it is called the diaphram.
diaphragm
Pectoralis major
The chest press primarily works the pectoral muscles, which are located in the chest area.
The heart is located in the mediastinum, in the center of the chest. It contains cardiac muscle fibers.
The muscle that is located on the ventral (anterior) side of the body is the pectorals major. The pectorals major is located in the chest of the human body/
The diaphragm (a sheet of muscle underneath the ribcage) and intercostal muscles (located between your ribs).
If the pain is in the upper chest, it can be indigestion, including heartburn. If the pain is in the lower left side of the abomen, it could be diverticulitis or diverticulosis.
The seated chest press primarily targets and works the pectoral muscles, which are located in the chest area.
The largest chest muscle in a cat's body is the pectoralis minor. In humans, the largest chest muscle if the pectoralis major.
diaphragm
it's were the dent is located (it's between the chest plate (breast)
The diaphragm is the muscle separating the abdomen from the chest