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The human body has more than 600 muscles that help us do everything from breathing and swallowing to running and jumping. Muscles are pieces of soft tissue that are responsible for movement and work with nearly all of the body's systems and functions. There are three types of muscles in the body: skeletal, smooth, and cardiac. Skeletal muscles are voluntary, meaning we control how and when they move. Smooth and cardiac muscles are involuntary and are controlled by the autonomic nervous system.
| Characteristics | Values |
|---|---|
| Number of muscles in the body | More than 600 |
| Types of muscles | Skeletal, cardiac, smooth |
| Skeletal muscle composition | 30% to 40% of total body mass |
| Skeletal muscle control | Voluntary |
| Skeletal muscle function | Contraction in response to a stimulus, producing movement, maintaining posture, stabilising joints, maintaining body temperature, storing nutrients |
| Cardiac muscle function | Pumping blood around the body |
| Cardiac muscle control | Involuntary |
| Smooth muscle function | Moving waste through intestines, helping lungs expand during breathing, playing a role in the female and male reproductive systems, urinary system, respiratory system, digestive system |
| Smooth muscle control | Involuntary |
| Muscle fibre composition | Actin, myosin, support proteins |
| Muscle fibre types | Type I (slow oxidative fibres), Type II (fast oxidative fibres), Type IIX (fast glycolytic fibres) |
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What You'll Learn
Muscles allow for movement
The human body has more than 600 muscles, comprising 30% to 40% of total body mass. These muscles work together to allow for movement, including large, coordinated motions like walking and running, as well as more subtle movements such as facial expressions and eye movements.
Skeletal muscles, the most common type of muscle in the body, are attached to bones and allow for a wide range of movements. They are voluntary, meaning you control how and when they work. For example, when you reach for a book on a shelf, you are using the skeletal muscles in your neck, arm, and shoulder. These muscles also help with maintaining posture and stability. When you lift something heavy, fixator muscles hold your body upright and immobile so that you maintain your balance.
In contrast, cardiac and smooth muscles are involuntary. Cardiac muscle, found only in the heart, pumps blood around the body and stimulates its own contractions to form our heartbeat. Smooth muscles, on the other hand, are found in the blood vessels, gastrointestinal tract, and urinary system. They help with digestion and control the release of urine.
Muscles work in groups to produce precise movements. For example, the biceps brachii muscle flexes the arm at the elbow, while its antagonist, the triceps brachii muscle, extends the arm.
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They help maintain posture
The human body has more than 600 muscles, which help the body perform a wide range of movements and functions. Skeletal muscles, which are under voluntary control, are the most common type of muscle in the body, comprising 30% to 40% of total body mass. These muscles are connected to bones and allow us to perform a wide range of movements and functions, from holding the body still to running a marathon.
Skeletal muscles are essential for maintaining posture and keeping the body in the correct position when sitting or standing. Good posture relies on strong and flexible muscles. Stiff, weak, or tight muscles can contribute to poor posture and misalignment of the body. Over time, bad posture can lead to joint and muscle pain in the shoulders, back, neck, and other areas.
To maintain posture, skeletal muscles work in groups to produce precise movements. For example, when lifting something heavy, fixator muscles in the trunk region help to stabilize the movement by holding the body upright and immobile, allowing for balance. Type I muscle fibres, or slow oxidative fibres, are particularly suited for maintaining posture as they have a low rate of fatigue and are slow-twitch fibres.
In addition to skeletal muscles, the body also has cardiac and smooth muscles, which are involuntary. Cardiac muscle, found only in the heart, pumps blood around the body through rhythmic contractions. Smooth muscles line the inside of some organs and play essential roles in the female and male reproductive systems, the urinary system, the respiratory system, and the digestive system.
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Muscles protect bones and organs
The human body has more than 600 muscles that help us move, breathe, swallow, and stay alive. Muscles are pieces of soft tissue that are present throughout the body. They help us do everything from holding our body still to running a marathon.
Muscles also move and support our organs. The heart is a muscle that beats thousands of times a day to keep us alive. Skeletal muscles, which are attached to bones by tendons, help us generate heat in the body, protect organs, and maintain our posture. They work in pairs, with one muscle lengthening as the other shortens. For example, when the bicep muscle in the front of the upper arm contracts, the tricep muscle in the back of the upper arm lengthens.
