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03.02 Muscle Cytology

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  1. General features
    1. Elongated cells along line of contraction
    2. Force of contraction on ends toward center → o ←
      1. IF cell moves during contraction
        1. Length shortens
        2. Diameter increases
    3. Convert chemical energy from ATP into a contractile force
    4. Sarcolemma = cell membrane
    5. Sarcoplasm = cytoplasm
    6. Myofibrils in sarcoplasm of skeletal and cardiac
      1. Protein myofilaments
        1. Actin
        2. Myosin
        3. Tropomyosin
        4. Troponin
      2. Play a large role in muscle contraction

Nursing Points


  1. Specific features
    1. Skeletal muscle
      1. Elongated cylinders
      2. Longest cells
      3. Cross-striations
      4. Up to 1000 nuclei per cell
    2. Cardiac muscle
      1. Elongated cylinders
      2. Shortest cells
      3. Cross-striations
      4. Branched
      5. Intercalated discs between cardiac cells
      6. One nucleus
    3. Smooth muscle
      1. Elongated—pointy ends
      2. Intermediate in length
      3. No striations
      4. One nucleus

ReferencesBetts, J.G., et al. (2017). Anatomy and physiology. Houston, TX: OpenStax, Rice University. Retrieved from

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Video Transcript

In this lesson we’re going to look at muscle cytology. So we’re looking at the microscopic structure and function of muscles.

The first thing I want you to recognize about muscle cells, is that they’re elongated. They stretch along a particular line of contraction. And the force of the contraction moved outward from the outside of the muscle cell to the center of the cell. What this means is that the length of the cell shortens, and a diameter of the cell actually increases.

Muscle cells convert chemical energy from ATP and that’s results in a contractile force of the muscles. And I’m also cells aren’t just your regular cells, so we have a couple of new terms that you need to look at. The sarcolemma is the cell membrane of a muscle cell, and the sarcoplasm is the cytoplasm of a cell membrane.

In muscles we have these particular units called myofibrils, And they contain important proteins. These proteins are actin, myosin, troponin, and tropomyosin, and they are are at the foundation of muscle contraction. There’s another lesson which discusses this at length, so be sure to check that out

Now when we look at the features of skeletal muscle, there are a couple of really important points about it. Number one there elongated cylinders, and they are the longest cells. They have these cross striations and they’re multinucleated. This differentiates them from other types of muscle.

Cardiac muscle is much different from smooth muscle and skeletal muscle.

We Know the cardiac muscle is important, because it’s an important component of the heart. But why?

First off do the shortest cells and they contain cross striations. They are branch which is what you could see here. And they have these things called intercalated discs. Now, intercalated discs are really important and here is why. Intercalated discs allows for synchronicity among all of the cells. So in the heartbeat, all of the cells of beat in unison. That’s why the intercalated discs are important.

Smooth muscle cells are also very distinctive. They’re elongated and they have pointy ends and their intermediate and length. Another important feature is that they don’t have any striations and they have a one single nucleus.
Okay, so let’s recap.

An important feature of a muscle cell is that it has force and contraction. Contraction is at or word the center of the cell, and that makes the cells shorter, but it makes it wider.

Skeletal muscle is long and cylindrical and it can contain up to 1000 nuclei per cell.

Cardiac muscle are the shortest cells, and their branch and they have a intercalated discs which are important for Helping the heart to beat in sync.

Smooth muscle has no striations, it’s got one nucleus, and they are pointed on the ends. They’re also intermediate length.

That’s it for our lesson on muscle cytology. Make sure you check out all of the resources attached to this lesson. Now, go out and be your best selves today, and as always, happy nursing.