One of the basic tissue types, the muscle tissue consists of fibers or muscle cells and the connective tissue coverings. The muscle can be further subdivided into three, according to their function and characteristic. The three kinds of muscle tissues are the smooth, cardiac and skeletal muscles. Depending on the nerve impulse being sent by brain, the muscles respond by either contracting or relaxing. The surrounding connective tissue transfers the force of contraction from cell to cell and supports the muscle fibers and the many blood capillaries and nerves that supply them.
The Skeletal Muscles
To say it simply, the skeletal muscles are responsible in constricting certain cavities and moves bones at joints. A lay man may interpret the skeletal muscles as the muscles of working out, because when you exercise, the skeletal muscles are being developed and these are the muscles that you can feel. The muscle fibers are striated, long and formed of myofibrils. The belly of the muscle is formed with the collection of muscle cells. The skeletal muscles are highly vascularized and are responsible for giving the body its shape and contour. One thing to remember is that the muscles always pull and never push. As the muscles are connected to the bones by tendons, the fibers cross each other, thus permitting movement. The muscle cells depend solely of the signal that they receive from the brain. When the muscle receives a signal, it shortens or reacts, when it does not receive a signal, it does not shorten. The process is called innervation and without reinnervation, the muscle cell will die. If the muscle part is no longer being used or is dead, it shrinks or atrophies, looses its tone and becomes flaccid.
We may like to think that we have complete control over our muscles but in reality, the brain involuntarily maintains a degree of contraction among the body’s skeletal muscle. When the muscle is subjected to injury, the muscle cells can regenerate from myoblasts with moderate functional significance. Regeneration also occurs when the muscle region is repeatedly being used, for example during exercise certain muscle regions develop.
The Cardiac Muscles
The word cardiac is already a giveaway to know that this type of muscle is concentrated on the heart. Cardiac muscle cells make up the heart muscle and are connected with one another by junctional complexes called intercalated discs. When examined under a microscope, they are similar to the skeletal muscles yet they are somewhat less organized. What makes the cardiac muscle special is that they don’t receive signals from nerves but from impulse-conducting muscles cells, ensuring a rhythmic, well-regulated and strong contraction. With such high demand of work, the cardiac muscle is able to keep up with it because it is highly vascularized. The regulation of the rates related to contraction is mediated by the autonomic nervous system. Unlike the skeletal muscle, the cardiac muscles are not capable of regeneration.
The Smooth Muscles
Smooth muscles are best defined as the involuntary muscles, the ones which cannot be controlled. As the name suggest, these muscles are nonstriated and are capable of slow, rhythmic, strong contraction. Smooth muscles can be seen in the lining of cavities, referred as viscera. In some instance, smooth muscles serve as gates in specific sites, like in regulating the flow of urine. This type of muscle is capable of regeneration to some extent after injury, partly due to the reason that they are highly vascularized so nutrient exchange is somewhat increased. The fibers contract in response to both autonomic nerves and hormones.
Often we take for granted the role that muscles play in our life. They help us lift things, walk straight, summon tremendous amounts of strength in dire need and when we are tired, assist us to sit. Our muscles interact with our day to day living in more ways than you can imagine.