The muscular system also maintains normal body temperature. Almost 85% of the heat generated in the body comes from contracting muscles. When body heat falls below optimal levels, skeletal muscles increase their activity to generate heat. Shivering is an example of this mechanism.
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They control heartbeat and breathing
The human body has more than 600 muscles that help with a variety of functions, including breathing and heartbeats. Muscles are pieces of soft tissue that move and support the body and its organs. They are made of thousands of small fibres that stretch and press together to move the organs or the body.
The diaphragm, a dome-shaped sheet of muscle that separates the chest cavity from the abdomen, is the most important muscle used for breathing in (called inhalation or inspiration). The diaphragm is attached to the base of the sternum, the lower parts of the rib cage, and the spine. As the diaphragm contracts, it increases the length and diameter of the chest cavity and thus expands the lungs. The intercostal muscles and neck muscles help move the rib cage and thus assist in breathing. Abdominal muscles are sometimes involved in breathing out. The process of breathing out (called exhalation or expiration) is usually passive when a person is not exercising. However, during vigorous exercise, a number of muscles participate in exhalation. The abdominal muscles are the most important of these. Abdominal muscles contract, raise abdominal pressure, and push a relaxed diaphragm against the lungs, causing air to be pushed out.
The heart is a hardworking muscle that beats thousands of times a day to keep us alive. Cardiac muscle (myocardium) makes up the middle layers of the heart. It doesn't exist anywhere else in the body. It squeezes and relaxes to pump blood through the cardiovascular system. The heart is an involuntary muscle, meaning it beats on its own without any external input. The heart's pumping action is regulated by an electrical conduction system that coordinates the contraction of the various chambers of the heart. An electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node). This is a small mass of specialized tissue located in the right upper chamber (atria) of the heart. The sinus node generates an electrical stimulus regularly, 60 to 100 times per minute under normal conditions.
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Muscles aid in digestion
The human body has more than 600 muscles that help us move, breathe, swallow, and stay alive. The muscular system's main function is to enable movement, but muscles also play a role in all other functions of the body, including digestion.
The digestive system consists of the gastrointestinal tract, which begins at the mouth and ends at the anus, as well as accessory organs and glands. Food enters the tract at the mouth, where the muscles of the jaw and tongue break it into pieces. The tongue then pushes the food into the throat, and the muscles of the throat move it down the oesophagus.
Once food reaches the end of the oesophagus, a ring-like muscle called the lower oesophageal sphincter relaxes to let food pass into the stomach. The stomach muscles then churn the food to break it into smaller pieces and mix it with digestive juices. The pyloric sphincter regulates the movement of food from the stomach into the small intestine, where the muscles mix the food with digestive juices from the pancreas, liver, and intestine, and push the mixture forward for further digestion.
The large, hollow organs of the gastrointestinal tract contain a layer of muscle that enables their walls to move. The muscle behind the food contracts and squeezes the food forward, while the muscle in front of the food relaxes to allow it to move through. This process is called peristalsis and it helps to move food and liquid through the gastrointestinal tract.
The muscular system, therefore, plays a crucial role in the digestive process, from the mechanical breakdown of food in the mouth to the movement of food through the gastrointestinal tract.
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Frequently asked questions
Muscles are pieces of soft tissue that help your body perform a variety of functions, from holding your body still to running a marathon. There are over 600 muscles in the human body.
There are three types of muscles in the human body: skeletal, smooth, and cardiac. Skeletal muscles are voluntary muscles that you control consciously. They make up 30-40% of your body mass and are attached to bones, allowing you to perform a wide range of movements. Smooth and cardiac muscles are involuntary. Smooth muscles line the inside of some organs and perform essential functions like moving waste through your intestines. Cardiac muscle is only found in the heart, where it pumps blood through your body.
Skeletal muscles help with posture and body positioning, maintaining body temperature, storing nutrients, and stabilizing joints. They also assist in producing a wide range of movements, from large, coordinated motions to fine movements like flexing your wrist or fingers.
The heart muscle, or cardiac muscle, is responsible for pumping blood throughout your body. It contracts and relaxes rhythmically to form your heartbeat, and it does so involuntarily without any conscious input.
