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Muscles are groups of muscle tissues that contract together to produce a force, allowing for movement and the performance of various bodily functions. The human muscle system is divided into three types of muscle: striated or skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscles are attached to bones by tendons and are responsible for movement, posture, and balance. Smooth muscles, found in organs, are controlled by the unconscious part of the brain and facilitate body functions such as digestion. Cardiac muscle, found only in the heart, is responsible for pumping blood throughout the body and is also an involuntary muscle.
| Characteristics | Values |
|---|---|
| Definition | A muscle is a group of muscle tissues that contract together to produce a force. |
| Types | Striated muscle, smooth muscle, and cardiac muscle. |
| Function | Muscles allow us to move. They also help with posture and balance. |
| Structure | Each skeletal muscle fiber is a single cylindrical muscle cell. An individual skeletal muscle may be made up of hundreds or thousands of muscle fibers bundled together and wrapped in a connective tissue covering. |
| Contraction | Muscles contract when they receive a signal from the brain along a bundle of nerves. This signal triggers the release of acetylcholine, which tells the muscle fiber to contract. |
| Blood Supply | Skeletal muscles have an abundant supply of blood vessels and nerves. |
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Muscle structure
A muscle is a group of muscle tissues that contract and produce force or motion. The human muscle system is divided into three types of muscles: striated or skeletal muscle, smooth muscle, and cardiac muscle. Skeletal muscles are attached to bones by tendons and are responsible for movement, posture, and balance. They are named based on various factors, including location, origin, insertion, shape, and size. The origin is the stationary point of attachment, while the insertion is the moving point of attachment. The belly of the muscle is the fleshy part that contracts. Each skeletal muscle fiber is a single cylindrical muscle cell, and these cells are bundled together and wrapped in a connective tissue covering called the epimysium. The epimysium is surrounded by fascia, another type of connective tissue that separates the muscles.
Portions of the epimysium project inward to divide the muscle into compartments, each containing a bundle of muscle fibers called a fasciculus. The fasciculus is surrounded by the perimysium, a layer of connective tissue that allows nerves and blood to flow to the individual fibers. Each fiber is then wrapped in an endomysium, another protective layer of connective tissue. The epimysium, perimysium, and endomysium extend beyond the belly of the muscle to form a tendon or aponeurosis, which attaches the muscle to bones or other muscles. Skeletal muscles have a rich supply of blood vessels and nerves, which is essential for their primary function of contraction.
Smooth muscle, also known as visceral muscle, is found in organs and is responsible for moving substances through them. It is controlled by the unconscious part of the brain and is, therefore, an involuntary muscle. Smooth muscle has a uniform, banded appearance under a microscope. Cardiac muscle, on the other hand, is found only in the heart and is responsible for pumping blood throughout the body. It is also an involuntary muscle, as it cannot be consciously controlled. Cardiac muscle cells are branched X or Y-shaped cells that are tightly connected by intercalated discs, allowing them to withstand high blood pressures and the strain of pumping blood.
The structure of skeletal muscles varies, with some being broad and others narrow. The muscle fibers may be parallel to the long axis of the muscle or converge to a narrow attachment. When a signal is sent to a muscle or group of muscles, they contract, resulting in movement or force. This signal originates in the brain and travels along a bundle of nerves, releasing a chemical signal that tells the muscle fibers to contract. The contraction of muscles allows for various movements, such as rotating the head or bending the neck.
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Types of muscle
The human body has over 600 muscles, which can be broadly divided into three types: skeletal, smooth, and cardiac.
Skeletal Muscle
Skeletal muscles are attached to the bones by tendons and are responsible for movement, posture, and balance. They are also called striated muscles because they appear striped or banded when viewed under a microscope. Skeletal muscles are under voluntary control, meaning that their movement is consciously controlled by the brain. These muscles have an abundant supply of blood vessels and nerves. Skeletal muscles can be broad or narrow in shape, and each muscle is made up of hundreds or thousands of muscle fibres bundled together and wrapped in a connective tissue covering called the epimysium.
