Somatic pain is the type of pain that is usually described as sharp or severe. It is due to irritation of the peritoneum supplied by pain fibers from the spinal nerves. These nerves travel around through the abdominal muscles and send motor fibers to the muscles of the abdominal wall. They send sensory fibers to the skin over the trunk and fibers to the parietal peritoneum.
This type of pain is typically felt directly over the pathology causing it. For instance when the parietal peritoneum is irritated by inflammation from the gall bladder the pain is felt in the right upper quadrant, over the gall bladder. Similarly pain in the right iliac fossa may be due to irritation of the parietal peritoneum adjacent to an inflamed appendix.
This type of pain is usually severe, the patient curtails their movement, breathing is shallow and tenderness is marked.