Download Functions of Skeletal Muscle Tissue

Dr. Amal Hassan
Muscle tissues
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Structure
We know that living organisms can move on their own or can perform other types of movement.
Muscle tissue has a ability to relax and contrast and so bring about movement and mechanical
work in various parts of the body. There are other movements in the body too which are
necessary for the survival of the organism such as the heart beat and the movements of the
alimentary canal.
Muscles can be divided into three main groups according to their structure, e.g.:
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Smooth muscle tissue.
Skeletal muscle tissue.
Cardiac (heart) muscle tissue.
Types of 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. 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 .
Dr. Amal Hassan
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.
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 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 Aband). The actin filaments make up the light bands (I-bands) .
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.
o Skeletal muscles are directly involved in the breathing process.
Cardiac (Heart) Muscle Tissue.
This is a unique tissue found only in the walls of the heart. 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, 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.
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.
Dr. Amal Hassan
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