‫محاضرة األحياء عملي‬
Muscle Tissue
) 1 ( ‫األولى‬
There are three types of muscle tissue: skeletal, smooth, and cardiac.
Types of Muscle Tissue
1- Smooth Muscle Tissue
Smooth Smooth, or nonstriated, , the smooth muscle fiber
lacks the striped appearance of other muscle tissue.
This tissue is also called involuntary muscle because it is not under conscious control.
Smooth Involuntary (Smooth) Muscle Tissue
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Smooth Muscle Tissue
Smooth muscle tissue is made up of thin-elongated muscle cells, fibres.
These fibres are pointed at their ends and each has a single, large, oval nucleus.
Each cell is filled with a specialised cytoplasm, the sarcoplasm and is surrounded by a thin cell
membrane, the sarcolemma.
Each cell has many myofibrils which lie parallel to one another in the direction of the long axis
of the cell. They are not arranged in a definite striped (striated) pattern,
. Smooth muscle fibres interlace to form sheets or layers of muscle tissue rather than bundles.
Smooth muscle is involuntary tissue, i.e. it is not controlled by the brain.
Smooth muscle forms the muscle layers in the walls of hollow organs such as the digestive
tract (lower part of the oesophagus, stomach and intestines), the walls of
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the bladder, the uterus, various ducts of glands and the walls of blood vessels .
Functions of Smooth Muscle Tissue
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Smooth muscle controls slow, involuntary movements such as the contraction
of the smooth muscle tissue in the walls of the stomach and intestines.
The muscle of the arteries contracts and relaxes to regulate the blood
pressure and the flow of blood. .
Smooth Muscle
Smooth muscle is abundant throughout the internal organs of the body especially in regions
such as the digestive tract. As its contraction is not under conscious nervous control, it is
referred to as involuntary muscle.
Smooth muscle fibres are spindle-shaped structures with a prominent centrally located nucleu.
The cells occur as individual fibres within organs or as groups of fibres closely interlaced in
sheets or bands.
showing the cross-section of the small intestine.
But, the lack of cross-striations is usually apparent and so is the central location of the nucleus
(especially in the cells of the outer longitudinal layer).
showing isolated smooth muscle cells. Note the characteristic spindle cell shape, the absence of
cross-striations and the prominent nucleus.
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Schematic representation of smooth muscle.
Microscopic view of smooth muscle.
2- Skeletal (Striated) Muscle Tissue.
Skeletal Skeletal, or striated, muscle tissues are attached to
the bones and give shape to the body.
They are responsible for allowing body movement.
This type of muscle is sometimes referred to as striated because of
the striped appearance of the muscle fibers under a microscope).
They are also called voluntary muscles because they are under the control of our
conscious will.
Skeletal muscle is the most abundant tissue in the vertebrate body.
Skeletal muscles form the "flesh"; sometimes referred to as the "red meat" of an animal's body.
A typical skeletal muscle cell is a highly modified, giant, multi-nucleate cell (fibre).
Each fibre is cylindrical in shape with blunt, rounded ends.
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The flattened nuclei are located mainly at the periphery of the cell, just inside the sarcolemma.
The striated appearance of light and dark banding results from the arrangement of myofibrils,
small protein contractile units embedded in the sarcoplasm
Section of the tongue. Attempt to locate an area on the slide showing a longitudinal view of
parallel skeletal muscle fibres
(Note: this is often difficult as the tongue contains interlacing bundles of skeletal muscle cells
oriented at various angles.)
Note the position of the nuclei and the prominent, regular cross-striations .
Functions of Skeletal Muscle Tissue
Skeletal muscles function in pairs to bring about the co-ordinated movements of
the limbs, trunk, jaws, eyeballs, etc
: Schematic representation of skeletal muscle.
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Microscopic view of skeletal muscle.
3- Cardiac (Heart) Muscle Tissue
The cardiac muscle tissue forms the walls of the heart, as well as the origins of the large
blood vessels.
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The fibers of the cardiac muscle differ from those of the skeletal and smooth muscles in that
they are shorter and branch into a complicated network .
3-Cardiac Muscle Tissue
1. Cardiac
Muscle Cell
2. nuclei
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3. Intercalated
Discs
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Cardiac (Heart) Muscle Tissue shows some of the characteristics of smooth muscle and some
of skeletal muscle tissue.
Its fibres , like those of skeletal muscle, have cross-striations and contain numerous nuclei.
However, like smooth muscle tissue, it is involuntary.
Cardiac muscle differ from striated muscle in the following aspects:
-they are shorter, the striations are not so obvious,
- the sarcolemma is thinner and not clearly discernible,
- there is only one nucleus present in the centre of each cardiac fibre and adjacent fibres
branch but are linked to each other by so-called muscle bridges.
- The spaces between different fibres are filled with areolar connective tissue which contains
blood capillaries to supply the tissue with the oxygen and nutrients.
It differs from both skeletal muscle and smooth muscle in that its cells branch and are joined to
-one another via intercalated discs.
- Intercalated discs allow communication between the cells such that there is a sequential
contraction of the cells from the bottom of the ventricle to the top
Functions of Cardiac (Heart) Muscle Tissue
-Cardiac muscle tissue plays the most important role in the contraction of the atria
and ventricles of the heart.
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Cardiac Muscle Tissue
Cardiac Muscle Tissue is found in the Heart
. It is also an involuntary type of muscle, as its contraction is not consciously controlled.
Each cell has a somewhat cylindrical shape with one centrally-located, oval nucleus.
Cross-striations are apparent but they are not as regular nor as prominent as those of skeletal
muscle .
. Note the shape of cells, the intercalated discs and the, the nucleus, and the cross-striations.
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Schematic representation of cardiac muscle.
Microscopic view of cardiac muscle.
Cardiac muscle showing intercalated disks.
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Heart muscle showing branching fibers.
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