Logan Steele
Striated muscle tissue is a muscle tissue that features repeating functional units called sarcomeres. The two types of striated muscle are skeletal muscle and cardiac muscle. Skeletal muscle is the most common type of muscle in the human body, accounting for between 30% and 40% of total body mass. Cardiac muscle, on the other hand, is found in the walls of the heart. Striated muscles are highly organized tissues that convert chemical energy to physical work, such as generating force and contracting to support respiration, locomotion, and posture.
| Characteristics | Values |
|---|---|
| Types of striated muscle | Skeletal muscle, cardiac muscle |
| Skeletal muscle composition | Tissue, muscle fibres, blood vessels, nerve fibres, connective tissue |
| Skeletal muscle shape | Cylindrical |
| Skeletal muscle thickness | 20-100 µm |
| Skeletal muscle length | Up to 20 cm |
| Skeletal muscle function | Create force, contract, enable breathing, movement, posture maintenance |
| Cardiac muscle composition | Muscle cells (cardiomyocytes), mitochondria, intercalated discs |
| Cardiac muscle shape | Spindle-like with tapered ends |
| Cardiac muscle thickness | 10-20 µm |
| Cardiac muscle length | 50-100 µm |
| Cardiac muscle function | Pump blood throughout the body |
| Striated muscle contractions | Isometric, isotonic, concentric, eccentric |
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What You'll Learn
Skeletal muscle is the most common type of muscle in the body
Skeletal muscle, also known as striated muscle, is the most common type of muscle in the body. It is one of the three types of vertebrate muscle tissue, the other two being cardiac muscle and smooth muscle. Skeletal muscles are attached to the bones by collagen-rich tendons and make up between 30% and 40% of the body's total mass. They are part of the musculoskeletal system and work with bones, tendons, and ligaments to support the body's weight and enable movement.
Skeletal muscles consist of flexible muscle fibres that range from less than half an inch to just over 3 inches in diameter. Each muscle can contain thousands of fibres, and these fibres usually span the length of the muscle. The fibres contract, allowing the muscles to move the bones and enabling a wide range of movements. Skeletal muscles are voluntary muscles, meaning that you control how and when they move. They receive signals from nerves in the somatic nervous system, which cause the muscle fibres to depolarize and release calcium ions. This drives the movement of myosin and actin filaments, resulting in muscle contraction.
The tissue of skeletal muscle is striated, having a striped appearance due to the arrangement of sarcomeres, the functional units of muscle fibres. Under a microscope, the densely packed myofibrils in the muscle tissue can be seen, giving it a striated look. Skeletal muscle fibres are typically red and white and are surrounded by a type of connective tissue layer called fascia. The outermost layer of tissue surrounding the entire muscle is called the epimysium, which provides structural integrity during contractions. The perimysium forms the middle layer, surrounding bundles of muscle fibres, while the innermost layer, called the endomysium, surrounds individual muscle fibres.
Skeletal muscles play a vital role in everyday activities such as breathing, eating, and moving. They are also important for maintaining posture and supporting the body's weight. It is crucial to keep skeletal muscles strong and healthy to maintain overall health. Various exercises can induce changes in skeletal muscle fibres, and endurance activities may enhance the oxidative capacity of certain fibres, improving their metabolic performance.
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Striated muscle has two types: skeletal and cardiac
Muscle tissue is classified into three types according to structure and function: striated (skeletal), smooth, and cardiac. Striated muscle, also referred to as skeletal muscle, is attached to the skeleton and its contraction makes possible locomotion, facial expressions, posture, and other voluntary movements of the body. Skeletal muscles are the most common type of muscle in the human body, making up between 30% and 40% of total body mass. They are under voluntary control, meaning that a person can control how and when they move and work.
Skeletal muscles include skeletal muscle fibres, blood vessels, nerve fibres, and connective tissue. Skeletal muscle is wrapped in epimysium, allowing structural integrity despite contractions. The perimysium organises the muscle fibres, which are encased in collagen and endomysium, into fascicles. Skeletal muscle fibres are red and white and appear striated or striped. Each muscle can contain thousands of fibres, and these fibres usually span the length of the muscle. The fibres contract (tighten), which allows the muscles to move bones so you can perform a variety of movements.
Cardiac muscle, on the other hand, is the muscle found on the walls of the heart. It forms the contractile walls of the heart and is under involuntary control. Cardiac muscle cells, or cardiomyocytes, appear striated under the microscope. Unlike skeletal muscle fibres, cardiomyocytes are single cells typically with a single centrally located nucleus. A principal characteristic of cardiomyocytes is that they contract on their own intrinsic rhythms without any external stimulation.
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Striated muscle tissue features repeating units called sarcomeres
Striated muscle tissue is a muscle tissue that features repeating functional units called sarcomeres. The two types of striated muscle are skeletal muscle and cardiac muscle. Skeletal muscle is attached to some component of the skeleton, and cardiac muscle is found in the walls of the heart.
Sarcomeres are the segments between two neighbouring Z-lines (or Z-discs). Under a microscope, they are visible along muscle fibres, giving a striated appearance to the tissue. The sarcomere then shortens, causing the muscle to contract. In skeletal muscles, the contraction transfers to the mysia, then the tendon and the periosteum, causing the bone to move.
