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The function of the muscular system

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The most abundant tissue in the human body is muscle. Broadly, muscles are classified into three types. 
1. Skeletal muscle
2. Smooth muscle
3. Cardiac muscle1

Skeletal muscle is the main labor behind our sitting, standing, walking and jumping. The skeletal muscle is situated in the form of striae due to which we also call it striated muscle. Skeletal muscle also helps us in maintaining tone and posture of the body. Smooth muscle is the second type of muscle. It differentiates from the skeletal muscle as it does not have any striae. Smooth muscle is mostly used in maintaining the tone of the digestive tract, internal organs and in creating bowel movements2.

Cardiac muscle is the third and most crucial type of muscle. Its function is different: is the muscle of the heart, the never-tiring muscle due to which nutrient and oxygen-containing blood is supplied to each and every cell of the body from birth till death 3 4

If we consider the basic structure of muscles. Each muscle cell contains long fibers and the contraction of the muscles is produced by overlapping of these long fibers. There is only contraction and relaxation in the muscle fiber, no extension or elongation5 6 

The movements of the muscle are controlled by our brain. The brain sends signals to the muscle fibers through nerves which then cause the muscle to contract.

Generally, skeletal muscles are divided into two types.

1. Fast twitchers
2. Slow twitchers 7

We usually name slow twitchers as dark meat and fast twitchers as light meat. Fast twitchers are used in doing abrupt and power demanding movements while slow twitchers perform the movements which are needed for a longer period of time and demand low power. Our muscles are usually a mixture of fast and slow twitchers and we can alter it by exercise. So, if we observe, muscle is the tissue with the unique ability not found in any other tissue named as "contraction".

There are more than 600 muscles in our body, each one carrying its own function, contributing more than 40% to our body weight.
Along with the movements, there are three other important functions of muscles.

1. Heat production8
2. Posture maintenance
3. Joint stability

It is recorded that almost 85 % of the heat of the body is produced by muscles. Moreover, if we observe the joints, muscles overlapping the joints can easily be appreciated which helps in maintaining the joint stability9.

References
1. https://www.ncbi.nlm.nih.gov/books/NBK20361/
2. https://www.ncbi.nlm.nih.gov/pubmed/14627618
3. https://www.ncbi.nlm.nih.gov/books/NBK20168/
4. https://www.ncbi.nlm.nih.gov/pubmed/10655038
5. https://www.ncbi.nlm.nih.gov/books/NBK21670/
6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC493720/
7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2269891/ 
8. https://www.ncbi.nlm.nih.gov/books/NBK21670/
9. https://www.ncbi.nlm.nih.gov/books/NBK20168/

Topics: muscular system

Dr. Owais Amin

Written by Dr. Owais Amin