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The human body has more than 600 muscles, which are made of the same elastic tissue material, with each muscle consisting of thousands of small fibres. They come in all shapes and sizes, from the delta or triangular shape of the deltoids to the diamond shape of the rhomboid major. Some muscles are visible and can be felt, especially after a workout, while others, like the heart, are internal and work to keep us alive. Skeletal muscles are voluntary and move when we think about moving, while smooth muscles are involuntary and cannot be controlled consciously.
| Characteristics | Values |
|---|---|
| Number of muscles in the human body | More than 600 |
| Muscle composition | Pieces of soft tissue |
| Muscle function | Help with movement, breathing, swallowing, and staying alive |
| Types of muscles | Skeletal, cardiac, and smooth |
| Skeletal muscle composition | Skeletal muscle tissue, connective tissue, nerve tissue, and blood or vascular tissue |
| Skeletal muscle characteristics | Voluntary, attached to bones, and make up 30-40% of body mass |
| Cardiac muscle characteristics | Involuntary, exist only in the heart, and are striated |
| Smooth muscle characteristics | Involuntary, exist in organs, blood vessels, digestive tract, skin, and other areas |
| Muscle shape | Vary from delta or triangular to diamond or cylindrical |
| Muscle appearance | Striated or smooth |
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What You'll Learn
- Skeletal muscles are voluntary and striated, or striped
- Cardiac muscles are involuntary and only found in the heart
- Smooth muscles are involuntary and found in organs, blood vessels, and the digestive tract
- Visceral muscles are the weakest of all muscle tissues and are found in the stomach, intestines, and blood vessels
- Facial muscles attach under the skin, allowing for a wide range of expressions
Skeletal muscles are voluntary and striated, or striped
The human body has over 600 muscles, which are pieces of soft tissue that help us move, breathe, swallow and stay alive. Skeletal muscles, which connect to the bones, comprise 30 to 40% of our total body mass. They are voluntary muscles, meaning that we control how and when they move and work. For instance, when you reach for a book on a shelf, you are using the skeletal muscles in your neck, arm and shoulder.
Skeletal muscles are also striated, or striped, and are often called striated muscles. They are red and white and are attached to the skeleton. Cardiac muscles are also striated, but smooth muscles are not. Smooth muscles are involuntary and line the inside of some organs like the heart, performing essential jobs like moving waste through the intestines and helping the lungs expand when we breathe.
Skeletal muscles are named based on several factors, including their location, origin and insertion, number of origins, shape, size, direction, and function. For example, the deltoids are delta or triangular in shape, while the serratus muscles have a serrated or saw-like shape. The size of the muscle can also be used to distinguish between two muscles found in the same region. For instance, the gluteal region contains three muscles differentiated by size – the gluteus maximus (large), gluteus medius (medium), and gluteus minimus (smallest).
Skeletal muscles are susceptible to various conditions, such as strains and age-related degeneration. Muscle injuries account for 10 to 55% of all sports injuries, with strains constituting about 90% of these injuries. Tendons, which connect skeletal muscles to bones, can become inflamed due to overuse, causing pain when using these muscles. Maintaining muscle health is essential, and regular strength conditioning, a balanced diet, and warming up before physical activity can help prevent injuries.
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Cardiac muscles are involuntary and only found in the heart
The human body is made up of more than 600 muscles, some of which are visible and some of which are internal and keep our organs functioning. Cardiac muscles, also called the myocardium, are involuntary muscles that are only found in the heart. They make up the middle layers of the heart and are responsible for pumping blood throughout the body.
The heart is made up of three layers—the pericardium, myocardium, and endocardium. The endocardium is not a cardiac muscle and forms the inner lining of the heart chambers and valves. The pericardium is a fibrous sac surrounding the heart. The cardiac muscle is responsible for the contractility of the heart and, therefore, the pumping action. The cardiac muscle must contract with enough force and blood to supply the metabolic demands of the entire body.
The generation of a cardiac action potential is involuntary and proceeds via a process known as excitation-contraction coupling (ECC). Action potentials travel along the sarcolemma and into the t-tubules to depolarize the membrane. The sarcolemma of cardiac muscle cells contains voltage-gated calcium channels, specialized ion channels that skeletal muscle does not possess. This increased intracellular calcium concentration triggers the sarcoplasmic reticulum to release more calcium through the ryanodine receptor, known as calcium-induced calcium release.
Cardiac muscles are striated or striped, and they appear branched under a microscope. They are under involuntary control, meaning they work without conscious input. The autonomic nervous system controls them, and hormones and signals from the brain adjust their rate of contraction.
