Muscular tissue consists of elongated cells, also called muscle fibres. This tissue is responsible for movement in our body.
Muscles contain special proteins called contractile proteins, which contract and relax to cause movement.
We can move some muscles by conscious will. Muscles present in our limbs move when we want them to, and stop when we so decide.
Such muscles are called voluntary muscles
Fig – Types of muscles fibres: (a) skeletal muscle, (b) smooth muscle, (c) cardiac muscle
These muscles are also called skeletal muscles as they are mostly attached to bones and help in body movement. Under the microscope, these muscles show alternate light and dark bands or striations when stained appropriately. As a result, they are also called striated muscles. The cells of this tissue are long, cylindrical, unbranched and multinucleate (having many nuclei).
The movement of food in the alimentary canal or the contraction and relaxation of blood vessels are involuntary movements. We cannot
really start them or stop them simply by wanting to do so! Smooth muscles or involuntary muscles control such movements. They are also found in the iris of the eye, in ureters and in the bronchi of the lungs. The cells are long with pointed ends (spindle-shaped) and uninucleate (having a single nucleus). They are also called unstriated muscles .
The muscles of the heart show rhythmic contraction and relaxation throughout life.
These involuntary muscles are called cardiac muscles . Heart muscle cells are cylindrical, branched and uninucleate.