Dominic Stone
Muscle is a soft tissue and one of the four primary types of animal tissue. It is composed of specialized cells or fibres capable of contracting to effect movement. The body contains three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle. Skeletal muscle is attached to bones and facilitates locomotion, facial expressions, posture, and other voluntary movements of the body. Cardiac muscle is found in the heart and pumps blood through the circulatory system. Smooth muscle is found within the walls of organs and structures such as the oesophagus, stomach, and intestines, and is responsible for involuntary movements.
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What You'll Learn
Muscle is a soft tissue
There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Skeletal muscle is a type of striated muscle, meaning it has a striped appearance due to the regular alternation of contractile proteins. It is composed of long, fine fibres, each of which is a bundle of finer myofibrils. Skeletal muscle is attached to bones and is responsible for locomotion, facial expressions, posture, and other voluntary movements of the body. It constitutes the bulk of the body's muscle tissue, with the average adult male's body mass being made up of 42% skeletal muscle, and the average adult female's being 36%.
Cardiac muscle is found only in the walls of the heart and is responsible for generating force and building pressure gradients to drive blood flow throughout the body. It is also a type of striated muscle, consisting of elongated cells with many centrally located nuclei. Cardiac muscle contracts rhythmically and is not under voluntary control.
Smooth muscle is non-striated and is found within the walls of organs and structures such as the oesophagus, stomach, intestines, bronchi, uterus, urethra, bladder, blood vessels, and the arrector pili in the skin. It is responsible for involuntary movements in the internal organs and is activated by the interaction of the central nervous system or by innervation from the peripheral plexus or endocrine (hormonal) system.
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There are three types of muscle tissue: skeletal, smooth, and cardiac
Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue: skeletal, smooth, and cardiac.
Skeletal muscle is the most common type of muscle in the body, making up between 30% and 40% of the average adult's total body mass. These muscles are attached to the skeleton and are responsible for movement. They are cylindrical, striated, multinucleated, and under voluntary control. Skeletal muscle can be further classified into two fiber types: type I (slow-twitch) and type II (fast-twitch).
Smooth muscle, on the other hand, is non-striated and involuntary. It is found within the walls of organs and structures such as the esophagus, stomach, intestines, bronchi, uterus, urethra, bladder, blood vessels, and the arrector pili in the skin. Smooth muscle in the walls of arteries is critical for regulating blood pressure and blood flow through the circulatory system.
Cardiac muscle is striated, like skeletal muscle, but it is under involuntary control. It is found only in the walls of the heart and functions to generate force and build pressure gradients to drive blood flow throughout the body. The contraction of cardiac muscle is not under voluntary control but is regulated by the autonomic nervous system.
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Muscle tissue is contractile
Muscle is one of the four primary types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Skeletal muscle is attached to bones and gives the body structure and strength. Cardiac muscle is found only in the walls of the heart and functions to generate force and build pressure gradients to drive blood flow throughout the body. Smooth muscle is found within the walls of organs and structures such as the oesophagus, stomach, intestines, bronchi, uterus, urethra, bladder, blood vessels, and the arrector pili in the skin that control the erection of body hair.
A unique property common to all three types of muscle is contractility, which is the ability of the cells to shorten and generate force. While muscle tissue can shorten with contractions, it also displays extensibility or the ability to stretch and extend beyond the resting length of the cells. After being stretched, the elasticity of the muscle allows it to recoil back to its original length. The muscles all begin the mechanical process of contracting when a protein called actin is pulled by a protein called myosin, and differences in the microscopic organization of these contractile proteins exist among the three muscle types.
The physiological concept of muscle contraction is based on two variables: length and tension. Tension within the muscle can be produced without changes in the length of the muscle, as when holding a dumbbell in the same position or holding a sleeping child in your arms. Upon termination of muscle contraction, muscle relaxation occurs, which is the return of muscle fibres to a low-tension state.
The primary function of skeletal muscle contraction is to allow for the performance of specific movements. Skeletal muscle also provides structural support, maintains the body's posture, stores amino acids, and maintains core body temperature via shivering. Cardiac muscle contraction occurs via excitation-contraction coupling (ECC), utilizing a mechanism called calcium-induced calcium release (CICR). CICR involves the conduction of Ca ions into the cardiomyocyte, leading to the further release of ions into the cytoplasm. Smooth muscle in the walls of arteries is a critical component that regulates blood pressure and blood flow through the circulatory system.
