Anatomy of the chest muscles

Among the muscles that move the chest, there are those that only expand the chest, but do not compress it. These include the thoraco-abdominal barrier, which separates the respiratory organs from the nutritional organs; we will describe it later. Then there is a pair of muscles located under the collarbone; they grow from that part of it that stretches to the top of the scapula, and we will describe them later; these muscles are adjacent to the first rib, right and left.

There are also a couple of muscles, where each muscle is double: it consists of two parts, with the upper part adjacent to the neck and moving it, and the lower part moving the chest. There is another muscle fused with it, which we will mention shortly; this is the muscle that adjoins the fifth and sixth ribs.

A pair of muscles are embedded in the concave surface of the scapula; a pair of muscles descending from the first vertebra adjoins it and deviates towards the scapula; they form, as it were, one muscle that is adjacent to the posterior ribs.

The third pair begins on the seventh cervical vertebra, as well as on the first and second thoracic vertebrae and is adjacent to the ribs of the sternum. These are the essence of the dilatator muscles.

As for the muscles that compress the chest, among them there is a muscle that compresses the chest in a secondary way, namely the thoraco-abdominal obstruction when it is motionless, as well as muscles that essentially compress the chest. The latter include a pair of muscles stretched under the roots of the upper ribs; their functions are to compress and compress the chest. This also includes a pair of muscles at the edges of the ribs - it adjoins the sternum between the dagger-shaped process and the clavicle, as well as the rectus abdominis muscle - and two other pairs that help the mentioned pair. 6 As for the muscles that both compress and expand the chest, these are the muscles located between the ribs. However, exhaustive observation proves that the contraction muscles are not dilators.

The fact is that between each pair of true ribs there are four muscles, although they are mistaken for one, and that this muscle, taken for one, is woven from fibers running obliquely, some of which are located inside, and some cover them outside. The covering muscles partly lie near the cartilaginous end of the rib, and partly near the other end, which is strong. The intrinsic muscles are all in the opposite direction to the covering muscles, and those at the cartilaginous end of the rib are all in the opposite direction to the fibers at the other end. And since the number of fiber directions is four, then the number of muscles should also be four. Those located on top are expansive, and those located below are compressive. Therefore, the total number of muscles reaches eighty-eight.

The chest muscles are assisted by two muscles that grow from the collarbone towards the top of the shoulder blade. They are adjacent to the first rib and, lifting it up, contribute to the expansion of the chest.