Muscular Tissue

Muscular Tissue

Muscular tissues are made of muscle cells and form the major part of contractile tissue. The muscle cells are elongated, large sized and are composed of numerous myofibrils. Each muscle is made up of many long cylindrical fibres arranged parallel to one another. The movement of the body and limbs are brought about by the contraction and relaxation of contractile proteins present in muscle cells. According to their structure, location and functions, there are three main types of muscles

a. Skeletal muscle (or) striated muscle

b. Smooth muscle (or) non-striated muscle

c. Cardiac muscle

a. Skeletal muscle:

These muscles are attached to the bones and are responsible for the body movements and are called skeletal muscles. They work under our control and are also known as voluntary muscles. The muscle fibres are elongated, non-tapering, cylindrical, unbranched and showing alternating dark and light bands, giving them the striped or striated appearance. These cells possess many nuclei (multinucleate). They occur in the muscles of limbs (biceps and triceps of arms).They undergo rapid contraction.

b. Smooth muscle:

These muscles are spindle shaped with broad middle part and tapering ends. There is a single centrally located nucleus (uninucleate). These fibrils do not bear any stripes or striations and hence are called non-striated. They are not under the control of our will and so are called involuntary muscles. The walls of the internal organs such as the blood vessels, gastric glands, intestinal villi and urinary bladder contain this type of smooth muscle. Movement of food in the alimentary canal or the contraction and relaxation of blood vessels are involuntary movements.

c. Cardiac muscle:

It is a contractile tissue present in the heart. The muscle fibres are cylindrical, branched and uninucleate. The branches join to form a network called as intercalated disc which are unique distinguishing features of the cardiac muscles. The intercellular spaces of the cardiac muscle are filled with loose connective tissue supplied with blood capillaries. The contraction of cardiac muscle is involuntary and rhythmic.