The sarcomere is composed of actin and myosin filaments. The actin filaments are attached to the Z-line, which is found in the middle of the I-bands. The myosin filaments bind to the actin filaments through cross-bridges. The contraction of the muscle results from the ATP-dependent rowing motion of the myosin heads, causing a shift of the actin filaments. The concentration of calcium within muscle cells is controlled by the sarcoplasmic reticulum, a unique form of endoplasmic reticulum in the sarcoplasm.
The length of the actin and myosin filaments (taken together as sarcomere length) affects force and velocity. Longer sarcomeres have more cross-bridges, which increases the force output. The structure of the sarcomere also affects its function in several ways. For example, the overlap of actin and myosin gives rise to the length-tension curve, which shows how sarcomere force output decreases if the muscle is stretched so that fewer cross-bridges can form.
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Skeletal muscle is attached to the skeleton
Skeletal muscle, also known as striated muscle, is the most common type of muscle in the human body, accounting for around 30-40% of total body mass. It is a type of voluntary muscle, meaning that we are able to control how and when it moves. This is in contrast to cardiac and smooth muscle, which are involuntary muscles controlled by the autonomic nervous system.
Skeletal muscle consists of flexible muscle fibres that range from less than half an inch to just over 3 inches in diameter. Each muscle can contain thousands of fibres, which are surrounded by different types of sheaths, or coverings. The outermost layer is the epimysium, which surrounds the entire muscle and provides structural integrity during contractions. The middle layer is the perimysium, which organises the muscle fibres into fascicles, or bundles of muscle fibres. The innermost layer is the endomysium, which surrounds individual muscle fibres.
Skeletal muscle fibres are red and white and have a striped appearance due to the arrangement of sarcomeres, which are repeating functional units. The interaction of contractile proteins myosin and actin within the sarcomeres results in muscle contraction. The contraction of skeletal muscle is controlled by the somatic nervous system, which sends signals to the muscle fibres to depolarise and release calcium ions from the sarcoplasmic reticulum. This release of calcium drives the movement of the myosin and actin filaments, causing the sarcomere to shorten and the muscle to contract.
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Striated muscle is composed of elongated eosinophilic cells
Striated muscle tissue is composed of two types of tissue: skeletal muscle and cardiac muscle. Skeletal muscle is the most common type of muscle in the body, making up between 30% and 40% of total body mass. It is composed of elongated eosinophilic cells, also known as muscle fibres. These cells are multinucleated, with each cell containing many nuclei. The nuclei are located in the cell's periphery, adjacent to the sarcolemma. The sarcolemma is a tubular sheath that encases and defines each muscle fibre, forming a barrier between extracellular and intracellular compartments. The sarcolemma is composed of a plasma membrane and a polysaccharide coating that fuses with tendon fibres.
Skeletal muscle cells are much longer than the other types of muscle tissue and are formed from the fusion of developmental myoblasts in a process known as myogenesis. This results in long multinucleated cells. Skeletal muscle is attached to the bones of the skeleton by collagen-rich tendons and is under voluntary control. It serves a variety of functions, including chewing and swallowing, expanding and contracting the chest cavity for inhalation and exhalation, and moving bones to enable different movements.
Cardiac muscle, on the other hand, is the muscle found on the walls of the heart. It is under involuntary control. Cardiac muscle cells are about 10-20 µm thick and 50-100 µm long. The cytoplasm contains myofibrils and densely packed mitochondria. The fibrils do not run strictly parallel to each other but rather branch in a complex pattern. The cardiac muscle cell has one centrally located nucleus.
The striated appearance of skeletal and cardiac muscle is due to the arrangement of sarcomeres, which are functional units composed of actin and myosin myofilaments. The sarcomeres are visible along the muscle fibres, giving the tissue its striated appearance. The contraction of the muscle results from the ATP-dependent rowing motion of the myosin heads, causing a shift of the actin filaments.
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Frequently asked questions
Striated muscles are highly organized tissues that convert chemical energy to physical work. They are capable of briefly producing tremendous forces and also of maintaining a state of 'semi-contraction' for long periods of time. The two types of striated muscle are skeletal muscle and cardiac muscle. Skeletal muscle is the most common type of muscle in the body.
The primary function of striated muscles is to generate force and contract to support respiration, locomotion, and posture (skeletal muscle) and to pump blood throughout the body (cardiac muscle). Striated muscles also serve functions such as chewing and swallowing, and expanding and contracting the chest cavity to inhale and exhale.
There are four types of striated muscle contractions: isometric, isotonic, concentric, and eccentric. Isometric striated muscle contraction is when there is a change in muscle tension without a change in muscle length, for example, when pushing against an immovable object. Isotonic striated muscle contraction is when there is a constant muscle tension with a change in muscle length, for example, when walking or running. Concentric striated muscle contraction occurs when there is sufficient muscle tension to overcome the load, and the muscle contracts and shortens.
Smooth muscles are not striated as they do not have sarcomeres. Smooth muscle cells are spindle-like with tapered ends, while striated muscle cells are cylindrical with blunt ends. Smooth muscle is found in hollow structures such as the walls of intestines or blood vessels.
