is smooth muscle tissue an organ

Is smooth muscle a tissue or organ?

Smooth muscle is a type of tissue found in the walls of hollow organs, such as the intestines, uterus and stomach. You can also find smooth muscle in the walls of passageways, including arteries and veins of de cardiovascular system.

What is smooth muscle tissue?

smooth muscle, also called involuntary muscle, muscle that shows no cross stripes under microscopic magnification. It consists of narrow spindle-shaped cells with a single, centrally located nucleus. Smooth muscle tissue, unlike striated muscle, contracts slowly and automatically.

What organ is not a smooth muscle?

the heartGross anatomy Most smooth muscle is of the single-unit type, and is found in the walls of most internal organs (viscera); and lines blood vessels (except large elastic arteries), the urinary tract, and the digestive tract. It is not found in the heart which has cardiac muscle.

What organs use smooth muscle?

Smooth muscle (so-named because the cells do not have striations) is present in the walls of hollow organs like the urinary bladder, uterus, stomach, intestines, and in the walls of passageways, such as the arteries and veins of the circulatory system, and the tracts of the respiratory, urinary, and reproductive ...

Which is a true statement about smooth muscle?

Which is a TRUE statement about smooth muscle? Smooth muscle does not use troponin-tropomyosin to regulate cross-bridge activity.

Where is smooth muscle tissue?

Smooth muscle fibers are located in walls of hollow visceral organs (such as the liver, pancreas, and intestines), except the heart, appear spindle-shaped, and are also under involuntary control.

How many organ systems are in the human body?

The body includes nine major organ systems, each composed of various organs and tissues that work together as a functional unit.

What are the types of smooth muscle?

Types of Smooth muscle Smooth muscles are of two types. They are: Single-unit (visceral) smooth muscle: All the cells function collectively and simultaneously as a single unit (unitary). Multiunit smooth muscle: It is a type of muscle in which all the cells cannot function collectively and work independently.

What are 3 types of muscle tissue?

The three main types of muscle include:Skeletal muscle – the specialised tissue that is attached to bones and allows movement. ... Smooth muscle – located in various internal structures including the digestive tract, uterus and blood vessels such as arteries. ... Cardiac muscle – the muscle specific to the heart.

How do you identify smooth muscle tissue?

Muscle tissue can be categorized into skeletal muscle tissue, smooth muscle tissue, and cardiac muscle tissue. Skeletal muscle fibers are cylindrical, multinucleated, striated, and under voluntary control. Smooth muscle cells are spindle shaped, have a single, centrally located nucleus, and lack striations.

Where is smooth muscle found quizlet?

Smooth muscle is found in the walls of the hollow internal organs, including all blood vessels except the capillaries, the gastrointestinal tract, and the urinary bladder. Smooth muscle is not striated and it is not subject to voluntary control.

What are characteristics of smooth muscle?

Smooth muscle is typically non-striated, uni-nucleated, and involuntary or reflexive. This muscle type is slow twitch and often rhythmic in contraction.

What does smooth muscle cell do?

Smooth muscle cells are quite heterogeneous, depending on the organ system in which they serve their function. Their major role is to control the diameter, wall movement, and wall stiffness of hollow organs like the vascular, bronchial, gastrointestinal or urogenital system as well as the uterus.

What are characteristics of smooth muscle?

Smooth muscle is typically non-striated, uni-nucleated, and involuntary or reflexive. This muscle type is slow twitch and often rhythmic in contraction.

How do you identify smooth muscle tissue?

Muscle tissue can be categorized into skeletal muscle tissue, smooth muscle tissue, and cardiac muscle tissue. Skeletal muscle fibers are cylindrical, multinucleated, striated, and under voluntary control. Smooth muscle cells are spindle shaped, have a single, centrally located nucleus, and lack striations.

What role do smooth muscle cells perform in a human body?

Smooth muscle cells are responsible for involuntary contractions and are found in the walls of blood vessels and hollow organs such as the gastrointestinal tract, uterus , and bladder. They are also present in the eye and contract changing the shape of the lens causing the eye to focus.

Where is smooth muscle found?

