Block IV: Skeletal muscle Flashcards
What are the types of muscle?
- Skeletal : visceral striated (voluntary striated)
- cardiac muscle (involuntary striated)
- smooth muscle (involuntary non-striated)
what is the main function of muscles?
movement or tension
main functions of skeletal muscle?
(also visceral striated muscle)- movements & tension in the skeletal system/ tongue, some eye muscles, voluntary sphincters.
main functions of cardiac muscle?
heart beat
main functions of smooth muscle
walls of tubular organs (digestive/respiratory) and some solid organs
identify
skeletal muscle
identify
cardiac muscle
identify
smooth muscle
What are some histological characteristics of skeletal muscle?
- striated: cross-striations
- large diameter fibers: 30- 50 nuclear diameters across. (The terms fiber and skeletal muscle cell are equivalent in this case)
- peripheral location of nuclei: vs central for cardiac & smooth
- multiple nuclei: vs. single nucleus cardiac & smooth
- physical syncytium: arises from fusion of myoblasts (200-300
myoblasts) during embryonic development
identify
cross-section through skeletal muscle
identify
longitudinal section of skeletal muscle with inset showing cross-striation pattern
identify
Low magnification micrograph of cross section of skeletal muscle showing the perimysium and Endomysium
identify
high magnification micrograph of cross-section skeletal muscle showing muscle fibers surrounded by endomysium CT
identify
Scanning EM of endomysium layer after removal of muscle cell
What are the connective tissues of skeletal muscle?
- Epimysium
- Perimysium
- Edomysium
What is the epimysium?
Continuous with tendons, and forms a sheath on the surface of
muscle (outer layer) surrounds entire muscle
What is the Perimysium?
Surrounds small bundles or fasicles of muscle fibers.
What is the endomysium?
fine layer of reticular fibers surrounding each fiber/skeletal muscle cell.
What is a sarcomere?
Is the repeating structural unit of skeletal muscle that gives
the striated appearance.
What are the divisions of the sarcomere?
- Z-bands -dense-staining thin lines
- I-bands - lighter staining regions adjacent to Z-bands
- A-band – broad dense staining region at center of sarcomere
- H-band -lighter staining zone at center of A-band
identify the regions
In what layer are the small capillaries and small nerves serving the individual sekeletal muscles cells/fibers?
endomysium
How does the sarcomere appear in TEM?
Within the electron microscope (TEM) it can be seen that the sarcomere consists in large part of interdigitating arrays of actincontaining thin filaments (orange) attached to Z-band and myosin-containing thick filaments (yellow) and their associated
proteins
What are the contents of the Z-bands?
contain alpha-actinin that crosslinks the thin filaments of
adjacent sarcomeres
What are the contents of the I-bands?
contain actincontaining thin filaments attaching to Z-band
What are the contents of the A-band?
myosin-containing thick filaments (overlapping with thin filaments at ends)
What are the contents of the M-band?
3-5 bands - strut-like connections between thick filaments at center of A-band formed by proteins myomysium, M-protein, and obscurin.
What are the contents of the H-band?
Light-staining region at center of A-band where have only thick filaments (non-overlap region thick & thin)
What are myofibrils?
The myofibril is a linear array of sarcomeres end to end within the cytoplasm of the muscle cell. Hundreds of myofibrils are present in cytoplasm
WHta separates the myofibrils and how do they appear?
The myofibrils are separated by regions of cytoplasm with mitochondria, glycogen, and membranes. Appear as dots in CX of
muscle fiber in light microscope
identify
EM of skeletal muscle showing Myofibrils
identify
High magnification micrograph of cross-section through
skeletal muscle fibers showing stippled appearance due to
sectioned myofibrils
identify
EM of cross-section through skeletal muscle fiber showing
myofibrils cut in cross-section in cytoplasm
What is the major contractile unit within the skeletal muscle cell?
myofibrils
identify
EM showing high magnification and very high magnification images of cross-section of skeletal muscle showing myofibrils with cross-sectioned thick and thin filaments in hexagonal arrays
how are thick and thin filaments seen in EM?
In cross-sections of the myofibril in the EM the thick and thin
filaments can be seen to be arranged in hexagonal arrays with each thick filament surrounded by 6 thin filaments.