Smooth Muscle
Smooth muscle tissue lines some of the body's organs, especially the hollow visceral organs like the liver, pancreas, and intestines. It is also located in various internal structures, including the digestive tract, uterus, and blood vessels. Smooth muscle is often used to describe visceral muscle because it has a very smooth, uniform appearance when viewed under a microscope. Smooth muscle is under involuntary control, meaning its movement happens without conscious awareness.
Cardiac Muscle
Cardiac muscle tissue is found only in the heart and is responsible for pumping blood throughout the body. It is also called myocardium as it makes up the middle layers of the heart. Cardiac muscle is considered autorhythmic or intrinsically controlled because it stimulates itself to contract. The cells of cardiac muscle tissue are striated, appearing with light and dark stripes due to the arrangement of protein fibres inside the cells. These striations indicate that a muscle cell is very strong. Cardiac muscle is under involuntary control, meaning its movement is not consciously controlled by the brain.
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Function of muscle
The human body has more than 600 muscles that help us do everything, from moving and breathing to giving birth and staying alive. Muscles are pieces of soft tissue made up of thousands of small fibres woven together. These fibres stretching and pressing together is what moves our organs and bodies.
The muscular system consists of various types of muscle that each play a crucial role in the body's function. The main function of the muscular system is to enable movement. When muscles contract, they contribute to gross and fine movement. Gross movement refers to large, coordinated motions. The muscular system is also responsible for maintaining body temperature, as well as stability, posture, and circulation.
There are three types of muscle tissue in the human body: skeletal, smooth, and cardiac. Skeletal muscles are voluntary muscles that are attached to bones by tendons. They are the only muscles that can be consciously controlled. Skeletal muscles have an abundant supply of blood vessels and nerves. Before a skeletal muscle fibre can contract, it has to receive an impulse from a nerve cell.
Smooth muscles are involuntary muscles that line the inside of some organs. They do essential jobs like moving waste through the intestines and helping the lungs expand when breathing. Smooth muscles play an important role in many body systems, including the female and male reproductive systems, and the urinary system.
Cardiac muscle is found only in the heart and is responsible for pumping blood throughout the body. Cardiac muscle tissue cannot be consciously controlled. While hormones and signals from the brain adjust the rate of contraction, cardiac muscle stimulates itself to contract. The cells of cardiac muscle tissue are striated and appear to have light and dark stripes when viewed under a light microscope.
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Skeletal muscle
Each skeletal muscle may be made up of hundreds or thousands of muscle fibres bundled together and wrapped in a connective tissue covering called the epimysium. The connective tissue outside the epimysium, called fascia, surrounds and separates the muscles. The epimysium projects inward to divide the muscle into compartments, each containing a bundle of muscle fibres called a fasciculus. Each fasciculus is surrounded by a layer of connective tissue called the perimysium, and within this, each individual muscle fibre is surrounded by a layer of connective tissue called the endomysium.
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Smooth muscle
Muscle, in anatomy, is broadly divided into three types: striated or skeletal muscle, smooth muscle, and cardiac muscle. Smooth muscle is a type of muscle tissue that works automatically and is found throughout the body. It gets its name from its appearance under a microscope—smooth and uniform, unlike the banded appearance of skeletal and cardiac muscles. Smooth muscle is not under voluntary control and is instead regulated by the nervous system using hormones, neurotransmitters, and other receptors.
In the skin, smooth muscle causes hairs to stand on end, resulting in goosebumps. In the eye, it helps control focus and pupil dilation or constriction. During labour, contractions occur in the smooth muscle of the uterus. Smooth muscle is also involved in disease processes, such as in the use of bronchodilators to relax airway smooth muscle in asthma treatment.
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Frequently asked questions
A muscle is a group of muscle tissues that contract together to produce a force.
Skeletal muscles are attached to the bones by tendons and are responsible for movement, posture, and balance.
Smooth muscle is a type of involuntary muscle that contracts to move substances through organs. It is called "smooth" because of its smooth, uniform appearance under a microscope.
Cardiac muscle is found only in the heart and is responsible for pumping blood throughout the body. It is an involuntary muscle that stimulates itself to contract.
Striated muscle, also known as skeletal muscle, is made up of long fibres that appear to have light and dark stripes when viewed under a microscope. This indicates that the muscle is very strong.