Smooth muscle is a type of tissue found in the walls of hollow organs, such as the intestines, uterus and stomach . You can also find smooth muscle in the walls of passageways, including arteries and veins of de cardiovascular system. This type of involuntary non-striated muscle is also found in the tracts of the urinary, respiratory and reproductive systems. In addition to that, you can find smooth muscle in the eyes, where it acts to change the size of the iris and the shape of the lens. The skin is also contains smooth muscle which allows hair to raise in response to cold temporatures or fear.

How thick is a smooth muscle cell?

The smooth muscle cell is 3-10 µm thick and 20-200 µm long. The cytoplasm is homogeneously eosinophilic and consists mainly of myofilaments. The nucleus is located in the center and takes a cigar-like shape during contraction. The cell membrane forms small pouch-like invaginations into the cytoplasm (caveolae) which are functionally equivalent to the T-tubules of the skeletal musculature. The smooth muscle cells are anchored to the surrounding connective tissue by a basal lamina.

What is the function of myofibroblasts in smooth muscle?

They produce connective tissue proteins such as collagen and elastin for which reason they are also referred to as fixed (or stationary) connective tissue cells.

What type of tissue does myofibroblasts produce?

Myofibroblasts produce connective tissue proteins such as collagen and elastin.

Which muscle group allows for cells to contract much stronger than those of striated musculature?

Fibers of smooth muscle group in branching bundles, which allows for cells to contract much stronger than those of striated musculature.

What is the cell membrane of skeletal muscle?

The cell membrane forms small pouch-like invaginations into the cytoplasm (caveolae) which are functionally equivalent to the T-tubules of the skeletal musculature. The smooth muscle cells are anchored to the surrounding connective tissue by a basal lamina. The smooth muscle fibers group in branching bundles.

Which muscle fibers are branching bundles?

The smooth muscle fibers group in branching bundles. As opposed to skeletal muscle fibers these bundles do not run strictly parallel and ordered but consist in a complex system. Thus the cells can contract much stronger than striated musculature.

What is the function of smooth muscle?

Similar to the blood supply, the innervation of smooth muscle varies widely by location and function. Vascular smooth muscle is primarily innervated by the sympathetic nervous system. Alpha-1 and alpha-2 receptors function to cause vasoconstriction by contracting vascular smooth muscle cells leading to systemic hypertension. Beta-2 receptors also respond to sympathetic stimulation but produce a vasodilatory effect and which will lead to systemic hypotension. However, parasympathetic stimulation also plays an important role in the contraction of smooth muscle cells. Studies performed as early as 1925 demonstrated the effect of parasympathetic innervation on the gastrointestinal tract.[8]  More recently researchers have been able to show how the sympathetic, parasympathetic, and enteric nervous systems all work uniformly to effect and contract smooth muscle.[9]  Sympathetic stimulation of smooth muscle is received by contributions from spinal levels T1 to L2 of the spine. Each of these contributions finds its way into the sympathetic trunk which functions to route autonomic nervous supply to organs and tissue throughout the body. The parasympathetic nervous system functions in three parts, the cranial nerves, vagus nerve, and pelvic splanchnic nerves. Each nerve in the parasympathetic system regulates a specific portion of the body, the vagus, for instance, innervates the gastrointestinal tract from the esophagus to the proximal portion of the large intestines, while also sending out branches to the heart, larynx, trachea, bronchi, liver, and pancreas. The sympathetic and parasympathetic nervous systems are collectively referred to as the autonomic nervous system. The complex nature of the autonomic nervous system allows for tight unconscious control of digestions, respiratory rate, urination, heart rate, blood pressure, and many other critical body functions.

How does smooth muscle differ from skeletal muscle?

Smooth muscle differs from skeletal muscle in function.  Unlike skeletal muscle, smooth muscle is capable of maintaining tone for extended periods and often contracts involuntarily. At a cellular level, smooth muscle can be described as an involuntary, non-striated muscle. Smooth muscle consists of thick and thin filaments that are not arranged into sarcomeres giving it a non-striated pattern. On microscopic examination, it will appear homogenous. Smooth muscle cytoplasm contains a large amount of actin and myosin. Actin and myosin act as the main proteins involved in muscle contraction. Actin filaments attach to dense bodies that are spread throughout the cell. Dense bodies can be observed under an electron microscope and appear dark. Another important structure is the calcium-containing sarcoplasmic reticulum which aids in sustaining contraction. The shape of the smooth muscle is described as fusiform, which is described as being round in the center and tapering at each end. Smooth muscle can tense and relax but has greater elastic properties than striated muscle. This is important in organ systems like the urinary bladder where contractile tone must be preserved.

