Logan Steele
The human body has more than 600 muscles, which are a type of elastic tissue made up of thousands of small muscle fibres. These muscles do everything from pumping blood around the body to helping lift heavy objects. There are three main types of muscle: skeletal, smooth, and cardiac. Skeletal muscles are attached to bones and allow movement, while smooth muscles are involuntary and are located in various internal structures such as the digestive tract, uterus, and blood vessels. Cardiac muscles make up the mass of the heart and are responsible for its rhythmic contractions.
| Characteristics | Values |
|---|---|
| Number of muscles in the human body | More than 600 |
| Muscle tissue types | Three: visceral, cardiac, and skeletal |
| Skeletal muscle tissue percentage of body mass | 30% to 40% |
| Skeletal muscle composition | Thousands of small fibers woven together |
| Muscle movement | Muscles move by shortening their length, pulling on tendons, and moving bones closer to each other |
| Muscle control | Some muscles are controlled consciously, while others work involuntarily |
| Muscle functions | Breathing, speaking, swallowing, digestion, movement, posture, balance, pumping blood, giving birth, and storing/releasing energy |
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What You'll Learn
Types of muscle tissue: skeletal, smooth, and cardiac
The human body has over 600 muscles, which are pieces of soft tissue that help us move, breathe, swallow, and even speak. They also support our organs and help keep our bodies healthy. There are three main types of muscle tissue: skeletal, smooth, and cardiac.
Skeletal muscles are attached to bones and allow movement. They are also known as striated muscles because they look striped under a microscope. They are under our conscious control and are therefore also called voluntary muscles. The brain, nerves, and skeletal muscles work together to cause movement, and this is collectively known as the neuromuscular system. Skeletal muscles are the most common type of muscle in the human body.
Smooth muscles are located in various internal structures, including the digestive tract, uterus, blood vessels, and the walls of hollow visceral organs such as the liver, pancreas, and intestines. They are arranged in layered sheets that contract in waves along the length of the structure. Smooth muscles are involuntary, meaning they contract without our conscious awareness. They help with functions like focusing our eyes, moving food through our bodies, and going to the bathroom.
Cardiac muscle makes up the mass of the heart and is responsible for its rhythmic contractions. It is also an involuntary type of muscle and appears striped under a microscope. The heart is the only organ that is also a muscle and the only place in the body with cardiac tissue.
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Voluntary vs involuntary muscles
The human body has two main types of muscles: voluntary and involuntary. Voluntary muscles, such as those in your arms and legs, are under conscious control, allowing you to move and perform actions. They are also known as skeletal muscles, as they are attached to bones and respond to nerve signals from the brain that lead to muscle contraction. These muscles are typically striated, meaning they have a striped appearance under a microscope, and they fatigue easily.
Voluntary muscles exhibit rapid contraction and relaxation compared to involuntary muscles. However, this also means that they tire quickly and require regular intervals of rest. These muscles are essential for the movement of body parts and locomotion. Some examples of voluntary muscles include the biceps, triceps, quadriceps, diaphragm, pectoral muscles, abdominals, and hamstrings.
Involuntary muscles, on the other hand, work without conscious effort and are also known as smooth muscles. They control essential functions like digestion, heartbeat, and breathing. These muscles are smooth, lacking striations, and can work tirelessly without tiring. Examples include the muscles in the stomach, intestines, heart, blood vessels, urogenital tracts, and respiratory tract.
Involuntary muscles are involved in the movements of internal organs and aid in the passage of fluids and food in the digestive system. The contraction and relaxation of these muscles occur slowly and at regular intervals, allowing them to work continuously without fatiguing. They have less energy requirement and fewer mitochondria compared to voluntary muscles.
The myocardium, or heart muscle, is an exception among involuntary muscles. While it is composed of cardiac muscle cells, it is controlled by both the autonomic nervous system and its own pacemaker cells, causing it to contract automatically and rhythmically.
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Muscle movements
The human body is believed to have over 600 muscles, which help us move, breathe, swallow, and stay alive. These muscles are made of thousands of small fibres woven together, and they work by either contracting or relaxing to cause movement. This movement may be voluntary, or done without our conscious awareness (involuntary).
Voluntary movements are actions that we control. We use our nervous system to control these movements. For example, flicking your thumb to scroll through an article on your phone and sprinting around a track are both voluntary movements.
