Blake_Anatomy_10_Development of Neuro System Flashcards
Ectoderm yields:
Epithelium
Nervous tissue
Mesoderm yields:
muscle and connective tissue
from which primary germ layer is epithelium derived?
Ectoderm
Mesoderm
Endothelium
from which primary germ layer is muscle and connective tissue derived?
mesoderm
from which primary germ layer is nervous tissue derived?
ectoderm
Endoderm yields:
epithelium; specifically, the gut tube
Steps in Neurulation (4)
- Neuroectodermal tissue differentiate from the ectoderm and thicken into the neural plate. The neural plate border separated the ectoderm from the neural plate.
- The neural plate bends dorsally, with the two ends eventually joining at the neural plate borders which are now referred to as the neural crest
- The closure of the nural tube disconnects the neural crest from the epidermis. Neural Crest cells differentiate to form most ot the peripheral nervous system
- The notochord degenerates and only persists as the nucleus pulposus of the intervertebral discs. Other mesoderm cells differentiate into the somites, the precursers of the axial skeleton and skeletal muscle
Coronal (dorsal/ventral) divisions of the Early Cord (5)
- Roof plate
- alar plate
- sulcus limitans
- basal plate
- floor plate
What type of tissue comprises the early neural tube?
Pseudostratified columnar (neuro) epithelium
how are the epithelial cells of the early neural tube characterized?
High degree of mitotic activity
What is the result of celular division and maturation of the early nerual tube?
a population of bipotential progenitor cells, which will give rise to either neuronal or glial progenitor cells.
Cell lineages in developing CNS (beginning with bipotential progenitor cell)
Bipotential progenitor cells of the Neural tube:
- Neuronal Lineage Progenitor
- Neurons - transmit electrochemical signals
- Glial Lineage Progenitor
- Neuroglia - Supporting cells of the CNS - Insulate, nourish, suport and protect neurons
Cytodifferentiation
Postmitotic neurons and glioblasts migrate outward to form an ____1___ ______ or _______ _____. This will become the ___2____ ______ ______ that contains neuronal cell bodies and neuroglia.
____3___ ________ (myelinated) move out to surround the developing grey matter and form the outer white matter (also called the____4___ ________).
- Intermediate mantle or cortical zone
- inner grey matter
- Neuronal processes
- marginal zone
Molecular regulation of nerve differentiation in the cross-sectional spinal cord: (4)
- BMP4 and 7 secreted in the ectoderm establish a signaling center in the roof plate
- BMP4 in the roof plate upregulates a cascade of TGF-ß proteins, including BMP5 and 7, activin, and dorsalin
- SHH from the notochord establishes an SHH signaling center in the floor plate
- OVERLAPPING gradient involving the dorsal and ventral factors is established in the neural tube
As the neural tube is differentiating, what is happening to the mesoderm lateral to it?
Mesoderm is divided into different regions on the basis of spatial position with respect to the notochord.
Axial to Lateral arrangement of the Mesoderm
- Notochord
- Paraxial Mesoderm
- Intermediate mesoderm
- Lateral plate mesoderm
Paraxial Mesoderm
Longitudinal blocks of tissue on either side of the notochord. It gives rise to the axial skeleton and skeletal muscle
Intermediate mesoderm
gives rise to the urogenital system
Lateral plate mesoderm
gives rise to connetive tissue and skeleton of the limbs and smooth muscle and connective tissue of viscera and blood vessels. DOES NOT GIVE RISE TO SKELETAL MUSCLE
Somitomeres and Somites
Segmented series of tissue blocks on each side of the neural tube
Somitomeres are the seven more cranial somites
Somites are loccated caudally from occipital region
Growth and differentiation of the head is regulated by ___ genes.
Hox
Segmentation of Axial Mesoderm is controled by:
- pulses of gene expression (AKA clock and wave front)
- Hox genes
How are somites separated from each other?
- NOTCH Pathway
- Segmentation clock Hox
- Retinoic acid + FGF8 and WNT3a Gradient
- RA - Cranially expressed
- FGF8 and WNT3a - Caudally expressed
- OVERLAPING GRADIENTS CONTROL CLOCK AND NOTCH
Somite divides into 3 parts:
- Sclerotome
- Dermamyotome
- Dermatome
- Myotome
Sclerotome
Derived from the somite. Ventromedial portion closest to the notochord. Move medially and condense around the notochord to surround the nerual tube. Ultimately they form the vertebrea.
Dermatome
Derived from the somite. Will become the dermis (under the epidermis) Skin=epidermis from surface ectoderm
Myotome
derived from the somite. gives rise to muscles
How are the types of vertebra determined?
- Not on a one-to-one basis by the Hox genes, but rather by their interactions:
- Cervical - Hox 5
- Throracic - Hox 6, Hox 9
- Lumbar/Sacral/Coccygeal - Hox 10
Molecular Regulation of Muscle Development (2)
- Many regulators, some are specific to epaxial or hypaxial muscle only
- Both MyoD and MYF5 are members of a family of transcription factors called myogenic regulatory factors (MRFs)
MyoD and MYF5
MRFs - Myogenic Regulatory Factors
Intermediate Mesoderm (3)
- Moves anteriomedially posteriorly to abdominal wall
- Forms gonads (except primative germ cells)
- Forms ducts, accessory glands of Urinary and reproductive tracts
What parts does the gut need?
How do the Inner spanchic mesoderm layer and the somatic mesoderm layer leave room for the abdominal cavity
Mesoderm, Viscera, Body wall
Inner splanchic closes more quickly
The gut tube and umbilical cord are reminants of ______
the yolk sac
What effect does the folding of the embryo have on the lateral plate mesoderm?
the lateral mesoderm differentiates into somatic and splanchnic mesodermes and closes around the abdominal cavity and the gut tube respectively.
