Monday, March 7, 2016
MUSCLE TISSUE - TEXT
Muscle tissue are responsible for the movements of hands and legs and also of several internal organs such as intestine and heart.
Small amount of muscle tissue is also present in blood vessels. These help in increasing or decreasing the diameter of blood of the blood vessel and thus regulate the blood flow.
Heart is made of only muscle cells and they help in pumping the blood. Muscle cells have the capacity to shorten this is called contraction and generates enough force for movement. The muscle remains contracted only for s short time and returns to its originals length. This is called relaxation. Each muscle is supplied with a nerve.
Inside the muscle tissue, the nerve divides into several branches so that each muscle cells is connected to the nerve. When nerve is stimulated reaches each muscle cell in the tissue and the entire muscle contracts at one time as a unit.
Based on their structure, location and function muscles are of three types – striated muscles, non-striated muscles and cardiac muscles.
Striated muscles: this is also called skeletal muscle at it is attached to the bones in the skeleton and is responsible for the movements.
Movement of these muscles are under our control if we want we can move hands and legs.Hence these muscle are also called voluntary muscles. Each muscle has several long , thin and unbranced fibre like cells.
Each cell is as long as the muscle. There are several thin lines or striation s cross the muscle. Hence the name striated muscle.
Muscle contraction also produces heat. When body is exposed to cold , we shiver. During shivering, muscles contract and relax rapidly producing large amounts of heat. This keeps the body warm.
Non-striated muscle – This muscle consists of short, elongated, spindle shaped cells. These cells do not have striations. Hence the name non-striated muscle or smooth muscle.
Contraction and relaxation of this muscle or not under our control. Hence it is called as involuntary muscle. These muscle are present in the blood vessels, intestine and other tissues which exhibit involuntary movements.
Cardiac muscle- as the name itself indicates, this muscle is present in the heart and is responsible for pumping of blood.
The cells are long branched and have nuclei. Cells are joined to each other at their ends.
All the muscle cells in cardiac muscle have striations. Though it resembles the striated muscle in its structure, it is an involuntary.