Muscles and contractile proteins in animals: Muscles play an important role in body movements as well as the movement of internal organs. Without muscles, it would be impossible to bend, stretch, walk or perform any activity. In fact, muscles constitute about 40 to 50 per cent of body weight in adults. Muscle is a specialised tissue that originates in the mesoderm.
Interestingly, it is the only tissue in your body that has special properties like contractility, extensibility, elasticity and excitability.
Based on their location, muscles are classified into three types, namely skeletal, visceral and cardiac. Skeletal muscle tissues are attached to the bones of the body by collagen fibres called tendons.These muscles are striated or striped and are also referred to as voluntary muscles as they are under the control of the nervous system. Skeletal muscles help in locomotion and different body postures. The myofibrils in muscle fibre show alternate light and dark bands due to the alternate distribution of two important proteins – actin and myosin.
Other types of muscles are visceral muscles. They are found in the inner walls of hollow visceral organs such as the alimentary canal and reproductive tract. Visceral muscles are unstriated and involuntary.
These muscles help to carry food through the digestive tract and gametes through the genital tract. The third type of muscle is the cardiac muscle, which is found only in the heart. Cardiac muscle cells are branched, striated, and involuntary and contain a single nucleus. Several cardiac muscle cells assemble in a branched manner to form a cardiac muscle.