Development of the Musculoskeletal System (Embryology) Flashcards
The neural tube is derived from what germ layer?
Ectoderm
What component of the nervous system to neural crest cells form?
PNS
Somites are derived from what germ layer?
mesoderm
What type of cells are in the early notchord?
undifferentiated neuroepithelial cells; they are pseudostratified and highly mitotic.
Division of the neuroepithelial cells in the neural tube gives rise to what 2 kinds of cells?
neural and glial progenitor cells
What do neuroglia cells do?
Support cells of the CNS. They insulate, nourish and protect neurons.
What does the marginal layer contain?
neuronal processes (axons)
Where do postmitotic neurons and glioblasts migrate towards?
the intermediate mantle/cortical zone.
What does the intermediate mantle/cortical zone contain?
inner gray matter (neuronal cell bodies and microglia).
What does the marginal zone contain?
myelinated neuronal proceses (axons).
What does the ectoderm secrete (it is also eventually secreted by the dorsal portion of the neural tube?)
BMP 4 and 7.
What does the notochord secrete (it is also eventually secreted by the ventral portion of theneural tube?)
Shh (sonic hedgehog)
BMP4, 7, and Shh create what in the neural tube?
A gradient; it tells what kinds of neurons will be developed in particular parts of the tube.
What are the 3 divisions of the mesoderm?
paraxial, intemediate and lateral
What does the paraxial mesoderm give rise to?
axial skeleton and ALL skeletal muscle
What does the intermediate mesoderm give rise to?
kidneys and gonads (urogential system).
What does the lateral plate mesoderm give rise to?
connective tissue, skeleton of the llimbs, sooth muscle/connective tissue of blood vessels.
What is the paraxial mesoderm?
A “segmented” series of tissue blocks on each side of the neural tube. It contains somitomeres (head) and somites (spinal cord)
What genes regulate growth/differentiation in the head?
hox genes
What is segmentation controlled by?
pulses of gene expression.
What does the somite of the paraxial mesoderm differentiate into?
sclerotome (cartilage), dermotome (dermis), myotome (muscle)
What is the function of notch?
activates other segment-patterning genes in the somites.it helps to break up somites.
Notch expression ___ in somites destined to be formed and ___ in already-developed somites.
increases, decreases
What is the function of retinoic acid?
It sets up boundaries for somites, and works with notch to cut off regions of segmentation. It also controls the segmentation clock and activity of notch.
Where is retinoic acid expression the highest?
in caudal regions.
Animals with extensive vertebrae (e.g. a snake) generally have a ____ level of gene activity.
higher
What does the somite divide into?
sclerotome, dermatome and myotome.
Which region of the somite is closest to the neural tube?
sclerotome; they move medially and surround the notochord.
Cells facing the surface ectoderm differentiate into what?
the dermomyotome.
What is resegmentation?
The segmentation of sclerotome segments into caudal and rostral halves; they eventually fuse to form vertebrae.
What do the caudal and rostral halves of the sclerotome eventually form?
vertebrae
What does the notochord form in the intervertebral disc?
the nucleus pulposus
A type of vertebrae a somite becomes i s controlled by ___ hox genes.
mutliple.
What kinds of muscle does the myotome create?
epaxial (dorsal) and hypaxial (ventral).
What are MyoD and MYF5?
Transcription factors that signal the development of epaxial and hypaxial muscles.
What would happen if MyoD and MYF5 were not present?
Differentiation into hypaxial and epaxial muscles would not occur.
Spinal nerves from the neural tube innervate what derivative of the paraxial mesoderm?
myotomes
What does the lateral plate segment into?
A region that forms the gut, and a region that forms the outer body wall. The region that forms the outer body wall will surround and trap the gut region.
What is another term for the exterior lateral plate?
somatic mesoderm
What is another term for the interior lateral plate?
splanchnic mesoderm
