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the function of the diaphragm

To analyze the origins and insertions of a muscle that is shaped like an indented umbrella is a bit daunting, but that is what we must do if we want to understand how the diaphragm functions in breathing and posture. We'll begin with the simplest situation, which is found in supine postures. Here the base of the rib cage and the lumbar spine act as fixed origins for the diaphragm, and under those circumstances the central tendon has to

crus right left".

tibias: right, left '

clavicle v humerus -

Figure 2.8. Respiratory diaphragm and other deep muscles of the body. With internal organs removed and most of the rib cage and sternum cut away, the dome-like structure of the diaphragm is readily apparent (Albinus).

ulna radius forearm supinated (radius and ulna in parallel configuration)

left forearm is partially pronated (no1 quite enough for X-like configuration of radius and ulna to be apparent)

,, circumferential attachment of the costal portion of the diaphragm to the base of the rib cage left iliacus muscle left psoas muscle left femur

- adductor muscles left fibula respiratory diaphragm: - costal portion scalenes inserting on left clavicle subscapularis muscle (left)

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act as the movable insertion. The dome of the "cup," including the central tendon, descends and flattens during inhalation, putting pressure on the contents of the abdomen and creating a slight vacuum in the chest thai draws air into the lungs. By contrast, the dome of the diaphragm is drawn upward during exhalation by the inherent elasticity of the lungs, and as that happens air escapes into the atmosphere.

Whenever the chest and spine are fixed, as typically occurs during relaxed breathing in a supine position, the top of the dome of the diaphragm is pulled straight downward during inhalation, like a piston, with the chest wall acting as the cylinder. During a supine inhalation the fibers of the diaphragm shorten concentrically and pull the central tendor inferiorly. During a supine exhalation its fibers lengthen eccentrically as-the central tendon is both pushed from below and pulled from above-pushed by gravity acting on the abdominal organs and pulled by the elasti< recoil of the lungs. The abdominal wall remains relaxed. It stretches oui sixth rit impression of heart is located here respiratory diaphragn the liver and its large impression on the interior surface of the diaphragm lower end of ascending colon greater omentum (draping down from stomach)

stomach and its impressic i external ar<

internal intercostal?

3 layers of abdomina muscles. . in fig. 2.7

descendir colon spleen and it impression unnary bladdc

Figure 2.9. Abdominal organs in place, with the diaphragm and lower half of the rib cage cut to illustrate the extensive zone of apposition, into which the lungs do not descend even during the course of a maximum inhalation (Sappey).

the liver and its large impression on the interior surface of the diaphragm sixth rit stomach and its impressic i zone of apposition pleural cavity is shown as a substantial space for clarity; the diaphragm at this site is actually in intimate apposition to the chest wall lower end of ascending colon greater omentum (draping down from stomach)

external ar<

internal intercostal?

3 layers of abdomina muscles. . in fig. 2.7

descendir colon unnary bladdc impression of heart is located here respiratory diaphragn spleen and it impression

Figure 2.9. Abdominal organs in place, with the diaphragm and lower half of the rib cage cut to illustrate the extensive zone of apposition, into which the lungs do not descend even during the course of a maximum inhalation (Sappey).

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anteriorly (forward) as the dome of the diaphragm descends during inhalation, and it moves back posteriorly (toward the back of the body) as the diaphragm relaxes and rises during exhalation. Only in supine and inverted postures do we sec the diaphragm act with such purity of movement.

This kind of breathing is carried out in its entirety by the diaphragm, but it is often referred to as abdominal breathing, or belly breathing, because this is where movement can be seen and felt. It is also known as deep diaphragmatic breathing in recognition of its effects in the lower abdomen. Finally, we can call it abdomino-diaphragmatic breathing to indicate that the downward movement of the dome of the diaphragm not only draws air into the lungs, it also pushes the lower abdominal wall anteriorly.

Another type of diaphragmatic breathing operates very differently. Amazingly, its principal mechanical features were accurately described by Galen (a first century Roman physician and the founder of experimental physiology) almost two thousand years ago, even though his concept of why we breathe was pure fantasy. During inhalation the primary action of this type of breathing is not to enlarge the lungs by pulling the dome of the diaphragm inferiorly, but to lift the base of the chest and expand it laterally, posteriorly, and anteriorly. It works like this. If there is even mild tension in the lower abdominal wall, that tension will impede the downward movement of the dome of the diaphragm. And since the.abdominal organs cannot be compressed, they can act only as a fulcrum, causing the diaphragm to cantilever its costal site of attachment on the rib cage outwardly, spreading the base of the rib cage to the front, to the rear, and to the sides, while at the same time pulling air into the lower portions of the lungs. In contrast to the pump handle analogy for intercostal hreathing, diaphragmatic breathing has been likened to lifting a bucket handle up and out from its resting position alongside the bucket (see Anderson and Sovik's Yoga, Mastering the Basics for illustration and further explanation). Without the resistance of the abdominal organs, the diaphragm cannot create this result. The intercostal muscles serve to support the action of the diaphragm, not so much to lift and enlarge the chest but to keep it from collapsing during inhalation.

[Technical note: Precise language does not exist, at least in English, lor describing m ¡1 single word or phrase how the respiratory diaphragm operates to expand the rib cage in diaphragmatic hreathing. A "cantilever truss," however, from civil engineering, describes a horizontal truss supported in the middle and sustaining a load at both ends, and this comes close. In the special case of the human torso, the abdominal organs and intra-abdominal pressure provide horizontal support for the dome of the diaphragm, and the lift and outward expansion of the base of the rib cage is a load sustained at the perimeter of the base of the rib cage. |

The origins and insertions of the diaphragm for abdominal inhalations ---—- —-

subtleties of these functional shifts will further clarify the differences between the two types of breathing. For abdominal breathing in the corpse and inverted postures, both the costal attachment to the rib cage and the crural attachment to the spine act as stationary origins; the only part of the diaphragm that can move (the insertion, by definition) is the central tendon in the dome, which moves inferiorly during inhalation and superiorly (toward the head) during exhalation. By contrast, for diaphragmatic breathing, the central tendon is held static by the relative tautness of the abdominal wall and serves mainly as a link between the spinal attachments of the crura, which now act as the stationary origin, and the costal attachment to the base of the rib cage, which now acts as the movable insertion.

To summarize, diaphragmatic breathing occasions an expansion of the ril cage from its lower border. To differentiate it from abdomino-diaphragmatii breathing, in which the rib cage remains static, we can call it thoraco diaphragmatic breathing. It should be mentioned that the terms abdomin;i breathing, belly breathing, deep diaphragmatic breathing, and diaphragmatic breathing have all been in casual, although generally noncritical, use for ¡ long time, but the terms "abdomino-diaphragmatic" and "thoraco diaphragmatic" have not appeared in the literature before now.

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