Respiratory muscles: types, characteristics and functions when breathing

Breathing is one of the basic processes that our body goes through and one of the most fundamental for survival.

Each time we inhale, we are introducing oxygen into our body, which sustains the cells in our body. In turn, with each exhale, we expel wastes such as CO2, which allows the body to cleanse the remnants of cellular activity.

But the act of breathing, while semi-unconscious (it can be controlled voluntarily although it’s usually done unconsciously), requires a series of muscle movements to occur. And there are several respiratory muscles that mobilize for this. Throughout this article let’s see what respiratory muscles are, The most relevant and the others which, although less important, also play a role in the process.

    Main muscles of breathing

    Below we will take a look at the main and most relevant muscles that participate in and enable the respiratory process. While there are many ways to categorize them into different categories, this time we are going to divide them into four main groups.

    1. Diaphragm

    The diaphragm is one of the main and most important respiratory muscles, in addition to being among the best known.

    It is a relatively large cylindrical muscle, with a dome also formed of tendon tissue and which is located under the lungs and ribs.

    This muscle, which separates the torso from the abdomen, is the key to both the inspiration and experience processes. When contracted, it moves the viscera downward, leaving space and elevating the chest cavity in a way that allows the lungs to expand.

    2. Intercostal muscles

    The second major group of muscles essential for breathing are the intercostals, which they allow displacement of the rib cage which in turn allows lung expansion. We can find two types of intercostal muscles.

    2.1. External intercostal

    Muscle which covers the internal zone of the ribs and which results in a muscle subgroup of greater importance to allow breathing. It is essential to be able to inspire, Since it is they who open the rib cage and allow lung expansion.

    2.2. Internal intercostal

    The internal intercostal muscles have an essentially expiratory function: their contraction lowers the ribs, return to starting position.

      3. Abdominal muscles

      The abdominal muscles are a series of muscles located in the abdomen and actively involved in the respiratory process. Technically, they’re not as essential when it comes to maintaining unconscious breathing, but they are actively involved in voluntary exhalation.

      3.1. internal obliques

      these muscles they are located in the front and side of the abdomen and have particular relevance for enabling conscious and controlled breathing. It allows you to flex your chest, causing the diaphragm to stretch and making it easier to breathe in. It also allows you to exhale by moving towards the inside of the stomach wall.

      3.2. external obliques

      The external obliques are the muscles we have in the front and laterally more external, and can visualize around the abdominal rectum. These muscles perform functions similar to those of the internal obliques, encourage inspiration and participate in forced or voluntary expiration.

      3.3. Abdominal rectus muscle

      One of the abdominal muscles whose movement is most noticeable when breathing, divides into several intersections separated by connective tissue and extends from the pubis to the lower part of the rib cage. With the oblique muscles, they lower the lower ribs and facilitate the exhalation. It allows you to compress the lower chest.

      3.4. Transverse muscle

      The transverse muscle can be attached to the internal oblique. It is the muscle located deepest among the widths of the abdomen, And goes from the column to the white line and ribs (inserted in the ribs from seven to twelve). It helps compress the abdominal viscera and the lower part of the chest, and participates in voluntary breathing both in inspiration and in expiration.

      4. Accessory muscles

      In the group of accessory muscles, we include the set of muscles which, although not primarily responsible for respiratory movement, have an important role in which it occurs. We will include in it muscles that could be considered part of the other groups, but which are not so fundamental.

      Similar to the abdominals, they are usually mobilized during forced respiratory movements, and especially in situations such as difficulty breathing, coughing, or strenuous exercise. Below we will see some of the better known, although there are many more involved to a greater or lesser extent in the respiratory process.

      4.1. Scales: 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 at the beginning of the torso. They run from the cervical vertebrae to the first two ribs and participate in breathing 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 helps to lift and dilate the rib cage with its contraction, facilitating the pumping movement and being something that can facilitate voluntary inhalation in case of extreme need.

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

      4.3. trapezoids

      Trapezius are muscles that connect the man, the spine, the scapula and the skull, connecting these areas and for example allowing the shoulders to stay in the same position when carrying weight. It consists of three parts: upper, middle and lower. They participate in the voluntary inhalation movement, lifting the rib cage as it contracts.

      4.4. pectoralis major

      Located in the chest and forming one of the most visible and powerful parts of the pectoral muscles, this muscle is also one of the accessories of breathing. It allows mechanical inspiration, because when it contracts the rib cage rises.

      4.5. pectoralis minor

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

      4.6. jagged muscles

      Divided into main, anterior and posterior, the serrated muscles, which are located in the posterior thoracic part of the body and contribute to voluntary inspiration. It also participates in deep breathing in great efforts.

      4.7. Supracostal muscles

      It’s a dozen small muscles that they are placed between the ribs, and they help to elevate them when they contract and retract them when they relax. They participate in both inspiration and expiration.

      Bibliographical references:

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

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