Abdomen

The (colloquially called the, , , stomach,  or ) is the part of the body between the  (chest) and , in humans and in other. The abdomen is the front part of the abdominal segment of the. The area occupied by the abdomen is called the. In it is the   of the body; it follows the thorax or.

In humans, the abdomen stretches from the thorax at the to the pelvis at the. The pelvic brim stretches from the (the  between  and ) to the  and is the edge of the. The space above this inlet and under the thoracic diaphragm is termed the. The boundary of the abdominal cavity is the in the front and the peritoneal surface at the rear.

In vertebrates, the abdomen is a large enclosed by the abdominal muscles, at front and to the sides, and by part of the  at the back. Lower ribs can also enclose ventral and lateral walls. The abdominal cavity is continuous with, and above, the pelvic cavity. It is attached to the by the. Structures such as the, inferior and  pass through the diaphragm. Both the abdominal and pelvic cavities are lined by a serous membrane known as the. This membrane is continuous with the lining the organs. The abdomen in vertebrates contains a number of belonging to, for instance, the, , and.

Contents in humans
The contains most organs of the, including the , the , and the  with its attached. Other digestive organs are known as the accessory digestive organs and include the, its attached , and the , and these communicate with the rest of the system via various ducts. The, and organs of the including the s, and  also lie within the abdomen, along with many blood vessels including the  and. The, , , and may be seen as either abdominal organs or as pelvic organs. Finally, the abdomen contains an extensive membrane called the. A fold of peritoneum may completely cover certain organs, whereas it may cover only one side of organs that usually lie closer to the abdominal wall. This is called the, and the kidneys and ureters are known as retroperitoneal organs.

Abdominal organs can be highly specialized in some animals. For example, the stomach of, (a of mammals that includes  and ), is divided into four chambers – , ,  and.

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