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Muscles are pieces of soft tissue that help your body move, breathe, swallow, and stay alive. There are over 600 muscles in the human body, and they make up over 40% of your body weight. They are made of thousands of small elastic fibres, woven together like a quilt, that contract and relax to cause movement. The three main types of muscle tissue are skeletal, smooth, and cardiac. Skeletal muscles help with movement and are controlled by the brain. Smooth muscles are located in various internal structures, such as the digestive tract, and contract involuntarily. Cardiac muscles are found in the heart and are also involuntary.
| Characteristics | Values |
|---|---|
| Number of muscles in the human body | Over 600 |
| Number of named skeletal muscles | Over 650 |
| Number of muscles used to smile | 17 |
| Number of muscles used to frown | 43 |
| Smallest muscle | Stapedius in the ear |
| Material | Elastic tissue |
| Types | Skeletal, smooth, and cardiac |
| Skeletal muscle structure | Striated, or striped |
| Skeletal muscle control | Voluntary |
| Smooth muscle control | Involuntary |
| Smooth muscle shape | Rounded at the centre and tapered at the sides |
| Smooth muscle location | Stomach, digestive system, blood vessels, bladder, airways, uterus, eyes, heart, etc. |
| Cardiac muscle location | Heart |
| Cardiac muscle structure | Striated |
| Cardiac muscle control | Involuntary |
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What You'll Learn
Muscle types: skeletal, smooth, cardiac
The human body has over 600 muscles that work to pump blood throughout the body and help with lifting heavy objects. There are three types of muscles: skeletal, cardiac, and smooth.
Skeletal muscles are the most common type of muscle in the human body. They are also called striated muscles because they have a striped appearance. These muscles are attached to the bones and help with a wide range of movements and functions. They make up around 30% to 40% of the total body mass. Skeletal muscles are voluntary, meaning you can control how and when they move. They are also a vital part of the musculoskeletal system, working with the bones to give the body strength and power.
Cardiac muscle, also called myocardium, is the muscle that makes up the heart. It is responsible for the contractility of the heart and the pumping action that propels blood into circulation. The cardiac muscle must contract with enough force to supply blood to the entire body. Cardiac muscle is under involuntary control, meaning it works without conscious thought.
Smooth muscle is found throughout the body, including the gastrointestinal, reproductive, urinary, vascular, and respiratory systems. It gets its name from its smooth appearance, which is different from skeletal muscle. Smooth muscle works automatically and is under involuntary control. It handles important functions such as blood pressure, circulation, vision, and digestion. Smooth muscles contract and relax to allow food to pass through the digestive system. They are also involved in labour during childbirth, allowing the baby to be pushed out of the mother's body.
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Muscle functions: movement, breathing, digestion
Muscles are pieces of soft tissue that are found throughout the body. They are made up of thousands of small fibres woven together, which stretch and press together to move our organs and body. There are over 600 muscles in the human body, and they are constantly being used, whether consciously or not.
Movement
The muscular system's main function is to allow movement. Muscle movement can be conscious, such as running or jumping, or reflexive, such as withdrawing a hand from a hot surface. Skeletal muscles are voluntary muscles that move when you think about moving. They work with bones, tendons, and ligaments to support your weight and move you. Tendons attach skeletal muscles to bones all over the body. Some skeletal muscles move slowly, like back muscles that help with posture, while others contract quickly and use short bursts of energy, like muscles that control eye movements.
Breathing
Muscles play a vital role in breathing. The diaphragm and external intercostals are the primary inspiratory muscles, while the abdominal muscles, including the rectus abdominis and internal oblique, are accessory expiratory muscles. The accessory muscles are recruited during exercise or when there is a dysfunction in the respiratory system.
Digestion
Muscles also play a crucial role in digestion. The large, hollow organs of the gastrointestinal (GI) tract contain a layer of muscle that enables their walls to move. The muscles contract and relax to push food and liquid through the GI tract, mixing the contents within each organ. In the stomach, muscles mix food and liquid with digestive juices. In the small intestine, muscles push the mixture forward for further digestion and absorption of nutrients into the bloodstream.
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Muscle health: soreness, pain, injury
The human body has over 600 muscles, made of thousands of small fibres woven together like a quilt. These fibres stretching and pressing together is what moves your organs and body. Muscles are pieces of soft tissue that help you move, breathe, swallow, and stay alive. They also help to move and support your organs. For example, your heart is a hard-working muscle that beats thousands of times a day to keep you alive.
