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There are three types of muscle tissue: cardiac, smooth, and skeletal. 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. Smooth muscle, unlike skeletal and cardiac muscle, is not striated as it does not contain sarcomeres. Skeletal muscle is responsible for the voluntary movements of bones and makes up 30 to 40% of the human body weight. Cardiac muscle, on the other hand, is the muscle found in the walls of the heart and is under involuntary control.
| Characteristics | Values |
|---|---|
| Types of muscle tissue | Cardiac, smooth, and skeletal |
| Striated muscle tissue | Skeletal and cardiac |
| Smooth muscle tissue | Not striated |
| Skeletal muscle composition | Skeletal muscle fibers, blood vessels, nerve fibers, and connective tissue |
| Skeletal muscle function | Voluntary movements of bones |
| Skeletal muscle weight percentage | 30 to 40% of total body mass |
| Cardiac muscle composition | Cardiac muscle cells |
| Cardiac muscle function | Contractions due to a myogenic response of the heart's pacemaker cells |
| Cardiac muscle appearance | Striated |
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What You'll Learn
- Skeletal muscle is striated and makes up 30-40% of body mass
- Cardiac muscle is striated and located in the heart
- Smooth muscle is not striated and is located in the walls of visceral organs
- Skeletal muscle can be classified as slow-oxidative (Type I) or fast-oxidative (Type II)
- Skeletal muscle can regenerate better than cardiac muscle due to satellite cells
Skeletal muscle is striated and makes up 30-40% of body mass
Skeletal muscle is a type of striated muscle tissue that includes skeletal muscle fibres, blood vessels, nerve fibres, and connective tissue. It is attached to the skeleton and allows for a wide range of movements and functions. Skeletal muscle is also under voluntary control, meaning an individual can control how and when they work. This is in contrast to the other two types of muscle tissue, cardiac and smooth muscle, which are under involuntary control.
Skeletal muscle is striated due to the arrangement of actin and myosin, which gives it a striped appearance when viewed under a microscope. This arrangement also creates functional units called sarcomeres. Each muscle cell contains myofibrils composed of actin and myosin myofilaments repeated as a sarcomere. The sarcomere then shortens, causing the muscle to contract. The functional unit of a muscle fibre is called a sarcomere, and each muscle cell contains myofibrils composed of actin and myosin filaments.
Skeletal muscle makes up 30-40% of body mass in humans, with men having about 36% more skeletal muscle mass than women. Skeletal muscle is also the most common type of muscle in the body, with over 600 skeletal muscles. The strength of a skeletal muscle is determined by its cross-sectional area, with a shorter muscle being stronger "pound for pound" than a longer muscle of the same cross-sectional area. Skeletal muscle uses more calories than other organs, consuming 13.0 kcal/kg per day at rest.
Skeletal muscle is also more susceptible to injury and disease, with muscle injuries accounting for 10-55% of all sports injuries. Skeletal muscle disorders typically manifest as muscle weakness and can include muscular dystrophies, congenital myopathies, inflammatory disorders, and diseases affecting the neuromuscular junction. Sarcopenia, the age-related loss of skeletal muscle mass, can also lead to a loss of function, mobility, and balance problems.
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Cardiac muscle is striated and located in the heart
The heart is made up of three layers: the pericardium, myocardium, and endocardium. The endocardium is not a cardiac muscle and forms the inner lining of the heart chambers and valves. The myocardium, or cardiac muscle, is the thick middle layer between the outer layer of the heart wall (the pericardium) and the inner layer (the endocardium). The cardiac muscle constitutes the main tissue of the wall of the heart.
The cardiac muscle is responsible for the contractility of the heart and, therefore, the pumping action. The contractile functions of the heart require ATP, which can be obtained through various substrates, including fatty acids, carbohydrates, proteins, and ketones. The cardiac muscle cells contain branched fibers connected via intercalated discs that contain gap junctions and desmosomes. These interconnections allow the cardiomyocytes to contract together synchronously to enable the heart to work as a pump.
The heart begins as a single chamber, but four separate chambers are created through the growth of various septa. The muscular ventricular septum originates from the bottom of the ventricle, with a membranous septum forming shortly after, joining with the aortic-pulmonary septum. The endocardial cushions also appear at this time and separate the left and right atria and ventricles.
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Smooth muscle is not striated and is located in the walls of visceral organs
Not all muscles contain striations. Smooth muscle, for example, is a type of muscle tissue that is not striated. This is because smooth muscle does not contain sarcomeres, which are the functional units that give striated muscles their striated appearance. Smooth muscle consists of thick and thin filaments that are not arranged into sarcomeres, resulting in a non-striated pattern. Under a microscope, smooth muscle appears homogeneous, with a fusiform shape that is round in the center and tapers at each end.
