Dominic Stone
Muscles are made of elastic tissue, with thousands of small fibres making up each muscle. There are three types of muscles in the body: skeletal, cardiac, and smooth. Skeletal muscles are striated, or striped, and make up around 35% of body weight. Smooth muscles are usually in sheets or layers, and are involuntary. The shape of muscles varies: the deltoids are triangular, the serratus muscles are serrated, and the rhomboid major is diamond-shaped. When drawing muscles, shading can be used to mark them out.
| Characteristics | Values |
|---|---|
| Shape | Triangular, serrated, saw-like, diamond, spindle |
| Size | Large, medium, small |
| Direction | The direction in which the muscle fibres run can be used to identify a muscle |
| Appearance | Striped, striated, smooth, uniform, banded |
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What You'll Learn
- Skeletal muscle has a striped or 'striated' appearance, with fibres packed into regular parallel bundles
- Cardiac muscle tissue also has a striated appearance, with branched bundles connected at both ends
- Smooth muscle cells are spindle-shaped and have no striations
- Visceral muscle is the weakest of all muscle tissues and is found inside organs like the stomach and intestines
- The size of a muscle can be used to distinguish between two muscles found in the same region
Skeletal muscle has a striped or 'striated' appearance, with fibres packed into regular parallel bundles
Skeletal muscle has a striped or striated appearance, with fibres packed into regular parallel bundles. This is because the fibres contain alternating light and dark bands (striations) like horizontal stripes on a rugby shirt. The striated appearance of skeletal muscle tissue is a result of repeating bands of the proteins actin and myosin that are present along the length of myofibrils. Dark A bands and light I bands repeat along myofibrils, and the alignment of myofibrils in the cell causes the entire cell to appear striated or banded.
There are three types of muscle tissue: visceral, cardiac, and skeletal. Visceral muscle is found inside organs like the stomach, intestines, and blood vessels. It is the weakest of all muscle tissues and is controlled by the unconscious part of the brain, so it is known as involuntary muscle. The term "smooth muscle" is often used to describe visceral muscle because it has a very smooth, uniform appearance when viewed under a microscope. This smooth appearance contrasts with the banded appearance of cardiac and skeletal muscles. Cardiac muscle tissue, like skeletal muscle tissue, looks striated or striped. The bundles are branched, like a tree, but connected at both ends. Unlike skeletal muscle tissue, the contraction of cardiac muscle tissue is usually not under conscious control, so it is also called involuntary.
Muscles can be classified by their shapes. For example, the deltoids have a delta or triangular shape, the serratus muscles feature a serrated or saw-like shape, and the rhomboid major is a rhombus or diamond shape. The size of the muscle can be used to distinguish between two muscles found in the same region, for example, the three muscles in the gluteal region: the gluteus maximus (large), gluteus medius (medium), and gluteus minimus (smallest). Finally, the direction in which the muscle fibres run can be used to identify a muscle. In the abdominal region, there are several sets of wide, flat muscles.
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Cardiac muscle tissue also has a striated appearance, with branched bundles connected at both ends
There are three types of muscle tissue: visceral, cardiac, and skeletal. Each type has a distinct appearance. Skeletal muscle tissue, for example, has a striated or striped appearance, with fibres containing alternating light and dark bands. These fibres are packed into regular, parallel bundles.
Cardiac muscle tissue, like skeletal muscle tissue, also has a striated appearance. However, the bundles are branched, like the branches of a tree, and connected at both ends. This gives cardiac muscle tissue a unique structure that sets it apart from skeletal muscle tissue.
The contraction of cardiac muscle tissue is usually not under conscious control, which is why it is often referred to as involuntary muscle tissue. In contrast, skeletal muscle contractions are typically conscious and voluntary.
The appearance of cardiac muscle tissue can be further distinguished from smooth muscle, which lacks the striated or banded appearance. Smooth muscle, also known as visceral muscle, is found inside organs such as the stomach, intestines, and blood vessels. It is the weakest of all muscle tissues and has a smooth, uniform appearance when viewed under a microscope.
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Smooth muscle cells are spindle-shaped and have no striations
There are three types of muscle tissue: visceral, cardiac, and skeletal. Smooth muscle cells are a type of visceral muscle, which is found inside organs like the stomach, intestines, and blood vessels.
The shape of a muscle can be used to classify it. For example, the deltoids have a delta or triangular shape, the serratus muscles feature a serrated or saw-like shape, and the rhomboid major is a rhombus or diamond shape. The size of the muscle can also be used to distinguish between two muscles found in the same region. For example, in the gluteal region, there are three muscles differentiated by size: the gluteus maximus (large), gluteus medius (medium), and gluteus minimus (smallest).
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Visceral muscle is the weakest of all muscle tissues and is found inside organs like the stomach and intestines
There are three types of muscle tissue: visceral, cardiac, and skeletal. Visceral muscle is the weakest of all muscle tissues and is found inside organs like the stomach, intestines, and blood vessels.
Visceral muscle is controlled by the unconscious part of the brain, so it is known as an involuntary muscle as it cannot be directly controlled by the conscious mind. This type of muscle makes organs contract to move substances through the organ.
Visceral muscle is also referred to as 'smooth muscle' because it has a very smooth, uniform appearance when viewed under a microscope. This is in contrast to the banded appearance of cardiac and skeletal muscles.
Cardiac and visceral muscles are primarily responsible for transporting substances like blood or food from one part of the body to another.
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The size of a muscle can be used to distinguish between two muscles found in the same region
Muscles can also be classified by their shape. For instance, the deltoids have a delta or triangular shape, the serratus muscles feature a serrated or saw-like shape, and the rhomboid major is a rhombus or diamond shape.
Additionally, the direction in which the muscle fibres run can be used to identify a muscle. In the abdominal region, there are several sets of wide, flat muscles.
Under a microscope, skeletal, smooth, and cardiac muscle also have different appearances. Skeletal muscle looks striped or "striated", with fibres packed into regular parallel bundles. Cardiac muscle tissue is similar, with branched, tree-like bundles connected at both ends. Smooth muscle cells are small and spindle-shaped, with no striations. Instead, they have bundles of thin and thick filaments.
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Frequently asked questions
The three types of muscle tissue are visceral, cardiac and skeletal.
Visceral muscle has a very smooth, uniform appearance when viewed under a microscope.
Skeletal muscle looks striped or 'striated'. The fibres are packed into regular parallel bundles.
Cardiac muscle tissue has a similar appearance to skeletal muscle tissue but the bundles are branched, like a tree, and connected at both ends.
Skeletal muscle fibres are packed into regular parallel bundles, whereas cardiac muscle fibres are branched like a tree.
