090914 dev of musc Flashcards
skeletal muscle precursor is
paraxial mesoderm
smooth muscle precursor is
splanchnic mesoderm and local mesenchyme
cardiac muscle precursor is
splanchnic mesoderm
when does somite formation occur
week 3
intraembryonic mesoderm is composed of what at early week 3
paraxial mesoderm
intermediate mesoderm
lateral mesoderm
what do somites become?
skeletal muscle
bone (ribs, spine)
somatocoel’s significance
the middle of the somite
these cells undergo differentiation and goto places to form mature tissue
dermomyotome
the cells that grow as a layer under the epithelial layer of the somite
somite gets signals from
neural tube and notochord (sonic hedgehog, wnt) lateral mesoderm (BMP)
establishes boundary called lateral somite frontier
some cells in epithelial cluster of somite will migrate underneath and form layer called the myotome
muscle cells that migrate away from the myotome and associate with the lateral mesoderm form
the abaxial domain (muscle of ventrolateral abdominal wall and limbs
muscle cells that migrate to the medial side of the lateral somite frontier form the
primaxial muscle domain (muscles that attach to scleartome-derived bones–so muscles of the vertebral column, base of skull, ribs)
somite has what
scleratome
myotome
myogenic cells
how does skeletal muscle form from myotome?
from myotome, you get cells that migrate out (myogenic progenitor cells). these cells become myobalsts, which fuse to become multinucleated myotubules, which then become myofibers
the path is a multi step process with different factors (molecules) regulating it
what do myogenic progenitor cells express?
myf-5
how do skeletal muscles become innervated
early on, innervated as pre muscle masses (myotome stage)
some pre muscle masses will take their innervation with them as they migrate
spinal nerves innervate somite derived skeletal muscles of trunk and limbs
myotome has two definitions-what are they?
structural definition–muscle from the pair of dermomyotomes at that somite level
innervation definition-muscles innervated by 1 spinal cord segment
epaxial muscles
muscles innervated by the dorsal primary rami
all develop in priaxial domain
includes MOST priaxial muscles
hypaxial muscles
innervated by ventral primary rami
includes all abaxial muscles and some primaxial muscles
week 8 marks what in muscle development
muscle groups have formed and are located close to their final place int he body
Poland syndrome
missing pectoralis major
prune belly syndrome
abdominal muscle missing
congenital muscular torticollis
SCM muscle involved; SCM is shortened
skeletal muscle of trunk and limbs (as opposed to head) is derived from
somite dermomyotomes
primaxial domain muscles come from
myoblasts from the dorsomedial dermomyotome
abaxial domain muscles come from
myobalsts from dorsolateral dermomyotome
MyoD
master gene family for skeletal muscle differentiation
