Everything in your body is made up of cells. Each cell is programmed by your DNA to perform a specific function for the body. Muscle tissue is made of individual muscle cells that contain microscopic layers and molecules that allow the body to move. Without the complex structure of a muscle cell, we'd be stuck static our whole lives.
Anatomy
There are seven different types of muscles, dependent on the direction in which they pull your bones. These types are fusiform, parallel, convergent, unipennate, bipennate, multipennate and circular. You can tell the differences based on their shapes. Each type of muscle has an origin, insertion and belly. The origin is the stationary point of attachment to the bone. The insertion is the moveable attachment, usually on the opposing side of the origin. The belly is the thick, middle region, where most of the muscle cells are located.
Connective Tissue
Skeletal muscles are made up of both muscle and connective tissue. A skeletal muscle cell is surrounded by a layer called the endomysium. Muscle fibers are grouped into fascicles. Fascicles are surrounded by a sheet of connective tissue called a perimysium. Beyond that, the entire muscle is surrounded by an epimysium. All of the connective tissue run together to form the deep and superficial fascia, which ultimately come together to form the tendon. The function of each of these layers is to provide nerve innervation to each working muscle cell.
Muscle Microstructure
Each muscle cell is composed of a myofibril and sarcoplasm. The myofibril is the point inside of a muscle cell in which the molecules that contract the muscle cell are located. The sarcoplasm stores myofibrils, protein filaments, glycogen, enzymes, the mitochondria and sarcoplasmic reticulum, which are all essential to the work that occurs inside the myofibril.
Muscle Contractions
The sarcomere is inside of each myofibril and is where all the action occurs. Inside of each sarcomere lies actin and myosin, the two major players that function during a muscle contraction. The way a muscle moves can be answered by the sliding filament theory. This theory states that actin filaments attach to myosin filaments by sliding inward, resulting in muscle movement. Your body contains thousands upon thousands of muscle fibers and these microscopic filaments do most of the work.
References
- "Anatomy and Physiology"; Kenneth S. Saladin; 2004
- "Essentials of Strength and Conditioning"; National Strength and Conditioning Assciation; Thomas Baechle, Roger Earle, editors; 2000
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