Mesodermal Layer Flashcards
Paraxial mesoderm (overview)
longitudinal blocks of mesoderm on either side of notochord
becomes axial skeleton and skeletal muscle
Intermediate mesoderm (overview)
gives rise to urogenitals
Lateral plate mesoderm (overview)
gives rise to connective tissues, appendicular skeleton
smooth muscle
connective tissue of viscera and blood vessels
Paraxial M. —-> what two important structures on developing embryo
Somitomeres (cranially) and Somites (caudally from occipital region)
Paraxial meso produces the ____ and somites
head
somites develop into
sclerotome (cartilage), myotome (skeletal muscle), dermatome (dermis)
the D.M.S
dermatomes, mytotomes, sclerotomes all from paraxial
“clock” and wavefront model
somites develop according to this model of gene expression. there are four regions
it begins posteriorly and moves anteriorly (I think)
“waves”
development of somites uses the segmentation clock of cyclic expression of NOTCH and WNT signaling pathways.
Notch
notch protein accumulates in presomitic mesoderm destined to form the next somite and then decreases as that somite is established
the increase in notch protein activates other segment patterning genes that –> somite
ok, so the “simple” version of notch
notch protein accumulates and activates other Somite differentiating genes
what regulates the “boundaries” of each somite?
retinoic acid (RA) and FGF8 and WNT3
RA is expressed in high concentrations ____ and ______ ______
cranially, but decreases concentration caudally
FGF8 and WNT3 expressed higher in caudal region
RA, FGF8 and WNT3 concentrations
RA cranially, FGF8/WNT3 caudally
THESE control the segmentation clock and activity of NOTH pathway
Sclerotomes
ventromedial portion closest to the notochord, develops into skeletal parts
Dermamyotome
divides into the dermis
Epidermis develops from ____ while dermis develops from
ectoderm, paraxial mesoderm
myotome
develops into muscle
which of the DMS move medially and concentrate around the notochord?
the sclerotomes
which of the DMS is closest to surface ectoderm, and what does it do
dermomyotomes —->
dermatomes (dermis forming) and myotomes (muscle forming)
develops into
Resegmentation
only occurs in sclerotome: they divide and then refuse with their neighbor to form vertebrae
Sclerotomes do what
they condense around the notochord and form the vertebrae
Hox gene control of somite development into vertebrae
it’s not a “one to one” basis but through hox gene interactions
the “big” hox genes noted in class were
hox5-hox6 –> cervical v.
ho6-hox-9 –> thoracic
hox 9+ hox X–> lumbar/Sacral/Coccygeal
epaxial genes =
MYF5
hypaxial genes =
MYOD
dermis forming genes =
NT-3
MRFs
myogenic regulatory factors, essentially transcription factors
Dermatome —>
Myotome –>
Sclerotome –>
dermis + nerve component
epaxial/hypaxial muscles+ nerve component (dorsal/ventral rami)
intermediate mesoderm
most to posterior wall to form gonads, ducts, accessory glands or urinary reproductive tracks
Caudal Dysplasia
total or partial failure of development of the lower vertebrae, including sacrum
results in associated abnormalities of lower extremities: spine, kidenys, gastrointestinal and genitourinary tracks
BROAD range of symptoms/abnormalities
Caudal Dysplasia MAY reflect _______ (3 things) but is highly associated with
toxic, infective, or ischemic insult
there is a significant association with maternal diabetes
Lateral Plate mesoderm —> (from colorful image she showed a zillion times)
splanchnic mesoderm (circulatory system and visceral mesoderm), somatic mesoderm, extraembryonic mesoderm
Somatic
wall of body cavity
Splanchnic
viscera
In the lateral plate mesoderm, splanchnic or somatic is closest to the intraembryonic coleom?
Splanchnic
The embryonic gut tube is surrounded by
lateral plate splanchnic mesoderm, which is surrounded by lateral plate somatic mesoderm, which is surrounded by ectoderm on the surface
somatiopleure
somatic mesoderm surrounding the splanchnic mesoderm which surrounds the gut tube
