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Muscles are organs that are essential to the human body. They are made of thousands of small fibres woven together, stretching and pressing together to move our organs and body. There are three types of muscles: skeletal, cardiac and smooth muscle. Skeletal muscles are voluntary muscles that connect to our bones and allow us to perform a wide range of movements and functions. They are also the largest organ in the body. Cardiac muscles are involuntary muscles, like the heart, which beats without our input. Smooth muscles are also involuntary and line the inside of some organs, performing essential jobs like moving waste through our intestines and helping our lungs expand when we breathe.
| Characteristics | Values |
|---|---|
| Definition | An organ is a collection of tissues that work together to perform bodily functions. |
| Muscle as an organ | Skeletal muscles are organs that consist of muscle tissue, blood vessels, lymphatics, tendons, nerves, and the fascia that wraps around and within the organ. |
| Muscle movement | Muscles move your body. They perform voluntary and involuntary movements. |
| Types of muscles | There are three types of muscles in the body: skeletal, cardiac and smooth muscle. |
| Skeletal muscle | Skeletal muscles are the most common type of muscle in the body. They are voluntary muscles and comprise 30% to 40% of your total body mass. |
| Cardiac muscle | Cardiac muscle (myocardium) makes up the middle layers of your heart. It is an involuntary muscle. |
| Smooth muscle | Smooth muscles are involuntary muscles that line the inside of some organs. They play an important role in the female and male reproductive systems, the urinary system, the respiratory system, and the digestive system. |
| Muscle function | Muscles require a constant inpouring of nutrients from the blood and an outpouring of waste products into the lymphatic system. |
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What You'll Learn
Skeletal muscle is the largest organ in the body
Skeletal muscle is the largest organ in the human body. Each skeletal muscle is made up of skeletal muscle tissue, connective tissue, nerve tissue, and blood or vascular tissue. Skeletal muscles vary in size, shape, and arrangement of fibres. They range from very small strands, such as the stapedius muscle in the middle ear, to large masses such as the muscles in the thigh.
Skeletal muscles are characterised by their mechanical activity, which is required for posture, movement, and breathing. This mechanical activity is dependent on muscle fibre contractions. Before a skeletal muscle fibre can contract, it must receive an impulse from a nerve cell. Skeletal muscles are voluntary muscles, meaning they move when you think about moving.
However, skeletal muscle is not just a component of the locomotor system. It has also been identified as a secretory organ. Cytokines and other peptides produced, expressed, and released by muscle fibres are classified as "myokines". The muscle secretome consists of several hundred secreted peptides, which may contribute to the health benefits of exercise. This discovery provides a new way of understanding how muscles communicate with other organs, such as adipose tissue, the liver, the pancreas, bones, and the brain.
Skeletal muscle fibres differ significantly from other tissues in the body due to their highly specialised functions. The sarcolemma, for example, is the cell membrane of muscle fibres and acts as a conductor for electrochemical signals that stimulate muscle cells.
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Skeletal muscle is a secretory organ
A muscle organ is a part of the muscular system, comprising skeletal muscle tissue, connective tissue, nerve tissue, and blood or vascular tissue. Skeletal muscles are the most common type of muscle in the body, accounting for 30% to 40% of total body mass. They are also the largest organ in the body. These muscles are attached to bones by tendons and work with them, along with ligaments, to support body weight and enable movement.
Skeletal muscles are voluntary muscles, meaning an individual can control how and when they move and work. They are characterised by their mechanical activity, which includes posture, movement, and breathing, all of which depend on muscle fibre contractions. These muscles have an abundant supply of blood vessels and nerves, which is directly related to their primary function of contraction. Before a skeletal muscle fibre can contract, it must receive an impulse from a nerve cell.
Skeletal muscle has been identified as a secretory organ, producing, expressing, and releasing several hundred secreted peptides, known as myokines. This discovery has led to a new understanding of how skeletal muscles communicate with other organs, such as adipose tissue, liver, pancreas, bones, and the brain. Myokines are believed to mediate the health benefits of exercise, as many proteins produced by skeletal muscle are dependent on contraction.
The muscle secretome, or the collection of secreted peptides, includes cytokines and other peptides that exert autocrine, paracrine, or endocrine effects. Some myokines, such as myostatin, LIF, IL-6, and IL-7, have effects within the muscle itself, contributing to muscle hypertrophy and myogenesis. IL-6 also has systemic effects on the liver, adipose tissue, and the immune system, and mediates crosstalk between intestinal L cells and pancreatic islets.
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Skeletal muscle is a movement organ
Skeletal muscles are voluntary muscles, meaning they move when you think about moving that part of your body. They are under conscious control, receiving neural inputs that allow for the conscious control of muscles. Skeletal muscles work in groups to produce precise movements. The muscle that produces any particular movement of the body is known as an agonist or prime mover. The agonist always pairs with an antagonist muscle that produces the opposite effect on the same bones. For example, the biceps brachii muscle flexes the arm at the elbow, and the triceps brachii muscle extends the arm at the elbow.
