Corpus: Abdomen
from Latin: abdomen - stomach
Synonym: belly
1. Definition
In anatomy, the abdomen refers to the belly, which consists of the abdominal wall, abdominal cavity, and abdominal organs.
Along with the thorax and pelvis, the abdomen forms the trunk.
2. Anatomy
2.1. Borders
The upper border of the abdomen is defined by the lowest ribs and the tip of the sternum. The lower border is formed by the bony upper edge of the pelvis and the inguinal ligament. The front and sides of the abdomen are enclosed by the abdominal muscles, the layer of subcutaneous fat, and the abdominal skin stretched over these structures.
2.2. Surface
The external appearance of the abdomen varies based on a person’s nutritional and physical condition. In individuals with obesity, the abdomen appears rounded (convex) due to a thick layer of fat and typically lacks noticeable anatomical features apart from the navel (umbilicus), located along the midline. In lean or physically fit individuals, the contours of the abdominal muscles may be visible, particularly the indentations of the rectus abdominis muscle caused by the three horizontal tendinous intersections.
2.3. Topography
The abdomen can be topographically divided into three main sections and six anatomical regions.
2.3.1. Upper abdomen
The upper abdomen, or epigastrium, is the area above the navel enclosed by the ribs. It includes the following regions:
- Epigastric region
- Hypochondriac regions (right and left)
2.3.2. Midline abdomen
The middle abdomen, or mesogastrium, is the central area around the belly button. It has the approximate shape of a narrow corset and consists of:
- Umbilical region
- Lateral regions (right and left)
2.3.3. Lower abdomen
The lower abdomen, or hypogastrium, is the area below the navel, bordered by the pelvis. In everyday language, it is often simply called the "abdomen." It can be further divided into:
- Pubic region
- Inguinal regions (right and left)
2.4. Abdominal cavity
The abdominal cavity is a large hollow space within the abdominal region that contains the abdominal organs. It is enclosed by the abdominal walls, lies above the pelvic cavity, and is separated from the chest by the diaphragm.
2.5. Abdominal organs
The abdominal organs are the most important structures within the abdomen. These organs are categorized based on their peritoneal covering as either intraperitoneal or extraperitoneal. The abdominal organs include:
3. Clinic
The clinical examination of the abdomen is a key aspect of medical diagnosis. It consists primarily of inspection, auscultation, percussion and palpation. In addition to these basic physical examination techniques, a variety range of diagnostic tools are available to evaluate the abdomen, including:
- Sonography
- X-ray
- Computed tomography
- Magnetic resonance imaging