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There are three types of muscle tissue in the human body: smooth, skeletal, and cardiac. Striated muscles, which are characterised by their striped appearance, include skeletal and cardiac muscles. Smooth muscles lack striations and are found in the walls of hollow visceral organs such as the liver, pancreas, and intestines. These muscles are involuntary and do not require external stimulation to contract. Skeletal muscles, which are also known as voluntary muscles, are the most common type of muscle in the body and are responsible for the movement of the limbs. Cardiac muscles are striated and responsible for pumping blood throughout the body.
| Characteristics | Values |
|---|---|
| Striated or not | Not striated |
| Type | Smooth muscle |
| Location | Walls of hollow visceral organs (liver, pancreas, intestines) |
| Shape | Spindle-shaped |
| Control | Involuntary |
| Function | Undergoes spontaneous activity |
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What You'll Learn
- Smooth muscles lack striations and are found in the gut
- Cardiac muscles are striated and located in the heart
- Skeletal muscles are attached to the skeleton and are striated
- Striated muscles are highly organized tissues that convert chemical energy to physical work
- Striated muscles are made up of repeating functional units called sarcomeres
Smooth muscles lack striations and are found in the gut
There are three major types of vertebrate muscle tissue: skeletal, cardiac, and smooth muscle. Skeletal and cardiac muscles are striated, while smooth muscles are not. Smooth muscles get their name from their lack of striations or stripes, which are visible in skeletal and cardiac muscles under a microscope. This is because smooth muscles do not have sarcomeres, which are repeating functional units that give striated muscles their distinct appearance.
Smooth muscles are 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 walls of blood vessels and lymph vessels, excluding the capillaries, where they are known as vascular smooth muscle. Additionally, smooth muscle can be found in the tracts of the respiratory, urinary, and reproductive systems. For example, in the eyes, the ciliary muscles, iris dilator muscle, and iris sphincter muscle are all types of smooth muscles.
One important function of smooth muscle is its role in the digestive system, specifically in the gut. In the gut, special pacemaker cells called interstitial cells of Cajal produce rhythmic contractions that aid in digestion and the movement of food through the intestines. Smooth muscle contractions in the gut can also be influenced by various physiochemical agents, such as hormones, drugs, and neurotransmitters from the autonomic nervous system.
Smooth muscles differ from skeletal and cardiac muscles in terms of their structure and function. Skeletal muscles, also known as striated muscles, are the most common type of muscle in the body and are responsible for breathing, eating, and moving bones. They consist of flexible muscle fibers that contract to enable movement. Cardiac muscles, on the other hand, are responsible for pumping blood throughout the body through their contractions.
In summary, smooth muscles lack striations and are found in various parts of the body, including the gut, where they play a crucial role in digestion and the movement of food through contractions. Smooth muscles have distinct structural and functional characteristics compared to skeletal and cardiac muscles, which are the other two types of muscle tissue in the body.
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Cardiac muscles are striated and located in the heart
There are three types of muscle tissues in the body: cardiac, smooth, and skeletal. Cardiac muscles, also known as myocardium or heart muscles, are striated muscles located in the heart. They form the thick middle layer of the heart wall, between the outer layer of the heart wall (the pericardium or epicardium) and the inner layer (the endocardium).
Cardiac muscles are involuntary muscles, meaning that their movement is not under conscious control. They are composed of individual cardiac muscle cells, or cardiomyocytes, joined by intercalated discs. These cells are surrounded by an extracellular matrix produced by supporting fibroblast cells. Cardiomyocytes are the contractile cells of the heart, and their primary function is to contract and generate the pressure needed to pump blood through the circulatory system.
The contractions in cardiac muscle are due to a myogenic response of the heart's pacemaker cells, which set the rhythm of the heart contractions. These pacemaker cells are located in the sinoatrial node (the primary pacemaker) on the wall of the right atrium and the atrioventricular node (secondary pacemaker). They respond to signals from the autonomic nervous system to either increase or decrease the heart rate.
Cardiac muscle tissue contains repeating functional units called sarcomeres, which are the fundamental contractile units of the muscle cells. The sarcomeres consist of thick and thin filaments, or myofilaments, composed of long proteins. When calcium ions are released from the sarcoplasmic reticulum, the rise in calcium causes the myofilaments to slide past each other in a process called excitation-contraction coupling, resulting in muscle contraction.
