Abdomen: topographical anatomy

The abdomen is the part of the body located between the chest at the top and the pelvis at the bottom. The upper border of the abdomen runs from the base of the xiphoid process along the costal arches to the 12th thoracic vertebra. From the lateral side, the borders of the abdomen are determined by the posterior axillary line from the costal arch at the top to the iliac crest at the bottom. The lower border of the abdomen on the right and left is formed by the anterior segment of the iliac crest and a line conditionally drawn at the level of the inguinal folds from the superior anterior iliac spine to the pubic tubercle. These are the external borders of the abdomen. They do not coincide with the borders of the abdominal cavity, which at the top (cranial) extends to the dome of the diaphragm (level of the 4th rib), and at the bottom reaches the bottom of the pelvic cavity.

In order to more accurately determine the location of the organs in the abdominal cavity, their topography and projection onto the outer layers, the abdomen is divided into three floors by two horizontal lines. One line runs between the cartilages of the 10th ribs - the intercostal line (lmea bicostarum). The other line connects the upper anterior iliac spines - the interspinous line (linea bispinatum). Thus, above the intercostal line is the upper floor - the epigastrium (epigastrium). Between the intercostal and interspinous lines is the middle floor - the belly (mesogastrium), and below the interspinous line is the hypogastrium (hypogdstrium). In addition, each of the specified floors is subdivided into three separate areas by two vertical lines drawn along the lateral edges of the rectus abdominis muscles from the costal arch to the pubic tubercle. Accordingly, the epigastrium is divided into the right and left hypochondric regions (regiones hypochondricae dextra et sinistra) and the epigastric region (regio epigastrica). The abdomen is divided into the right and left lateral regions (regiones laterales dextra et sinistra), and between them is the umbilical region (regio umbilicalis). The hypogastrium is divided into the right and left inguinal regions (regiones inguinales dextra et sinistra) and the pubic region (regio pubica).

The internal organs located in the abdominal cavity are projected onto the anterior abdominal wall. The stomach, duodenum, left lobe of the liver, and pancreas are projected into the epigastric region proper. The right hypochondrium corresponds to the right lobe of the liver with the gallbladder, the upper pole of the right kidney and the right adrenal gland, the right (hepatic) flexure of the colon. The spleen, fundus of the stomach, left (splenic) flexure of the colon, the upper pole of the left kidney and the left adrenal gland, and the tail of the pancreas are projected into the left hypochondrium.

In the umbilical region are located the greater curvature of the stomach, the lower horizontal and ascending parts of the duodenum, loops of the mesenteric part of the small intestine, the transverse colon, the renal hilum, and the ureters. In the right lateral region are located part of the loops of the small (ileal) intestine, the ascending colon, and the lower pole of the right kidney. In the left lateral region are determined part of the loops of the small (jejunum) intestine, the descending colon, and the lower pole of the left kidney.

The pubic region projects the urinary bladder (filled) and the lower sections of the ureters, the uterus with the fallopian tubes (in women), and part of the loops of the small intestine. In the right inguinal region are the terminal section of the small (ileum), the cecum, the vermiform appendix, and the right ureter; in the left inguinal region are part of the loops of the small intestine, the sigmoid colon, and the left ureter.

The skin in the abdominal wall area is thin and easily gathers into folds. The hair in men (in the pubic area) rises in a narrow strip to the navel, and sometimes to the anterior surface of the sternum. In women, hair is present only in the pubic area, the upper hairline is horizontal. Subcutaneous tissue is more developed in the lower part of the abdominal walls.

The anterior and lateral walls of the abdominal cavity are formed by three paired broad abdominal muscles, their tendon extensions, and the rectus abdominis muscles with their fasciae. The muscles and fasciae of the abdominal walls form the abdominal press, which protects the viscera from external influences, exerts pressure on them and holds them in a certain position, and also participates in the movements of the spine and ribs. The posterior wall of the abdominal cavity includes the lumbar spine, as well as the paired large lumbar and square lumbar muscles. The lower wall is formed by the iliac bones, muscles and fasciae of the pelvic floor - the pelvic diaphragm and the urogenital diaphragm.

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