Do you not know what a skeletal muscle is
? Do you want to understand the functions of these muscles?
The concept of skeletal muscle is simple to understand but of vital importance to understand the functioning of the system in charge of movement in animals and human beings.
In this article you will find in a simple way, answers to everything related to this concept of anatomy.

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1. What is a skeletal muscle
? 2. What are skeletal muscles used for?
3. Types of skeletal muscles.
4. How skeletal muscles are structured.

What is a skeletal muscle Skeletal

muscles are part of the group known as striated muscles . These are attached to the skeleton (bones) and are made up of cells and fibers with elongated and polynucleated characteristics (with several nuclei along them).
To give us an idea, around 90% of the muscles in the human body are part of this type of muscle.
Structure of a skeletal muscle. | Image: Courtesy.

What are striated muscles
As we just said, skeletal muscles are one of the types of striated muscles.
This category is made up of striated muscles attached to bone or skin and functioning under voluntary control. They are also characterized by high-velocity contractions.

What are the skeletal muscles for? Skeletal
muscles, as might be expected, have a long list of functions since they cover a large part of our body and make up much of its tissue. Next we are going to see the functions of the most important skeletal muscles:

1. Movement
Thanks to the nervous system, which is in charge of sending the signals, the skeletal muscles react to these stimuli to elongate or contract them.

2. Displacement
Unlike other non-skeletal muscles (such as the heart), they produce movement but also displacement . This allows an organism to move through space without having to return to the starting point.

3. Mechanical
energy Thanks to chemical energy, the muscles are responsible for obtaining mechanical energy . It would be the biochemical process necessary for the two previous functions of higher order.

4. Joint stability
One of the main functions of the skeletal muscles, even when they do not receive signals from the nervous system, is to keep the joints in their places .

5. Protection
Although the body has several types of protection (from the skin to the immune system, for example), the skeletal muscles also do their bit to achieve this goal.

6. Posture
Since it keeps the joints in a certain position (with little or no effort), skeletal muscles allow us to maintain a position over time.

7. Proprioception
We have all heard of senses such as smell and sight, but what is proprioception?
Well, it is the sense that allows you to know what position a part of your body is in , without the need to look at it or what come into contact with another object.

8. Interoception
Similar to the previous one, only in this case it warns us of the state of the internal organs. An example is what happens in colic.

9. Thermoregulation
When an area is too cold (or hot) the blood, which circulates through the skeletal muscles, is responsible for regulating this variable.

10. Blood irrigation
Although it is not the main function, the contraction of the muscles promotes the pumping of blood to the activated muscles.

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Types of Skeletal Muscles
There are several ways to classify the types of striated muscles. Here we present the main ones.

1. Types according to group action
Muscles never act alone; therefore, we can classify the muscles depending on the relationship established between them.

1.1. Agonist

They are the muscles that follow the direction of the movement , allowing its realization. Of course, there does not have to be only one (in fact, it can be said that there are always several agonist muscles and several antagonists). The agonists, then, are the ones that contract.

1.2. Antagonist
Contrary to agonists. These muscles must relax to allow the action of the agonist skeletal muscle.

1.3. Synergist
It could be said that synergists are agonist muscles but with less relevance to perform the action. In other words, they are like auxiliary muscles.

2. Types according to movements
There are 5 different types of skeletal muscles depending on the movement they perform.

2.1. Flexors

The most typical example of muscle movement . It is for example the contraction of the biceps to lift the forearm.

2.2. Extensors
To continue with the example, the extensor muscle of the previous case would be the triceps. 23.

The skeletal muscles that perform this type of movement are those that allow a separation with respect to the reference plane.. For example, if we are standing in a straight position, raising our arms as if we wanted to fly like a bird would be a movement of shoulder abduction.

2.4. Rotators
A movement that consists of turning on its own axis. There are two subtypes: pronation and supination .

2.5. Fixators
Also known as stabilizers, these skeletal muscles hold a part in a static position while simultaneously exerting tension in another direction (or directions).

3. Types according to their fibers
There are two types of muscle fibers. Each one has its own biochemical characteristics.. All muscles are composed of both types, what changes is the proportion. In addition, it can change depending on the type of training (more speed or more resistance).

3.1. Muscles composed of type I fibers
They are characterized by having a redder color. They are also more resistant but have a lower speed.

3.2. Muscles composed of type II fibers
They are more whitish in color. They allow faster and more explosive movements . They use more glucose than type I, but they tire more easily.

    How are skeletal muscles structured?
    The cells that make up skeletal muscles are structured in a cylindrical shape, generating long fibers that are grouped in parallel, one next to the other .
    The muscles of the body, and especially the skeletal muscles, are the organs with the greatest capacity for adaptation in the body (whether animal or human). They are able to strengthen and grow through training and atrophy to unsuspected limits in the absence of use.
    For example, if we immobilize an arm in a contracted position (for example, folding the arm completely), the length of the muscle will be significantly reduced in a short time.
    On the contrary, given the structure of skeletal muscles, if a muscle remains maximally stretched for a long time, it can have a negative impact, causing joint instability due to hyperlaxity .

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