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Smooth muscle is a type of muscle tissue that is found throughout the human body and is involved in many of its most important functions, including blood pressure, circulation, vision, and digestion. Smooth muscle is one of the three major types of vertebrate muscle tissue, the other two being skeletal and cardiac muscle. It is found in the walls of hollow organs, including the stomach, intestines, bladder, and uterus, as well as in the tracts of the respiratory, urinary, and reproductive systems. Smooth muscle is also involved in the disease process throughout the body, and many treatments rely on modifying the signaling pathways that affect it.
| Characteristics | Values |
|---|---|
| Type of Muscle Tissue | Smooth muscle is one of the three major types of vertebrate muscle tissue, the others being skeletal and cardiac muscle. |
| Control | Smooth muscle is controlled by the autonomic nervous system. |
| Striation | Smooth muscle is non-striated, meaning it has no sarcomeres and therefore no striations (bands or stripes). |
| Subgroups | Smooth muscle can be divided into two subgroups: single-unit and multi-unit smooth muscle. |
| Location | Smooth muscle is found in the walls of hollow organs, including the stomach, intestines, bladder, and uterus. It is also found in the tracts of the respiratory, urinary, and reproductive systems, as well as in the skin and eyes. |
| Function | Smooth muscle controls the resistance of blood vessels, digestion of food, uterine contraction, and more. It is involved in the body's automated self-management processes. |
| Structure | Smooth muscle cells are spindle-shaped with a wide middle and tapering ends. They are smaller than skeletal muscle cells and have a different structure. |
| Contraction | Smooth muscle can contract and relax, and it contracts involuntarily. |
| Conditions | Smooth muscle is vulnerable to conditions such as anti-smooth muscle autoantibodies, muscular dystrophies, spasms, and visceral myopathies. |
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What You'll Learn
- Smooth muscle is one of the three major types of vertebrate muscle tissue
- Smooth muscle is found in the walls of hollow organs, including the stomach, intestines, bladder and uterus
- Smooth muscle is controlled by the autonomic nervous system and can contract involuntarily
- Smooth muscle cells are spindle-shaped with a wide middle and tapering ends
- Smooth muscle is involved in important body functions such as blood pressure, circulation and digestion
Smooth muscle is one of the three major types of vertebrate muscle tissue
Smooth muscle is an involuntary, non-striated muscle, meaning it cannot be controlled consciously. It consists of thick and thin filaments that are not arranged into sarcomeres, giving it a non-striated pattern. On microscopic examination, it appears homogeneous. Smooth muscle is found in the walls of hollow internal organs, including the stomach, intestines, bladder, and uterus. It is also found in the walls of blood vessels, the urinary tract, the digestive tract, and the respiratory, urinary, and reproductive systems.
Smooth muscle plays a crucial role in the body's automated self-management processes, such as blood pressure and circulation, vision, and digestion. It can flex together to push the contents of tubelike passages in the body, such as the digestive tract. It also controls the width of passages, such as blood and lymph vessels and airways. Most muscles stay relaxed and only flex when needed, but smooth muscle in sphincters, such as the bladder or anus, stays flexed and only relaxes when needed.
Smooth muscle is also involved in specific functions, such as causing hairs to stand on end (goosebumps) and controlling how the eyes focus by pulling on zonule fibers. In the uterus, smooth muscle contractions occur during labour, and a shift in myosin expression has been hypothesized to allow for changes in the directions of uterine contractions during the menstrual cycle. Smooth muscle is also important in the disease process throughout the body, with treatments for conditions such as asthma and ischemic heart disease targeting the signalling pathways that affect smooth muscle.
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Smooth muscle is found in the walls of hollow organs, including the stomach, intestines, bladder and uterus
Smooth muscle is one of the three major types of vertebrate muscle tissue, the others being skeletal and cardiac muscle. Smooth muscle is found throughout the body and serves a variety of functions. It is part of the body's most important automated functions, from blood pressure and circulation to vision and digestion.
Smooth muscle is found in the walls of hollow organs, including the stomach, intestines, bladder, and uterus. In the walls of blood vessels and lymph vessels, it is known as vascular smooth muscle. It is also found in the tracts of the respiratory, urinary, and reproductive systems. Smooth muscle in the skin causes hairs to stand on end, like with goosebumps.
In the stomach and intestines, smooth muscle helps with digestion and nutrient collection. It is also found throughout the urinary system, where it helps rid the body of toxins and works to maintain electrolyte balance. Smooth muscle in the uterus is where contractions happen during labour.
Smooth muscle is an involuntary, non-striated muscle. It consists of thick and thin filaments that are not arranged into sarcomeres, giving it a non-striated pattern. Actin and myosin are the main proteins involved in smooth muscle contraction. The shape of the smooth muscle is described as fusiform, which is round in the center and tapers at each end. Smooth muscle can tense and relax but has greater elastic properties than striated muscle.
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Smooth muscle is controlled by the autonomic nervous system and can contract involuntarily
Smooth muscle is one of the three major types of vertebrate muscle tissue, the others being skeletal and cardiac muscle. It can be found throughout the body, serving a variety of functions. Smooth muscle is an involuntary, non-striated muscle, meaning it contracts and relaxes without conscious thought. It is controlled by the autonomic nervous system, which includes the sympathetic and parasympathetic nervous systems. This system allows for unconscious control of critical body functions such as digestion, respiratory rate, urination, heart rate, and blood pressure.