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Muscle tissue is composed of specialised cells
Muscle is a soft tissue and is one of the four primary types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue is composed of specialised cells known as muscle cells or myocytes (from the Greek 'mys', meaning muscle). These cells are often referred to as muscle fibres due to their extensive length and appearance.
Myocytes are characterised by protein filaments known as actin and myosin, which interact to cause movement. These contractile proteins slide past one another, producing contractions that move body parts, including internal organs. The arrangement of actin and myosin filaments within each sarcomere contributes to the formation of distinct striations (or stripes) of dark A bands and light I bands when viewed under a light microscope. Myosin is visible as the A band of the sarcomere, while actin filaments are anchored to a structure known as the Z disc (or Z line) at either end of the sarcomere.
The different types of muscle tissue vary in their response to neurotransmitters and hormones such as acetylcholine, noradrenaline, adrenaline, and nitric oxide. Skeletal muscle fibres are cylindrical, multinucleated, striated, and under voluntary control. They are responsible for movements of the body and are anchored by tendons or aponeuroses to bones. Cardiac muscle, on the other hand, has branching fibres, one nucleus per cell, striations, and intercalated discs. Its contraction is not under voluntary control. Smooth muscle cells are spindle-shaped, have a single, centrally located nucleus, and lack striations. They are also involuntary muscles.
The body mass of an average adult man is made up of 42% skeletal muscle, while an average adult woman is made up of 36%. Skeletal muscle can be further classified into two fibre types: type I (slow-twitch) and type II (fast-twitch). Type I muscle is dense with capillaries and rich in mitochondria and myoglobin, giving it a red colour. Type II muscle has three subtypes, with varying contractile speeds, mitochondrial density, and myoglobin content.
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Muscle tissue is categorised by structure and function
Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Each muscle can contain thousands of fibres, and muscles are present throughout the body, helping with everything from holding the body still to running a marathon.
Skeletal muscle is the most common type of muscle in the body, making up between 30% and 42% of the average adult man's body mass and 36% of the average adult woman's. It is striated, consisting of elongated, multinucleate muscle cells called muscle fibres, and is responsible for movements of the body. Skeletal muscle fibres are cylindrical, striated, and under voluntary control. Tendons attach skeletal muscles to bones all over the body. Skeletal muscles are further classified into two fibre types: type I (slow-twitch) and type II (fast-twitch).
Cardiac muscle tissue is found only in the walls of the heart as myocardium and is an involuntary muscle controlled by the autonomic nervous system. It is striated like skeletal muscle, containing sarcomeres in highly regular arrangements of bundles. Cardiac muscle fibres have one nucleus per cell and exhibit branching fibres and intercalated discs.
Smooth muscle is non-striated and involuntary. It is found within the walls of organs and structures such as the oesophagus, stomach, intestines, bronchi, uterus, urethra, bladder, blood vessels, and the arrector pili in the skin that controls the erection of body hair. Smooth muscle cells are spindle-shaped and have a single, centrally located nucleus.
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Frequently asked questions
Muscle tissue is one of the four primary types of animal tissue, the other three being epithelial, nervous, and connective tissues. Muscle tissue is composed of specialized cells known as muscle cells or myocytes, commonly referred to as muscle fibres. These muscle fibres are capable of contracting in order to effect movement.
There are three types of muscle tissue: skeletal muscle, cardiac muscle, and smooth muscle. Skeletal muscle is attached to bones and is responsible for locomotion, facial expressions, posture, and other voluntary movements of the body. Cardiac muscle is found in the heart and pumps blood through the body. Smooth muscle is found within the walls of organs and structures such as the oesophagus, stomach, intestines, and blood vessels.
Muscle tissue is characterized by properties that allow movement. Muscle cells are excitable, meaning they respond to a stimulus. They are contractile, allowing them to shorten and generate a pulling force. Some muscle movements are voluntary and under conscious control, while others are involuntary and not under conscious control.
