which stimulates changes of ectoderm into neural tissue to make the neural plate
Explain the development of the Somites
1- As notochord and neural tube forms a longitudinal column of paraxial mesoderm is also forming
2- Paraxial mesoderm differentiates and divides into paired cuboidal bodies ( somites )
6- By end of Week 5 there is 42-44 pairs of somites
What are the somites & what do they form
Blocks of mesoderm located on either side of the neural tube that give rise to multiple cell/structures
1- Cartilage of axial skeleton : vertebrae
2- Muscles of rib cage, limbs and back
3- Cells that contribute to connective tissue of dermis
When the neural tube starts folding where does it start
In the midline , then extends cranially and then posteriorly
Which area does the neural tube seal/ fold last
The posterior portion of the spinal cord
What is the anterior neuropore and posterior neuropore
Last regions to close :
anterior will become head
and posterior will develop limbs ( legs )
What are the different cells of the somite
1- Sclerotome : bone
2- Myotome : muscle
3- Dermatome : connective tissue
What embryonic structure makes up the intervertebral disk
The notochord , the core of it called nucleus pulpous makes up the intervertebral disk
Explain the differentiation within the Somites
1- Initially somite is composed of sclerotome and demomyotome cells
2- Sclerotome cells lose their adhesion to each other and migrate leaving dermomyotome cells to divide
3- Myotome muscle cell precursors form beneath epithelial dermatome
Sclerotome gives rise to
Bone , vertebrae
Myotome gives rise to
Muscle of back