The autonomic nervous system regulates smooth muscle contraction through the release of calcium in smooth muscle tissue. This calcium release is essential for sustaining smooth muscle contraction. Smooth muscle consists of thick and thin filaments that are not arranged into sarcomeres, giving it a non-striated pattern. It is named for its smooth appearance, which differs from the grooved appearance of skeletal muscle.
Smooth muscle cells are spindle-shaped with a wide middle and tapering ends, and they contain a large amount of actin and myosin, the main proteins involved in muscle contraction. These proteins form continuous chains within the cell, anchored at dense bodies. The actin filaments attach to these dense bodies, which can be observed under an electron microscope and appear dark. The dense bodies are connected to adjacent smooth muscle cells, forming a mesh-like network that allows for uniform contraction in a spiral corkscrew fashion.
Smooth muscle can be divided into two subgroups: single-unit and multi-unit smooth muscle. Single-unit smooth muscle, also known as visceral smooth muscle, is found in the walls of most internal organs and lines blood vessels, the urinary tract, and the digestive tract. It contracts as a whole unit, with each cell innervated by an autonomic nerve fiber. Multi-unit smooth muscle, on the other hand, has finer control, with each cell receiving its synaptic input. It is found in the airways of the lungs, large arteries, and ciliary muscles of the eye.
The unique properties of smooth muscle make it an important topic for medical professionals to understand, as many treatments rely on modifying the signaling pathways that affect it. For example, bronchodilators are used to relax airway smooth muscle in asthmatic patients, and medications like metoclopramide stimulate gastric emptying by increasing smooth muscle signaling.
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Smooth muscle cells are spindle-shaped with a wide middle and tapering ends
Smooth muscle is a type of muscle tissue that works automatically and is found throughout the body. It is one of the three major types of vertebrate muscle tissue, the others being skeletal and cardiac muscle. Smooth muscle cells are spindle-shaped with a wide middle and tapering ends, and a single nucleus. They are much shorter than skeletal muscle cells, ranging from 30 to 200 micrometers in length. Smooth muscle cells are built from sheets of cells that are linked together by various junctional contacts, including gap junctions, that serve as sites of cell-cell communication. These cells are active in the synthesis and deposition of connective tissue matrix, which helps to limit the distension of hollow organs.
The shape of smooth muscle cells can be described as fusiform, which is round in the center and tapering at each end. This unique shape allows the cells to contract in a coordinated fashion, with the entire muscle contracting or relaxing as a unit. The thin and thick filaments within the cells are not arranged into sarcomeres, giving the muscle a non-striated appearance. The thick filaments are made of the protein myosin, while the thin filaments are made of actin. These two proteins work together to enable the muscle to contract.
The structure of smooth muscle cells differs from that of skeletal muscle cells, which are long and cylindrical. Skeletal muscle cells form bundles that give the muscle a grooved appearance. In contrast, smooth muscle cells are smaller in size and have a slower response time, making them highly resistant to fatigue. They are also involuntary muscles, meaning they contract and relax without conscious control. This is in contrast to skeletal muscles, which respond to an individual's control.
Smooth muscle cells can be found in various parts of the body, including the walls of hollow organs such as the stomach, intestines, bladder, and uterus. They are also present in the urinary, respiratory, and reproductive systems, as well as in the skin and eyes. In the skin, smooth muscle cells cause hairs to stand on end, such as when experiencing goosebumps or fear. In the eyes, they control how the eyes focus by pulling on fibers called zonules.
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Smooth muscle is involved in important body functions such as blood pressure, circulation and digestion
Smooth muscle is one of the three main types of muscle in the body, the other two being skeletal and cardiac. Smooth muscle is a type of muscle tissue that works automatically and is found throughout the body. It is involved in some of the body's most important functions, including blood pressure, circulation, and digestion.
Smooth muscle movements happen without conscious thought. They are a key part of the body's automated self-management processes. Smooth muscles manage the width of passages inside the body, such as blood and lymph vessels and airways. They can flex together to push what's inside a tubular passage, which is how multiple sections of the digestive tract work.
Smooth muscles in the intestinal wall produce tonic contractions that maintain organ dimension against an imposed load, such as a bolus of food. They also produce forceful contractions that propel the bolus along the gastrointestinal tract. Smooth muscles in the bladder and anus stay flexed and only relax when needed.
Smooth muscle is also involved in other specific functions. For example, it is what causes hairs to stand on end, like with goosebumps. Smooth muscles in the ciliary body of the eye pull on fibers called zonules to control how the eyes focus. Smooth muscles in the iris control how the pupils dilate or constrict. In the uterus, smooth muscles are where contractions happen during labor.
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Frequently asked questions
Smooth muscle is one of the three major types of vertebrate muscle tissue, the others being skeletal and cardiac muscle. It is found throughout the body and is controlled by the autonomic nervous system.
Smooth muscle is described as fusiform, which means it is round in the center and tapers at each end. It is non-striated, meaning it has no sarcomeres and therefore no bands or stripes.
Smooth muscle is involved in many of the body's most important functions, including blood pressure, circulation, vision, and digestion. It is also responsible for the width of passages inside the body, such as blood and lymph vessels and airways.
Some conditions that can affect smooth muscle include anti-smooth muscle autoantibodies, muscular dystrophies, spasms, and visceral myopathies.
Smooth muscle is found in the walls of hollow internal organs, including the stomach, intestines, bladder, and uterus. It is also found in the urinary and reproductive systems, as well as the skin and eyes.
