Dominic Stone
There are three types of muscle tissue in vertebrates: skeletal, cardiac, and smooth muscle. Skeletal muscles are attached to bones and allow humans to perform a wide range of movements and functions. They make up between 30% and 40% of a person's total body mass. Cardiac muscle is found only in the heart and is responsible for pumping blood throughout the body. Smooth muscle is found within the walls of organs and structures such as the esophagus, stomach, intestines, and blood vessels.
| Characteristics | Values |
|---|---|
| Number of muscles in the human body | 600-700 |
| Percentage of body weight | 30-40% |
| Types | Skeletal, Cardiac, Smooth |
| Skeletal Muscle Characteristics | Voluntary, Striated, 30-40% of body weight, 35% in humans |
| Cardiac Muscle Characteristics | Involuntary, Striated, Found in heart walls |
| Smooth Muscle Characteristics | Involuntary, Non-Striated, Found in organ walls |
| Skeletal Muscle Fiber Types | Type I (Slow-Twitch), Type II (Fast-Twitch) |
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What You'll Learn
Skeletal muscle makes up 30-40% of body mass
Skeletal muscle, also known as striated muscle, is the most common type of muscle in the human body. Skeletal muscles are attached to the bones of the skeletal system and make up about half of a person's body weight. They are under voluntary control, meaning that you decide how and when they move. For example, when you decide to reach for a book on a shelf, you're using the skeletal muscles in your neck, arm, and shoulder.
Skeletal muscles are made of thousands of small fibres that stretch and press together to move your bones and allow you to perform a wide range of movements and functions. Each muscle can contain thousands of fibres, and these fibres usually span the length of the muscle. Skeletal muscles also vary in size, ranging from less than half an inch to just over 3 inches in diameter.
Skeletal muscle mass varies from person to person and is influenced by factors such as height, weight, age, gender, diet, ethnicity, and fitness level. On average, skeletal muscle makes up 30-40% of an individual's total body mass. Males generally have more skeletal muscle mass than females. As people age, they naturally begin to lose muscle mass, a process known as sarcopenia, which can make everyday activities more challenging.
Maintaining muscle mass is crucial for overall health, particularly as people get older. Strong skeletal muscles contribute to improved mobility, balance, and strength, helping to prevent falls and illnesses. Higher muscle mass also increases metabolic rate, which can provide benefits such as burning more calories at rest.
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Cardiac muscle pumps blood through the body
The human body has three types of muscles: skeletal, cardiac, and smooth muscle. Skeletal muscles are voluntary muscles, meaning a person can control how and when they move and work. Cardiac and smooth muscles are involuntary muscles controlled by the autonomic nervous system.
Cardiac muscle, also known as myocardium, makes up the middle layers of the heart. It is the only place in the body where cardiac muscle is found. This muscle is responsible for pumping blood throughout the body. It squeezes and relaxes to pump blood through the cardiovascular system.
The heart is a vital organ that pumps blood through the body. It is the circulatory system's main organ. The heart contains four muscular sections or chambers that briefly hold blood before moving it. Electrical impulses make the heart beat, moving blood through these chambers. The brain and nervous system direct the heart's function.
The heart has four chambers: two on the top (the atria) and two on the bottom (the ventricles), one on each side of the heart. Blood enters the heart and flows to the lungs to gain oxygen and get rid of waste. It then flows back to the heart, which pumps the refreshed blood out through the aorta to nourish the body.
The heart walls are the muscles that contract (squeeze) and relax to send blood throughout the body. A layer of muscular tissue called the septum divides the heart walls into the left and right sides.
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Smooth muscle is an involuntary muscle
Smooth muscle differs from skeletal muscle in several ways, including its ability to be contracted and controlled involuntarily. Skeletal muscles are voluntary muscles that are controlled by the somatic nervous system and are responsible for a wide range of movements and functions. They make up between 30% to 40% of an individual's total body mass.
In contrast, smooth muscle is controlled by the autonomic nervous system and functions without conscious thought. For example, smooth muscle in the urinary system helps rid the body of waste and toxins, and smooth muscle in the respiratory system helps the lungs expand during breathing. Smooth muscle also plays a crucial role in the disease process, and many medical treatments involve modifying the signalling pathways that affect it.
At a cellular level, smooth muscle has a non-striated appearance under a microscope due to the arrangement of its thick and thin filaments. It contains large amounts of actin and myosin, the main proteins involved in muscle contraction. The shape of smooth muscle is fusiform, round in the center, and tapering at each end. It exhibits greater elastic properties compared to striated muscle, which is important in organ systems like the urinary bladder, where contractile tone must be preserved.
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Skeletal muscle is made up of myofibers
Skeletal muscle is one of the three types of vertebrate muscle tissue, the others being cardiac and smooth muscle. Skeletal muscles are attached to bones by tendons and make up about 30% to 40% of an average human's total body mass. They are part of the voluntary muscular system, meaning that their movement is controlled by the somatic nervous system.
The muscle fibers are composed of myofibrils, which are made up of actin and myosin filaments called myofilaments. These myofilaments form units called sarcomeres, which are the basic functional, contractile units of the muscle fiber necessary for muscle contraction. The actin and myosin filaments have specific functions in the contraction process. The actin filaments form a "ladder" along which the myosin filaments "climb" to generate motion. This process is known as the sliding filament theory of muscle contraction.
The sarcomeres also contain other important regulatory proteins such as troponin and tropomyosin, which work together with actin to make muscle contraction possible. When a muscle contracts, the actin is pulled along the myosin towards the center of the sarcomere, causing the two types of filaments to overlap and the muscle to shorten. This sliding action results in the production of movement by the skeletal muscle.
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Skeletal muscles are attached to bones
Skeletal muscles are part of the musculoskeletal system and work with bones, tendons, and ligaments to support body weight and facilitate movement. These muscles are voluntary, meaning that they move when you consciously decide to move that part of your body. They are also known as striated muscles due to their striped appearance. Skeletal muscles are the most common type of muscle in the body, comprising 30% to 40% of total body mass.
There are about 700 named skeletal muscles in the human body, each constructed of skeletal muscle tissue, blood vessels, tendons, and nerves. They are located between the bones of the skeletal system and are responsible for a wide range of movements and functions. Skeletal muscles can be named based on various factors, including their location, origin, insertion, number of origins, shape, size, direction, and function. For example, the tibialis anterior muscle is named after the bone it is attached to, the tibia.
The health of skeletal muscles is crucial, as they play a vital role in everyday activities such as breathing, eating, and moving. Maintaining strong and healthy muscles can be achieved through various means, such as exercise and physical activity. However, it is important to properly stretch and warm up before engaging in strenuous activities to prevent muscle injuries.
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Frequently asked questions
The sternocleidomastoid (SCM) muscle is an S-shaped muscle in the neck. It is the largest muscle in the front of the neck and it allows you to bend your neck and turn or tilt your head.
The trapezius muscle in the posterior neck is large and flat and forms a triangular shape, which could resemble an S-shape. The serratus muscles also have an S-shaped form, with a serrated or saw-like shape.
The SCM muscle helps to stabilise your neck, even when you are not moving. It also works with other neck muscles to lift your breastbone and collarbone when you inhale, creating space for your lungs to take in air. It also supports the temporomandibular joint (TMJ) that connects your jaw to your skull, allowing you to open and close your mouth.
