Structure and Functions of Muscular Tissue
Note: This page is part
of the section about the structure and function of different
Tissue Types,
which is related to the section about Histology
and Cells (incl. structure
of animal cells, cell
division, mitosis,
meiosis).
The tissue types section is included to
complete description of the knowledge of "Histology
- The Cell" required by some courses in First-Level
Anatomy and Physiology. To read about other tissue types
see the list of on the left.
There are 3 types of muscle tissue:
- Skeletal muscle tissue,
- Cardiac muscle tissue, and
- Smooth muscle tissue.
The structure of these muscle tissues can be described
from the level of detail of the muscle
fibres (muscle
cells) through all the other muscle
structures and parts of structures that bind muscle
cells together enabling them to perform their functions.
The functions of muscle tissues depend on the type
of muscle tissues and their locations in the body.
Here is an overview of the 3 types of
muscle tissues:
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(a) Skeletal Muscle Tissue |
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Structure:
Skeletal muscle is called "striated"
because of its appearance consisting of
light and dark bands visible using a light
microscope. As shown in the diagram (on
the right), a single skeletal muscle cell
is long and approximately cylindrical in
shape, with many nuclei located at the edges
(periphery) of the cell.
Function:
- Movement of the skeleton
under concious control, including movement
of limbs, fingers, toes, neck, etc.
- Movement of tissues
of facial expression under concious control,
e.g. ability to smile and to frown.
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Above: Diagram of Skeletal Muscle Tissue
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(b) Cardiac Muscle Tissue
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Structure:
Cardiac muscle fibers are striated, branched
(sometimes described as Y-shaped), and have
a single central nucleus. These fibers are
attached at their ends to adjoining fibers
by thick plasma membranes called intercalated
discs (shown in digram on the right).
Function:
- Pumping of blood through the heart:
Alternate contraction and relaxation of
cardiac muscle pumps
- De-oxygenated blood through the Right
Atrium and Right Ventricle to the lungs,
and
- Oxygenated blood through the Left Atrium
and Left Ventricle to the aorta, then the
rest of the body.
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Above: Diagram of Cardiac Muscle Tissue
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(c) Smooth Muscle Tissue
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Structure:
Unlike Skeletal and Cardiac muscle tissue,
Smooth muscle is not striated. Smooth
muscle fibers are small and tapered - with
the ends reducing in size, in contrast to
the cylindrical shape of skeletal muscle.
Each smooth muscle fiber has a single centrally
located nucleus.
Function:
Contractions of smooth muscle constrict
(i.e. narrow = reduce the diameter of) the
vessels they surround. This is particularly
important in the digestive system in which
the action of smooth muscle helps to move
food along the gastrointestinal tract as
well as breaking the food down further.
Smooth muscle also contributes to moving
fluids through the body and to the elimination
of indigestible matter from the gastrointestinal
system. |
Above: Diagram of Smooth Muscle Tissue
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Table comparing the 3 types of muscle tissue:
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Type of Muscle
Tissue |
Locations in body |
Voluntary
or
involuntary |
Striations
? |
Cell
Nuclei |
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Skeletal Muscle Tissue |
- Attached to bones (of the skeleton).
- In the case of facial
muscles, attached to other tissues
including skin - hence muscles "of facial
expression".
|
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Yes:
Striated Muscle |
Many
nuclei (located at periphery of long
cylindrical muscle fiber) |
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Cardiac Muscle Tissue |
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Yes:
Striated Muscle |
One (centrally located) nucleus |
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Smooth
Muscle Tissue |
Walls of hollow internal
structures, incl.
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No:
"Nonstriated"
= "Smooth"
(Muscle) |
One (centrally located) nucleus |
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