Given the large number of muscles in the body, injuries and health conditions affecting them are common. Muscle soreness and pain are normal occurrences, especially after exercise or physical activity. This type of pain is usually temporary and not serious, often improving with rest and
Localized muscle pain or soreness in one spot is typically related to an event, such as an injury or recent stress on that muscle group. Traumatic injuries, including sports injuries and accidents, can cause muscle bruising (contusion) or small tears in the fibres from overuse, requiring time and rest to recover. On the other hand, diffuse or all-over body aches are more likely related to a disease or condition affecting the entire body. Chronic diseases, such as inflammatory and autoimmune disorders, can lead to ongoing and widespread muscle pain. Certain medications can also cause or contribute to muscle pain as a side effect or during withdrawal.
If you are experiencing persistent or severe muscle pain, it is important to seek medical advice. Healthcare providers can classify and diagnose muscle pain, determining whether it is localized or diffuse, and identify any underlying causes. They may recommend treatments such as medications or physical therapy to address specific conditions.
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Muscle structure: fibres, proteins, actin, myosin
The human body is composed of hundreds of muscles, each made up of thousands of small fibres woven together. These fibres are able to stretch and press together, allowing for movement.
Each muscle fibre is composed of several hundred to several thousand myofibrils, which are blocks of proteins. Myofibrils contain a specialised protein called myoglobin, as well as molecules that provide the oxygen and energy required for muscle contraction. Each myofibril contains thin and thick filaments that fold together when signalled to contract. This contraction shortens the length of the muscle fibre, which, in turn, shortens the entire muscle.
The thin filaments are composed of actin, a double-helical structure known as filamentous-actin (F-actin), which is made up of monomeric G-actin units. The thick filaments are composed of myosin protein complexes, which consist of six proteins: two myosin heavy chains and four light chain molecules. The heavy chains have a tail region, a flexible hinge region, and a globular head that contains an actin-binding site and a binding site for ATP, a high-energy molecule. The light chains play a regulatory role at the hinge region, while the heavy chain head region interacts with actin and is the most important factor for generating force.
The sliding filament model of muscle contraction describes the process by which the thin filaments are pulled and slide past the thick filaments within the sarcomeres of the muscle fibres. This results in the shortening of the sarcomeres without any change in filament length. The contraction of skeletal muscle is triggered by nerve impulses, which stimulate the release of calcium ions from the sarcoplasmic reticulum, a specialised network of internal membranes. The increased concentration of calcium ions signals muscle contraction via the action of two accessory proteins bound to the actin filaments: tropomyosin and troponin.
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Muscle groups: chest, leg, back, abs
Muscles are pieces of soft tissue made of thousands of small fibres woven together. They help your body move, breathe, swallow, and stay alive. There are over 600 muscles in the human body, and they can be grouped by their location or the type of movement they perform.
Chest Muscles
The chest includes some of the body's most prominent muscles, which are constantly at work. The pectoralis major is the largest and strongest muscle of the chest, and its main function is to bring the arms closer to the body. Other chest muscles include the pectoralis minor, which assists with shoulder movement, and the serratus anterior, which is known as the "boxer muscle" due to its function of enabling a long and strong reach.
Leg Muscles
Leg muscles allow for big and small movements and support the body's weight. They also help stabilize the body and enable actions such as walking, running, jumping, and flexing and pointing the feet. The upper leg muscles include the quadriceps and hamstrings, while the calf muscles are part of the lower leg muscles.
Back Muscles
Back muscles support the torso, enable movement, and assist with breathing. They are woven layers of groups that run from the neck to just above the hips. Back muscles can be divided into three groups: superficial (extrinsic), intermediate, and intrinsic (deep) back muscles. Superficial muscles include the latissimus dorsi (lats), levator scapulae, rhomboids, and trapezius.
Abdominal Muscles
Abdominal muscles, or abs, are strong bands of muscles lining the walls of the abdomen. There are five main abdominal muscles: pyramidalis, rectus abdominus, external obliques, internal obliques, and transversus abdominis. They help hold organs in place, support the body during movement, and maintain posture.
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Frequently asked questions
Muscles are pieces of soft tissue that help your body move, breathe, swallow, pump blood, and stay alive. They are made of thousands of small elastic fibres woven together, which contract and relax to cause movement.
There are over 600 muscles in the human body, making up over 40% of your body weight.
There are three main types of muscle: skeletal, smooth, and cardiac. Skeletal muscles are attached to bones and allow movement. Smooth muscles are located in various internal structures, including the digestive tract, uterus, and blood vessels. Cardiac muscles are found in the walls of the heart and are involuntary.
