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, allowing our body cells to survive. In turn, with every exhalation we expel waste such as CO2, something that allows the body to cleanse itself of the remains of cell activity.

But the act of breathing, although semi-conscious (it can be voluntarily controlled but is usually carried out unconsciously), requires a series of muscular movements to take place. And there are multiple muscles of respiration that are mobilized for this purpose. Throughout this article we will see which are the muscles of respiration , both the most relevant and others that although less essential also have a role in the process.

Major breathing muscles

Next we will see the main and most relevant muscles that participate and allow the breathing 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 major and most important respiratory muscles, and is among the best known.

It is a relatively large cylindrical muscle, with a dome also made up of tendon tissue and located below the lungs and ribs.

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

2. Intercostal muscles

The second large group of muscles that are fundamental to breathing are the intercostals, which allow the displacement of the rib cage which in turn allows lung expansion . We can find two types of intercostal muscle.

2.1. External intercostal

The muscle that covers the internal area of the ribs and results in a muscle subgroup of greater importance when it comes to allowing breathing. It is fundamental when it comes to breathing in , given that they are the ones that open the ribcage and allow lung expansion.

2.2. Internal intercostal

The internal intercostal muscles have a predominantly exhalatory function: their contraction causes the ribs to lower, 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 breathing process. Technically, they are not so essential when it comes to maintaining an unconscious breath, but they actively participate in voluntary expiration.

3.1. Internal obliques

These muscles are located in the front and side of the abdomen and are particularly relevant in allowing consciously controlled breathing. They allow the chest to be flexed, making the diaphragm stretch and facilitating inspiration. It also allows 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 front and in a lateral way more external, and they can be visualized around the abdominal rectum. These muscles fulfil similar functions to those of the internal obliques, favouring 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 divides into several intersections separated by connective tissue and extends from the pubic bone to the lower part of the ribcage. Together with the oblique muscles, they pull the lower ribs down and facilitate exhalation . It allows the lower chest to be compressed.

3.4. Transverse muscle

The transverse muscle may be attached to the internal oblique. This is the muscle located deepest between the widths of the abdomen , and runs from the spine to the linea alba and from the ribs (it is inserted in ribs seven to twelve). It helps to compress the abdominal viscera and the lower chest, and participates in voluntary breathing both on inspiration and especially on 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, do have a relevant role in making it happen. We will include in it muscles that could be considered part of the rest of groups, but that are not so fundamental.

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

4.1. Scalenes: anterior, middle and posterior

The scalenus muscles are a set of three muscles (anterior, mid and posterior scalenus) located at the level of the neck and early torso. They range from the cervical vertebrae to the first two ribs and participate in breathing by helping to raise 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 in cases of extreme need .

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

4.3. Trapeziums

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

4.4. Major pectoral

Located in the thorax and forming one of the most visible and powerful parts of the pectoral muscles, this muscle is also one of the accessories in breathing. It allows mechanical inspiration, given that when contracting the rib cage rises .

4.5. Pectoral minor

Located behind the pectoralis major, this muscle helps raise and rotate the scapula so that it is away from the ribs. This allows and facilitates deep, 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. It also participates in deep breathing with great effort.

4.7. Supracostal muscles

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

Biliographic 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.