肝臓の解剖学

The liver is positioned under the diaphragm, primarily in the right hypochondriac and epigastric regions, extending across the midline into the left hypochondriac region. Almost entirely protected by the rib cage, the liver is the largest gland in the body, weighing approximately 1.4 to 1.5 kg in adults. Its wedge shape and superior position make it well-shielded from external trauma.

The liver comprises four main lobes: the right lobe, left lobe, caudate lobe, and quadrate lobe. The falciform ligament divides the right and left lobes anteriorly. The caudate lobe is smaller and located posteriorly, while the quadrate lobe sits between the left lobe and the gallbladder on the inferior surface.

The falciform ligament is a mesentery that divides the right and left lobes of the liver anteriorly and suspends the organ from the diaphragm and anterior abdominal wall. The round ligament, a fibrous remnant of the fetal umbilical vein, runs along its inferior edge, marking an important anatomical landmark on the liver's surface.

The liver is covered by a robust fibrous capsule and a layer of visceral peritoneum, except for a small bare area on its superior surface that contacts the diaphragm directly. This peritoneal covering, combined with the protection of the rib cage, shields the liver from injury while allowing it to move slightly with respiration.

The lesser omentum anchors the liver to the lesser curvature of the stomach, while the falciform ligament suspends it from the diaphragm and anterior abdominal wall. Blood vessels and other structures reach the liver through the connective tissue of the lesser omentum, converging at the porta hepatis, a critical region for hepatic blood supply to the digestive system.

The gallbladder is located in a recess on the inferior surface of the right liver lobe. The quadrate lobe, situated between the left lobe and the gallbladder, helps define the gallbladder's anatomical position. This arrangement allows the gallbladder to store bile produced by the liver for use in digestion.

The round ligament is a fibrous remnant of the fetal umbilical vein that runs along the inferior edge of the falciform ligament. This structure serves as an important anatomical landmark on the liver's anterior surface and represents a vestigial remnant from fetal circulation that becomes non-functional after birth.