Muscular System Muscle work as a body supporting movement organ and help homeostatic. As an acive movement organ muscle has three abilities, that are contractibility ( the ability shorten ocontract) , extensibility (the ability to stretch or relax), and elasticity (the ability to return to the initial position).
Structure of Muscle
The basic unit of the muscle is called muscle fiber or myofibril. The group of myofibril gathers in muscle mass. Each myofibril is a cell that contains general components of a cell.
Myofibril comprises of a large amount of myofilament protein consisting of thick filament (myosin) and thin filament (actin). The thin filaments are connected to each other forming the light band (I band ). The same group of thick filaments are connected to each other forming a dark band (A band ). Some thick and thin filament overlap so that they will form more compact part and less compact part in a band which is called H zone. The anchoring point of thin filament or Z line will cross myofibril in the middle of I band. The part of myofibril between two Z lines is called sarcomere.