Muscle Tissue outline
(Click the above link for a summary outline of muscle tissue)

Additional Images - Muscle Tissue
(Click on link above to go to a web site with good images)

Also see Atlas of Histilogy by Eroshenko, chapter 5 (available in PT Learning Lab)

STATION # 1

This is a transverse section through some skeletal muscle.

It is divided into fascicles by connective tissue that appears as a few loosely arranged bundles of collagen in some large clear spaces between the groups of muscle cells.

STATION # 2

At low magnification note the fascicular arrangement of the skeletal muscle fibers.

At high magnification the pointer indicates a muscle cell nucleus.

Note the granular appearance of the cytoplasm (sarcoplasm)

Questions:
1. Why is there more than one nucleus per muscle cell?
2. What structural feature accounts for the granular appearance of the sarcoplasm?

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STATION # 3

This is a longitudinally cut section of skeletal muscle showing striations made of dark (A) and light (I) bands.

If you look carefully at the I bands (clear zone) you should note a thin line in the I band. This is the Z line.

Questions:
1. What contractile protein attaches to the Z line?
2. What is the region between two Z lines called?

STATION # 4

DO NOT MOVE THE STAGE

• At the pointer is the perimysium component of skeletal muscle.
  

• The connective tissue fibers are thin and faint, but some fat cells and blood vessels can be seen.

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STATION # 5

Note the following of cardiac muscle:

• centrally placed nuclei
• split and branching muscle fibers
• intercalated discs within muscle fibers
• numerous small blood vessels & capillaries between the muscle fibers
• no perimysium or muscle fascicles

STATION # 6

This is a medium power view of longitudinally oriented cardiac muscle.

Note that striations are present but somewhat indistinct.

Although it might look somewhat like dense irregular connective tissue at this level, observe that the cell nuclei are centrally placed within the cell cytoplasm and many of the fibers have dark lines running through them.

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STATION # 7

low mag

medium mag

high mag

At the pointer is a intercalated disc.

Questions:
1. What membrane specializations are important features of intercalated discs?
2. List the features you observe that allow you classify this as cardiac muscle?

STATION # 8

DO NOT MOVE THE STAGE

Here is a piece of smooth muscle taken from the wall of the GI tract.

At medium magnification, below the pointer the muscle is running longitudinally, while above the pointer the muscle fibers are oriented perpendicular and cut transversely.

Having two bands of perpendicularly oriented smooth muscle fibers is characteristic of the GI tract (but not for the circulatory or respiratory systems).

Note the large number of generally uniform cell nuclei that appear within cytoplasm.

Questions:
1. What contractile proteins are found in smooth muscle?
2. What do the smooth muscle contractile proteins attach to?
3. What happens to the width of a smooth muscle cell when it contracts?

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