Muscle is derived from the mesodermal layer of the embryonic germinativas cells. The muscular cells contain filaments contract that to move themselves between itself and to modify the size of the cell. They are classified as skeletal, cardiac or muscular smooth. Its function is to produce force and movement cause. The muscles can in such a way cause the locomotion of the proper organism or the circulation of internal agencies. Cardiopath and contraction of the smooth muscle occur without conscientious thought and are necessary for the survival. Examples of this are the contraction of the heart and the peristaltismo, that pushes the food through the digestive system. Voluntary contraction of the skeletal muscles is used to put into motion the body and can finely be controlled. Examples of this are the rude movements of the eyes, or movements, as the muscle quadriceps of the thigh. Two main types of voluntary muscular staple fibres exist: slow contraction and fast contraction. Staple fibres of slow contraction contract for long periods of time, but with little force, while staple fibres of fast contraction contract quickly and with force, but the fatigue very quickly.

The muscles predominantly are moved by the oxidation of fats and carbohydrates, but the anaerobic chemical reactions also are used, mainly for staple fibres of fast contraction. These chemical reactions to produce trifosfato of adenosine (ATP), molecules that are used to feed the movement of the miosina head.

Three types of muscles exist:

• The skeletal muscle or “voluntary muscle” is anchored by the tendons (or aponeuroses in some places) for the bone and is used for effect of movement of the skeleton, such as locomotion and in the maintenance of the position. Although this postural control generally is kept as a subconscious consequence, the responsible muscles to react to the conscientious control as the muscles non-postural. An adult male is composed of 42% of the esquelético muscle and an average adult female is composed of 36% (in percentage of 3 corporal mass).

• smooth muscle or “involuntary muscle” is found inside of the walls of agencies and structures, as the esophagus, stomach, intestines, the bronchis, uterus, uretra, sanguineous bladder, vases, the eretor of the one for and the skin (where it controls the erection of for the ones in the body). In contrast of the skeletal muscle, smooth muscle is not under conscientious control.

• cardiac muscle is also an involuntary muscle “, but it is more similar in structure to the skeletal muscle, and is only found in the heart. Cardiopath and the skeletal muscles “are estriado” in the measure where they contain sarcomerious and conditioned in regimen highly to regulate of packages; smooth muscle does not have none. While the skeletal muscles are made use in regulating, parallel beams, the cardiac muscle if connects the irregular ramification, angles (called intercalated records). estriadas muscular contracts and relax in short and intense, to the step that the smooth muscle supports more, or same contractions almost permanent.