Skeletal muscles vary considerably in size, shape, and arrangement of fibers. They range from extremely tiny strands such as the stapedium muscle of the middle ear to large masses such as the muscles of the thigh. Some skeletal muscles are broad in shape, while others are narrow. Each skeletal muscle fiber is a single cylindrical muscle cell, and an individual skeletal muscle may be made up of hundreds or even thousands of muscle fibers bundled together and wrapped in a connective tissue covering.
The outermost connective tissue sheath surrounding the entire muscle is known as the epimysium. Portions of the epimysium project inward to divide the muscle into compartments, and each compartment contains a bundle of muscle fibers called a fasciculus. The connective tissue covering provides support and protection for the delicate cells and allows them to withstand the forces of contraction. It also provides pathways for the passage of blood vessels and nerves.
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Smooth muscle is an involuntary organ
A muscle is a tissue made up of thousands of small fibres woven together. These fibres are what allow us to move our organs and body. There are three types of muscle tissue: skeletal, smooth, and cardiac.
Skeletal muscles are voluntary muscles that support our weight and move us. They work with our bones, tendons, and ligaments. Skeletal muscles are also the largest organ in the body.
Smooth muscle, on the other hand, is an involuntary organ. It lines the inside of some organs and performs essential functions like moving waste through our intestines and helping our lungs expand when we breathe. Smooth muscle is present throughout the body, serving a variety of functions. It is found in the stomach and intestines, where it helps with digestion and nutrient collection. It is also present in the urinary system, where it helps to rid the body of toxins and maintain electrolyte balance. Smooth muscle is also found in arteries and veins, where it plays a vital role in regulating blood pressure and tissue oxygenation.
The nervous system can use smooth muscle to regulate many of the body's subsystems without any conscious thought from the individual. For example, the body can adapt to increasing oxygen demands from exercise without a person needing to think about it. The nervous system uses hormones, neurotransmitters, and other receptors to control smooth muscle spontaneously. Smooth muscle also plays an important role in the disease process throughout the body. For example, the use of bronchodilators to relax airway smooth muscle is a life-saving treatment for asthmatics.
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Cardiac muscle is a special type of organ tissue
A muscle is a tissue that moves our body and organs. There are three types of muscle tissue in the body: skeletal, smooth, and cardiac. The cardiac muscle is a special type of organ tissue that exists only in the heart. It is also called heart muscle or myocardium. The cardiac muscle forms a thick middle layer between the outer layer of the heart wall (the pericardium) and the inner layer (the endocardium). The endocardium is not cardiac muscle and is comprised of simple squamous epithelial cells and forms the inner lining of the heart chambers and valves. The pericardium, on the other hand, is a fibrous sac surrounding the heart. The cardiac muscle constitutes the main tissue of the wall of the heart and forms both the atria and the ventricles of the heart.
The cardiac muscle is composed of individual cardiac muscle cells or cardiomyocytes, joined by intercalated discs and encased by collagen fibres and other substances that form the extracellular matrix. The extracellular matrix (ECM) surrounds the cardiomyocyte and fibroblasts. The ECM is composed of proteins including collagen and elastin along with polysaccharides (sugar chains) known as glycosaminoglycans. Together, these substances give support and strength to the muscle cells, create elasticity in cardiac muscle, and keep the muscle cells hydrated by binding water molecules. The cardiac muscle cells contain mitochondria, which many people call the powerhouses of the cells. These are organelles that convert oxygen and glucose into energy in the form of adenosine triphosphate (ATP).
The cardiac muscle is under involuntary control, which means that it contracts and expands automatically in response to electrical impulses from the nervous system. These cardiac cells work together to produce the rhythmic, wave-like contractions known as the heartbeat. The cardiac muscle must contract with enough force and blood to supply the metabolic demands of the entire body. Regular aerobic exercise can help strengthen cardiac muscle tissue and lower the risk of heart attack, stroke, and other cardiovascular conditions.
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Frequently asked questions
A muscle organ is a collection of tissues that work together to perform bodily functions. Skeletal muscles, for example, consist of muscle tissue, blood vessels, lymphatics, tendons, nerves, and fascia, which wraps around and within the organ.
There are three types of muscle organs in the human body: skeletal, cardiac and smooth muscle. Skeletal muscles are voluntary muscles that you can control, whereas cardiac and smooth muscles are involuntary.
Muscle organs are responsible for movement and supporting the body. They also play a role in protecting vital organs, maintaining posture and balance, and ensuring healthy circulation.
Muscle organs require a constant supply of nutrients from the blood and the removal of waste products into the lymphatic system. This flow of blood and lymph is maintained through movement, which helps to keep the muscle organ functioning properly.