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Smooth muscles are involuntary and found in organs, blood vessels, and the digestive tract
Muscles are pieces of soft tissue that help the body move, breathe, swallow, and stay alive. There are more than 600 muscles in the human body, and they are constantly being used. Some muscles are visible and can be felt, especially after a workout, while others, like the heart and those lining some organs, work silently in the background.
Smooth muscles are involuntary muscles that are found in the walls of hollow organs, such as the intestines, uterus, and stomach, as well as in the walls of passageways, including arteries and veins of the cardiovascular system. They are also found in the tracts of the urinary, respiratory, and reproductive systems, and even in the skin and eyes. Smooth muscles are derived from both mesoderm and neural crest cells, with the latter playing a crucial role in their development during embryological development.
The shape of smooth muscle is fusiform, round in the center, and tapering at each end. They can tense and relax, and their elastic properties are greater than those of striated muscles. This quality is essential in organ systems like the urinary bladder, where maintaining contractile tone is vital. Smooth muscles are controlled by the unconscious part of the brain and are often referred to as visceral muscles. They have a smooth, uniform appearance when viewed under a microscope, in contrast to the banded appearance of skeletal and cardiac muscles.
Smooth muscles serve a variety of functions in the body. They aid in digestion and nutrient collection in the stomach and intestines, help regulate blood pressure and tissue oxygenation in arteries and veins, and contribute to the regulation of blood flow and vessel stability. They also play a role in the female and male reproductive systems and the urinary system.
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Visceral muscles are the weakest of all muscle tissues and are found in the stomach, intestines, and blood vessels
The human body is made up of over 600 muscles, which are pieces of soft tissue that help us move, breathe, swallow, and stay alive. These muscles can be skeletal, cardiac, or visceral.
Skeletal muscles are voluntary, meaning they move when you consciously decide to move a part of your body. They are attached to bones and have a striated appearance. Cardiac muscles, on the other hand, are found in the walls of the heart and are responsible for pumping blood throughout the body. They are involuntary, meaning they contract and relax on their own without conscious input.
Visceral muscles, also known as smooth muscles, are the weakest of all muscle tissues. They are found inside organs like the stomach, intestines, and blood vessels. These muscles are involuntary and are controlled by the unconscious part of the brain. They contract to move substances through the organs, such as food through the digestive tract. Smooth muscles get their name from their uniform, banded appearance when viewed under a microscope, which contrasts with the striated appearance of skeletal and cardiac muscles.
The main function of the muscular system is movement, and visceral muscles play a crucial role in this process by aiding in the movement of substances inside the body. While they may be the weakest in terms of tissue strength, they are essential for transporting nutrients and waste products through our organs.
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Facial muscles attach under the skin, allowing for a wide range of expressions
The human body is made up of more than 600 muscles, which are pieces of soft tissue that help us move, breathe, swallow and
Facial muscles are positioned around facial openings such as the mouth, eyes, nose and ears, or stretch across the skull and neck. They are categorised into several groups, with the specific location and attachments of the facial muscles enabling them to produce movements of the face, such as smiling, grinning and frowning. The corrugator supercilii, for example, pulls the eyebrows together and produces vertical wrinkles over the glabella, creating a facial expression of frowning.
The orbicularis oculi sphincter muscles close the eyes, depress the brows, and produce "crow's feet" wrinkles at the eyes' corners. The procerus is a superficial midline muscle that causes horizontal rhytides at the nasal root. The frontalis, connected to the occipitalis via the galea aponeurotica, raises the eyebrows and produces transverse forehead rhytides. The orbicularis oris produces movements of the lips, such as lip pouting, puckering, and twisting, which facilitate speech and help produce various facial expressions.
The facial muscles are derived from the second branchial/pharyngeal arch and typically begin forming around the eighth week of embryonic development. An inability to form facial expressions on one side of the face may be the first sign of damage to the nerve of these muscles, which can occur with a stroke, Bell palsy, or parotid salivary gland cancer.
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Frequently asked questions
Muscles are pieces of soft tissue that help your body move, breathe, swallow and stay alive. They have the ability to bend, stretch and relax. They also vary in size, shape and arrangement of fibres. Some muscles are visible and can be felt, especially after a workout.
Skeletal muscles are attached to bones and are visible. They make up 30-40% of your total body mass. Examples include the shoulder muscles, hamstring muscles and abdominal muscles. The tongue is also made up of a group of muscles.
Skeletal muscles are striated or striped. They are also named based on their location, origin and insertion, number of origins, shape, size, direction and function. For example, the deltoids are delta or triangular in shape, while the serratus muscles have a serrated or saw-like shape.
Smooth muscles line your organs, blood vessels, digestive tract, skin and other areas. They are involuntary and cannot be controlled consciously. Smooth muscles have a very smooth, uniform appearance when viewed under a microscope. Cardiac muscles, found only in the heart, are also striated and involuntary.