Involuntary movements happen automatically without us thinking about them. The muscles in and around our organs move involuntarily to keep our bodies working properly. For example, the beating of our heart and the muscles in our chest and back moving our ribs when we breathe are involuntary movements.
Muscles are attached to the bones of the skeletal system and make up roughly half of a person's body weight. Each muscle is a discrete organ constructed of skeletal muscle tissue, blood vessels, tendons, and nerves. There are three types of muscle tissue: visceral, cardiac, and skeletal. Visceral muscle is found inside organs like the stomach, intestines, and blood vessels. Cardiac muscle, or myocardium, makes up the middle layers of the heart and does not exist anywhere else in the body. Skeletal muscle is the specialised tissue that is attached to bones and allows movement.
The brain, nerves, and skeletal muscles work together to cause movement, and this is collectively known as the neuromuscular system. A typical muscle is serviced by anywhere between 50 and 200 (or more) branches of specialised nerve cells called motor neurones.
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Muscle injuries
One of the most common muscle injuries is a strain, which occurs when the muscle fibres tear due to excessive tensile forces. Strains are often sports-related, affecting muscles that cross more than one joint, such as the hamstrings and gastrocnemius. However, accidental strains can also occur in everyday life due to repetitive movements, overtraining, or a lack of flexibility and strength. The severity of a strain can vary from mild to severe, with a grade 1 strain involving a few broken fibres, while a grade 3 strain results in a complete tear of the muscle.
Another type of muscle injury is a contusion, which occurs when there is a compressive force to the muscle, typically in contact sports such as football or rugby. Bruising, or haematoma, can also occur due to blunt trauma and can range from minor to more severe, leading to internal bleeding or fractures. Muscle cramps are another common issue, characterised by sudden, involuntary muscle contractions that can be painful.
Treatment for muscle injuries depends on their severity. Most pulled muscles can be treated at home using the RICE method (Rest, Ice, Compression, and Elevation). Severe tears, however, may require medical care or even surgery, especially in the case of a complete muscle tear. Physical therapy is also important in the recovery process, with gentle movement reintroduced after the initial days of rest.
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Muscle anatomy
The human body has over 600 muscles, which make up about 40% of a person's weight. Muscles are responsible for movement, posture, and balance. They perform both voluntary and involuntary movements. Voluntary movements are actions that we consciously control, such as walking or writing, while involuntary movements happen automatically without our conscious thought, such as our heart beating or breathing.
There are three main types of muscle tissue in the human body: skeletal, smooth, and cardiac. Skeletal muscles are attached to bones by tendons and allow us to move. They are the only voluntary muscle tissue in the human body. Skeletal muscle fibres are striated, multinucleated cells that appear striped under a microscope. They derive their name from the fact that they always connect to the skeleton.
Smooth muscles, on the other hand, are involuntary muscles that line the inside of some organs and are found in the walls of blood vessels, the urinary bladder, intestines, and stomach. They are arranged in layered sheets that contract in waves along the length of the structure. Cardiac muscle, also known as myocardium, makes up the middle layers of the heart and is responsible for its rhythmic contractions. It is an involuntary muscle that squeezes and relaxes to pump blood through the cardiovascular system.
Individual muscle fibres are made up of proteins called myofibrils, which contain a specialized protein called myoglobin that provides the oxygen and energy required for muscle contraction. Each myofibril contains filaments that fold together when signalled to contract, shortening the length of the muscle fibre and, in turn, the entire muscle. The brain, nerves, and skeletal muscles work together to cause movement, collectively known as the neuromuscular system.
Muscles can be categorized into different shapes, including triangular (deltoid muscles of the shoulder) and circular (sphincters surrounding the mouth, pupils, and anus). Muscle disorders can cause weakness, pain, loss of movement, and even paralysis. Common muscle injuries include strains, sprains, cramps, and tendonitis.
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Frequently asked questions
Muscles are a type of elastic tissue made up of thousands, or tens of thousands, of small muscle fibres. They work with bones to help the body move.
The three main types of muscles are skeletal, smooth, and cardiac. Skeletal muscles are attached to bones and are under our conscious control. Smooth muscles are arranged in layered sheets and are found in the digestive tract, uterus, and blood vessels. Cardiac muscles make up the heart and are responsible for its rhythmic contractions.
Muscles help us move, sit up straight, and keep our balance. They also pump blood around our bodies, help us breathe, and move food through our digestive system.
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