MUSCLE

1
MUSCLE

• Histology SSN
• October 17, 2005
• Presented By
• Tabassum Sardharwala Shannon Watkins

2
Muscle Types
Which is Which? Cardiac?
Skeletal? Smooth?

• Smooth
• Smooth
• Involuntary

• Cardiac
• Striated
• Involuntary

• Skeletal
• Striated
• Voluntary

What other places can skeletal muscle be found?
3
Skeletal Muscle Cross section

• Endomysium
• Perimysium
• Epimysium

4
Skeletal Muscle Organization
Ross Fig 10-3 (p.250, 4th ed.)
5
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

6
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

7
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

8
Motor End Plates

• Motor unit motor nerve muscle cells it
  innervates

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Other Things to Know

• Muscle-tendon Junction

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Cardiac Muscle

• Like skeletal muscle, cardiac muscle has
• Sarcomeres (striations)
• T-tubules
• Calcium regulation at level of thin filaments
• So whats different?

Lab 7 Slide 13
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Cardiac Muscle Defining Characteristics

Branching myofibrils
Large, central, ovoid nuclei

• Intercalated Disks

Lab 7 Slide 14
12
Intercalated Disks
Also, T Tubules and SR arranged in a diad, not
triad
Lab 7 Slide 16
13
Which is which?
Skeletal
Cardiac
14
Which is which?
Lab 7. Slide 15.
Cardiac
Lab 17. Slide 10.
Skeletal
15
Smooth Muscle
Located in blood vessels, ducts, and here, in the
GI tract. (This is the colon.)
Lab 7 Slide 17
16
Smooth Muscle
Longitudinal section
Myenteric Ganglion
?
Cross Section
17
A Closer Look
Elongated nuclei
Indistinct boundaries (w/ HE)
Wrinkled nuclei
Centrally located nuclei
Lab 7 Slide19
18
Smooth Muscle
Cardiac Muscle
19
Smooth Muscle vs. CT
Smooth Muscle

• Darker Staining
• Nuclei within fibers
• Wrinkled nuclei

DIACT

• Lighter Staining
• Fewer nuclei, outside fibers

Lab 4. Slide 16.
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Smooth Muscle v. CT
Smooth Muscle
DRACT
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Silver Stain
Clear Basal Lamina
Lab 7 Slide 23
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A Closer Look Why the Dotted Lines?
Interrupted basal lamina due to GAP JUNCTIONS

• Ensure coordination during contraction

Lab 7 Slide 24
23
What Muscle??
Smooth
Nerve
Skeletal
Esophagus Where Smooth and Skeletal Muscle
Combine
Lab 17. Slide 14
24
1.
B
A
25
2.
26
3.
A
B
C
D
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4.
28
5.