How does calcium release in smooth muscle tissue?

Ultimately innervation from the autonomic nervous system leads to a calcium release in smooth muscle tissue.  Smooth muscle contraction is dependent on calcium influx. Calcium is increased within the smooth muscle cell through two different processes. First depolarization, hormones, or neurotransmitters cause calcium to enter the cell through L-type channels located in the caveolae of the membrane. Intracellular calcium then stimulates the release of calcium from the sarcoplasmic reticulum (SR) by way of ryanodine receptors and IP3, this process is referred to as calcium-induced calcium release.[10]  Unlike skeletal muscle, smooth muscle calcium release from the sarcoplasmic reticulum is not physically coupled to the ryanodine receptor. Once calcium has entered the cell it is free to bind calmodulin, which transforms into activated calmodulin. Calmodulin then activates the enzyme myosin light chain kinase (MLCK), MLCK then phosphorylates a regulatory light chain on myosin. Once phosphorylation has occurred a conformational change takes place in the myosin head, this increases myosin ATPase activity which promotes interaction between the myosin head and actin. Cross-bridge cycling then occurs, and tension is generated. The tension generated is relative to the amount of calcium concentration within the cell. ATPase activity is much lower in smooth muscle than it is in skeletal muscle. This factor leads to the much slower cycling speed of smooth muscle. However, the longer period of contraction leads to a potentially greater force of contraction in smooth muscle. Smooth muscle contraction is enhanced even further through the use of connexins. Connexins allow for intercellular communication by allowing calcium and other molecules to flow to neighboring smooth muscle cells. This action allows for rapid communication between cells and a smooth contraction pattern.

How does smooth muscle work?

A person does not need to think about their blood pressure for it to adapt to increasing oxygen demands from exercise. The nervous system instead uses hormones, neurotransmitters, and other receptors to control smooth muscle spontaneously.

How does smooth muscle affect blood flow?

It becomes more important to recognize how smooth muscles impact blood supply themselves. For example, within the cardiovascular system, smooth muscle helps to regulate blood flow by controlling the diameter of the vessel. As previously discussed vascular pathologies of smooth muscle can have devasting effects on the body and lead to significant pathology. Atherosclerosis once thought to be only a function of hemodynamics and vessel structure has more recently been shown to be linked as well to smooth muscle development.[4]  Research has even shown that continuous vascular smooth muscle activation can lead to the formation of pulmonary hypertension.[6]  Within the lungs, pathologic activation of smooth muscle can lead to the development of asthma. Asthma occurs when smooth muscle constriction leads to obstruction of the airway. Recent studies have shown that the smooth muscle layer may be increased in thickness before the onset of asthma even occurs, from which a genetic link may be derived. [7]

Why are smooth muscle cells important?

Vascular smooth muscle cells arise from multiple origins; this becomes medically significant because it may contribute to the site-specific localization of vascular diseases. For example, atherosclerosis and aortic aneurysms often present at specific vascular locations. In the past, this was thought to be related to hemodynamics and underlying vessel structure. However, there is increasing evidence that smooth muscle cell embryonic lineage may play a role in determining the location and presentation of the disease.[4]  Smooth muscle cell development is also an important factor in the development of the endothelial network. Vascular smooth muscle cells sometimes referred to as mural cells, are important for vascular development and stability. Mural cells wrap around larger vessels and are heavily relied upon in the regulation of blood flow, endothelial network growth, and vessel stability. However, little is know about the effect of their developmental origins or the signaling process that leads to vessel development. The development of vascular smooth muscle cells is an important target for vascular tissue engineering and therapeutic revascularization. [5]

Which muscle is responsible for sensory perception?

Sensory: Ciliary muscle and iris of the eye

Where is smooth muscle found?