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Skeletal muscles are attached to the skeleton and are striated
Skeletal muscles exhibit a distinctive banding pattern when viewed under a microscope due to the arrangement of two contractile proteins, myosin and actin. These two proteins form thick and thin filaments, respectively, and are arranged in repeating units called sarcomeres, which give skeletal muscles their striated appearance. Each muscle fibre contains hundreds or thousands of sarcomeres, and each sarcomere is attached to other organelles such as the mitochondria. The interaction of myosin and actin results in muscle contraction, which allows for movement and the performance of various physical tasks.
The strength of a skeletal muscle, in terms of force exerted on the skeleton, depends on several factors, including length, shortening speed, cross-sectional area, pennation, sarcomere length, myosin isoforms, and neural activation of motor units. Skeletal muscle mass varies from person to person, with males generally having more skeletal muscle mass than females. Additionally, taller individuals and those with higher body weight tend to have greater muscle mass.
Skeletal muscles are composed of flexible muscle fibres that range from less than half an inch to just over 3 inches in diameter. These fibres contract, allowing the muscles to move bones and perform different movements. Each muscle can contain thousands of fibres, and these fibres are surrounded by a connective tissue layer called fascia. Skeletal muscle fibres are red and white and are often called striated muscles due to their striped appearance.
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Striated muscles are highly organized tissues that convert chemical energy to physical work
There are two types of striated muscle: skeletal muscle and cardiac muscle. Skeletal muscle, also known as voluntary muscle, is the most common type of muscle in the human body. It is attached to the skeleton and responsible for movements of the limbs and bones. Skeletal muscle fibers are red and white, and they range from less than half an inch to just over 3 inches in diameter. Each muscle can contain thousands of fibers, and these fibers contract to enable various movements.
Cardiac muscle, on the other hand, is found only in the heart, where it contracts rhythmically to pump blood throughout the body. These contractions are due to the myogenic response of the heart's pacemaker cells, which respond to signals from the autonomic nervous system to regulate heart rate. Cardiac muscle exhibits a stronger active force with increased muscle length, allowing for more forceful contraction at larger diastolic fillings.
Striated muscles are characterized by their structural and functional units called sarcomeres, which are responsible for muscle contraction. Sarcomeres consist of myosin thick filaments and actin thin filaments, along with associated structural and regulatory proteins. When the muscle shortens, the myosin molecules in the thick filaments pull the thin filaments towards the center, resulting in contraction. The thin and thick filaments interdigitate, forming complex arrangements within the muscle fiber.
The regeneration process of striated muscles involves three phases: the inflammatory response, the activation, differentiation, and fusion of satellite cells, and the maturation and remodeling of newly formed myofibrils. Skeletal muscle has a better regenerative capacity than cardiac muscle due to the presence of satellite cells, which are dormant in healthy skeletal muscle tissue.
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Striated muscles are made up of repeating functional units called sarcomeres
There are three types of muscle tissue in the human body: smooth, cardiac, and skeletal. Striated muscles are skeletal muscles, which are the most common type of muscle in the body. They are called striated muscles because they have a striped appearance under a microscope. This is due to the regular arrangement of filaments made of two types of protein: actin and myosin. These filaments slide past each other, creating muscle contractions.
Sarcomeres are the structural and functional units of striated muscles, including both skeletal and cardiac muscles. They line up sequentially and are tied together by a complex protein assembly called a Z-disc to form contractible myofibrils. These myofibrils, in turn, are bound in bundles to form cardiomyocytes. The sarcomere consists mainly of myosin thick filaments and actin thin filaments, along with a large number of associated structural and regulatory proteins.
The thin filament is composed of polymerized G-actin subunits and contains the regulatory proteins troponin and tropomyosin, as well as the large protein nebulin. Troponin consists of three subunits: TN-C, a small calmodulin-like calcium-binding protein; TN-I, an inhibitory subunit; and TN-T, a tropomyosin-binding subunit. The thick filament is composed of myosin.
Striated muscles are highly organized tissues that convert chemical energy to physical work. Their primary function is to generate force and contract to support respiration, locomotion, and posture (skeletal muscle) and to pump blood throughout the body (cardiac muscle). Skeletal muscles are under voluntary control, meaning we can control how and when they work. They are responsible for the movement of the limbs and enable essential functions such as chewing, swallowing, and expanding and contracting the chest cavity for inhalation and exhalation.
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Frequently asked questions
Smooth muscles are not striated. These muscles are located in the walls of hollow visceral organs, such as the liver, pancreas, and intestines.
Yes, skeletal muscles are striated. They are also under voluntary control.
Cardiac muscles are striated. They are found in the walls of the heart and contract involuntarily.
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 have a striped appearance under a microscope due to the regular arrangement of filaments made of actin and myosin proteins. Non-striated, or smooth, muscles lack these striations and are typically found in the walls of the gut, where they undergo spontaneous activity.
