Which muscle of the pectoral girdle helps during forced inhalation in breathing?

The muscles of the anterior thorax provide movements to the arm and shoulder while the muscles of the posterior thorax also help change thoracic volume during breathing and reinforce the thoracic wall.

the abdomen (less formally called the belly, stomach, tummy or midriff) constitutes the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. the region occupied by the abdomen is termed the abdominal cavity. the stomach secretes acid and enzymes that digest food. ridges of muscle tissue called rugae line the stomach. the stomach muscles contract periodically, churning food to enhance digestion. the pyloric sphincter is a muscular valve that opens to allow food to pass from the stomach to the small intestine.