Muscular Tissue:
The particular type of contracting and expanding tissue originates from embryonic, mesoderm is called Muscular tissue. They are striated in appearance and are under voluntary control.
Structural Characteristics: Matrix is nearly absent in muscular tissue. The muscle cells are elongated and fiber-like. The fibers are spindle-shaped. The fibers are known as myofibril. The cytoplasm of muscle cell may have one or more nuclei. The cell membrane of the muscle cell is known as sarcolemma. The myofibrils with transverse striation are known as striated muscle and without striation are known as smooth muscle.
Function: Muscle cells through contraction or expansion take part in organ movement, locomotion, and internal circulation.
On the basis of location, structure, and functions, muscle tissue is of three types. Such as:
a) Voluntary or Striated Muscle: This Type of muscular tissue can be contracted or expanded at the will of the living beings. The cells of the voluntary muscle tissue are tubular, not branched and provided with transverse striations. These have generally more than one nucleus. This muscle can contract or expand quickly. This muscle is also, called striated or skeletal muscle.
Location: Voluntary muscles remain attached to the skeletal system as muscles of-hand, and feet of man.
Function: To control the movement and mobilization of different organs by voluntary movement of various bones.
b) Involuntary or Smooth Muscle: Structural Characteristics: The contraction and expansion of this muscle tissue are not at all of the living beings. This muscle tissue is spindle-shaped. Transverse striations are not present here. That is why this muscle is called smooth muscle. Location: Involuntary muscles are found on the walls of blood vessels, alimentary canal etc. of the vertebrate animals.
Function: Involuntary muscles mainly take part in the movement of internal organs, e.g. peristalsis. of intestine.
c) Cardiac Muscle: Structural Characteristics: The special type of involuntary muscle that forms the heart of vertebrate animals is called the cardiac muscle. The cells of this muscle tissue are tubular (very similar to those of voluntary muscle), branched and provided with transverse striations. Between the cells of this tissue intercalated disc is present. The contraction and relaxation of this tissue are not dependent on the will of the living beings. That is, the structure of heart muscles is, like that of voluntary muscle and the function is like that of involuntary muscle. The cells of cardiac muscle, attached by branch joined together by branch. The contraction and expansion of all cardiac muscles take part combined.
Function: Through rhythmic contraction and relaxation, the cardiac muscles control the circulation of blood within the body from a particular stage of the embryonic condition until death.
The structure of these muscle tissues can be described from the level of detail of the muscle fibers (muscle cells) through all the other muscle structures and parts of structures that bind muscle cells together enabling them to perform their functions.
