what is the abdomen

The abdomen is the part of the body between the thorax (chest) and pelvis, in humans and other vertebrates. It is the front part of the abdominal segment of the torso and is enclosed by the abdominal muscles at the front and sides, and by part of the vertebral column at the back. The area occupied by the abdomen is called the abdominal cavity, which is continuous with and above the pelvic cavity. The abdomen contains many vital organs, including the stomach, small intestine, large intestine, liver, spleen, gallbladder, pancreas, uterus, and parts of the reproductive system. The alimentary tract in the abdomen consists of most of the digestive tract, where most of the absorption and digestion of food occurs. The abdomen is also home to many blood vessels, including the aorta and inferior vena cava, and an extensive membrane called the peritoneum. The abdominal wall is composed of muscles, connective tissue, and small tunnels called the inguinal and femoral canals, which allow nerves, blood vessels, and other structures to pass between the abdomen and groin. Embryologically, the gastrointestinal system develops as the foregut, midgut, and hindgut. Clinically, the abdomen is roughly divided into nine regions by two sagittal planes from the midclavicular lines to the mid inguinal lines, and two transverse planes, one at the subcostal line and one at the iliac tubercles, with the umbilicus serving as the center of the nine regions.