Muscles of respiration: types, characteristics and functions when breathing.

The classification of the muscles of respiration, summarized and with descriptions.

Breathing is one of the basic processes carried out by our organism, and one of the most fundamental for survival.

Every time we inhale we introduce oxygen into our body, which allows the cells of our body to survive. At the same time, with each exhalation we expel waste such as CO2, which allows us to cleanse the body of the remains of cellular activity.

But the act of breathing, although semi-conscious (it can be voluntarily controlled although it is usually carried out unconsciously), requires a series of muscular movements in order to occur. And there are multiple muscles of respiration that are mobilized for this purpose. Throughout this article we are going to see which are the muscles of respirationThe most relevant ones as well as others that although less primordial also have a role in the process.

Main muscles of respiration

Below we will see the main and most relevant muscles that participate and enable the respiratory process. Although there are many ways to classify them into different categories, this time we will divide them into four main groups.

1. Diaphragm

The diaphragm is one of the main and most important respiratory muscles, as well as being among the best known.

It is a cylindrical a relatively large cylindrical muscle, with a dome also formed by tendinous tissue, and which is located underneath the and is located below the lungs and ribs.

This muscle, which separates the torso from the abdomen, is key in both inspiration and expiration processes. When contracted, it displaces the viscera downward, leaving space and elevating the thoracic cavity in such a way as to allow the lungs to expand.

2. Intercostal muscles

The second major group of muscles that are fundamental for respiration are the intercostal muscles, which allow for the displacement of the thoracic cage. allow the displacement of the thoracic cage, which in turn allows lung expansion.. There are two types of intercostal muscles.

2.1. External intercostal

Muscle that covers the internal area of the ribs and is the most important Muscle subgroup in allowing breathing. It is fundamental at the time of being able to inspireIt is the one that opens the thoracic cage and allows pulmonary expansion.

2.2. Internal intercostal

The internal intercostal muscles have a predominantly exhalatory function: their contraction causes the ribs to descend, returning to their initial position.

3. Abdominal muscles

The abdominal muscles are a series of muscles located in the abdomen that actively participate in the respiratory process. Technically they are not so essential in maintaining unconscious breathing, but they actively participate in voluntary expiration.

3.1. Internal obliques

These muscles are located in the anterior and lateral part of the abdomen and are particularly important in allowing consciously controlled breathing. They allow the thorax to flex, causing the diaphragm to stretch and facilitate inspiration. It also allows the exhalation to be performed by moving the wall of the belly inwards.

3.2. External obliques

The external obliques are the muscles that we have in the anterior and lateral most external part, and can be visualized around the rectus abdominis. These muscles perform similar functions to those of the internal obliques, favoring inspiration and participating in forced or voluntary expiration..

3.3. Rectus abdominis muscle

One of the abdominal muscles whose movement is most visible during breathing, it is divided into several intersections separated by connective tissue and extends from the pubis to the lower part of the rib cage. Together with the oblique muscles, they pull the lower ribs downward and facilitate exhalation.. It allows compression of the lower part of the chest.

3.4. Transverse muscle

The transverse muscle can be found next to the internal oblique. It is the deepest muscle among the broad muscles of the abdomen.It runs from the spine to the linea alba and from the ribs (it inserts on ribs seven through twelve). It contributes to compress the abdominal viscera and the lower part of the chest, and participates in voluntary respiration both in inspiration and especially in expiration.

4. Accessory muscles

Within the group of accessory muscles we include the set of muscles that although they are not the main responsible for the respiratory movement, they do have a relevant role in the respiratory movement. We will include muscles that could be considered part of the rest of the groups, but which are not so fundamental.

Similar to the abdominals, they are generally mobilized during forced respiratory movement, and especially in situations such as breathing difficulties. especially in situations such as when there are breathing difficulties, coughing or intense physical exercise.. Below we will see some of the best known, although there are many others involved to a greater or lesser extent in the respiratory process.

4.1. Scalene muscles: anterior, middle and posterior

The scalene muscles are a set of three muscles (anterior, middle and posterior scalene) located at the level of the neck and the beginning of the torso. They run from the cervical vertebrae to the first two ribs and participate in respiration by helping to elevate the first two ribs, facilitating voluntary inhalation.

4.2. Sternocleidomastoid

Also located in the neck, although in the anterolateral part. It contributes to elevate and dilate the thoracic cage with its contraction, facilitating the pumping movement and being something that can facilitate voluntary inhalation. can facilitate voluntary inhalation in cases of extreme necessity..

Sternal retraction is often used in emergency situations, and in fact is sometimes a sign of respiratory problems.

4.3. Trapezius muscles

The trapezius are muscles that join the man, the spine, the scapula and the skull, linking these areas and allowing, for example, the shoulders to remain in the same position when carrying weight. It consists of three parts: upper, middle and lower. They participate in the voluntary inhalatory movement, by lifting the rib cage when it contracts.

4.4. Pectoralis major

Located in the thorax and forming one of the most visible and powerful parts of the pectoral musculature, this muscle is also one of the accessories in respiration. It allows the mechanical inspiration, since when contracting the thoracic cage rises upwards..

4.5. Pectoralis minor

Located behind the pectoralis major, this muscle helps to lift and rotate the scapula away from the ribs. This allows and facilitates deep and voluntary inhalation.

4.6. Serratus muscles

Divided into major, anterior and posterior, the serratus muscles, which are located in the posterior thoracic part of the body and contribute to voluntary inspiration. They also participate in deep breathing during great efforts.

4.7. Supracostal muscles

These are about a dozen small muscles that are located between the ribs are located between the ribs, and help to raise them when they contract and retract them when they are relaxed.. They participate in both inspiration and expiration.

Bilbiographical references:

• García-Talavera, I., Díaz Lobato, S, Bolado, P.R. and Villasante, C. (1992). Respiratory muscles. Archivos de Bronconeumología, 28 (5). Madrid.
• Roussos, C.S and Macklem, PT, (1982). The respiratory muscles. N. Engl.J. Med, 307: 786-797.