Download Functions of Skeletal Muscle Tissue

NAME: OGBOGU NWAMAKA. O
MATRIC NO:14/MHS01/098
DEPARTMENT: MEDICINE AND
SURGERY
COURSE:HISTOLOGY
MUSCLE AS A TISSUE
Muscle tissue is a soft tissue that composes muscles in
animal bodies, and gives rise to muscles' ability to contract.
This is opposed to other components or tissues in muscle
such as tendons or perimysium. It is formed during
embryonic development through a process known as
myogenesis.
Muscle being considered as a tissue can be divided into
three main groups according to their structure, e.g.:

Smooth muscle tissue.
Skeletal muscle tissue.
Cardiac (heart) muscle tissue.
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Smooth Muscle Tissue.
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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, as in skeletal muscles - hence
the name smooth muscle . 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 the
bladder, the uterus, various ducts of glands and the
walls of blood vessels .
Functions of Smooth Muscle Tissue
o
o
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 Tissue

Skeletal Muscle Tissue.
Skeletal muscle is the most abundant tissue in the
vertebrate body. These muscles are attached to and
bring about the movement of the various bones of the
skeleton, hence the name skeletal muscles. The whole
muscle, such as the biceps, is enclosed in a sheath of
connective tissue, the epimysium. This sheath folds
inwards into the substance of the muscle to surround a
large number of smaller bundles, the fasciculi. These
fasciculi consist of still smaller bundles of elongated,
cylindrical muscle cells, the fibres. Each fibre is a
syncytium, i.e. a cell that have many nuclei. The nuclei
are oval in shaped and are found at the periphery of the
cell, just beneath the thin, elastic membrane
(sarcolemma). The sarcoplasm also has many
alternating light and dark bands, giving the fibre a
striped or striated appearance (hence the name striated
muscle). With the aid of an electron microscope it can
be seen that each muscle fibre is made up of many
smaller units, the myofibrils. Each myofibril consists of
small protein filaments, known as actin and myosin
filaments. The myosin filaments are slightly thicker and
make up the dark band (or A-band). The actin filaments
make up the light bands (I-bands) which are situated on
either side of the dark band. The actin filaments are
attached to the Z-line. This arrangement of actin and
myosin filaments is known as a sacromere.
During the contraction of skeletal muscle tissue, the
actin filaments slide inwards between the myosin
filaments. Mitochondria provide the energy for this to
take place. This action causes a shortening of the
sacromeres (Z-lines move closer together), which in
turn causes the whole muscle fibre to contract. This
can bring about a shortening of the entire muscle such
as the biceps, depending on the number of muscles
fibres that were stimulated. The contraction of skeletal
muscle tissue is very quick and forceful.
Functions of Skeletal Muscle Tissue
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Skeletal muscles function in pairs to bring about
the co-ordinated movements of the limbs, trunk,
jaws, eyeballs, etc.
Skeletal muscles are directly involved in the
breathing process.
Skeletal Muscle Tissue
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Cardiac (Heart) Muscle Tissue.
Cardiac muscle is striated muscle found only in the
heart. While there are many physiological differences
between cardiac and skeletal muscle, a major
histological difference between these two types of
striated muscle is that each cardiac muscle cell is
NOT a true syncytium of several cells that runs the
length of the organ, as is true of skeletal muscle cells.
Rather, each cardiac muscle cell is relatively small,
with respect to the organ, and has one nucleus
(sometimes two). Also, each cardiac muscle cell is
branched, unlike skeletal muscle fibers, and interacts,
through special types of intercellular junctional
complexes, with neighboring cells, forming a tissue
that is appropriately described as a functional
syncytium.
The specialized intercellular junctional complexes
that provide this tissue with its functional syncytial


character are intercalated disks. Intercalated disks
contain three basic types of intercellular junctions:
numerous fascia adherens and desmosomes, which
provide for adhesion between two cells, and numerous
gap junctions, which provide for the exchange of ions
between the two cells, and, therefore, a means of
direct electrical communication between two cells.
The functional organization of cardiac muscle tissue
goes hand-hand with the organization of its
innervation and nature of its control. Unlike skeletal
muscle cells, individual cardiac muscle cells exhibit
an inherent rythmicity. That is, an auto-generated
action potential that stimulates the cell's contraction.
At the tissue level, cardiac muscle inherently exhibits
the rhythmicity of the cardiac muscle cell with the
fastest rhythmicity. Once the action potential is
generated by this cell, the impulse quickly spreads
among the cells of the tissue via the gap junctions of
the intercalated disks. Thus, motor nurons are not
needed to generate the heart beat, and cardiac
muscle is NOT organized into motor units, as is
skeletal muscle. However, autonomic nerves innervate
portions of the cardiac muscle of the heart to modify
the rate of this inherent rhythmicity.
Like skeletal muscle fibers, each cardiac muscle fiber
is surrounded by an endomycium that is conspicuous
in typical cardiac muscle preparations. "Bundles" of
cardiac muscle fibers are grouped into fascicles by a
perimycium, but no epimycium is used to cover the
entire organ.
Functions of Cardiac (Heart) Muscle Tissue
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Cardiac muscle tissue plays the most important
role in the contraction of the atria and ventricles of
the heart.
It causes the rhythmical beating of the heart,
circulating the blood and its contents throughout
the body as a consequence.
Cardiac Muscle Tissue