1 Red blood cells (RBCs) are also called erythrocytes. They make up almost half of blood. Red blood cells are filled with hemoglobin. That's a protein that picks up oxygen in the lungs and brings it to cells all around the body.  White blood cells (WBCs) are also called leukocytes.
Pain originating in the stomach or esophagus is often felt in the upper abdomen and can be due to heartburn, gastroesophageal reflux disease (GERD), or hiatal hernia (weakening in the diaphragm that allows the stomach to protrude into the chest). You may also have gastritis (inflammation of the stomach lining) or ulcers.
Find a Gastroenterologist Near You. Pain in the upper abdomen may originate in the gallbladder or liver and may be due to gall stones, hepatitis, or liver abscess. More-generalized pain may originate in the intestines and may be related to inflammatory conditions or infections.ind a Gastroenterologist Near You. Pain in the upper abdomen may originate in the gallbladder or liver and may be due to gall stones, hepatitis, or liver abscess. More-generalized pain may originate in the intestines and may be related to inflammatory conditions or infections.