090914 dev of musc

Question 1

skeletal muscle precursor is

Answer 1

paraxial mesoderm

Question 2

smooth muscle precursor is

Answer 2

splanchnic mesoderm and local mesenchyme

Question 3

cardiac muscle precursor is

Answer 3

splanchnic mesoderm

Question 4

when does somite formation occur

Answer 4

week 3

Question 5

intraembryonic mesoderm is composed of what at early week 3

Answer 5

paraxial mesoderm
intermediate mesoderm
lateral mesoderm

Question 6

what do somites become?

Answer 6

skeletal muscle

bone (ribs, spine)

Question 7

somatocoel’s significance

Answer 7

the middle of the somite

these cells undergo differentiation and goto places to form mature tissue

Question 8

dermomyotome

Answer 8

the cells that grow as a layer under the epithelial layer of the somite

Question 9

somite gets signals from

Answer 9

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

Question 10

muscle cells that migrate away from the myotome and associate with the lateral mesoderm form

Answer 10

the abaxial domain (muscle of ventrolateral abdominal wall and limbs

Question 11

muscle cells that migrate to the medial side of the lateral somite frontier form the

Answer 11

primaxial muscle domain (muscles that attach to scleartome-derived bones–so muscles of the vertebral column, base of skull, ribs)

Question 12

somite has what

Answer 12

scleratome
myotome
myogenic cells

Question 13

how does skeletal muscle form from myotome?

Answer 13

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

Question 14

what do myogenic progenitor cells express?

Answer 14

myf-5

Question 15

how do skeletal muscles become innervated

Answer 15

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

Question 16

myotome has two definitions-what are they?

Answer 16

structural definition–muscle from the pair of dermomyotomes at that somite level

innervation definition-muscles innervated by 1 spinal cord segment

Question 17

epaxial muscles

Answer 17

muscles innervated by the dorsal primary rami

all develop in priaxial domain

includes MOST priaxial muscles

Question 18

hypaxial muscles

Answer 18

innervated by ventral primary rami

includes all abaxial muscles and some primaxial muscles

Question 19

week 8 marks what in muscle development

Answer 19

muscle groups have formed and are located close to their final place int he body

Question 20

Poland syndrome

Answer 20

missing pectoralis major

Question 21

prune belly syndrome

Answer 21

abdominal muscle missing

Question 22

congenital muscular torticollis

Answer 22

SCM muscle involved; SCM is shortened

Question 23

skeletal muscle of trunk and limbs (as opposed to head) is derived from

Answer 23

somite dermomyotomes

Question 24

primaxial domain muscles come from

Answer 24

myoblasts from the dorsomedial dermomyotome

Question 25

abaxial domain muscles come from

Answer 25

myobalsts from dorsolateral dermomyotome

Question 26

MyoD

Answer 26

master gene family for skeletal muscle differentiation