Maximus Gage
The human body is an intricate machine, and muscles are the driving force behind most of its functions. There are more than 600 muscles in our bodies, and they are all soft tissues that help us move, breathe, swallow and survive. The muscular system is an anatomical group that includes all our muscles, and they can also be parts of other systems in the body. The heart is the only organ that is also a muscle, and it is made of cardiac muscle tissue. Skeletal muscles are the most common type of muscle in our bodies, and they are attached to our bones, allowing us to perform a wide range of movements. These muscles are voluntary, meaning we control how and when they work. They are made up of thousands of small fibres woven together, and these fibres contract and stretch to move our bones and organs.
| Characteristics | Values |
|---|---|
| Number of muscles in the human body | 600-700 |
| Muscle composition | Tissue, blood vessels, tendons, nerves |
| Types of muscle | Skeletal, cardiac, smooth |
| Skeletal muscle composition | Muscle tissue, connective tissue, nerve tissue, blood or vascular tissue |
| Skeletal muscle fibres | Red and white |
| Skeletal muscle layers | Epimysium, perimysium, endomysium |
| Skeletal muscle functions | Storage source for amino acids, maintaining thermostasis, energy source during starvation |
| Cardiac muscle composition | Striated cells |
| Cardiac muscle functions | Pumping blood throughout the body |
| Smooth muscle location | Walls of blood vessels, urinary bladder, intestines, stomach |
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What You'll Learn
Skeletal muscle
Each skeletal muscle is made up of hundreds or even thousands of muscle fibres bundled together and wrapped in a connective tissue covering called the endomysium. The connective tissue covering provides support and protection for the delicate cells and allows them to withstand the forces of contraction. Skeletal muscles have an abundant supply of blood vessels and nerves, which is directly related to their primary function of contraction.
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Cardiac muscle
The human body has more than 600 muscles, which help us do everything from moving our bodies to breathing and staying alive. The heart is a hard-working muscle that beats thousands of times a day to keep us alive.
The heart is the only organ in the body that is also a muscle. It is made of a special type of muscle tissue called cardiac muscle. The heart is the only place in the body that has cardiac tissue. Cardiac muscle is also called the myocardium, and it makes up the thick middle layer of the heart. The heart consists mostly of cardiac muscle cells (or myocardium). The endocardium, which forms the inner lining of the heart chambers and valves, is not cardiac muscle. The pericardium is a fibrous sac surrounding the heart. The myocardium is surrounded by a thin outer layer called the epicardium (AKA visceral pericardium). Coronary arteries supply the cardiac muscle, and cardiac veins drain the blood.
The primary function of the cardiac muscle is to pump blood into circulation by generating sufficient force. The cardiac muscle must contract with enough force and blood to supply the metabolic demands of the entire body. The pumping action of the heart is made possible by the contractility of the cardiac muscle. The individual cardiac muscle cell (cardiomyocyte) is a tubular structure composed of chains of myofibrils, which are rod-like units within the cell. The myofibrils consist of repeating sections of sarcomeres, which are the fundamental contractile units of the muscle cells. Sarcomeres are composed of long proteins that organize into thick and thin filaments, called myofilaments. Thin myofilaments contain the protein actin, and thick myofilaments contain the protein myosin. The myofilaments slide past each other as the muscle contracts and relaxes. This process is activated by the release of calcium from the sarcoplasmic reticulum (SR) when delivering an action potential to the muscle, in a process called excitation-contraction coupling. The sliding of actin and myosin past each other produces the formation of “cross-bridges,” which causes contraction of the heart and the generation of force.
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Smooth muscle
The smooth muscle cell is typically 3-10 µm thick and 20-200 µm long, with a spindle shape and a single nucleus. The cytoplasm contains proteins, mainly myosin and actin, which enable contraction. The nucleus takes on a cigar-like shape during contraction. Smooth muscle fibres group in branching bundles, allowing for stronger contractions compared to striated musculature.
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Muscle tissue
The human body has more than 600 muscles, which help us do everything from moving our bodies to breathing and staying alive. These muscles are made of muscle tissue, which is a soft tissue constructed of skeletal muscle tissue, blood vessels, tendons, and nerves.
There are three types of muscle tissue: visceral, cardiac, and skeletal. Visceral muscle, also known as smooth muscle, is found inside organs like the stomach, intestines, and blood vessels. It is the weakest of all muscle tissues and is responsible for making organs contract to move substances through the organ. Smooth muscle is controlled by the unconscious part of the brain and is therefore an involuntary muscle.
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 controlled consciously. Cardiac muscle cells are striated, appearing striped when viewed under a microscope, and are branched X or Y-shaped cells that are tightly connected by intercalated discs.
Skeletal muscles, the third type of muscle tissue, are attached to the bones of the skeletal system by tendons and are under voluntary control. They are also known as striated muscles due to their striped appearance under a microscope. Skeletal muscles come in various shapes and are named based on factors such as location, origin, insertion, shape, and function.
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Muscle fibres
The human body is made up of more than 600 muscles, which help us do everything from moving our bodies to breathing and staying alive. The muscular system works to control the movement of our body and internal organs.
Muscles are made of thousands of small fibres woven together. These fibres stretch and press together to move our organs and body. Each muscle fibre contains smaller units made up of repeating thick and thin filaments. This causes the muscle tissue to be striated, or have a striped appearance.
There are several types of muscle fibre, each with different characteristics. Skeletal muscle fibres, for example, are classified into two types: type 1 and type 2. Type 2 is further broken down into subtypes. Type 1 fibres utilize oxygen to generate energy for movement and have a higher density of energy-generating organelles called mitochondria, which makes them dark. Type 2A fibres can also use oxygen to generate energy for movement but contain less mitochondria, making them light. Type 2B fibres don't use oxygen to generate energy but instead store energy that can be used for short bursts of movement. They contain even less mitochondria than type 2A fibres and appear white.
Skeletal muscles are the most common type of muscle in the body and comprise 30% to 40% of total body mass. They are attached to the bones of the skeletal system by tendons, which are made of dense fibrous connective tissue. Skeletal muscles are voluntary, meaning we control how and when they work. They are responsible for a wide range of movements and functions, including producing movement, maintaining body posture, controlling body temperature, and stabilizing joints.
It is possible for muscle fibres to develop issues due to direct injury, nerve conditions, or other underlying health conditions. Conditions affecting muscle fibres can, in turn, affect the function of a specific muscle or muscle group.
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Frequently asked questions
Muscles are pieces of soft tissue that help the body move, breathe, swallow and stay alive. They are made of thousands of small fibres woven together. There are three types of muscles: skeletal, cardiac and smooth muscle.
Skeletal muscles are the most common type of muscle in the body, comprising 30% to 40% of total body mass. They are attached to bones by tendons and are under voluntary control. Skeletal muscles are located between the bones and consist of flexible muscle fibres. These fibres contract, allowing the muscles to move bones so you can perform a wide range of movements.
Cardiac and smooth muscles are involuntary muscles, controlled by the autonomic nervous system. The heart is the only organ that is also a muscle and is made of cardiac muscle. Smooth muscle lines some of the organs and helps move substances through them.
