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Muscle tissue is classified into three types according to structure and function: striated (skeletal), smooth, and cardiac. Cardiac muscle, also called heart muscle or myocardium, is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart. The cardiac muscle forms a thick middle layer between the outer layer of the heart wall (the pericardium) and the inner layer (the endocardium). The cells of cardiac muscle, known as cardiomyocytes, also appear striated under the microscope.
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What You'll Learn
- Cardiac muscle cells are striated and have a single nucleus
- Striated muscle tissue features repeating functional units called sarcomeres
- Skeletal muscle is striated and attached to the skeleton
- Smooth muscle tissue is not striated and is found in hollow structures
- Cardiac muscle is involuntary and constitutes the main tissue of the heart wall
Cardiac muscle cells are striated and have a single nucleus
Muscle tissue is classified into three types according to structure and function: striated (skeletal), smooth, and cardiac. Cardiac muscle, also called heart muscle or myocardium, is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart.
Cardiac muscle cells, also known as cardiomyocytes, are the contractile myocytes of the cardiac muscle. They are responsible for the contractions of the heart muscle, which pump blood throughout the body. The contractions of cardiac muscle cells are due to a myogenic response of the heart's pacemaker cells. These pacemaker cells are specialized modified cardiomyocytes that set the rhythm of the heart contractions.
Cardiac muscle forms the contractile walls of the heart. It is composed of individual cardiac muscle cells joined by intercalated discs and encased by collagen fibers and other substances that form the extracellular matrix. The cardiac muscle cells attach to one another with specialized cell junctions called intercalated discs, forming long, branching cardiac muscle fibers.
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Striated muscle tissue features repeating functional units called sarcomeres
Muscle tissue is classified into three types according to structure and function: striated (skeletal), smooth, and cardiac. Striated muscle tissue, also referred to as skeletal muscle, is attached to bones and its contraction makes possible locomotion, facial expressions, posture, and other voluntary movements of the body.
The sarcomeres store Ca++ and are in bundles that lie side by side to make up the myofibril. Myocytes are cardiac muscle cells that contain many myofibrils, a cell nucleus, and mitochondria, which is a site of qi activity. The rise in calcium causes the cell's myofilaments to slide past each other in a process called excitation-contraction coupling.
Cardiac muscle cells (also called cardiomyocytes) are the contractile myocytes of the cardiac muscle. The cells are surrounded by an extracellular matrix produced by supporting fibroblast cells. Cardiomyocytes attach to one another with specialised cell junctions called intercalated discs. Intercalated discs have both anchoring junctions and gap junctions. Attached cells form long, branching cardiac muscle fibres that are, essentially, a mechanical and electrochemical syncytium allowing the cells to synchronise their actions.
The regular organisation of myofibrils into sarcomeres gives cardiac muscle cells a striped or striated appearance when viewed through a microscope, similar to skeletal muscle. These striations are caused by lighter I bands composed mainly of actin, and darker A bands composed mainly of myosin.
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Skeletal muscle is striated and attached to the skeleton
Skeletal muscle mass varies from person to person. Males have more skeletal muscle mass than females. People who are tall or overweight also tend to have higher muscle mass. Muscle mass decreases with age. Skeletal muscle comprises approximately 40% of the human body weight and contains 50-75% of all body proteins. Skeletal muscle disorders typically manifest as muscle weakness.
Skeletal muscle tissue is arranged in bundles surrounded by connective tissue. Under the light microscope, muscle cells appear striated with many nuclei squeezed along the membranes. The striation is due to the regular alternation of the contractile proteins actin and myosin, along with the structural proteins that couple the contractile proteins to connective tissues. The cells are multinucleated as a result of the fusion of the many myoblasts that fuse to form each long muscle fiber.
Skeletal muscle fibres are red and white. They look striated, or striped, so they are often called striated muscles. Cardiac muscles are also striated, but smooth muscles aren't. Skeletal muscles are voluntary muscles, meaning you control how and when they move and work. Nerves in your somatic nervous system send signals to make them function.