Smooth muscle is located in the walls of hollow visceral organs, such as the liver, pancreas, intestines, uterus, and stomach. It is also found in the walls of passageways, including arteries, veins, and bile ducts, as well as in sphincters, the urinary, respiratory, and reproductive tracts, and the eyes. Smooth muscle plays a crucial role in regulating various organ systems and maintaining their functions. For example, in the gastrointestinal tract, it helps propel food, while in the cardiovascular system, it regulates blood flow and pressure by controlling the diameter of blood vessels.
The function of smooth muscle can be categorized into two types: single-unit and multi-unit. Single-unit smooth muscle cells are electrically connected by gap junctions, allowing them to contract uniformly. They are found in the walls of internal organs, blood vessels, and visceral smooth musculature. Multi-unit smooth muscle cells, on the other hand, are independent and require individual innervation, allowing for more precise muscle control. These cells are found in the airways of the lungs, large arteries, ciliary muscles of the eye, iris, and hair erector muscles.
Smooth muscle has greater elastic properties than striated muscle due to its ability to tense and relax. This elasticity is particularly important in certain organ systems, such as the urinary bladder, where contractile tone must be preserved. Smooth muscle is derived from both mesoderm and neural crest cells, which contribute to its widespread presence throughout the body.
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Skeletal muscle can be classified as slow-oxidative (Type I) or fast-oxidative (Type II)
Striated muscle tissue is a muscle tissue that features repeating functional units called sarcomeres. Under a microscope, sarcomeres are visible along muscle fibres, giving a striated appearance to the tissue. The two types of striated muscle are skeletal muscle and cardiac muscle. Skeletal muscle is attached to the skeleton and is responsible for the voluntary movements of bones.
Type II fibres, on the other hand, have fast contractions and primarily use aerobic respiration. They produce ATP relatively quickly and can generate relatively high amounts of tension. Type II fibres are used for movements that require more energy than postural control but less energy than an explosive movement, such as walking.
In addition to Type I and Type II, there is another subtype of Type II fibres called Type IIx, also known as fast glycolytic fibres. These fibres primarily use anaerobic glycolysis as their energy source and have a large diameter. They are crucial for generating rapid and powerful muscular contractions and are used for activities that require short bursts of anaerobic effort, such as weightlifting, sprinting, and jumping.
The diversity in muscle fibres allows skeletal muscles to perform a wide range of movements. Furthermore, muscle fibres exhibit plasticity, meaning they can change in size or even convert to a different fibre type to adapt to new functions of the skeletal muscle. This plasticity serves as the basis for many physical therapy interventions designed to increase a patient's force development or endurance.
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Skeletal muscle can regenerate better than cardiac muscle due to satellite cells
Striated muscle tissue is a muscle tissue that has a "striated" or striped appearance under a microscope due to its densely packed myofibrils. The two types of striated muscle are skeletal muscle and cardiac muscle. Skeletal muscle is the tissue that most muscles attached to the bones are made of, while cardiac muscle is the muscle found in the walls of the heart.
Skeletal muscle can regenerate far better than cardiac muscle due to the presence of satellite cells. Satellite cells are a heterogeneous group of cells that includes stem cells and skeletal muscle progenitor cells. Each skeletal muscle fiber has its own pool of satellite cells that remain inactive until the muscle is damaged. When the muscle fibers are damaged or dead, their debris is removed by inflammatory macrophages, and muscle satellite cells (MuSCs) actively proliferate. The macrophages will eventually secrete anti-inflammatory cytokines, which results in the termination of inflammation. These macrophages can also facilitate the proliferation and differentiation of satellite cells. The satellite cells re-enter the cell cycle to multiply, and they then leave the cell cycle to self-renew or differentiate as myoblasts.
The process of muscle regeneration has been relatively well-investigated. During regeneration, muscle satellite cells rebuild multinuclear myofibers through a stepwise process of proliferation, differentiation, fusion, and maturation. The number of satellite cells and the speed of the regeneration processes that depend on them affect the time structure of an athlete's training.
Cardiac muscle, on the other hand, has a limited ability to regenerate. Cardiac muscle cells are generally unicellular and are connected to each other by intercalated discs. They contain many mitochondria and myoglobin, and their contractions are due to a myogenic response of the heart's pacemaker cells. While satellite cells have been found to be essential for skeletal muscle regeneration, they do not play the same role in cardiac muscle.
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Frequently asked questions
Striated muscle tissue is a muscle tissue that has a striped appearance due to repeating functional units called sarcomeres.
There are two types of striated muscle tissue: skeletal muscle and cardiac muscle.
Skeletal muscle is a type of striated muscle tissue that is attached to the skeleton and allows for a wide range of movements and functions. It is under voluntary control.
Cardiac muscle is a type of striated muscle tissue found in the walls of the heart. It is under involuntary control.
Smooth muscle is a type of muscle tissue that is not striated. It is found in the walls of hollow visceral organs such as the liver, pancreas, and intestines, as well as in blood vessels, the skin, and other areas. Smooth muscle is also under involuntary control.
