Abdomen
In mammals, the abdomen (belly) constitutes the part of the body between the thorax (chest) and pelvis. The region enclosed by the abdomen is termed the abdominal cavity. In arthropods it is the most distal section of the body which lies behind the thorax or cephalothorax.
Vertebrates[]
In vertebrates, the abdomen is a large cavity enclosed by the abdominal muscles, ventraly and lateraly, and by the vertebral column dorsally. Lower ribs can also enclose ventral and lateral walls. The abdominal cavity is continuous with the pelvic cavity. It is separated from the thoracic cavity by the diaphragm. Structures such as the aorta, inferior vena cava and esophagus pass through the diaphragm. Both the abdominal and pelvic cavities are lined by a serous membrane known as the parietal peritoneum. This membrane is continuous with the visceral peritoneum lining the organs[3]. The abdomen in vertebrates contains a number of organs belonging, for instance, to the digestive tract and urinary system.
Abdominal organs[]
- Digestive tract: Stomach, small intestine, large intestine with cecum and appendix
- Accessory organs of the digestive tract: Liver, gallbladder and pancreas
- Urinary system: Kidneys and ureters
- Other organs: Spleen
Abdominal organs can be highly specialized in some animals. For example the stomach of ruminants (a suborder of mammals) is divided into four chambers - rumen, reticulum, omasum and abomasum.
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