Smooth muscle is found in the walls of hollow organs, including the stomach, intestines, bladder and uterus; in the walls of passageways, such as blood, and lymph vessels, and in the tracts of the respiratory, urinary, and reproductive systems.

How does smooth muscle work?

This ability to stretch and still maintain contractility is important in organs like the intestines and urinary bladder. Smooth muscle in the gastrointestinal tract is activated by a composite of three types of cells – smooth muscle cells (SMCs), interstitial cells of Cajal (ICCs), and platelet-derived growth factor receptor alpha (PDGFRα) that are electrically coupled and work together as an SIP functional syncytium.

How does the number of myosin filaments change?

Also, the number of myosin filaments is dynamic between the relaxed and contracted state in some tissues as the ratio of actin to myosin changes, and the length and number of myosin filaments change.

What type of cells are involved in smooth muscle?

Smooth muscle in the gastrointestinal tract is activated by a composite of three types of cells – smooth muscle cells (SMCs), interstitial cells of Cajal (ICCs), and platelet-derived growth factor receptor alpha (PDGFRα) that are electrically coupled and work together as an SIP functional syncytium.

What causes muscle fibers to contract?

The dense bodies and intermediate filaments are networked through the sarcoplasm, which cause the muscle fiber to contract. A series of axon-like swellings, called varicosities from autonomic neurons, loosely form form motor units through the smooth muscle. Most smooth muscle is of the single-unit variety, that is, ...

What muscle is responsible for erecting the eye?

In the eyes, the ciliary muscle, a type of smooth muscle, dilate and contract the iris and alter the shape of the lens. In the skin, smooth muscle cells such as those of the arrector pili cause hair to stand erect in response to cold temperature or fear.

Where do smooth muscle tumors occur?

They can occur in any organ, but the usually occur in the uterus, small bowel, and esophagus. Malignant smooth muscle tumors are called leiomyosarcomas. Leiomyosarcomas are one of the more common types of soft-tissue sarcomas. Vascular smooth muscle tumors are very rare.

What are the types of smooth muscles in the human body?

Single-unit smooth muscle – a type of smooth muscle found in many organs, such as the stomach and intestines. It can be found both inside and outside these organ tissues.

Where is smooth muscle found?

Smooth muscle is a type of non-striated muscle that is found in the walls of hollow organs and blood vessels. Smooth muscle can be found throughout the body but is most common around the digestive tract, in the walls of blood vessels, arteries, and around other organs such as the eyes.

What disorders affect smooth muscles?

Certain disorders can also affect the functioning of smooth muscles. For instance, a genetic condition called Multisystemic smooth muscle dysfunction syndrome (MSMDS) results in an embryo to not develop enough smooth muscles for the digestive system. Some autoimmune disorders such as hepatitis, lupus or cirrhosis can also cause Anti-smooth muscle antibodies (ASMA).

What type of muscle is not striated?

As stated above, smooth muscle cells are not striated. This means they have no visible bands of contractile proteins like those found in skeletal muscles. These muscles are also involuntary, which means the contraction of these muscles is not dependent on conscious thought. They can contract in response to chemical or electrical signals, which they receive from autonomic nerves and hormones like epinephrine and vasopressin. Smooth muscle tissues are usually arranged as circular layers and tubes around the gut or as sheets between layers of connective tissue. Furthermore, this type of muscle has no more than one nucleus per cell.

What are the three types of muscular tissue?

The human body contains three main types of muscular tissue: skeletal, cardiac, and smooth. Smooth muscle is a type of non-striated muscle that is common in the walls of hollow organs and blood vessels. However, smooth muscle can be found throughout the body but is most common around the digestive tract, in the walls of blood vessels, arteries, and around other organs such as the eyes.

Which muscle is responsible for transporting blood throughout the body?

The vasculature system that transports blood throughout the body is controlled by smooth muscle. Smooth muscles contract to regulate blood pressure and other cardiovascular processes. They also aid in food digestion through peristalsis, which is the rhythmic wave-like contraction of muscles around the digestive tract.

What is smooth muscle?

