Mesoderm 1 Flashcards
The mesoderm is formed before the formation of the primitive streak. True of False?
False. It is formed after.
What is the inducing factor?
Probably the protein Nodal.
What is a triploblast?
An animal with three germ layers.
Mesoderm cells that ingress through the primitive node contribute to what structure?
The notochord.
What holds the notochord back from the prechordal plate?
A cushion of prechordal mesoderm.
Mesoderm cells that ingress through the primitive streak form what three layers of mesoderm?
Paraxial, Intermediate, Lateral Plate mesoderm.
What patterns the mesoderm?
Signals from the node, prechordal plate and notochord.
What is the notochord?
A rod of mesoderm cells that helps to pattern various components of the main body axis by induction.
Most of the notochord degenerates and is replaced by what?
Axial skeleton
Where is some of the notochord retained?
In the nucleous pulposus of invertabral discs
What main tissues does the mesoderm form?
muscle, cartilage/bone, connective tissue, blood, heart, kidney, gonads and reproductive tract.
The notochord is one of the defining features of the phylum Chordata. True or false?
True
What axis does the notochord run on?
Rostral-caudal
What does paraxial mesoderm form?
Somites
What determines the fate of somites?
signals from surrounding tissues
what are somites?
balls of epithelial cells
how often does a new pair of somites form?
every 4-5 hours in human embryos
how many pairs of somites are formed in a human embryo?
42-44. Subsequently reduced to 38.
Which end of the paraxial mesoderm do somites bud off from?
the rostral end
what are the three main types of somites?
Dermatome, mytome and sclerotome.
What does the dermatome form?
dermis of dorsal epidermus
what does myotome form?
skeletal muscle (striated)
What are two types of myotome?
expaxial (back muscles) and hypaxial (chest and abdomenal muscles)
What induces expaxial myotome?
SHH and WNT
What induces hypaxial mytome?
SHH and BMP
what does sclerotome form?
axial skeleton (vertebrae and ribs)
what induces sclerotome?
SHH
What does medial sclerotome form?
vertebrae
what does lateral sclerotome form?
ribs
Sclerotome is transformed into a mesenchymal population that migrates around the notochord and neural tube. True or false?
True.
What three types of lateral plate mesoderm are there?
Somatic, spanchnic and ceolem.
What does intermediate mesoderm form?
kidneys and reproductive tracts
what does the lateral plate mesoderm form?
cardiac muscle, connective tissue and smooth muscle of digestive tract, connective tissue and cartilage and bones of limbs, dermis of ventral skin and blood cells.
What is the mesoderm induced by?
the prospective endoderm
What is one of the first mesodermal genes induced by Nodal?
Brachyury
What does a remnant of notochord cells in abnormal locations in the axial vertebrae form?
Malugnant tumour called a chordoma.
What do cells closest to the notochord form?
paraxial mesoderm
Molecules released by prospective notochord act as what?
Morphogens
What do morphogens do?
pattern the mesoderm in a concentration dependent manner.
Signalling properties of the organizer were first demonstrated by who?
Spemann and Mangold
Spemann and Mangold transplanted the dorsal blastopore (future notochord) of a newt gastrula into the ventral side of a host gastrula. What did the observe?
The transplant produced a conjoined twin on the ventral side of the host embryo, in which the notochord was formed by the grafted cells. The paraxial and intermediate mesoderm were formed by host cells that would have otherwise formed the lateral plate mesoderm.
Proteins responsible for patterning the mesoderm are:
inhibitors of signalling proteins
What proteins are responsible for patterning the mesoderm?
Chordin and Noggin
What protein do Chrodin and Noggin inhibit?
BMP
If there is a high level of BMP, what mesoderm will arise?
Lateral plate mesoderm
If there is an absence of BMP, what mesoderm will arise?
Notochord
What do mesoderm cells that migrate throught the node form?
Notochord and prechordal plate
In which direction do somites appear?
rostral to caudal
What releases SHH?
the notochord and floor plate of the neural tube
In reponse to signals from the neural tube and lateral plate mesoderm, dermamyotome splits into what?
deratome and myotome
what region of the somites is skeletal muscle derived from?
myotome
what region of the mesoderm are cardiac and smooth muscles derived from?
lateral plate mesoderm
What does MyoD1 do?
regulates muscle differentiation by activating the transcription of muscle-specific genes by binding to a specific DNA sequence found in enhancers
what promotes the development of myoblasts?
Myogenic transcription factors
What are myoblasts?
Muscle precursors which indergo many rounds of cell proliferation
What maintains cell proliferation?
members of the fibroblast growth factor (FGF) family
What is skeletal muscle composed of?
elongated multinucleate myofibres arranged in bundles of fascicles.
