The Abdomen

The abdomen is the part of the body that contains all of the structures between the thorax (chest) and the pelvis, and is separated from the thorax via the diaphragm. The region occupied by the abdomen is called the abdominal cavity, and is enclosed by the abdominal muscles at front and to the sides, and by part of the vertebral column at the back.

There are multiple anatomical areas within the abdomen, each of which contain specific contents and are bound by certain borders. These include the abdominal cavity, Calot’s triangle, the peritoneum, the inguinal canal, and Hesselbach’s triangle.

The bones of the abdomen are made up of the lumbar spine, the third region of the vertebral column, located in the lower back between the thoracic (above) and sacral (below) vertebral segments.

The muscles of the abdomen work together to protect the internal organs (viscera) by covering them completely, and are made up of the muscles of the anterolateral abdominal wall and the muscles of the posterior abdominal wall.

The abdomen contains organs involved in the gastrointestinal tract, including the oesophagus, stomach, small intestine, cecum, appendix, colon, rectum and the anal canal. The gastrointestinal tract is an organ system that enables us to ingest food, digest it, absorb it, and then expel the remaining waste as faeces.

The abdomen contains many accessory organs, including the liver, gallbladder, pancreas, spleen, adrenal glands, kidneys and the mesentery. The role of these organs is to help the functioning of the other organs in the system.

The abdominal vasculature consists of various arterial branches that all come from the aorta, and two venous structures that help to drain the abdominal structures, carrying deoxygenated blood and waste products away.

In this section, learn more about the anatomy of the abdomen- its areas, bones, muscles, the gastrointestinal tract, accessory organs and the abdominal vasculature.