At a cellular level, smooth muscle functions as an involuntary non-striated muscle. Smooth muscle contains thick and thin filaments that do not arrange into sarcomeres, resulting in a non-striated pattern. On microscopic examination, it appears homogenous. Smooth muscle cytoplasm contains large amounts of actin and myosin. Actin and myosin act as the main proteins involved in muscle contraction. Actin filaments attach to dense bodies spread throughout the cell. Dense bodies can be observed under an electron microscope and appear dark. Another important structure is the calcium-containing sarcoplasmic reticulum, which aids in sustaining contraction. The shape of smooth muscle is fusiform, which is round in the center and tapering at each end. Smooth muscle can tense and relax but has greater elastic properties than striated muscle. This quality is important in organ systems like the urinary bladder, where the preservation of contractile tone is a necessity.

What is the function of smooth muscle?

The primary function of smooth muscle is contraction . Smooth muscle consists of two types: single-unit and multi-unit. Single-unit smooth muscle consists of multiple cells connected through connexins that can become stimulated in a synchronous pattern from only one synaptic input. Connexins allow for cell-to-cell communication between groups of single-unit smooth muscle cells. This intercellular communication allows ions and molecules to diffuse between cells giving rise to calcium waves. This unique property of single-unit smooth muscle allows for synchronous contraction to occur.[6]  Multi-unit smooth muscle differs from single-unit in that each smooth-muscle cell receives its own synaptic input, allowing for the multi-unit smooth muscle to have much finer control.

How does smooth muscle affect fertility?

In the genital system, smooth muscle is often a focus regarding its role in childbirth. Smooth muscle lines the uterus, which creates the contractile force during childbirth. Many pharmaceuticals exist specifically to help enhance smooth muscle contraction at the time of birth. While this may not represent an actual pathology, it is crucial to recognize that physicians can use a knowledge of smooth muscle physiology to prevent pathologies from occurring. In males, fertility is also a function of the contractions of smooth muscle in the epididymis and vas deferens. Without the contractile nature of smooth muscle, spermatozoa would never be able to assist in fertilization; this becomes important because of the apparent lack of information on the possible pathologic effects of smooth muscle and infertility. For example, many medications that are frequently used by males impact smooth muscle contractility and, therefore, may also affect fertility. Examples include nonsteroidal anti-inflammatory drugs, phosphodiesterase (PDE) inhibitors, nitrates, adrenergic receptor antagonists and agonists, psychotropic drugs, anticholinergic drugs, calcium antagonists, and ace inhibitors. [13]

How does calcium affect smooth muscle contraction?

Smooth muscle contraction depends on calcium influx. Calcium increases within the smooth muscle cell through two different processes. First, depolarization, hormones, or neurotransmitters cause calcium to enter the cell through L-type channels located in the caveolae of the membrane. Intracellular calcium then stimulates the release of calcium from the sarcoplasmic reticulum (SR) by way of ryanodine receptors and IP3; this process is referred to as calcium-induced calcium release.[7]  Unlike skeletal muscle, smooth muscle calcium release from the sarcoplasmic reticulum does not physically couple to the ryanodine receptor. Once calcium has entered the cell, it is free to bind calmodulin, which transforms into activated calmodulin. Calmodulin then activates the enzyme myosin light chain kinase (MLCK), MLCK then phosphorylates a regulatory light chain on myosin. Once phosphorylation has occurred, a conformational change takes place in the myosin head; this increases myosin ATPase activity, which promotes interaction between the myosin head and actin. Cross-bridge cycling then occurs, generating tension. The tension generated is relative to the amount of calcium concentration within the cell. ATPase activity is much lower in smooth muscle than it is in skeletal muscle. This factor leads to a much slower cycling speed of smooth muscle. However, the more extended period of contraction leads to a potentially greater force of contraction in smooth muscle. Smooth muscle contraction is enhanced even further through the use of connexins. Connexins allow for intercellular communication by allowing calcium and other molecules to flow to neighboring smooth muscle cells. This action allows for rapid communication between cells and a smooth contraction pattern.

What is the role of smooth muscle in asthma?