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Smooth muscle tissue is not striated and is found in hollow structures
Muscle tissue is classified into three types according to structure and function: striated (skeletal), smooth, and cardiac. Striated muscle tissue contains repeating functional units called sarcomeres, which give the tissue a striated appearance under a microscope. Cardiac muscle, also known as myocardium, is a type of striated muscle tissue that constitutes the main tissue of the heart wall. It is composed of individual muscle cells, known as cardiomyocytes, which are joined by intercalated discs and encased by collagen fibres and other substances that form the extracellular matrix.
Unlike skeletal and cardiac muscle tissue, smooth muscle tissue is not striated since it lacks sarcomeres. Smooth muscle is found throughout the body and serves a variety of functions. It is present in the stomach, intestines, urinary system, arteries, and veins, where it plays a vital role in digestion, nutrient collection, toxin removal, electrolyte balance, and blood pressure regulation. Smooth muscle differs from skeletal muscle in several ways, including its ability to maintain tone for extended periods and contract involuntarily.
Smooth muscle cells have a single nucleus and no visible striations. They consist of thick and thin filaments that are not arranged into sarcomeres, resulting in a non-striated pattern. On microscopic examination, smooth muscle appears homogeneous, with a large amount of actin and myosin, the main proteins involved in muscle contraction. Actin filaments attach to dense bodies spread throughout the cell, which can be observed under an electron microscope. Another important structure in smooth muscle is the calcium-containing sarcoplasmic reticulum, which aids in sustaining contraction.
Smooth muscle is found in the walls of hollow visceral organs, such as the liver, pancreas, and intestines, as well as in tubular structures like the blood vessels and airways. It helps regulate blood flow by controlling the diameter of the vessels. The development of vascular smooth muscle cells is crucial for vascular tissue engineering and therapeutic revascularization. Smooth muscle fibres group in branching bundles, allowing for stronger contractions than those of striated musculature. The innervation of smooth musculature is complex, as it lies under the influence of the visceral nervous system while also functioning autonomously.
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Cardiac muscle is involuntary and constitutes the main tissue of the heart wall
Cardiac muscle, also called myocardium or heart muscle, is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart. The cardiac muscle forms a thick middle layer between the outer layer of the heart wall (the pericardium or epicardium) and the inner layer (the endocardium).
The cardiac muscle is composed of individual cardiac muscle cells, or cardiomyocytes, joined by intercalated discs and encased by collagen fibres and other substances that form the extracellular matrix. These discs have both anchoring junctions and gap junctions. Attached cells form long, branching cardiac muscle fibres that are, essentially, a mechanical and electrochemical syncytium allowing the cells to synchronize their actions.
The cells of cardiac muscle, or cardiomyocytes, appear striated under a microscope. This striated appearance is due to the regular organization of myofibrils into sarcomeres, the fundamental contractile units of muscle cells. The myofibrils are composed of actin and myosin, which slide past each other during contraction. These are organized into sarcomeres, which give the muscle a striated appearance. These striations are caused by lighter I bands composed mainly of actin, and darker A bands composed mainly of myosin.
Cardiac muscle cells are autorhythmic and do not contract; they set the pace of contraction for other cardiac muscle cells, which the autonomic nervous system can modulate. The contractile cardiac cells (cardiomyocytes) constitute the majority of the heart muscle and can contract. They contract in a similar manner to skeletal muscle, although with some important differences. Electrical stimulation in the form of a cardiac action potential triggers the release of calcium from the cell's internal calcium store, the sarcoplasmic reticulum.
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Frequently asked questions
Cardiac muscle, also called heart muscle or myocardium, is one of three types of vertebrate muscle tissues, the others being skeletal muscle and smooth muscle. It is an involuntary, striated muscle that constitutes the main tissue of the wall of the heart.
Striated muscle tissue features repeating functional units called sarcomeres. Under the microscope, sarcomeres are visible along muscle fibers, giving a striated appearance to the tissue.
The cardiac muscle pumps blood through the body and is under involuntary control. The contractions in cardiac muscle will pump blood throughout the body.
