Transcript Muscle Histology

Muscle Histology
Connective coverings
► Muscles
are covered with fascia which
separates muscles. Deep fascia separates
muscles from each other, superficial fasciafrom skin.
► Fascia are continuous with tendons which
are continuous with ____________
Smaller picture
► Muscles
are grouped in to fascicles that are
covered with a sheath of connective tissue
called perimysium.
► Fascicles are divided into muscle fibers,
each surrounded by the endomysium
► Blood and nerves reach the muscle through
the endomysium
Cellular level
► Muscle
Fibers are made of myofibrils
 Plasma membrane= sarcolema
 Endoplasmic reticulum=sarcoplasmic reticulum
► Each
sarcoplasmic reticulum encases
ooodles of myofibrils
► Myofibrils are divided into sarcomeres
(p117) see drawing!
Muscle Contractions
► Motor
Unit: A single nerve ending and all
the muscle fibers attached to it
► With a nerve impulse- muscle fibers contract
completely. “all or none”
► Does a muscle have to contract completely?
►Partial
contraction of a muscle comes from only
contracting a portion of the fibers
Exercise
► Atrophy-
from lack of use, muscle fibers are
replaced with adipose and fibrous tissue
 Can cause muscle fibers to shorten enough to
force the body to contort.
► Hypertrophy-more
more use
myofibrils develop with
Going the Distance, or not?
► Slow
twitch- less fibers per motor unit
 Largely aerobic-extra mitochondria, extra
capillaries
 Presence of Myoglobin
►A
► Fast
dark, red oxygen carrying pigment
Twitch- more fibers per motor unit
 Few mitochondria
 Largley anerobic
 Easily hits maximum tension