Muscular System

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9  THE  muscular System

What is Muscular System?

9.1     Your muscular system enables your body to move. Each muscle consists of muscle cells that can contract or relax. Because muscle cells are usually long and slender, they are called fibres. Skeletal muscles move your bones and help protect your inner organs. Smooth muscles deep within your body help move food, air, and body fluids. Cardiac muscle is a special type of muscle found only in your heart. Your body has more than 600 muscles, which make up about 30 percent of the female body and about 40 percent of the male body.

 Skeletal Muscles

9.2     Muscles attached to bones are called skeletal muscles. They are also called “voluntary” muscles because a person can choose whether to move them. In addition to muscle fibres, skeletal muscles contain connective tissue, nerves, and blood vessels. Each muscle is surrounded by a fibrous membrane. At one end of the muscle, the fibres of this membrane connect with a tough band of elastic tissue called a tendon. Tendons connect most skeletal muscles to bones.

 Smooth and Cardiac Muscles

9.3         Smooth muscles are found in internal organs, such as the stomach, intestines, urinary bladder, uterus, and blood vessels. Unlike skeletal muscles, which can be contracted voluntarily, smooth muscles are involuntary. Smooth muscles are responsible for the contractions of the esophagus and the intestines called peristalsis. Smooth muscles are also responsible for the contractions of labour during childbirth. Cardiac muscle  fibres are strong like skeletal muscles, but the heart is an involuntary muscle. The contraction and relaxation of cardiac muscle fibres pumps blood through the body automatically and rhythmically.