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MUSCLE
Histology SSNOctober 17, 2005
Presented By:Tabassum Sardharwala & Shannon Watkins
Muscle Types
Smooth•Smooth•Involuntary
Cardiac•Striated•Involuntary
Skeletal•Striated•Voluntary
Which is Which?
Cardiac? Skeletal? Smooth?
What other places can “skeletal” muscle be found?
Skeletal Muscle Cross section
• Endomysium
• Perimysium
• Epimysium
Skeletal Muscle Organization
Ross Fig 10-3 (p.250, 4th ed.)
How do Muscles get their Stripes?
• Light band is the I band = actin only– Actin anchored at the Z
disc at center of I band
• Dark band is the A band = myosin + overlapping actin– Contains H band =
myosin only– Myosin anchored at the
M line
When Muscles Contract…
• The A band does NOT change length
• H and I bands shrink• Z discs are drawn closer
together• Actin & myosin filaments
do not actually shorten, they just slide past each other
The Triad
• Triad = 1 T tubule + 2 terminal cisternae of the sarcoplasmic reticulum
• There are 2 triads per sarcomere (in skeletal muscle) located at the ends of the A band (A-I junctions)
• Function- Depolarization of sarcolemma (T tubule) triggers Ca2+ release from sarcoplasmic reticulum to initiate contraction
Motor End Plates
Motor unit = motor nerve + muscle cells it innervates
Other Things to KnowMuscle-tendon Junction
Cardiac Muscle
Like skeletal muscle, cardiac muscle has:
• Sarcomeres (striations)
• T-tubules
• Calcium regulation at level of thin filaments
So what’s different?
Lab 7 Slide 13
Cardiac Muscle – Defining Characteristics
Lab 7 Slide 14
Intercalated Disks
Branching myofibrils
Large, central, ovoid nuclei
Intercalated Disks
Lab 7 Slide 16 Also, T Tubules and SR arranged in a diad, not triad
Which is which?
Cardiac Skeletal
Lab 7. Slide 15.
Lab 17. Slide 10.
Which is which?
CardiacSkeletal
Smooth Muscle
Located in blood vessels, ducts, and here, in the GI tract. (This is the colon.)
Lab 7 Slide 17
Smooth Muscle
Longitudinal section
Cross Section
? Myenteric Ganglion
A Closer Look
Elongated nuclei
Indistinct boundaries (w/ H&E)
Wrinkled nuclei
Centrally located nuclei
Lab 7 Slide19
Smooth Muscle
Cardiac Muscle
Smooth Muscle vs. CT
Lab 4. Slide 16.
Smooth Muscle•Darker Staining
•Nuclei within fibers
•Wrinkled nuclei
DIACT•Lighter Staining
•Fewer nuclei, outside fibers
Smooth Muscle v. CT
Smooth Muscle DRACT
Silver Stain
Clear Basal Lamina
Lab 7 Slide 23
A Closer Look – Why the “Dotted Lines”?
Interrupted basal lamina due to GAP JUNCTIONS
•Ensure coordination during contraction
Lab 7 Slide 24
What Muscle??
Smooth
Skeletal
Lab 17. Slide 14
Nerve
Esophagus – Where Smooth and Skeletal Muscle
Combine
1.
AB
2.
3.
A
B
C D
4.
5.
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