What are Muscles

Functions of the Muscles

The Human muscular system is made up of a complex network of soft tissues which are called muscles. Muscle tissue is found throughout the human body and it has the following functions;

  1. Movement. Skeletal muscles attached to the skeleton move the body by moving bones. The muscles in the walls of some of our visceral organs squeeze to produce movement of fluids and other substances through the hollow passage ways as well as regulating organ volume.
  2. Maintenance of Posture. Some skeletal muscles contract continuously to maintain posture, enabling the body to remain in standing or sitting positions
  3. Joint stabilization. The role of muscle tone in stabilizing and strengthening joints.
  4. Heat generation. Muscle contractions produce heat that plays a vital role in maintaining normal body temperature at 37°C (98.6°F)

Characteristics of Muscles

Muscle Tissue possesses some unique characteristics that help to differentiate it from other bodily tissue such as the following;

  1. Contractility. A notable characteristic of muscles are that they can contracts forcefully. Muscle cells shorten and generate a strong pulling force as they contract.
  2. Excitability. Nerve signals or other factors excite muscle cells, causing electrical impulses to travel along the cells’ plasma membrane. These impulses then stimulate the cells to contract.
  3. Extensibility. Muscle tissue can be stretched by the contraction of an opposing muscle.
  4. Elasticity. After being stretched, muscle tissue can recoil passively and resume its usual resting length.

Breakdown of Skeletal Muscles

Muscle components

A great illustration highlighting the different breakdown of a skeletal muscle

Several sheaths of connective tissue hold the fibers of a skeletal muscle together. These sheaths, from external to internal, are illustrated above. These sheaths from external to internal are as follows

  1. Epimysium. An “overcoat” of dense, irregular connective tissue surrounds the whole skeletal muscle. This coat is the epimysium , a name that means “outside the muscle.” Sometimes the epimysium blends with the deep fascia that lies between neighboring muscles.
  2. Perimysium. Within each skeletal muscle, the muscle fibers are separated into groups. Each group, which resembles a bundle of sticks tied together, is called a fascicle (bundle). Surrounding each fascicle is a layer of fibrous connective tissue called perimysium (around the muscle [fascicle]).
  3. Endomysium. Within a fascicle, each muscle fiber is surrounded by a fine sheath of loose connective tissue consisting mostly of reticular fibers. This layer is the endomysium (within the muscle).

These fibrous connective tissues bind muscle fibers together and hold them in parallel alignment so they can work together to produce force. These Muscle fibers are made up of millions of tiny protein filaments known as Myocytes which work together to that slide past each other to either contract (shorten) or relax (lengthen) the muscle, resulting in changing the length and size of the fiber. As a result of this contraction force is produced to create motion. This force exerted by the muscle is a result of converting chemical energy in complex chemical reactions inside the muscle which causes the muscles into tension and contraction. When muscle fibers contract, they pull on the surrounding endomysium. Because of the continuity between sheaths, this pull is then exerted on the perimysium, epimysium, and tendon, a sequence that transmits the force of contraction to the bone being moved. The sheaths also provide a muscle with much of its natural elasticity and carry the blood vessels and nerves that serve the muscle fibers. Muscles are used throughout the human body to assist in nearly all of our day to day functions such as walking, running, lifting, standing, squatting, driving, riding as well as looking in different directions, breathing, digestion of our food and most importantly the beating of our hearts.

Number of Muscles

How many muscles does the human body have? This is a difficult question to answer. Each human body possess in between 600 and 700 different muscles throughout the body. The exact number is not actually known due mainly to the many differing types of muscles found in the body. Opinions vary as to what should or should not be included in the muscle count. For example, each hair follicle has a tiny muscle surrounding it at the base and these muscles contract to make the hair stand on edge(goose bumps). There are five million of these tiny muscles. So in a nutshell it would be safe to estimate that there are around 650-700 muscles in the body not including the tiny muscles which give us goose bumps!


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