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The human body has more than 600 muscles, which are soft tissues that enable movement. There are three types of muscle tissue in vertebrates: skeletal, smooth, and cardiac. Skeletal muscles are voluntary muscles that help with movement, posture, and balance. They make up between 30% and 40% of a person's body weight. Smooth muscles, on the other hand, are involuntary and line the inside of some organs, aiding in vital functions such as digestion and respiration. Cardiac muscle, also known as myocardium, is responsible for the rhythmic contractions of the heart, pumping blood throughout the body.
| Characteristics | Values |
|---|---|
| Number of muscles in the human body | 600-700 |
| Muscle composition | Thousands of small fibers woven together |
| Types of muscles | Skeletal, Cardiac, Smooth |
| Skeletal muscle composition | Skeletal muscle tissue, blood vessels, tendons, nerves |
| Skeletal muscle function | Allows movement, chewing, swallowing, breathing, maintaining posture |
| Skeletal muscle mass in men | 42% of total body mass |
| Skeletal muscle mass in women | 36% of total body mass |
| Types of skeletal muscle | Type I (slow-twitch), Type II (fast-twitch) |
| Cardiac muscle function | Pumps blood throughout the body |
| Smooth muscle function | Moves waste through intestines, helps lungs expand during breathing, moves substances through organs |
| Smooth muscle location | Walls of organs and structures like esophagus, stomach, intestines, bladder, blood vessels |
| Muscle injuries | Strains, pulls, tears |
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What You'll Learn
- Skeletal muscles are voluntary muscles that support your weight and movement
- Cardiac muscles are involuntary and make up the middle layers of the heart
- Smooth muscles are involuntary and line the inside of organs
- Visceral muscles are smooth muscles that contract organs to move substances
- Skeletal muscles are made up of two fibre types: slow-twitch and fast-twitch
Skeletal muscles are voluntary muscles that support your weight and movement
Skeletal muscles are one of the three types of muscles in the body, the others being cardiac and smooth muscle. They are part of the voluntary muscular system, which means that they are controlled consciously. Skeletal muscles are attached to the bones of the skeletal system by tendons, and they allow the body to perform a wide range of movements and functions.
Skeletal muscles are located throughout the body and are responsible for producing movement, sustaining body posture and position, maintaining body temperature, storing nutrients, and stabilizing joints. They are composed of flexible muscle fibres that range from less than half an inch to just over 3 inches in diameter. Each muscle can contain thousands of fibres, and these fibres contract to allow the muscles to move bones.
Skeletal muscles are also known as striated muscles because they have a striped appearance due to the arrangement of sarcomeres. The tissue of a skeletal muscle is composed of bundles of muscle fibres called myofibers, which contain several myofibrils. These myofibrils are made up of actin and myosin filaments, which are necessary for muscle contraction.
The functions of skeletal muscles are powered by the oxidation of fats and carbohydrates, but anaerobic chemical reactions are also used, particularly by fast-twitch fibres. These chemical reactions produce adenosine triphosphate (ATP) molecules, which are used to power the movement of the myosin heads. Skeletal muscles comprise about 35% of the body weight of humans, and they are essential for supporting the body's weight and enabling movement.
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Cardiac muscles are involuntary and make up the middle layers of the heart
The human body has more than 600 muscles, which can be categorised into three types: skeletal, smooth, and cardiac. Cardiac muscles, also known as myocardium, are involuntary muscles that make up the middle layers of the heart. They are responsible for pumping blood throughout the body.
Cardiac muscles are one of the three types of muscle tissues in the body, the other two being visceral (or smooth) and skeletal. Skeletal muscles are voluntary muscles that work with bones, tendons, and ligaments to support body weight and facilitate movement. They are controlled by the somatic nervous system. On the other hand, cardiac and smooth muscles are involuntary muscles controlled by the autonomic nervous system.
Cardiac muscles are unique to the heart and are not found anywhere else in the body. They contract and relax to pump blood through the circulatory system. The heart itself is made up of three layers: the pericardium, myocardium, and endocardium. The myocardium, or cardiac muscle, forms the thick middle layer. The endocardium, the innermost layer, is not a cardiac muscle but is composed of simple squamous epithelial cells that form the inner lining of the heart chambers and valves. The pericardium, the outermost layer, is a fibrous sac surrounding the heart.
Cardiac muscle cells, or cardiomyocytes, are tubular structures composed of chains of myofibrils. These myofibrils consist of repeating sections of sarcomeres, which are the fundamental contractile units of muscle cells. The contractile forces of the cardiac muscle, along with the frequency of their activation, determine the cardiac output, which is defined as heart rate multiplied by stroke volume. The rapid, involuntary contraction and relaxation of cardiac muscles are crucial for pumping blood throughout the body.
In conclusion, cardiac muscles are involuntary muscles that make up the middle layers of the heart. They play a vital role in pumping blood through the circulatory system, ensuring the body receives the oxygenated blood it needs to function.