Smooth muscle also plays an essential role in the disease process throughout the body. The use of bronchodilators to relax airway smooth muscle is an important and life-saving treatment in asthmatics.[1]  Likewise, medications like metoclopramide can stimulate and promote gastric emptying by increasing smooth muscle signaling. Perhaps one of the most well-known uses of medical therapy and smooth muscle is the use of nitrates in the treatment of ischemic heart disease.[2]  Research showed that nitrates, in combination with ace inhibitors, can improve patient mortality.[3]  The uniquely significant impact that smooth muscle has throughout the body makes it an important topic for medical professionals to understand as many treatments at their core rely on modifying the signaling pathways that affect smooth muscle.

How does smooth muscle work?

A person does not need to think about their blood pressure for it to adapt to increasing oxygen demands from exercise. The nervous system instead uses hormones, neurotransmitters, and other receptors to control smooth muscle spontaneously.

Why is smooth muscle important?

Smooth muscle derives from both mesoderm and neural crest cells; this is because smooth muscle contributes to many different tissues throughout the body. One unique feature of neural crest cells is that their migration occurs during embryological development. For this reason, numerous tissues throughout the body originate from neural crest cells. Neural crest cells play a vital role in the development of smooth muscle throughout the body, specifically in the regulation of blood vessels.

What type of tissue is muscle?

Well, muscle is a type of tissue. There are three kinds: skeletal muscle which is the kind that you usually think of, and then smooth muscle which is involuntary and controlled by the autonomic nervous system and local factors, and then you've got cardiac muscle which is what most of the heart is made of.

Where is smooth muscle found?

Smooth muscle is found in the GI tract and in the walls of blood vessels. Skeletal muscle is what your "muscles" are made of, and those are individual structures with names like "trapezius", "gastrocnemius", "rectus abdominus", etc.

What is the difference between cardiac muscle and smooth muscle?

Smooth muscles are long, thin-shaped cells attached to bones in the body. Smooth muscles are also found in the blood vessels, helping blood to move around the body. Cardiac muscle is also known as myocardium. Similar to smooth muscle, cardiac muscle is an involuntary muscle.

What are the muscles that control the movements of the body?

Skeletal Muscle . Skeletal muscles are the voluntary muscles that allow you to control the movements of your body. Skeletal muscles also are striated and comprise the musculoskeletal system. These muscles are attached to your bones via tendons, which are cords of tissue.

Why are cardiac muscles thickened?

These muscles are thickened because they must contract frequently to move blood in and out of the heart. Cardiac muscle cells are quadrangular in terms of shape, and the muscles have striations resembling stripes or lines running through them.

What is cardiac muscle?

Cardiac muscle is also known as myocardium. Similar to smooth muscle, cardiac muscle is an involuntary muscle. These muscles are thickened because they must

What is skeletal muscle?

Skeletal muscle is what your "muscles" are made of, and those are individual structures with names like "trapezius", "gastrocnemius", "rectus abdominus", etc. If you wanted to think of those individual muscles as "organs. Continue Reading. Well, muscle is a type of tissue. There are three kinds: skeletal muscle which is the kind ...

What is a discrete organ made up of several kinds of tissues?

a discrete organ made up of several kinds of tissues; muscle fibers predominate, blood vessels nerve fibers and connective tissue also present

What is the term for the wrapping of connective tissue in a muscle?

the muscles connective tissue wrapping extend beyond the muscle either as a ropelike tendon or a a sheet like aponeurosis ; tendon or aponeurosis anchors the muscle to the connective tissue covering of a skeletal element or to the fascia of other muscles

What is the length of a rodlike muscle fiber?

rodlike and run parallel to length of muscle fibers; 1-2 um in daimeter; densely packed in muscle fiber that mitochondria and other organelles appear to be squeezed between them

Overview

Excitation-contraction coupling

A smooth muscle is excited by external stimuli, which causes contraction. Each step is further detailed below.
Smooth muscle may contract spontaneously (via ionic channel dynamics) or as in the gut special pacemakers cells interstitial cells of Cajal produce rhythmic contractions. Also, contraction, as well as relaxation, can be induced by a number of physiochemical agents (e.g., hormones, drugs, neu…

Structure

Invertebrate smooth muscle

Specific effects

Growth and rearrangement

Related diseases

See also