B6.020 Prework 1: Skeletal Muscle Histology

Question 1

discuss the development of a muscle cell

Answer 1

mesenchymal cells migrate out from somites in early development
myoblasts form and proliferate
usually around 2000 myoblasts align
myoblast membranes fuse, forming myotube
actin, myosin and proteins are produced and form a mature skeletal muscle cell (fiber)

Question 2

what are satellite cells

Answer 2

myoblasts
30-40 per mature skeletal muscle cell
source of repair of cell in event of damage

Question 3

endomesium

Answer 3

surround individual muscle fiber

Question 4

perimesium

Answer 4

surround fasicle

Question 5

epimesium

Answer 5

surround whole muscle group

Question 6

sarcolemma

Answer 6

plasma membrane of the muscle cell

Question 7

length of a sarcomere

Answer 7

Z band to Z band

Question 8

which part of a sarcomere varies with contraction

Answer 8

width of the I band

Question 9

which part of a sarcomere stays constant with contraction

Answer 9

A band

Question 10

function of T tubules

Answer 10

invaginations of membrane that run out to sarcolemma
full of extracellular fluid
help organize excitation/contraction coupling
coordinates release of Ca2+ from S.R.

Question 11

where is dystrophin located in a muscle fiber

Answer 11

periphery

expressed by all cells

Question 12

function of dystrophin

Answer 12

links dystroglycan (ECM) to cytoskeletal elements through the sarcolemma
helps organize structure

Question 13

significant of centrally placed nuclei on a muscle fiber

Answer 13

myopathy

signifies damage/repair

Question 14

some effects of muscular dystrophy on muscle fiber tissue

Answer 14

fibers turn to scar tissue and fat
splitting basal lamina
centrally placed nuclei
torn membranes that spill out Ca2+

Question 15

location of satellite cells

Answer 15

under endomesium and ECM

Question 16

what happens if satellite cells are not present on muscle fibers

Answer 16

will atrophy and die

if incomplete fusion, prone to reinjury