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Smooth muscles are involuntary and line the inside of organs
The human body is made up of about 700 named muscles, which account for roughly half of a person's body weight. There are three types of muscles in the body: skeletal, smooth, and cardiac. Skeletal muscles are voluntary muscles that connect to bones and allow for a wide range of movements and functions. They are controlled by the somatic nervous system. Cardiac muscles, on the other hand, are involuntary and constitute the middle layers of the heart, responsible for pumping blood throughout the body.
Smooth muscles are also involuntary and line the inside of some organs. They are composed of thick and thin filaments that give them a non-striated pattern. Smooth muscle cytoplasm contains a large amount of actin and myosin, which are the main proteins involved in muscle contraction. The actin filaments attach to dense bodies spread throughout the cell, and these can be observed as dark patches under an electron microscope. Another important structure is the calcium-containing sarcoplasmic reticulum, which aids in sustaining contraction. Smooth muscles have greater elastic properties than striated muscles, which is important in organ systems like the urinary bladder, where contractile tone must be preserved.
Smooth muscles play an important role in many body subsystems, including the female and male reproductive systems, the urinary system, the respiratory system, and the digestive system. They help with essential tasks such as moving waste through the intestines and facilitating lung expansion during breathing. Smooth muscles are also involved in the regulation of blood flow and pressure by controlling the diameter of blood vessels.
The term "smooth muscle" is often used interchangeably with "visceral muscle" to describe the muscle tissue associated with internal organs, especially those in the abdominal cavity. Smooth muscles are controlled by the autonomic nervous system, which uses hormones, neurotransmitters, and other receptors to regulate their contraction and relaxation.
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Visceral muscles are smooth muscles that contract organs to move substances
The human body is made up of about 700 named muscles, accounting for roughly half of a person's body weight. There are three types of muscle tissue: visceral, cardiac, and skeletal. Visceral muscles, also known as smooth muscles, are the weakest of all muscle tissues and are found inside organs like the stomach, intestines, and blood vessels. They are called smooth muscles because, unlike skeletal muscles, they do not have the band-like appearance of skeletal or cardiac muscles when viewed under a microscope. Instead, they have a very smooth and uniform appearance.
Smooth muscles are involuntary muscles, meaning they work without conscious thought. They are controlled by the unconscious part of the brain and cannot be directly controlled by the conscious mind. These muscles line the inside of some organs and perform essential functions such as moving waste through the intestines and helping the lungs expand during breathing. They also play a role in the female and male reproductive systems, the urinary system, and the digestive system.
The function of smooth muscles in organs is to contract and move substances through the organ. A single unit of smooth muscle produces a slow and steady contraction, allowing food and other substances from the digestive tract to pass through the body. Smooth muscles work in a spiral corkscrew fashion, with actin and myosin proteins generating tension and causing contraction. This is important in organ systems like the urinary bladder, where contractile tone must be preserved.
Smooth muscles are an integral part of the human body and are found in almost every organ system. In the cardiovascular system, they help maintain blood pressure and flow, while in the lungs, they open and close airways. In the gastrointestinal tract, they aid in motility and nutrition collection. Smooth muscles also serve a purpose in the reproductive system and are involved in the propulsion of the food bolus.
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Skeletal muscles are made up of two fibre types: slow-twitch and fast-twitch
Skeletal muscles are a vital part of the musculoskeletal system, comprising 30% to 40% of the human body's total mass. They are attached to bones and allow for a wide range of movements and functions. Skeletal muscles are made up of thousands of small fibres that stretch and press together to enable movement. These fibres are classified into two types: slow-twitch and fast-twitch.
Slow-twitch muscle fibres move slowly but provide endurance and long-lasting energy. They are used for low-intensity activities that require a steady, even supply of energy. These fibres are found in muscles that need to perform the same job for extended periods, such as those in the lower legs and back, which help with posture and stability. Slow-twitch fibres have a rich capillary supply, numerous mitochondria, and aerobic respiratory enzymes, as well as a high concentration of myoglobin, which enhances oxygen delivery. This abundance of oxygen and blood supply allows slow-twitch fibres to work for long periods without fatiguing.
On the other hand, fast-twitch muscle fibres provide sudden bursts of energy, but they fatigue quickly. They are used for high-intensity activities that require rapid and powerful movements. Fast-twitch fibres contract quickly and use a lot of energy in a short period. Unlike slow-twitch fibres, they do not rely heavily on oxygen and blood supply. Instead, they utilise an anaerobic energy system, making their own quick source of energy.
The ratio of slow-twitch to fast-twitch fibres varies between individuals and is determined by genetics. Those who excel at endurance sports tend to have a higher proportion of slow-twitch fibres, while sprinters and jumpers benefit from a greater number of fast-twitch fibres.
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